Merge branch 'master' of https://github.com/Microsoft/Typescript

src/compiler/binder.ts

@@ -2515,7 +2515,7 @@ namespace ts {
                     break;
 
                 default:
-                    Debug.fail(Debug.showSyntaxKind(thisContainer));
+                    Debug.failBadSyntaxKind(thisContainer);
             }
         }
 
@@ -2581,7 +2581,7 @@ namespace ts {
             // Fix up parent pointers since we're going to use these nodes before we bind into them
             node.left.parent = node;
             node.right.parent = node;
-            if (isIdentifier(lhs.expression) && container === file && isNameOfExportsOrModuleExportsAliasDeclaration(file, lhs.expression)) {
+            if (isIdentifier(lhs.expression) && container === file && isExportsOrModuleExportsOrAlias(file, lhs.expression)) {
                 // This can be an alias for the 'exports' or 'module.exports' names, e.g.
                 //    var util = module.exports;
                 //    util.property = function ...
@@ -2975,21 +2975,27 @@ namespace ts {
     }
 
     export function isExportsOrModuleExportsOrAlias(sourceFile: SourceFile, node: Expression): boolean {
-        return isExportsIdentifier(node) ||
-            isModuleExportsPropertyAccessExpression(node) ||
-            isIdentifier(node) && isNameOfExportsOrModuleExportsAliasDeclaration(sourceFile, node);
-    }
-
-    function isNameOfExportsOrModuleExportsAliasDeclaration(sourceFile: SourceFile, node: Identifier): boolean {
-        const symbol = lookupSymbolForNameWorker(sourceFile, node.escapedText);
-        return !!symbol && !!symbol.valueDeclaration && isVariableDeclaration(symbol.valueDeclaration) &&
-            !!symbol.valueDeclaration.initializer && isExportsOrModuleExportsOrAliasOrAssignment(sourceFile, symbol.valueDeclaration.initializer);
-    }
-
-    function isExportsOrModuleExportsOrAliasOrAssignment(sourceFile: SourceFile, node: Expression): boolean {
-        return isExportsOrModuleExportsOrAlias(sourceFile, node) ||
-            (isAssignmentExpression(node, /*excludeCompoundAssignment*/ true) && (
-                isExportsOrModuleExportsOrAliasOrAssignment(sourceFile, node.left) || isExportsOrModuleExportsOrAliasOrAssignment(sourceFile, node.right)));
+        let i = 0;
+        const q = [node];
+        while (q.length && i < 100) {
+            i++;
+            node = q.shift()!;
+            if (isExportsIdentifier(node) || isModuleExportsPropertyAccessExpression(node)) {
+                return true;
+            }
+            else if (isIdentifier(node)) {
+                const symbol = lookupSymbolForNameWorker(sourceFile, node.escapedText);
+                if (!!symbol && !!symbol.valueDeclaration && isVariableDeclaration(symbol.valueDeclaration) && !!symbol.valueDeclaration.initializer) {
+                    const init = symbol.valueDeclaration.initializer;
+                    q.push(init);
+                    if (isAssignmentExpression(init, /*excludeCompoundAssignment*/ true)) {
+                        q.push(init.left);
+                        q.push(init.right);
+                    }
+                }
+            }
+        }
+        return false;
     }
 
     function lookupSymbolForNameWorker(container: Node, name: __String): Symbol | undefined {

src/compiler/checker.ts

@@ -391,7 +391,7 @@ namespace ts {
 
         const tupleTypes = createMap<GenericType>();
         const unionTypes = createMap<UnionType>();
-        const intersectionTypes = createMap<IntersectionType>();
+        const intersectionTypes = createMap<Type>();
         const literalTypes = createMap<LiteralType>();
         const indexedAccessTypes = createMap<IndexedAccessType>();
         const substitutionTypes = createMap<SubstitutionType>();
@@ -3563,7 +3563,7 @@ namespace ts {
                     context.approximateLength += 6;
                     return createKeywordTypeNode(SyntaxKind.ObjectKeyword);
                 }
-                if (type.flags & TypeFlags.TypeParameter && (type as TypeParameter).isThisType) {
+                if (isThisTypeParameter(type)) {
                     if (context.flags & NodeBuilderFlags.InObjectTypeLiteral) {
                         if (!context.encounteredError && !(context.flags & NodeBuilderFlags.AllowThisInObjectLiteral)) {
                             context.encounteredError = true;
@@ -4302,6 +4302,11 @@ namespace ts {
             function lookupTypeParameterNodes(chain: Symbol[], index: number, context: NodeBuilderContext) {
                 Debug.assert(chain && 0 <= index && index < chain.length);
                 const symbol = chain[index];
+                const symbolId = "" + getSymbolId(symbol);
+                if (context.typeParameterSymbolList && context.typeParameterSymbolList.get(symbolId)) {
+                    return undefined;
+                }
+                (context.typeParameterSymbolList || (context.typeParameterSymbolList = createMap())).set(symbolId, true);
                 let typeParameterNodes: ReadonlyArray<TypeNode> | ReadonlyArray<TypeParameterDeclaration> | undefined;
                 if (context.flags & NodeBuilderFlags.WriteTypeParametersInQualifiedName && index < (chain.length - 1)) {
                     const parentSymbol = symbol;
@@ -4628,6 +4633,7 @@ namespace ts {
             inferTypeParameters: TypeParameter[] | undefined;
             approximateLength: number;
             truncating?: boolean;
+            typeParameterSymbolList?: Map<true>;
         }
 
         function isDefaultBindingContext(location: Node) {
@@ -5346,7 +5352,7 @@ namespace ts {
                     return type;
                 }
                 else if (declaredType !== errorType && type !== errorType && !isTypeIdenticalTo(declaredType, type)) {
-                    errorNextVariableOrPropertyDeclarationMustHaveSameType(declaredType, declaration, type);
+                    errorNextVariableOrPropertyDeclarationMustHaveSameType(/*firstDeclaration*/ undefined, declaredType, declaration, type);
                 }
             }
             return declaredType;
@@ -5689,7 +5695,7 @@ namespace ts {
                 type = getTypeOfEnumMember(symbol);
             }
             else {
-                return Debug.fail("Unhandled declaration kind! " + Debug.showSyntaxKind(declaration) + " for " + Debug.showSymbol(symbol));
+                return Debug.fail("Unhandled declaration kind! " + Debug.formatSyntaxKind(declaration.kind) + " for " + Debug.formatSymbol(symbol));
             }
 
             if (!popTypeResolution()) {
@@ -7651,15 +7657,20 @@ namespace ts {
             return hasNonCircularBaseConstraint(type) ? getConstraintFromIndexedAccess(type) : undefined;
         }
 
+        function getSimplifiedTypeOrConstraint(type: Type) {
+            const simplified = getSimplifiedType(type, /*writing*/ false);
+            return simplified !== type ? simplified : getConstraintOfType(type);
+        }
+
         function getConstraintFromIndexedAccess(type: IndexedAccessType) {
-            const indexConstraint = getConstraintOfType(type.indexType);
+            const indexConstraint = getSimplifiedTypeOrConstraint(type.indexType);
             if (indexConstraint && indexConstraint !== type.indexType) {
                 const indexedAccess = getIndexedAccessTypeOrUndefined(type.objectType, indexConstraint);
                 if (indexedAccess) {
                     return indexedAccess;
                 }
             }
-            const objectConstraint = getConstraintOfType(type.objectType);
+            const objectConstraint = getSimplifiedTypeOrConstraint(type.objectType);
             if (objectConstraint && objectConstraint !== type.objectType) {
                 return getIndexedAccessTypeOrUndefined(objectConstraint, type.indexType);
             }
@@ -9838,6 +9849,15 @@ namespace ts {
             return true;
         }
 
+        function createIntersectionType(types: Type[], aliasSymbol?: Symbol, aliasTypeArguments?: ReadonlyArray<Type>) {
+            const result = <IntersectionType>createType(TypeFlags.Intersection);
+            result.objectFlags = getPropagatingFlagsOfTypes(types, /*excludeKinds*/ TypeFlags.Nullable);
+            result.types = types;
+            result.aliasSymbol = aliasSymbol; // See comment in `getUnionTypeFromSortedList`.
+            result.aliasTypeArguments = aliasTypeArguments;
+            return result;
+        }
+
         // We normalize combinations of intersection and union types based on the distributive property of the '&'
         // operator. Specifically, because X & (A | B) is equivalent to X & A | X & B, we can transform intersection
         // types with union type constituents into equivalent union types with intersection type constituents and
@@ -9875,31 +9895,31 @@ namespace ts {
             if (typeSet.length === 1) {
                 return typeSet[0];
             }
-            if (includes & TypeFlags.Union) {
-                if (intersectUnionsOfPrimitiveTypes(typeSet)) {
-                    // When the intersection creates a reduced set (which might mean that *all* union types have
-                    // disappeared), we restart the operation to get a new set of combined flags. Once we have
-                    // reduced we'll never reduce again, so this occurs at most once.
-                    return getIntersectionType(typeSet, aliasSymbol, aliasTypeArguments);
-                }
-                // We are attempting to construct a type of the form X & (A | B) & Y. Transform this into a type of
-                // the form X & A & Y | X & B & Y and recursively reduce until no union type constituents remain.
-                const unionIndex = findIndex(typeSet, t => (t.flags & TypeFlags.Union) !== 0);
-                const unionType = <UnionType>typeSet[unionIndex];
-                return getUnionType(map(unionType.types, t => getIntersectionType(replaceElement(typeSet, unionIndex, t))),
-                    UnionReduction.Literal, aliasSymbol, aliasTypeArguments);
-            }
             const id = getTypeListId(typeSet);
-            let type = intersectionTypes.get(id);
-            if (!type) {
-                type = <IntersectionType>createType(TypeFlags.Intersection);
-                intersectionTypes.set(id, type);
-                type.objectFlags = getPropagatingFlagsOfTypes(typeSet, /*excludeKinds*/ TypeFlags.Nullable);
-                type.types = typeSet;
-                type.aliasSymbol = aliasSymbol; // See comment in `getUnionTypeFromSortedList`.
-                type.aliasTypeArguments = aliasTypeArguments;
+            let result = intersectionTypes.get(id);
+            if (!result) {
+                if (includes & TypeFlags.Union) {
+                    if (intersectUnionsOfPrimitiveTypes(typeSet)) {
+                        // When the intersection creates a reduced set (which might mean that *all* union types have
+                        // disappeared), we restart the operation to get a new set of combined flags. Once we have
+                        // reduced we'll never reduce again, so this occurs at most once.
+                        result = getIntersectionType(typeSet, aliasSymbol, aliasTypeArguments);
+                    }
+                    else {
+                        // We are attempting to construct a type of the form X & (A | B) & Y. Transform this into a type of
+                        // the form X & A & Y | X & B & Y and recursively reduce until no union type constituents remain.
+                        const unionIndex = findIndex(typeSet, t => (t.flags & TypeFlags.Union) !== 0);
+                        const unionType = <UnionType>typeSet[unionIndex];
+                        result = getUnionType(map(unionType.types, t => getIntersectionType(replaceElement(typeSet, unionIndex, t))),
+                            UnionReduction.Literal, aliasSymbol, aliasTypeArguments);
+                    }
+                }
+                else {
+                    result = createIntersectionType(typeSet, aliasSymbol, aliasTypeArguments);
+                }
+                intersectionTypes.set(id, result);
             }
-            return type;
+            return result;
         }
 
         function getTypeFromIntersectionTypeNode(node: IntersectionTypeNode): Type {
@@ -10086,6 +10106,7 @@ namespace ts {
                             error(indexNode, Diagnostics.Property_0_does_not_exist_on_type_1, unescapeLeadingUnderscores(propName), typeToString(objectType));
                         }
                     }
+                    errorIfWritingToReadonlyIndex(getIndexInfoOfType(objectType, IndexKind.Number));
                     return mapType(objectType, t => getRestTypeOfTupleType(<TupleTypeReference>t) || undefinedType);
                 }
             }
@@ -10107,13 +10128,7 @@ namespace ts {
                         error(indexNode, Diagnostics.Type_0_cannot_be_used_as_an_index_type, typeToString(indexType));
                         return indexInfo.type;
                     }
-                    if (indexInfo.isReadonly && accessExpression && (isAssignmentTarget(accessExpression) || isDeleteTarget(accessExpression))) {
-                        if (accessExpression) {
-                            error(accessExpression, Diagnostics.Index_signature_in_type_0_only_permits_reading, typeToString(objectType));
-                            return indexInfo.type;
-                        }
-                        return undefined;
-                    }
+                    errorIfWritingToReadonlyIndex(indexInfo);
                     return indexInfo.type;
                 }
                 if (indexType.flags & TypeFlags.Never) {
@@ -10173,6 +10188,12 @@ namespace ts {
                 return indexType;
             }
             return undefined;
+
+            function errorIfWritingToReadonlyIndex(indexInfo: IndexInfo | undefined): void {
+                if (indexInfo && indexInfo.isReadonly && accessExpression && (isAssignmentTarget(accessExpression) || isDeleteTarget(accessExpression))) {
+                    error(accessExpression, Diagnostics.Index_signature_in_type_0_only_permits_reading, typeToString(objectType));
+                }
+            }
         }
 
         function getIndexNodeForAccessExpression(accessNode: ElementAccessExpression | IndexedAccessTypeNode | PropertyName | BindingName | SyntheticExpression) {
@@ -10193,6 +10214,10 @@ namespace ts {
             return maybeTypeOfKind(type, TypeFlags.InstantiableNonPrimitive | TypeFlags.Index);
         }
 
+        function isThisTypeParameter(type: Type): boolean {
+            return !!(type.flags & TypeFlags.TypeParameter && (<TypeParameter>type).isThisType);
+        }
+
         function getSimplifiedType(type: Type, writing: boolean): Type {
             return type.flags & TypeFlags.IndexedAccess ? getSimplifiedIndexedAccessType(<IndexedAccessType>type, writing) :
                 type.flags & TypeFlags.Conditional ? getSimplifiedConditionalType(<ConditionalType>type, writing) :
@@ -13042,8 +13067,7 @@ namespace ts {
                     }
                     // A type S is assignable to keyof T if S is assignable to keyof C, where C is the
                     // simplified form of T or, if T doesn't simplify, the constraint of T.
-                    const simplified = getSimplifiedType((<IndexType>target).type, /*writing*/ false);
-                    const constraint = simplified !== (<IndexType>target).type ? simplified : getConstraintOfType((<IndexType>target).type);
+                    const constraint = getSimplifiedTypeOrConstraint((<IndexType>target).type);
                     if (constraint) {
                         // We require Ternary.True here such that circular constraints don't cause
                         // false positives. For example, given 'T extends { [K in keyof T]: string }',
@@ -16772,7 +16796,7 @@ namespace ts {
             }
 
             function narrowByInKeyword(type: Type, literal: LiteralExpression, assumeTrue: boolean) {
-                if ((type.flags & (TypeFlags.Union | TypeFlags.Object)) || (type.flags & TypeFlags.TypeParameter && (type as TypeParameter).isThisType)) {
+                if (type.flags & (TypeFlags.Union | TypeFlags.Object) || isThisTypeParameter(type)) {
                     const propName = escapeLeadingUnderscores(literal.text);
                     return filterType(type, t => isTypePresencePossible(t, propName, assumeTrue));
                 }
@@ -20092,7 +20116,7 @@ namespace ts {
                         return anyType;
                     }
                     if (right.escapedText && !checkAndReportErrorForExtendingInterface(node)) {
-                        reportNonexistentProperty(right, leftType.flags & TypeFlags.TypeParameter && (leftType as TypeParameter).isThisType ? apparentType : leftType);
+                        reportNonexistentProperty(right, isThisTypeParameter(leftType) ? apparentType : leftType);
                     }
                     return errorType;
                 }
@@ -20496,7 +20520,7 @@ namespace ts {
 
             const effectiveIndexType = isForInVariableForNumericPropertyNames(indexExpression) ? numberType : indexType;
             const accessFlags = isAssignmentTarget(node) ?
-                AccessFlags.Writing | (isGenericObjectType(objectType) ? AccessFlags.NoIndexSignatures : 0) :
+                AccessFlags.Writing | (isGenericObjectType(objectType) && !isThisTypeParameter(objectType) ? AccessFlags.NoIndexSignatures : 0) :
                 AccessFlags.None;
             const indexedAccessType = getIndexedAccessTypeOrUndefined(objectType, effectiveIndexType, node, accessFlags) || errorType;
             return checkIndexedAccessIndexType(indexedAccessType, node);
@@ -23361,14 +23385,16 @@ namespace ts {
             if (strictNullChecks && properties.length === 0) {
                 return checkNonNullType(sourceType, node);
             }
-            for (const p of properties) {
-                checkObjectLiteralDestructuringPropertyAssignment(sourceType, p, properties, rightIsThis);
+            for (let i = 0; i < properties.length; i++) {
+                checkObjectLiteralDestructuringPropertyAssignment(node, sourceType, i, properties, rightIsThis);
             }
             return sourceType;
         }
 
         /** Note: If property cannot be a SpreadAssignment, then allProperties does not need to be provided */
-        function checkObjectLiteralDestructuringPropertyAssignment(objectLiteralType: Type, property: ObjectLiteralElementLike, allProperties?: NodeArray<ObjectLiteralElementLike>, rightIsThis = false) {
+        function checkObjectLiteralDestructuringPropertyAssignment(node: ObjectLiteralExpression, objectLiteralType: Type, propertyIndex: number, allProperties?: NodeArray<ObjectLiteralElementLike>, rightIsThis = false) {
+            const properties = node.properties;
+            const property = properties[propertyIndex];
             if (property.kind === SyntaxKind.PropertyAssignment || property.kind === SyntaxKind.ShorthandPropertyAssignment) {
                 const name = property.name;
                 const exprType = getLiteralTypeFromPropertyName(name);
@@ -23385,18 +23411,25 @@ namespace ts {
                 return checkDestructuringAssignment(property.kind === SyntaxKind.ShorthandPropertyAssignment ? property : property.initializer, type);
             }
             else if (property.kind === SyntaxKind.SpreadAssignment) {
-                if (languageVersion < ScriptTarget.ESNext) {
-                    checkExternalEmitHelpers(property, ExternalEmitHelpers.Rest);
+                if (propertyIndex < properties.length - 1) {
+                    error(property, Diagnostics.A_rest_element_must_be_last_in_a_destructuring_pattern);
                 }
-                const nonRestNames: PropertyName[] = [];
-                if (allProperties) {
-                    for (let i = 0; i < allProperties.length - 1; i++) {
-                        nonRestNames.push(allProperties[i].name!);
+                else {
+                    if (languageVersion < ScriptTarget.ESNext) {
+                        checkExternalEmitHelpers(property, ExternalEmitHelpers.Rest);
                     }
+                    const nonRestNames: PropertyName[] = [];
+                    if (allProperties) {
+                        for (const otherProperty of allProperties) {
+                            if (!isSpreadAssignment(otherProperty)) {
+                                nonRestNames.push(otherProperty.name);
+                            }
+                        }
+                    }
+                    const type = getRestType(objectLiteralType, nonRestNames, objectLiteralType.symbol);
+                    checkGrammarForDisallowedTrailingComma(allProperties, Diagnostics.A_rest_parameter_or_binding_pattern_may_not_have_a_trailing_comma);
+                    return checkDestructuringAssignment(property.expression, type);
                 }
-                const type = getRestType(objectLiteralType, nonRestNames, objectLiteralType.symbol);
-                checkGrammarForDisallowedTrailingComma(allProperties, Diagnostics.A_rest_parameter_or_binding_pattern_may_not_have_a_trailing_comma);
-                return checkDestructuringAssignment(property.expression, type);
             }
             else {
                 error(property, Diagnostics.Property_assignment_expected);
@@ -25527,7 +25560,7 @@ namespace ts {
                     case SyntaxKind.ImportSpecifier: // https://github.com/Microsoft/TypeScript/pull/7591
                         return DeclarationSpaces.ExportValue;
                     default:
-                        return Debug.fail(Debug.showSyntaxKind(d));
+                        return Debug.failBadSyntaxKind(d);
                 }
             }
         }
@@ -26830,7 +26863,7 @@ namespace ts {
                 if (type !== errorType && declarationType !== errorType &&
                     !isTypeIdenticalTo(type, declarationType) &&
                     !(symbol.flags & SymbolFlags.Assignment)) {
-                    errorNextVariableOrPropertyDeclarationMustHaveSameType(type, node, declarationType);
+                    errorNextVariableOrPropertyDeclarationMustHaveSameType(symbol.valueDeclaration, type, node, declarationType);
                 }
                 if (node.initializer) {
                     checkTypeAssignableToAndOptionallyElaborate(checkExpressionCached(node.initializer), declarationType, node, node.initializer, /*headMessage*/ undefined);
@@ -26850,17 +26883,24 @@ namespace ts {
             }
         }
 
-        function errorNextVariableOrPropertyDeclarationMustHaveSameType(firstType: Type, nextDeclaration: Declaration, nextType: Type): void {
+        function errorNextVariableOrPropertyDeclarationMustHaveSameType(firstDeclaration: Declaration | undefined, firstType: Type, nextDeclaration: Declaration, nextType: Type): void {
             const nextDeclarationName = getNameOfDeclaration(nextDeclaration);
             const message = nextDeclaration.kind === SyntaxKind.PropertyDeclaration || nextDeclaration.kind === SyntaxKind.PropertySignature
                 ? Diagnostics.Subsequent_property_declarations_must_have_the_same_type_Property_0_must_be_of_type_1_but_here_has_type_2
                 : Diagnostics.Subsequent_variable_declarations_must_have_the_same_type_Variable_0_must_be_of_type_1_but_here_has_type_2;
-            error(
+            const declName = declarationNameToString(nextDeclarationName);
+            const err = error(
                 nextDeclarationName,
                 message,
-                declarationNameToString(nextDeclarationName),
+                declName,
                 typeToString(firstType),
-                typeToString(nextType));
+                typeToString(nextType)
+            );
+            if (firstDeclaration) {
+                addRelatedInfo(err,
+                    createDiagnosticForNode(firstDeclaration, Diagnostics._0_was_also_declared_here, declName)
+                );
+            }
         }
 
         function areDeclarationFlagsIdentical(left: Declaration, right: Declaration) {
@@ -29948,8 +29988,10 @@ namespace ts {
             // If this is from nested object binding pattern
             //     for ({ skills: { primary, secondary } } = multiRobot, i = 0; i < 1; i++) {
             if (expr.parent.kind === SyntaxKind.PropertyAssignment) {
-                const typeOfParentObjectLiteral = getTypeOfArrayLiteralOrObjectLiteralDestructuringAssignment(<Expression>expr.parent.parent);
-                return checkObjectLiteralDestructuringPropertyAssignment(typeOfParentObjectLiteral || errorType, <ObjectLiteralElementLike>expr.parent)!; // TODO: GH#18217
+                const node = cast(expr.parent.parent, isObjectLiteralExpression);
+                const typeOfParentObjectLiteral = getTypeOfArrayLiteralOrObjectLiteralDestructuringAssignment(node);
+                const propertyIndex = indexOfNode(node.properties, expr.parent);
+                return checkObjectLiteralDestructuringPropertyAssignment(node, typeOfParentObjectLiteral || errorType, propertyIndex)!; // TODO: GH#18217
             }
             // Array literal assignment - array destructuring pattern
             Debug.assert(expr.parent.kind === SyntaxKind.ArrayLiteralExpression);
@@ -30153,12 +30195,17 @@ namespace ts {
             return undefined;
         }
 
+        function isSymbolOfDestructuredElementOfCatchBinding(symbol: Symbol) {
+            return isBindingElement(symbol.valueDeclaration)
+                && walkUpBindingElementsAndPatterns(symbol.valueDeclaration).parent.kind === SyntaxKind.CatchClause;
+        }
+
         function isSymbolOfDeclarationWithCollidingName(symbol: Symbol): boolean {
             if (symbol.flags & SymbolFlags.BlockScoped && !isSourceFile(symbol.valueDeclaration)) {
                 const links = getSymbolLinks(symbol);
                 if (links.isDeclarationWithCollidingName === undefined) {
                     const container = getEnclosingBlockScopeContainer(symbol.valueDeclaration);
-                    if (isStatementWithLocals(container)) {
+                    if (isStatementWithLocals(container) || isSymbolOfDestructuredElementOfCatchBinding(symbol)) {
                         const nodeLinks = getNodeLinks(symbol.valueDeclaration);
                         if (resolveName(container.parent, symbol.escapedName, SymbolFlags.Value, /*nameNotFoundMessage*/ undefined, /*nameArg*/ undefined, /*isUse*/ false)) {
                             // redeclaration - always should be renamed

src/compiler/commandLineParser.ts

@@ -2361,7 +2361,7 @@ namespace ts {
             if (!host.fileExists(extendedConfigPath) && !endsWith(extendedConfigPath, Extension.Json)) {
                 extendedConfigPath = `${extendedConfigPath}.json`;
                 if (!host.fileExists(extendedConfigPath)) {
-                    errors.push(createDiagnostic(Diagnostics.File_0_does_not_exist, extendedConfig));
+                    errors.push(createDiagnostic(Diagnostics.File_0_not_found, extendedConfig));
                     return undefined;
                 }
             }
@@ -2372,7 +2372,7 @@ namespace ts {
         if (resolved.resolvedModule) {
             return resolved.resolvedModule.resolvedFileName;
         }
-        errors.push(createDiagnostic(Diagnostics.File_0_does_not_exist, extendedConfig));
+        errors.push(createDiagnostic(Diagnostics.File_0_not_found, extendedConfig));
         return undefined;
     }
 

src/compiler/core.ts

@@ -1686,89 +1686,6 @@ namespace ts {
     export type AnyFunction = (...args: never[]) => void;
     export type AnyConstructor = new (...args: unknown[]) => unknown;
 
-    export namespace Debug {
-        export let currentAssertionLevel = AssertionLevel.None;
-        export let isDebugging = false;
-
-        export function shouldAssert(level: AssertionLevel): boolean {
-            return currentAssertionLevel >= level;
-        }
-
-        export function assert(expression: boolean, message?: string, verboseDebugInfo?: string | (() => string), stackCrawlMark?: AnyFunction): void {
-            if (!expression) {
-                if (verboseDebugInfo) {
-                    message += "\r\nVerbose Debug Information: " + (typeof verboseDebugInfo === "string" ? verboseDebugInfo : verboseDebugInfo());
-                }
-                fail(message ? "False expression: " + message : "False expression.", stackCrawlMark || assert);
-            }
-        }
-
-        export function assertEqual<T>(a: T, b: T, msg?: string, msg2?: string): void {
-            if (a !== b) {
-                const message = msg ? msg2 ? `${msg} ${msg2}` : msg : "";
-                fail(`Expected ${a} === ${b}. ${message}`);
-            }
-        }
-
-        export function assertLessThan(a: number, b: number, msg?: string): void {
-            if (a >= b) {
-                fail(`Expected ${a} < ${b}. ${msg || ""}`);
-            }
-        }
-
-        export function assertLessThanOrEqual(a: number, b: number): void {
-            if (a > b) {
-                fail(`Expected ${a} <= ${b}`);
-            }
-        }
-
-        export function assertGreaterThanOrEqual(a: number, b: number): void {
-            if (a < b) {
-                fail(`Expected ${a} >= ${b}`);
-            }
-        }
-
-        export function fail(message?: string, stackCrawlMark?: AnyFunction): never {
-            debugger;
-            const e = new Error(message ? `Debug Failure. ${message}` : "Debug Failure.");
-            if ((<any>Error).captureStackTrace) {
-                (<any>Error).captureStackTrace(e, stackCrawlMark || fail);
-            }
-            throw e;
-        }
-
-        export function assertDefined<T>(value: T | null | undefined, message?: string): T {
-            if (value === undefined || value === null) return fail(message);
-            return value;
-        }
-
-        export function assertEachDefined<T, A extends ReadonlyArray<T>>(value: A, message?: string): A {
-            for (const v of value) {
-                assertDefined(v, message);
-            }
-            return value;
-        }
-
-        export function assertNever(member: never, message = "Illegal value:", stackCrawlMark?: AnyFunction): never {
-            const detail = typeof member === "object" && "kind" in member && "pos" in member ? "SyntaxKind: " + showSyntaxKind(member as Node) : JSON.stringify(member);
-            return fail(`${message} ${detail}`, stackCrawlMark || assertNever);
-        }
-
-        export function getFunctionName(func: AnyFunction) {
-            if (typeof func !== "function") {
-                return "";
-            }
-            else if (func.hasOwnProperty("name")) {
-                return (<any>func).name;
-            }
-            else {
-                const text = Function.prototype.toString.call(func);
-                const match = /^function\s+([\w\$]+)\s*\(/.exec(text);
-                return match ? match[1] : "";
-            }
-        }
-    }
-
     export function equateValues<T>(a: T, b: T) {
         return a === b;
     }

src/compiler/debug.ts

@@ -0,0 +1,261 @@
+/* @internal */
+namespace ts {
+    export namespace Debug {
+        export let currentAssertionLevel = AssertionLevel.None;
+        export let isDebugging = false;
+
+        export function shouldAssert(level: AssertionLevel): boolean {
+            return currentAssertionLevel >= level;
+        }
+
+        export function assert(expression: boolean, message?: string, verboseDebugInfo?: string | (() => string), stackCrawlMark?: AnyFunction): void {
+            if (!expression) {
+                if (verboseDebugInfo) {
+                    message += "\r\nVerbose Debug Information: " + (typeof verboseDebugInfo === "string" ? verboseDebugInfo : verboseDebugInfo());
+                }
+                fail(message ? "False expression: " + message : "False expression.", stackCrawlMark || assert);
+            }
+        }
+
+        export function assertEqual<T>(a: T, b: T, msg?: string, msg2?: string): void {
+            if (a !== b) {
+                const message = msg ? msg2 ? `${msg} ${msg2}` : msg : "";
+                fail(`Expected ${a} === ${b}. ${message}`);
+            }
+        }
+
+        export function assertLessThan(a: number, b: number, msg?: string): void {
+            if (a >= b) {
+                fail(`Expected ${a} < ${b}. ${msg || ""}`);
+            }
+        }
+
+        export function assertLessThanOrEqual(a: number, b: number): void {
+            if (a > b) {
+                fail(`Expected ${a} <= ${b}`);
+            }
+        }
+
+        export function assertGreaterThanOrEqual(a: number, b: number): void {
+            if (a < b) {
+                fail(`Expected ${a} >= ${b}`);
+            }
+        }
+
+        export function fail(message?: string, stackCrawlMark?: AnyFunction): never {
+            debugger;
+            const e = new Error(message ? `Debug Failure. ${message}` : "Debug Failure.");
+            if ((<any>Error).captureStackTrace) {
+                (<any>Error).captureStackTrace(e, stackCrawlMark || fail);
+            }
+            throw e;
+        }
+
+        export function assertDefined<T>(value: T | null | undefined, message?: string): T {
+            if (value === undefined || value === null) return fail(message);
+            return value;
+        }
+
+        export function assertEachDefined<T, A extends ReadonlyArray<T>>(value: A, message?: string): A {
+            for (const v of value) {
+                assertDefined(v, message);
+            }
+            return value;
+        }
+
+        export function assertNever(member: never, message = "Illegal value:", stackCrawlMark?: AnyFunction): never {
+            const detail = typeof member === "object" && "kind" in member && "pos" in member && formatSyntaxKind ? "SyntaxKind: " + formatSyntaxKind((member as Node).kind) : JSON.stringify(member);
+            return fail(`${message} ${detail}`, stackCrawlMark || assertNever);
+        }
+
+        export function getFunctionName(func: AnyFunction) {
+            if (typeof func !== "function") {
+                return "";
+            }
+            else if (func.hasOwnProperty("name")) {
+                return (<any>func).name;
+            }
+            else {
+                const text = Function.prototype.toString.call(func);
+                const match = /^function\s+([\w\$]+)\s*\(/.exec(text);
+                return match ? match[1] : "";
+            }
+        }
+
+        export function formatSymbol(symbol: Symbol): string {
+            return `{ name: ${unescapeLeadingUnderscores(symbol.escapedName)}; flags: ${formatSymbolFlags(symbol.flags)}; declarations: ${map(symbol.declarations, node => formatSyntaxKind(node.kind))} }`;
+        }
+
+        /**
+         * Formats an enum value as a string for debugging and debug assertions.
+         */
+        export function formatEnum(value = 0, enumObject: any, isFlags?: boolean) {
+            const members = getEnumMembers(enumObject);
+            if (value === 0) {
+                return members.length > 0 && members[0][0] === 0 ? members[0][1] : "0";
+            }
+            if (isFlags) {
+                let result = "";
+                let remainingFlags = value;
+                for (let i = members.length - 1; i >= 0 && remainingFlags !== 0; i--) {
+                    const [enumValue, enumName] = members[i];
+                    if (enumValue !== 0 && (remainingFlags & enumValue) === enumValue) {
+                        remainingFlags &= ~enumValue;
+                        result = `${enumName}${result ? "|" : ""}${result}`;
+                    }
+                }
+                if (remainingFlags === 0) {
+                    return result;
+                }
+            }
+            else {
+                for (const [enumValue, enumName] of members) {
+                    if (enumValue === value) {
+                        return enumName;
+                    }
+                }
+            }
+            return value.toString();
+        }
+
+        function getEnumMembers(enumObject: any) {
+            const result: [number, string][] = [];
+            for (const name in enumObject) {
+                const value = enumObject[name];
+                if (typeof value === "number") {
+                    result.push([value, name]);
+                }
+            }
+
+            return stableSort<[number, string]>(result, (x, y) => compareValues(x[0], y[0]));
+        }
+
+        export function formatSyntaxKind(kind: SyntaxKind | undefined): string {
+            return formatEnum(kind, (<any>ts).SyntaxKind, /*isFlags*/ false);
+        }
+
+        export function formatNodeFlags(flags: NodeFlags | undefined): string {
+            return formatEnum(flags, (<any>ts).NodeFlags, /*isFlags*/ true);
+        }
+
+        export function formatModifierFlags(flags: ModifierFlags | undefined): string {
+            return formatEnum(flags, (<any>ts).ModifierFlags, /*isFlags*/ true);
+        }
+
+        export function formatTransformFlags(flags: TransformFlags | undefined): string {
+            return formatEnum(flags, (<any>ts).TransformFlags, /*isFlags*/ true);
+        }
+
+        export function formatEmitFlags(flags: EmitFlags | undefined): string {
+            return formatEnum(flags, (<any>ts).EmitFlags, /*isFlags*/ true);
+        }
+
+        export function formatSymbolFlags(flags: SymbolFlags | undefined): string {
+            return formatEnum(flags, (<any>ts).SymbolFlags, /*isFlags*/ true);
+        }
+
+        export function formatTypeFlags(flags: TypeFlags | undefined): string {
+            return formatEnum(flags, (<any>ts).TypeFlags, /*isFlags*/ true);
+        }
+
+        export function formatObjectFlags(flags: ObjectFlags | undefined): string {
+            return formatEnum(flags, (<any>ts).ObjectFlags, /*isFlags*/ true);
+        }
+
+        export function failBadSyntaxKind(node: Node, message?: string): never {
+            return fail(
+                `${message || "Unexpected node."}\r\nNode ${formatSyntaxKind(node.kind)} was unexpected.`,
+                failBadSyntaxKind);
+        }
+
+        export const assertEachNode = shouldAssert(AssertionLevel.Normal)
+            ? (nodes: Node[], test: (node: Node) => boolean, message?: string): void => assert(
+                test === undefined || every(nodes, test),
+                message || "Unexpected node.",
+                () => `Node array did not pass test '${getFunctionName(test)}'.`,
+                assertEachNode)
+            : noop;
+
+        export const assertNode = shouldAssert(AssertionLevel.Normal)
+            ? (node: Node | undefined, test: ((node: Node | undefined) => boolean) | undefined, message?: string): void => assert(
+                test === undefined || test(node),
+                message || "Unexpected node.",
+                () => `Node ${formatSyntaxKind(node!.kind)} did not pass test '${getFunctionName(test!)}'.`,
+                assertNode)
+            : noop;
+
+        export const assertOptionalNode = shouldAssert(AssertionLevel.Normal)
+            ? (node: Node, test: (node: Node) => boolean, message?: string): void => assert(
+                test === undefined || node === undefined || test(node),
+                message || "Unexpected node.",
+                () => `Node ${formatSyntaxKind(node.kind)} did not pass test '${getFunctionName(test)}'.`,
+                assertOptionalNode)
+            : noop;
+
+        export const assertOptionalToken = shouldAssert(AssertionLevel.Normal)
+            ? (node: Node, kind: SyntaxKind, message?: string): void => assert(
+                kind === undefined || node === undefined || node.kind === kind,
+                message || "Unexpected node.",
+                () => `Node ${formatSyntaxKind(node.kind)} was not a '${formatSyntaxKind(kind)}' token.`,
+                assertOptionalToken)
+            : noop;
+
+        export const assertMissingNode = shouldAssert(AssertionLevel.Normal)
+            ? (node: Node, message?: string): void => assert(
+                node === undefined,
+                message || "Unexpected node.",
+                () => `Node ${formatSyntaxKind(node.kind)} was unexpected'.`,
+                assertMissingNode)
+            : noop;
+
+        let isDebugInfoEnabled = false;
+
+        /**
+         * Injects debug information into frequently used types.
+         */
+        export function enableDebugInfo() {
+            if (isDebugInfoEnabled) return;
+
+            // Add additional properties in debug mode to assist with debugging.
+            Object.defineProperties(objectAllocator.getSymbolConstructor().prototype, {
+                __debugFlags: { get(this: Symbol) { return formatSymbolFlags(this.flags); } }
+            });
+
+            Object.defineProperties(objectAllocator.getTypeConstructor().prototype, {
+                __debugFlags: { get(this: Type) { return formatTypeFlags(this.flags); } },
+                __debugObjectFlags: { get(this: Type) { return this.flags & TypeFlags.Object ? formatObjectFlags((<ObjectType>this).objectFlags) : ""; } },
+                __debugTypeToString: { value(this: Type) { return this.checker.typeToString(this); } },
+            });
+
+            const nodeConstructors = [
+                objectAllocator.getNodeConstructor(),
+                objectAllocator.getIdentifierConstructor(),
+                objectAllocator.getTokenConstructor(),
+                objectAllocator.getSourceFileConstructor()
+            ];
+
+            for (const ctor of nodeConstructors) {
+                if (!ctor.prototype.hasOwnProperty("__debugKind")) {
+                    Object.defineProperties(ctor.prototype, {
+                        __debugKind: { get(this: Node) { return formatSyntaxKind(this.kind); } },
+                        __debugNodeFlags: { get(this: Node) { return formatNodeFlags(this.flags); } },
+                        __debugModifierFlags: { get(this: Node) { return formatModifierFlags(getModifierFlagsNoCache(this)); } },
+                        __debugTransformFlags: { get(this: Node) { return formatTransformFlags(this.transformFlags); } },
+                        __debugIsParseTreeNode: { get(this: Node) { return isParseTreeNode(this); } },
+                        __debugEmitFlags: { get(this: Node) { return formatEmitFlags(getEmitFlags(this)); } },
+                        __debugGetText: {
+                            value(this: Node, includeTrivia?: boolean) {
+                                if (nodeIsSynthesized(this)) return "";
+                                const parseNode = getParseTreeNode(this);
+                                const sourceFile = parseNode && getSourceFileOfNode(parseNode);
+                                return sourceFile ? getSourceTextOfNodeFromSourceFile(sourceFile, parseNode, includeTrivia) : "";
+                            }
+                        }
+                    });
+                }
+            }
+
+            isDebugInfoEnabled = true;
+        }
+    }
+}

src/compiler/diagnosticMessages.json

@@ -655,7 +655,7 @@
         "category": "Error",
         "code": 1207
     },
-    "Cannot compile namespaces when the '--isolatedModules' flag is provided.": {
+    "All files must be modules when the '--isolatedModules' flag is provided.": {
         "category": "Error",
         "code": 1208
     },
@@ -3811,10 +3811,6 @@
         "category": "Error",
         "code": 6189
     },
-    "Found 'package.json' at '{0}'. Package ID is '{1}'.": {
-        "category": "Message",
-        "code": 6190
-    },
     "Whether to keep outdated console output in watch mode instead of clearing the screen.": {
         "category": "Message",
         "code": 6191
@@ -3923,6 +3919,14 @@
         "category": "Message",
         "code": 6217
     },
+    "======== Module name '{0}' was successfully resolved to '{1}' with Package ID '{2}'. ========": {
+        "category": "Message",
+        "code": 6218
+    },
+    "======== Type reference directive '{0}' was successfully resolved to '{1}' with Package ID '{2}', primary: {3}. ========": {
+        "category": "Message",
+        "code": 6219
+    },
 
     "Projects to reference": {
         "category": "Message",
@@ -4975,7 +4979,7 @@
         "code": 95079
     },
 
-    "No value exists in scope for the shorthand property '{0}'. Either declare one or provide an initializer." :{
+    "No value exists in scope for the shorthand property '{0}'. Either declare one or provide an initializer.": {
         "category": "Error",
         "code": 18004
     },

src/compiler/emitter.ts

@@ -4527,6 +4527,8 @@ namespace ts {
                 case SyntaxKind.GetAccessor:
                 case SyntaxKind.SetAccessor:
                     return generateNameForMethodOrAccessor(<MethodDeclaration | AccessorDeclaration>node);
+                case SyntaxKind.ComputedPropertyName:
+                    return makeTempVariableName(TempFlags.Auto, /*reserveInNestedScopes*/ true);
                 default:
                     return makeTempVariableName(TempFlags.Auto);
             }

src/compiler/moduleNameResolver.ts

@@ -16,12 +16,23 @@ namespace ts {
         push(value: T): void;
     }
 
-    function withPackageId(packageId: PackageId | undefined, r: PathAndExtension | undefined): Resolved | undefined {
+    function withPackageId(packageInfo: PackageJsonInfo | undefined, r: PathAndExtension | undefined): Resolved | undefined {
+        let packageId: PackageId | undefined;
+        if (r && packageInfo) {
+            const packageJsonContent = packageInfo.packageJsonContent as PackageJson;
+            if (typeof packageJsonContent.name === "string" && typeof packageJsonContent.version === "string") {
+                packageId = {
+                    name: packageJsonContent.name,
+                    subModuleName: r.path.slice(packageInfo.packageDirectory.length + directorySeparator.length),
+                    version: packageJsonContent.version
+                };
+            }
+        }
         return r && { path: r.path, extension: r.ext, packageId };
     }
 
     function noPackageId(r: PathAndExtension | undefined): Resolved | undefined {
-        return withPackageId(/*packageId*/ undefined, r);
+        return withPackageId(/*packageInfo*/ undefined, r);
     }
 
     function removeIgnoredPackageId(r: Resolved | undefined): PathAndExtension | undefined {
@@ -307,7 +318,12 @@ namespace ts {
             const { fileName, packageId } = resolved;
             const resolvedFileName = options.preserveSymlinks ? fileName : realPath(fileName, host, traceEnabled);
             if (traceEnabled) {
-                trace(host, Diagnostics.Type_reference_directive_0_was_successfully_resolved_to_1_primary_Colon_2, typeReferenceDirectiveName, resolvedFileName, primary);
+                if (packageId) {
+                    trace(host, Diagnostics.Type_reference_directive_0_was_successfully_resolved_to_1_with_Package_ID_2_primary_Colon_3, typeReferenceDirectiveName, resolvedFileName, packageIdToString(packageId), primary);
+                }
+                else {
+                    trace(host, Diagnostics.Type_reference_directive_0_was_successfully_resolved_to_1_primary_Colon_2, typeReferenceDirectiveName, resolvedFileName, primary);
+                }
             }
             resolvedTypeReferenceDirective = { primary, resolvedFileName, packageId, isExternalLibraryImport: pathContainsNodeModules(fileName) };
         }
@@ -663,7 +679,12 @@ namespace ts {
 
         if (traceEnabled) {
             if (result.resolvedModule) {
-                trace(host, Diagnostics.Module_name_0_was_successfully_resolved_to_1, moduleName, result.resolvedModule.resolvedFileName);
+                if (result.resolvedModule.packageId) {
+                    trace(host, Diagnostics.Module_name_0_was_successfully_resolved_to_1_with_Package_ID_2, moduleName, result.resolvedModule.resolvedFileName, packageIdToString(result.resolvedModule.packageId));
+                }
+                else {
+                    trace(host, Diagnostics.Module_name_0_was_successfully_resolved_to_1, moduleName, result.resolvedModule.resolvedFileName);
+                }
             }
             else {
                 trace(host, Diagnostics.Module_name_0_was_not_resolved, moduleName);
@@ -968,10 +989,9 @@ namespace ts {
             }
             const resolvedFromFile = loadModuleFromFile(extensions, candidate, onlyRecordFailures, state);
             if (resolvedFromFile) {
-                const nm = considerPackageJson ? parseNodeModuleFromPath(resolvedFromFile) : undefined;
-                const packageInfo = nm && getPackageJsonInfo(nm.packageDirectory, nm.subModuleName, /*onlyRecordFailures*/ false, state);
-                const packageId = packageInfo && packageInfo.packageId;
-                return withPackageId(packageId, resolvedFromFile);
+                const packageDirectory = considerPackageJson ? parseNodeModuleFromPath(resolvedFromFile) : undefined;
+                const packageInfo = packageDirectory ? getPackageJsonInfo(packageDirectory, /*onlyRecordFailures*/ false, state) : undefined;
+                return withPackageId(packageInfo, resolvedFromFile);
             }
         }
         if (!onlyRecordFailures) {
@@ -998,13 +1018,12 @@ namespace ts {
      * (Not neeeded for `loadModuleFromNodeModules` as that looks up the `package.json` as part of resolution.)
      *
      * packageDirectory is the directory of the package itself.
-     * subModuleName is the path within the package.
-     *   For `blah/node_modules/foo/index.d.ts` this is { packageDirectory: "foo", subModuleName: "index.d.ts" }. (Part before "/node_modules/" is ignored.)
-     *   For `/node_modules/foo/bar.d.ts` this is { packageDirectory: "foo", subModuleName": "bar/index.d.ts" }.
-     *   For `/node_modules/@types/foo/bar/index.d.ts` this is { packageDirectory: "@types/foo", subModuleName: "bar/index.d.ts" }.
-     *   For `/node_modules/foo/bar/index.d.ts` this is { packageDirectory: "foo", subModuleName": "bar/index.d.ts" }.
+     *   For `blah/node_modules/foo/index.d.ts` this is packageDirectory: "foo"
+     *   For `/node_modules/foo/bar.d.ts` this is packageDirectory: "foo"
+     *   For `/node_modules/@types/foo/bar/index.d.ts` this is packageDirectory: "@types/foo"
+     *   For `/node_modules/foo/bar/index.d.ts` this is packageDirectory: "foo"
      */
-    function parseNodeModuleFromPath(resolved: PathAndExtension): { packageDirectory: string, subModuleName: string } | undefined {
+    function parseNodeModuleFromPath(resolved: PathAndExtension): string | undefined {
         const path = normalizePath(resolved.path);
         const idx = path.lastIndexOf(nodeModulesPathPart);
         if (idx === -1) {
@@ -1016,9 +1035,7 @@ namespace ts {
         if (path.charCodeAt(indexAfterNodeModules) === CharacterCodes.at) {
             indexAfterPackageName = moveToNextDirectorySeparatorIfAvailable(path, indexAfterPackageName);
         }
-        const packageDirectory = path.slice(0, indexAfterPackageName);
-        const subModuleName = removeExtension(path.slice(indexAfterPackageName + 1), resolved.ext) + Extension.Dts;
-        return { packageDirectory, subModuleName };
+        return path.slice(0, indexAfterPackageName);
     }
 
     function moveToNextDirectorySeparatorIfAvailable(path: string, prevSeparatorIndex: number): number {
@@ -1026,19 +1043,6 @@ namespace ts {
         return nextSeparatorIndex === -1 ? prevSeparatorIndex : nextSeparatorIndex;
     }
 
-    function addExtensionAndIndex(path: string): string {
-        if (path === "") {
-            return "index.d.ts";
-        }
-        if (endsWith(path, ".d.ts")) {
-            return path;
-        }
-        if (path === "index" || endsWith(path, "/index")) {
-            return path + ".d.ts";
-        }
-        return path + "/index.d.ts";
-    }
-
     function loadModuleFromFileNoPackageId(extensions: Extensions, candidate: string, onlyRecordFailures: boolean, state: ModuleResolutionState): Resolved | undefined {
         return noPackageId(loadModuleFromFile(extensions, candidate, onlyRecordFailures, state));
     }
@@ -1119,61 +1123,29 @@ namespace ts {
     }
 
     function loadNodeModuleFromDirectory(extensions: Extensions, candidate: string, onlyRecordFailures: boolean, state: ModuleResolutionState, considerPackageJson = true) {
-        const packageInfo = considerPackageJson ? getPackageJsonInfo(candidate, "", onlyRecordFailures, state) : undefined;
-        const packageId = packageInfo && packageInfo.packageId;
+        const packageInfo = considerPackageJson ? getPackageJsonInfo(candidate, onlyRecordFailures, state) : undefined;
         const packageJsonContent = packageInfo && packageInfo.packageJsonContent;
         const versionPaths = packageInfo && packageInfo.versionPaths;
-        return withPackageId(packageId, loadNodeModuleFromDirectoryWorker(extensions, candidate, onlyRecordFailures, state, packageJsonContent, versionPaths));
+        return withPackageId(packageInfo, loadNodeModuleFromDirectoryWorker(extensions, candidate, onlyRecordFailures, state, packageJsonContent, versionPaths));
     }
 
     interface PackageJsonInfo {
-        packageJsonContent: PackageJsonPathFields | undefined;
-        packageId: PackageId | undefined;
+        packageDirectory: string;
+        packageJsonContent: PackageJsonPathFields;
         versionPaths: VersionPaths | undefined;
     }
 
-    function getPackageJsonInfo(packageDirectory: string, subModuleName: string, onlyRecordFailures: boolean, state: ModuleResolutionState): PackageJsonInfo | undefined {
+    function getPackageJsonInfo(packageDirectory: string, onlyRecordFailures: boolean, state: ModuleResolutionState): PackageJsonInfo | undefined {
         const { host, traceEnabled } = state;
         const directoryExists = !onlyRecordFailures && directoryProbablyExists(packageDirectory, host);
         const packageJsonPath = combinePaths(packageDirectory, "package.json");
         if (directoryExists && host.fileExists(packageJsonPath)) {
             const packageJsonContent = readJson(packageJsonPath, host) as PackageJson;
-            if (subModuleName === "") { // looking up the root - need to handle types/typings/main redirects for subModuleName
-                const path = readPackageJsonTypesFields(packageJsonContent, packageDirectory, state);
-                if (typeof path === "string") {
-                    subModuleName = addExtensionAndIndex(path.substring(packageDirectory.length + 1));
-                }
-                else {
-                    const jsPath = readPackageJsonMainField(packageJsonContent, packageDirectory, state);
-                    if (typeof jsPath === "string" && jsPath.length > packageDirectory.length) {
-                        const potentialSubModule = jsPath.substring(packageDirectory.length + 1);
-                        subModuleName = (forEach(supportedJSExtensions, extension =>
-                            tryRemoveExtension(potentialSubModule, extension)) || potentialSubModule) + Extension.Dts;
-                    }
-                    else {
-                        subModuleName = "index.d.ts";
-                    }
-                }
-            }
-
-            if (!endsWith(subModuleName, Extension.Dts)) {
-                subModuleName = addExtensionAndIndex(subModuleName);
-            }
-
-            const versionPaths = readPackageJsonTypesVersionPaths(packageJsonContent, state);
-            const packageId: PackageId | undefined = typeof packageJsonContent.name === "string" && typeof packageJsonContent.version === "string"
-                ? { name: packageJsonContent.name, subModuleName, version: packageJsonContent.version }
-                : undefined;
             if (traceEnabled) {
-                if (packageId) {
-                    trace(host, Diagnostics.Found_package_json_at_0_Package_ID_is_1, packageJsonPath, packageIdToString(packageId));
-                }
-                else {
-                    trace(host, Diagnostics.Found_package_json_at_0, packageJsonPath);
-                }
+                trace(host, Diagnostics.Found_package_json_at_0, packageJsonPath);
             }
-
-            return { packageJsonContent, packageId, versionPaths };
+            const versionPaths = readPackageJsonTypesVersionPaths(packageJsonContent, state);
+            return { packageDirectory, packageJsonContent, versionPaths };
         }
         else {
             if (directoryExists && traceEnabled) {
@@ -1328,27 +1300,36 @@ namespace ts {
         const candidate = normalizePath(combinePaths(nodeModulesDirectory, moduleName));
 
         // First look for a nested package.json, as in `node_modules/foo/bar/package.json`.
-        let packageJsonContent: PackageJsonPathFields | undefined;
-        let packageId: PackageId | undefined;
-        let versionPaths: VersionPaths | undefined;
-
-        const packageInfo = getPackageJsonInfo(candidate, "", !nodeModulesDirectoryExists, state);
+        let packageInfo = getPackageJsonInfo(candidate, !nodeModulesDirectoryExists, state);
         if (packageInfo) {
-            ({ packageJsonContent, packageId, versionPaths } = packageInfo);
             const fromFile = loadModuleFromFile(extensions, candidate, !nodeModulesDirectoryExists, state);
             if (fromFile) {
                 return noPackageId(fromFile);
             }
 
-            const fromDirectory = loadNodeModuleFromDirectoryWorker(extensions, candidate, !nodeModulesDirectoryExists, state, packageJsonContent, versionPaths);
-            return withPackageId(packageId, fromDirectory);
+            const fromDirectory = loadNodeModuleFromDirectoryWorker(
+                extensions,
+                candidate,
+                !nodeModulesDirectoryExists,
+                state,
+                packageInfo.packageJsonContent,
+                packageInfo.versionPaths
+            );
+            return withPackageId(packageInfo, fromDirectory);
         }
 
         const loader: ResolutionKindSpecificLoader = (extensions, candidate, onlyRecordFailures, state) => {
             const pathAndExtension =
                 loadModuleFromFile(extensions, candidate, onlyRecordFailures, state) ||
-                loadNodeModuleFromDirectoryWorker(extensions, candidate, onlyRecordFailures, state, packageJsonContent, versionPaths);
-            return withPackageId(packageId, pathAndExtension);
+                loadNodeModuleFromDirectoryWorker(
+                    extensions,
+                    candidate,
+                    onlyRecordFailures,
+                    state,
+                    packageInfo && packageInfo.packageJsonContent,
+                    packageInfo && packageInfo.versionPaths
+                );
+            return withPackageId(packageInfo, pathAndExtension);
         };
 
         const { packageName, rest } = parsePackageName(moduleName);
@@ -1356,14 +1337,13 @@ namespace ts {
             const packageDirectory = combinePaths(nodeModulesDirectory, packageName);
 
             // Don't use a "types" or "main" from here because we're not loading the root, but a subdirectory -- just here for the packageId and path mappings.
-            const packageInfo = getPackageJsonInfo(packageDirectory, rest, !nodeModulesDirectoryExists, state);
-            if (packageInfo) ({ packageId, versionPaths } = packageInfo);
-            if (versionPaths) {
+            packageInfo = getPackageJsonInfo(packageDirectory, !nodeModulesDirectoryExists, state);
+            if (packageInfo && packageInfo.versionPaths) {
                 if (state.traceEnabled) {
-                    trace(state.host, Diagnostics.package_json_has_a_typesVersions_entry_0_that_matches_compiler_version_1_looking_for_a_pattern_to_match_module_name_2, versionPaths.version, version, rest);
+                    trace(state.host, Diagnostics.package_json_has_a_typesVersions_entry_0_that_matches_compiler_version_1_looking_for_a_pattern_to_match_module_name_2, packageInfo.versionPaths.version, version, rest);
                 }
                 const packageDirectoryExists = nodeModulesDirectoryExists && directoryProbablyExists(packageDirectory, state.host);
-                const fromPaths = tryLoadModuleUsingPaths(extensions, rest, packageDirectory, versionPaths.paths, loader, !packageDirectoryExists, state);
+                const fromPaths = tryLoadModuleUsingPaths(extensions, rest, packageDirectory, packageInfo.versionPaths.paths, loader, !packageDirectoryExists, state);
                 if (fromPaths) {
                     return fromPaths.value;
                 }

src/compiler/program.ts

@@ -2232,7 +2232,10 @@ namespace ts {
                     if (isRedirect) {
                         inputName = getProjectReferenceRedirect(fileName) || fileName;
                     }
-                    if (getNormalizedAbsolutePath(checkedName, currentDirectory) !== getNormalizedAbsolutePath(inputName, currentDirectory)) {
+                    // Check if it differs only in drive letters its ok to ignore that error:
+                    const checkedAbsolutePath = getNormalizedAbsolutePathWithoutRoot(checkedName, currentDirectory);
+                    const inputAbsolutePath = getNormalizedAbsolutePathWithoutRoot(inputName, currentDirectory);
+                    if (checkedAbsolutePath !== inputAbsolutePath) {
                         reportFileNamesDifferOnlyInCasingError(inputName, checkedName, refFile, refPos, refEnd);
                     }
                 }
@@ -2855,10 +2858,10 @@ namespace ts {
                     createDiagnosticForOptionName(Diagnostics.Option_isolatedModules_can_only_be_used_when_either_option_module_is_provided_or_option_target_is_ES2015_or_higher, "isolatedModules", "target");
                 }
 
-                const firstNonExternalModuleSourceFile = find(files, f => !isExternalModule(f) && !f.isDeclarationFile && f.scriptKind !== ScriptKind.JSON);
+                const firstNonExternalModuleSourceFile = find(files, f => !isExternalModule(f) && !isSourceFileJS(f) && !f.isDeclarationFile && f.scriptKind !== ScriptKind.JSON);
                 if (firstNonExternalModuleSourceFile) {
                     const span = getErrorSpanForNode(firstNonExternalModuleSourceFile, firstNonExternalModuleSourceFile);
-                    programDiagnostics.add(createFileDiagnostic(firstNonExternalModuleSourceFile, span.start, span.length, Diagnostics.Cannot_compile_namespaces_when_the_isolatedModules_flag_is_provided));
+                    programDiagnostics.add(createFileDiagnostic(firstNonExternalModuleSourceFile, span.start, span.length, Diagnostics.All_files_must_be_modules_when_the_isolatedModules_flag_is_provided));
                 }
             }
             else if (firstNonAmbientExternalModuleSourceFile && languageVersion < ScriptTarget.ES2015 && options.module === ModuleKind.None) {

src/compiler/transformers/es2015.ts

@@ -145,7 +145,7 @@ namespace ts {
         loopOutParameters: LoopOutParameter[];
     }
 
-    type LoopConverter = (node: IterationStatement, outermostLabeledStatement: LabeledStatement | undefined, convertedLoopBodyStatements: Statement[] | undefined) => Statement;
+    type LoopConverter = (node: IterationStatement, outermostLabeledStatement: LabeledStatement | undefined, convertedLoopBodyStatements: Statement[] | undefined, ancestorFacts: HierarchyFacts) => Statement;
 
     // Facts we track as we traverse the tree
     const enum HierarchyFacts {
@@ -163,11 +163,12 @@ namespace ts {
         ExportedVariableStatement = 1 << 5,     // Enclosed in an exported variable statement in the current scope
         TopLevel = 1 << 6,                      // Enclosing block-scoped container is a top-level container
         Block = 1 << 7,                         // Enclosing block-scoped container is a Block
-        IterationStatement = 1 << 8,            // Enclosed in an IterationStatement
+        IterationStatement = 1 << 8,            // Immediately enclosed in an IterationStatement
         IterationStatementBlock = 1 << 9,       // Enclosing Block is enclosed in an IterationStatement
-        ForStatement = 1 << 10,                 // Enclosing block-scoped container is a ForStatement
-        ForInOrForOfStatement = 1 << 11,        // Enclosing block-scoped container is a ForInStatement or ForOfStatement
-        ConstructorWithCapturedSuper = 1 << 12, // Enclosed in a constructor that captures 'this' for use with 'super'
+        IterationContainer = 1 << 10,           // Enclosed in an outer IterationStatement
+        ForStatement = 1 << 11,                 // Enclosing block-scoped container is a ForStatement
+        ForInOrForOfStatement = 1 << 12,        // Enclosing block-scoped container is a ForInStatement or ForOfStatement
+        ConstructorWithCapturedSuper = 1 << 13, // Enclosed in a constructor that captures 'this' for use with 'super'
         // NOTE: do not add more ancestor flags without also updating AncestorFactsMask below.
         // NOTE: when adding a new ancestor flag, be sure to update the subtree flags below.
 
@@ -184,11 +185,11 @@ namespace ts {
 
         // A source file is a top-level block scope.
         SourceFileIncludes = TopLevel,
-        SourceFileExcludes = BlockScopeExcludes & ~TopLevel,
+        SourceFileExcludes = BlockScopeExcludes & ~TopLevel | IterationContainer,
 
         // Functions, methods, and accessors are both new lexical scopes and new block scopes.
         FunctionIncludes = Function | TopLevel,
-        FunctionExcludes = BlockScopeExcludes & ~TopLevel | ArrowFunction | AsyncFunctionBody | CapturesThis | NonStaticClassElement | ConstructorWithCapturedSuper,
+        FunctionExcludes = BlockScopeExcludes & ~TopLevel | ArrowFunction | AsyncFunctionBody | CapturesThis | NonStaticClassElement | ConstructorWithCapturedSuper | IterationContainer,
 
         AsyncFunctionBodyIncludes = FunctionIncludes | AsyncFunctionBody,
         AsyncFunctionBodyExcludes = FunctionExcludes & ~NonStaticClassElement,
@@ -205,16 +206,16 @@ namespace ts {
         // 'do' and 'while' statements are not block scopes. We track that the subtree is contained
         // within an IterationStatement to indicate whether the embedded statement is an
         // IterationStatementBlock.
-        DoOrWhileStatementIncludes = IterationStatement,
+        DoOrWhileStatementIncludes = IterationStatement | IterationContainer,
         DoOrWhileStatementExcludes = None,
 
         // 'for' statements are new block scopes and have special handling for 'let' declarations.
-        ForStatementIncludes = IterationStatement | ForStatement,
+        ForStatementIncludes = IterationStatement | ForStatement | IterationContainer,
         ForStatementExcludes = BlockScopeExcludes & ~ForStatement,
 
         // 'for-in' and 'for-of' statements are new block scopes and have special handling for
         // 'let' declarations.
-        ForInOrForOfStatementIncludes = IterationStatement | ForInOrForOfStatement,
+        ForInOrForOfStatementIncludes = IterationStatement | ForInOrForOfStatement | IterationContainer,
         ForInOrForOfStatementExcludes = BlockScopeExcludes & ~ForInOrForOfStatement,
 
         // Blocks (other than function bodies) are new block scopes.
@@ -228,8 +229,8 @@ namespace ts {
         // Subtree facts
         //
 
-        NewTarget = 1 << 13,                            // Contains a 'new.target' meta-property
-        CapturedLexicalThis = 1 << 14,                  // Contains a lexical `this` reference captured by an arrow function.
+        NewTarget = 1 << 14,                            // Contains a 'new.target' meta-property
+        CapturedLexicalThis = 1 << 15,                  // Contains a lexical `this` reference captured by an arrow function.
 
         //
         // Subtree masks
@@ -2227,7 +2228,7 @@ namespace ts {
 
         function visitIterationStatementWithFacts(excludeFacts: HierarchyFacts, includeFacts: HierarchyFacts, node: IterationStatement, outermostLabeledStatement: LabeledStatement | undefined, convert?: LoopConverter) {
             const ancestorFacts = enterSubtree(excludeFacts, includeFacts);
-            const updated = convertIterationStatementBodyIfNecessary(node, outermostLabeledStatement, convert);
+            const updated = convertIterationStatementBodyIfNecessary(node, outermostLabeledStatement, ancestorFacts, convert);
             exitSubtree(ancestorFacts, HierarchyFacts.None, HierarchyFacts.None);
             return updated;
         }
@@ -2434,7 +2435,7 @@ namespace ts {
             return restoreEnclosingLabel(forStatement, outermostLabeledStatement, convertedLoopState && resetLabel);
         }
 
-        function convertForOfStatementForIterable(node: ForOfStatement, outermostLabeledStatement: LabeledStatement, convertedLoopBodyStatements: Statement[]): Statement {
+        function convertForOfStatementForIterable(node: ForOfStatement, outermostLabeledStatement: LabeledStatement, convertedLoopBodyStatements: Statement[], ancestorFacts: HierarchyFacts): Statement {
             const expression = visitNode(node.expression, visitor, isExpression);
             const iterator = isIdentifier(expression) ? getGeneratedNameForNode(expression) : createTempVariable(/*recordTempVariable*/ undefined);
             const result = isIdentifier(expression) ? getGeneratedNameForNode(iterator) : createTempVariable(/*recordTempVariable*/ undefined);
@@ -2447,13 +2448,18 @@ namespace ts {
             hoistVariableDeclaration(errorRecord);
             hoistVariableDeclaration(returnMethod);
 
+            // if we are enclosed in an outer loop ensure we reset 'errorRecord' per each iteration
+            const initializer = ancestorFacts & HierarchyFacts.IterationContainer
+                ? inlineExpressions([createAssignment(errorRecord, createVoidZero()), values])
+                : values;
+
             const forStatement = setEmitFlags(
                 setTextRange(
                     createFor(
                         /*initializer*/ setEmitFlags(
                             setTextRange(
                                 createVariableDeclarationList([
-                                    setTextRange(createVariableDeclaration(iterator, /*type*/ undefined, values), node.expression),
+                                    setTextRange(createVariableDeclaration(iterator, /*type*/ undefined, initializer), node.expression),
                                     createVariableDeclaration(result, /*type*/ undefined, next)
                                 ]),
                                 node.expression
@@ -2665,7 +2671,7 @@ namespace ts {
             }
         }
 
-        function convertIterationStatementBodyIfNecessary(node: IterationStatement, outermostLabeledStatement: LabeledStatement | undefined, convert?: LoopConverter): VisitResult<Statement> {
+        function convertIterationStatementBodyIfNecessary(node: IterationStatement, outermostLabeledStatement: LabeledStatement | undefined, ancestorFacts: HierarchyFacts, convert?: LoopConverter): VisitResult<Statement> {
             if (!shouldConvertIterationStatement(node)) {
                 let saveAllowedNonLabeledJumps: Jump | undefined;
                 if (convertedLoopState) {
@@ -2676,7 +2682,7 @@ namespace ts {
                 }
 
                 const result = convert
-                    ? convert(node, outermostLabeledStatement, /*convertedLoopBodyStatements*/ undefined)
+                    ? convert(node, outermostLabeledStatement, /*convertedLoopBodyStatements*/ undefined, ancestorFacts)
                     : restoreEnclosingLabel(visitEachChild(node, visitor, context), outermostLabeledStatement, convertedLoopState && resetLabel);
 
                 if (convertedLoopState) {
@@ -2708,7 +2714,7 @@ namespace ts {
             let loop: Statement;
             if (bodyFunction) {
                 if (convert) {
-                    loop = convert(node, outermostLabeledStatement, bodyFunction.part);
+                    loop = convert(node, outermostLabeledStatement, bodyFunction.part, ancestorFacts);
                 }
                 else {
                     const clone = convertIterationStatementCore(node, initializerFunction, createBlock(bodyFunction.part, /*multiLine*/ true));

src/compiler/transformers/es2018.ts

@@ -77,6 +77,8 @@ namespace ts {
                     return visitObjectLiteralExpression(node as ObjectLiteralExpression);
                 case SyntaxKind.BinaryExpression:
                     return visitBinaryExpression(node as BinaryExpression, noDestructuringValue);
+                case SyntaxKind.CatchClause:
+                    return visitCatchClause(node as CatchClause);
                 case SyntaxKind.VariableDeclaration:
                     return visitVariableDeclaration(node as VariableDeclaration);
                 case SyntaxKind.ForOfStatement:
@@ -272,6 +274,28 @@ namespace ts {
             return visitEachChild(node, visitor, context);
         }
 
+        function visitCatchClause(node: CatchClause) {
+            if (node.variableDeclaration &&
+                isBindingPattern(node.variableDeclaration.name) &&
+                node.variableDeclaration.name.transformFlags & TransformFlags.ContainsObjectRestOrSpread) {
+                const name = getGeneratedNameForNode(node.variableDeclaration.name);
+                const updatedDecl = updateVariableDeclaration(node.variableDeclaration, node.variableDeclaration.name, /*type*/ undefined, name);
+                const visitedBindings = flattenDestructuringBinding(updatedDecl, visitor, context, FlattenLevel.ObjectRest);
+                let block = visitNode(node.block, visitor, isBlock);
+                if (some(visitedBindings)) {
+                    block = updateBlock(block, [
+                        createVariableStatement(/*modifiers*/ undefined, visitedBindings),
+                        ...block.statements,
+                    ]);
+                }
+                return updateCatchClause(
+                    node,
+                    updateVariableDeclaration(node.variableDeclaration, name, /*type*/ undefined, /*initializer*/ undefined),
+                    block);
+            }
+            return visitEachChild(node, visitor, context);
+        }
+
         /**
          * Visits a VariableDeclaration node with a binding pattern.
          *

src/compiler/tsconfig.json

@@ -8,6 +8,7 @@
 
     "files": [
         "core.ts",
+        "debug.ts",
         "performance.ts",
         "semver.ts",
 

src/compiler/utilities.ts

@@ -2073,7 +2073,7 @@ namespace ts {
     }
 
     export function importFromModuleSpecifier(node: StringLiteralLike): AnyValidImportOrReExport {
-        return tryGetImportFromModuleSpecifier(node) || Debug.fail(Debug.showSyntaxKind(node.parent));
+        return tryGetImportFromModuleSpecifier(node) || Debug.failBadSyntaxKind(node.parent);
     }
 
     export function tryGetImportFromModuleSpecifier(node: StringLiteralLike): AnyValidImportOrReExport | undefined {
@@ -4186,78 +4186,6 @@ namespace ts {
         return getNewLine ? getNewLine() : sys ? sys.newLine : carriageReturnLineFeed;
     }
 
-    /**
-     * Formats an enum value as a string for debugging and debug assertions.
-     */
-    function formatEnum(value = 0, enumObject: any, isFlags?: boolean) {
-        const members = getEnumMembers(enumObject);
-        if (value === 0) {
-            return members.length > 0 && members[0][0] === 0 ? members[0][1] : "0";
-        }
-        if (isFlags) {
-            let result = "";
-            let remainingFlags = value;
-            for (let i = members.length - 1; i >= 0 && remainingFlags !== 0; i--) {
-                const [enumValue, enumName] = members[i];
-                if (enumValue !== 0 && (remainingFlags & enumValue) === enumValue) {
-                    remainingFlags &= ~enumValue;
-                    result = `${enumName}${result ? ", " : ""}${result}`;
-                }
-            }
-            if (remainingFlags === 0) {
-                return result;
-            }
-        }
-        else {
-            for (const [enumValue, enumName] of members) {
-                if (enumValue === value) {
-                    return enumName;
-                }
-            }
-        }
-        return value.toString();
-    }
-
-    function getEnumMembers(enumObject: any) {
-        const result: [number, string][] = [];
-        for (const name in enumObject) {
-            const value = enumObject[name];
-            if (typeof value === "number") {
-                result.push([value, name]);
-            }
-        }
-
-        return stableSort<[number, string]>(result, (x, y) => compareValues(x[0], y[0]));
-    }
-
-    export function formatSyntaxKind(kind: SyntaxKind | undefined): string {
-        return formatEnum(kind, (<any>ts).SyntaxKind, /*isFlags*/ false);
-    }
-
-    export function formatModifierFlags(flags: ModifierFlags | undefined): string {
-        return formatEnum(flags, (<any>ts).ModifierFlags, /*isFlags*/ true);
-    }
-
-    export function formatTransformFlags(flags: TransformFlags | undefined): string {
-        return formatEnum(flags, (<any>ts).TransformFlags, /*isFlags*/ true);
-    }
-
-    export function formatEmitFlags(flags: EmitFlags | undefined): string {
-        return formatEnum(flags, (<any>ts).EmitFlags, /*isFlags*/ true);
-    }
-
-    export function formatSymbolFlags(flags: SymbolFlags | undefined): string {
-        return formatEnum(flags, (<any>ts).SymbolFlags, /*isFlags*/ true);
-    }
-
-    export function formatTypeFlags(flags: TypeFlags | undefined): string {
-        return formatEnum(flags, (<any>ts).TypeFlags, /*isFlags*/ true);
-    }
-
-    export function formatObjectFlags(flags: ObjectFlags | undefined): string {
-        return formatEnum(flags, (<any>ts).ObjectFlags, /*isFlags*/ true);
-    }
-
     /**
      * Creates a new TextRange from the provided pos and end.
      *
@@ -7646,6 +7574,14 @@ namespace ts {
         return root + pathComponents.slice(1).join(directorySeparator);
     }
 
+    export function getNormalizedAbsolutePathWithoutRoot(fileName: string, currentDirectory: string | undefined) {
+        return getPathWithoutRoot(getNormalizedPathComponents(fileName, currentDirectory));
+    }
+
+    function getPathWithoutRoot(pathComponents: ReadonlyArray<string>) {
+        if (pathComponents.length === 0) return "";
+        return pathComponents.slice(1).join(directorySeparator);
+    }
 }
 
 /* @internal */
@@ -8420,29 +8356,6 @@ namespace ts {
         return pathext ? path.slice(0, path.length - pathext.length) + (startsWith(ext, ".") ? ext : "." + ext) : path;
     }
 
-    export namespace Debug {
-        export function showSymbol(symbol: Symbol): string {
-            const symbolFlags = (ts as any).SymbolFlags;
-            return `{ flags: ${symbolFlags ? showFlags(symbol.flags, symbolFlags) : symbol.flags}; declarations: ${map(symbol.declarations, showSyntaxKind)} }`;
-        }
-
-        function showFlags(flags: number, flagsEnum: { [flag: number]: string }): string {
-            const out: string[] = [];
-            for (let pow = 0; pow <= 30; pow++) {
-                const n = 1 << pow;
-                if (flags & n) {
-                    out.push(flagsEnum[n]);
-                }
-            }
-            return out.join("|");
-        }
-
-        export function showSyntaxKind(node: Node): string {
-            const syntaxKind = (ts as any).SyntaxKind;
-            return syntaxKind ? syntaxKind[node.kind] : node.kind.toString();
-        }
-    }
-
     export function tryParsePattern(pattern: string): Pattern | undefined {
         // This should be verified outside of here and a proper error thrown.
         Debug.assert(hasZeroOrOneAsteriskCharacter(pattern));

src/compiler/visitor.ts

@@ -1558,100 +1558,4 @@ namespace ts {
     function aggregateTransformFlagsForChildNodes(transformFlags: TransformFlags, nodes: NodeArray<Node>): TransformFlags {
         return transformFlags | aggregateTransformFlagsForNodeArray(nodes);
     }
-
-    export namespace Debug {
-        let isDebugInfoEnabled = false;
-
-        export function failBadSyntaxKind(node: Node, message?: string): never {
-            return fail(
-                `${message || "Unexpected node."}\r\nNode ${formatSyntaxKind(node.kind)} was unexpected.`,
-                failBadSyntaxKind);
-        }
-
-        export const assertEachNode = shouldAssert(AssertionLevel.Normal)
-            ? (nodes: Node[], test: (node: Node) => boolean, message?: string): void => assert(
-                test === undefined || every(nodes, test),
-                message || "Unexpected node.",
-                () => `Node array did not pass test '${getFunctionName(test)}'.`,
-                assertEachNode)
-            : noop;
-
-        export const assertNode = shouldAssert(AssertionLevel.Normal)
-            ? (node: Node | undefined, test: ((node: Node | undefined) => boolean) | undefined, message?: string): void => assert(
-                test === undefined || test(node),
-                message || "Unexpected node.",
-                () => `Node ${formatSyntaxKind(node!.kind)} did not pass test '${getFunctionName(test!)}'.`,
-                assertNode)
-            : noop;
-
-        export const assertOptionalNode = shouldAssert(AssertionLevel.Normal)
-            ? (node: Node, test: (node: Node) => boolean, message?: string): void => assert(
-                test === undefined || node === undefined || test(node),
-                message || "Unexpected node.",
-                () => `Node ${formatSyntaxKind(node.kind)} did not pass test '${getFunctionName(test)}'.`,
-                assertOptionalNode)
-            : noop;
-
-        export const assertOptionalToken = shouldAssert(AssertionLevel.Normal)
-            ? (node: Node, kind: SyntaxKind, message?: string): void => assert(
-                kind === undefined || node === undefined || node.kind === kind,
-                message || "Unexpected node.",
-                () => `Node ${formatSyntaxKind(node.kind)} was not a '${formatSyntaxKind(kind)}' token.`,
-                assertOptionalToken)
-            : noop;
-
-        export const assertMissingNode = shouldAssert(AssertionLevel.Normal)
-            ? (node: Node, message?: string): void => assert(
-                node === undefined,
-                message || "Unexpected node.",
-                () => `Node ${formatSyntaxKind(node.kind)} was unexpected'.`,
-                assertMissingNode)
-            : noop;
-
-        /**
-         * Injects debug information into frequently used types.
-         */
-        export function enableDebugInfo() {
-            if (isDebugInfoEnabled) return;
-
-            // Add additional properties in debug mode to assist with debugging.
-            Object.defineProperties(objectAllocator.getSymbolConstructor().prototype, {
-                __debugFlags: { get(this: Symbol) { return formatSymbolFlags(this.flags); } }
-            });
-
-            Object.defineProperties(objectAllocator.getTypeConstructor().prototype, {
-                __debugFlags: { get(this: Type) { return formatTypeFlags(this.flags); } },
-                __debugObjectFlags: { get(this: Type) { return this.flags & TypeFlags.Object ? formatObjectFlags((<ObjectType>this).objectFlags) : ""; } },
-                __debugTypeToString: { value(this: Type) { return this.checker.typeToString(this); } },
-            });
-
-            const nodeConstructors = [
-                objectAllocator.getNodeConstructor(),
-                objectAllocator.getIdentifierConstructor(),
-                objectAllocator.getTokenConstructor(),
-                objectAllocator.getSourceFileConstructor()
-            ];
-
-            for (const ctor of nodeConstructors) {
-                if (!ctor.prototype.hasOwnProperty("__debugKind")) {
-                    Object.defineProperties(ctor.prototype, {
-                        __debugKind: { get(this: Node) { return formatSyntaxKind(this.kind); } },
-                        __debugModifierFlags: { get(this: Node) { return formatModifierFlags(getModifierFlagsNoCache(this)); } },
-                        __debugTransformFlags: { get(this: Node) { return formatTransformFlags(this.transformFlags); } },
-                        __debugEmitFlags: { get(this: Node) { return formatEmitFlags(getEmitFlags(this)); } },
-                        __debugGetText: {
-                            value(this: Node, includeTrivia?: boolean) {
-                                if (nodeIsSynthesized(this)) return "";
-                                const parseNode = getParseTreeNode(this);
-                                const sourceFile = parseNode && getSourceFileOfNode(parseNode);
-                                return sourceFile ? getSourceTextOfNodeFromSourceFile(sourceFile, parseNode, includeTrivia) : "";
-                            }
-                        }
-                    });
-                }
-            }
-
-            isDebugInfoEnabled = true;
-        }
-    }
 }

src/harness/client.ts

@@ -424,6 +424,10 @@ namespace ts.server {
             return renameInfo;
         }
 
+        getSmartSelectionRange() {
+            return notImplemented();
+        }
+
         findRenameLocations(fileName: string, position: number, findInStrings: boolean, findInComments: boolean): RenameLocation[] {
             if (!this.lastRenameEntry ||
                 this.lastRenameEntry.inputs.fileName !== fileName ||

src/harness/fourslash.ts

@@ -798,8 +798,8 @@ namespace FourSlash {
         }
 
         private verifyCompletionEntry(actual: ts.CompletionEntry, expected: FourSlashInterface.ExpectedCompletionEntry) {
-            const { insertText, replacementSpan, hasAction, isRecommended, kind, kindModifiers, text, documentation, tags, source, sourceDisplay } = typeof expected === "string"
-                ? { insertText: undefined, replacementSpan: undefined, hasAction: undefined, isRecommended: undefined, kind: undefined, kindModifiers: undefined, text: undefined, documentation: undefined, tags: undefined, source: undefined, sourceDisplay: undefined }
+            const { insertText, replacementSpan, hasAction, isRecommended, kind, kindModifiers, text, documentation, tags, source, sourceDisplay, sortText } = typeof expected === "string"
+                ? { insertText: undefined, replacementSpan: undefined, hasAction: undefined, isRecommended: undefined, kind: undefined, kindModifiers: undefined, text: undefined, documentation: undefined, tags: undefined, source: undefined, sourceDisplay: undefined, sortText: undefined }
                 : expected;
 
             if (actual.insertText !== insertText) {
@@ -825,6 +825,7 @@ namespace FourSlash {
             assert.equal(actual.hasAction, hasAction);
             assert.equal(actual.isRecommended, isRecommended);
             assert.equal(actual.source, source);
+            assert.equal(actual.sortText, sortText || ts.Completions.SortText.LocationPriority, this.messageAtLastKnownMarker(`Actual entry: ${JSON.stringify(actual)}`));
 
             if (text !== undefined) {
                 const actualDetails = this.getCompletionEntryDetails(actual.name, actual.source)!;
@@ -1417,12 +1418,7 @@ Actual: ${stringify(fullActual)}`);
         }
 
         public baselineCurrentFileBreakpointLocations() {
-            let baselineFile = this.testData.globalOptions[MetadataOptionNames.baselineFile];
-            if (!baselineFile) {
-                baselineFile = this.activeFile.fileName.replace(this.basePath + "/breakpointValidation", "bpSpan");
-                baselineFile = baselineFile.replace(ts.Extension.Ts, ".baseline");
-
-            }
+            const baselineFile = this.getBaselineFileName().replace("breakpointValidation", "bpSpan");
             Harness.Baseline.runBaseline(baselineFile, this.baselineCurrentFileLocations(pos => this.getBreakpointStatementLocation(pos)!));
         }
 
@@ -1497,8 +1493,7 @@ Actual: ${stringify(fullActual)}`);
         }
 
         public baselineQuickInfo() {
-            const baselineFile = this.testData.globalOptions[MetadataOptionNames.baselineFile] ||
-                ts.getBaseFileName(this.activeFile.fileName).replace(ts.Extension.Ts, ".baseline");
+            const baselineFile = this.getBaselineFileName();
             Harness.Baseline.runBaseline(
                 baselineFile,
                 stringify(
@@ -1508,6 +1503,39 @@ Actual: ${stringify(fullActual)}`);
                     }))));
         }
 
+        public baselineSmartSelection() {
+            const n = "\n";
+            const baselineFile = this.getBaselineFileName();
+            const markers = this.getMarkers();
+            const fileContent = this.activeFile.content;
+            const text = markers.map(marker => {
+                const baselineContent = [fileContent.slice(0, marker.position) + "/**/" + fileContent.slice(marker.position) + n];
+                let selectionRange: ts.SelectionRange | undefined = this.languageService.getSmartSelectionRange(this.activeFile.fileName, marker.position);
+                while (selectionRange) {
+                    const { textSpan } = selectionRange;
+                    let masked = Array.from(fileContent).map((char, index) => {
+                        const charCode = char.charCodeAt(0);
+                        if (index >= textSpan.start && index < ts.textSpanEnd(textSpan)) {
+                            return char === " " ? "•" : ts.isLineBreak(charCode) ? `↲${n}` : char;
+                        }
+                        return ts.isLineBreak(charCode) ? char : " ";
+                    }).join("");
+                    masked = masked.replace(/^\s*$\r?\n?/gm, ""); // Remove blank lines
+                    const isRealCharacter = (char: string) => char !== "•" && char !== "↲" && !ts.isWhiteSpaceLike(char.charCodeAt(0));
+                    const leadingWidth = Array.from(masked).findIndex(isRealCharacter);
+                    const trailingWidth = ts.findLastIndex(Array.from(masked), isRealCharacter);
+                    masked = masked.slice(0, leadingWidth)
+                        + masked.slice(leadingWidth, trailingWidth).replace(/•/g, " ").replace(/↲/g, "")
+                        + masked.slice(trailingWidth);
+                    baselineContent.push(masked);
+                    selectionRange = selectionRange.parent;
+                }
+                return baselineContent.join(fileContent.includes("\n") ? n + n : n);
+            }).join(n.repeat(2) + "=".repeat(80) + n.repeat(2));
+
+            Harness.Baseline.runBaseline(baselineFile, text);
+        }
+
         public printBreakpointLocation(pos: number) {
             Harness.IO.log("\n**Pos: " + pos + " " + this.spanInfoToString(this.getBreakpointStatementLocation(pos)!, "  "));
         }
@@ -1562,6 +1590,11 @@ Actual: ${stringify(fullActual)}`);
             Harness.IO.log(stringify(help.items[help.selectedItemIndex]));
         }
 
+        private getBaselineFileName() {
+            return this.testData.globalOptions[MetadataOptionNames.baselineFile] ||
+                ts.getBaseFileName(this.activeFile.fileName).replace(ts.Extension.Ts, ".baseline");
+        }
+
         private getSignatureHelp({ triggerReason }: FourSlashInterface.VerifySignatureHelpOptions): ts.SignatureHelpItems | undefined {
             return this.languageService.getSignatureHelpItems(this.activeFile.fileName, this.currentCaretPosition, {
                 triggerReason
@@ -3960,6 +3993,10 @@ namespace FourSlashInterface {
             this.state.baselineQuickInfo();
         }
 
+        public baselineSmartSelection() {
+            this.state.baselineSmartSelection();
+        }
+
         public nameOrDottedNameSpanTextIs(text: string) {
             this.state.verifyCurrentNameOrDottedNameSpanText(text);
         }
@@ -4398,18 +4435,63 @@ namespace FourSlashInterface {
         }
     }
     export namespace Completion {
-        const functionEntry = (name: string): ExpectedCompletionEntryObject => ({ name, kind: "function", kindModifiers: "declare" });
-        const varEntry = (name: string): ExpectedCompletionEntryObject => ({ name, kind: "var", kindModifiers: "declare" });
-        const moduleEntry = (name: string): ExpectedCompletionEntryObject => ({ name, kind: "module", kindModifiers: "declare" });
-        const keywordEntry = (name: string): ExpectedCompletionEntryObject => ({ name, kind: "keyword" });
-        const methodEntry = (name: string): ExpectedCompletionEntryObject => ({ name, kind: "method", kindModifiers: "declare" });
-        const propertyEntry = (name: string): ExpectedCompletionEntryObject => ({ name, kind: "property", kindModifiers: "declare" });
-        const interfaceEntry = (name: string): ExpectedCompletionEntryObject => ({ name, kind: "interface", kindModifiers: "declare" });
-        const typeEntry = (name: string): ExpectedCompletionEntryObject => ({ name, kind: "type", kindModifiers: "declare" });
+        export import SortText = ts.Completions.SortText;
+
+        const functionEntry = (name: string): ExpectedCompletionEntryObject => ({
+            name,
+            kind: "function",
+            kindModifiers: "declare",
+            sortText: SortText.GlobalsOrKeywords
+        });
+        const varEntry = (name: string): ExpectedCompletionEntryObject => ({
+            name,
+            kind: "var",
+            kindModifiers: "declare",
+            sortText: SortText.GlobalsOrKeywords
+        });
+        const moduleEntry = (name: string): ExpectedCompletionEntryObject => ({
+            name,
+            kind: "module",
+            kindModifiers: "declare",
+            sortText: SortText.GlobalsOrKeywords
+        });
+        const keywordEntry = (name: string): ExpectedCompletionEntryObject => ({
+            name,
+            kind: "keyword",
+            sortText: SortText.GlobalsOrKeywords
+        });
+        const methodEntry = (name: string): ExpectedCompletionEntryObject => ({
+            name,
+            kind: "method",
+            kindModifiers: "declare",
+            sortText: SortText.LocationPriority
+        });
+        const propertyEntry = (name: string): ExpectedCompletionEntryObject => ({
+            name,
+            kind: "property",
+            kindModifiers: "declare",
+            sortText: SortText.LocationPriority
+        });
+        const interfaceEntry = (name: string): ExpectedCompletionEntryObject => ({
+            name,
+            kind: "interface",
+            kindModifiers: "declare",
+            sortText: SortText.GlobalsOrKeywords
+        });
+        const typeEntry = (name: string): ExpectedCompletionEntryObject => ({
+            name,
+            kind: "type",
+            kindModifiers: "declare",
+            sortText: SortText.GlobalsOrKeywords
+        });
 
         const res: ExpectedCompletionEntryObject[] = [];
         for (let i = ts.SyntaxKind.FirstKeyword; i <= ts.SyntaxKind.LastKeyword; i++) {
-            res.push({ name: ts.Debug.assertDefined(ts.tokenToString(i)), kind: "keyword" });
+            res.push({
+                name: ts.Debug.assertDefined(ts.tokenToString(i)),
+                kind: "keyword",
+                sortText: SortText.GlobalsOrKeywords
+            });
         }
         export const keywordsWithUndefined: ReadonlyArray<ExpectedCompletionEntryObject> = res;
         export const keywords: ReadonlyArray<ExpectedCompletionEntryObject> = keywordsWithUndefined.filter(k => k.name !== "undefined");
@@ -4516,11 +4598,15 @@ namespace FourSlashInterface {
             moduleEntry("Intl"),
         ];
 
+        export const globalThisEntry: ExpectedCompletionEntry = {
+            name: "globalThis",
+            kind: "module",
+            sortText: SortText.GlobalsOrKeywords
+        };
         export const globalTypes = globalTypesPlus([]);
-
         export function globalTypesPlus(plus: ReadonlyArray<ExpectedCompletionEntry>): ReadonlyArray<ExpectedCompletionEntry> {
             return [
-                { name: "globalThis", kind: "module" },
+                globalThisEntry,
                 ...globalTypeDecls,
                 ...plus,
                 ...typeKeywords,
@@ -4569,7 +4655,11 @@ namespace FourSlashInterface {
         export const classElementInJsKeywords = getInJsKeywords(classElementKeywords);
 
         export const constructorParameterKeywords: ReadonlyArray<ExpectedCompletionEntryObject> =
-            ["private", "protected", "public", "readonly"].map((name): ExpectedCompletionEntryObject => ({ name, kind: "keyword" }));
+            ["private", "protected", "public", "readonly"].map((name): ExpectedCompletionEntryObject => ({
+                name,
+                kind: "keyword",
+                sortText: SortText.GlobalsOrKeywords
+            }));
 
         export const functionMembers: ReadonlyArray<ExpectedCompletionEntryObject> = [
             methodEntry("apply"),
@@ -4798,13 +4888,18 @@ namespace FourSlashInterface {
             "await",
         ].map(keywordEntry);
 
+        export const undefinedVarEntry: ExpectedCompletionEntry = {
+            name: "undefined",
+            kind: "var",
+            sortText: SortText.GlobalsOrKeywords
+        };
         // TODO: many of these are inappropriate to always provide
         export const globalsInsideFunction = (plus: ReadonlyArray<ExpectedCompletionEntry>): ReadonlyArray<ExpectedCompletionEntry> => [
             { name: "arguments", kind: "local var" },
             ...plus,
-            { name: "globalThis", kind: "module" },
+            globalThisEntry,
             ...globalsVars,
-            { name: "undefined", kind: "var" },
+            undefinedVarEntry,
             ...globalKeywordsInsideFunction,
         ];
 
@@ -4813,10 +4908,10 @@ namespace FourSlashInterface {
         // TODO: many of these are inappropriate to always provide
         export const globalsInJsInsideFunction = (plus: ReadonlyArray<ExpectedCompletionEntry>): ReadonlyArray<ExpectedCompletionEntry> => [
             { name: "arguments", kind: "local var" },
-            { name: "globalThis", kind: "module" },
+            globalThisEntry,
             ...globalsVars,
             ...plus,
-            { name: "undefined", kind: "var" },
+            undefinedVarEntry,
             ...globalInJsKeywordsInsideFunction,
         ];
 
@@ -4954,34 +5049,34 @@ namespace FourSlashInterface {
         })();
 
         export const globals: ReadonlyArray<ExpectedCompletionEntryObject> = [
-            { name: "globalThis", kind: "module" },
+            globalThisEntry,
             ...globalsVars,
-            { name: "undefined", kind: "var" },
+            undefinedVarEntry,
             ...globalKeywords
         ];
 
         export const globalsInJs: ReadonlyArray<ExpectedCompletionEntryObject> = [
-            { name: "globalThis", kind: "module" },
+            globalThisEntry,
             ...globalsVars,
-            { name: "undefined", kind: "var" },
+            undefinedVarEntry,
             ...globalInJsKeywords
         ];
 
         export function globalsPlus(plus: ReadonlyArray<ExpectedCompletionEntry>): ReadonlyArray<ExpectedCompletionEntry> {
             return [
-                { name: "globalThis", kind: "module" },
+                globalThisEntry,
                 ...globalsVars,
                 ...plus,
-                { name: "undefined", kind: "var" },
+                undefinedVarEntry,
                 ...globalKeywords];
         }
 
         export function globalsInJsPlus(plus: ReadonlyArray<ExpectedCompletionEntry>): ReadonlyArray<ExpectedCompletionEntry> {
             return [
-                { name: "globalThis", kind: "module" },
+                globalThisEntry,
                 ...globalsVars,
                 ...plus,
-                { name: "undefined", kind: "var" },
+                undefinedVarEntry,
                 ...globalInJsKeywords];
         }
     }
@@ -5014,6 +5109,7 @@ namespace FourSlashInterface {
         readonly documentation?: string;
         readonly sourceDisplay?: string;
         readonly tags?: ReadonlyArray<ts.JSDocTagInfo>;
+        readonly sortText?: ts.Completions.SortText;
     }
 
     export interface VerifyCompletionsOptions {

src/harness/harnessLanguageService.ts

@@ -472,6 +472,9 @@ namespace Harness.LanguageService {
         getRenameInfo(fileName: string, position: number, options?: ts.RenameInfoOptions): ts.RenameInfo {
             return unwrapJSONCallResult(this.shim.getRenameInfo(fileName, position, options));
         }
+        getSmartSelectionRange(fileName: string, position: number): ts.SelectionRange {
+            return unwrapJSONCallResult(this.shim.getSmartSelectionRange(fileName, position));
+        }
         findRenameLocations(fileName: string, position: number, findInStrings: boolean, findInComments: boolean, providePrefixAndSuffixTextForRename?: boolean): ts.RenameLocation[] {
             return unwrapJSONCallResult(this.shim.findRenameLocations(fileName, position, findInStrings, findInComments, providePrefixAndSuffixTextForRename));
         }

src/lib/dom.generated.d.ts

@@ -17328,7 +17328,8 @@ interface WorkerEventMap extends AbstractWorkerEventMap {
 /** An interface of the Web Workers API represents a background task that can be easily created and can send messages back to its creator. Creating a worker is as simple as calling the Worker() constructor and specifying a script to be run in the worker thread. */
 interface Worker extends EventTarget, AbstractWorker {
     onmessage: ((this: Worker, ev: MessageEvent) => any) | null;
-    postMessage(message: any, transfer?: Transferable[]): void;
+    postMessage(message: any, transfer: Transferable[]): void;
+    postMessage(message: any, options?: PostMessageOptions): void;
     terminate(): void;
     addEventListener<K extends keyof WorkerEventMap>(type: K, listener: (this: Worker, ev: WorkerEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;

src/lib/es5.d.ts

@@ -513,7 +513,7 @@ interface Boolean {
 
 interface BooleanConstructor {
     new(value?: any): Boolean;
-    <T>(value?: T): value is Exclude<T, false | null | undefined | '' | 0>;
+    <T>(value?: T): boolean;
     readonly prototype: Boolean;
 }
 

src/lib/webworker.generated.d.ts

@@ -4231,7 +4231,8 @@ interface WorkerEventMap extends AbstractWorkerEventMap {
 /** An interface of the Web Workers API represents a background task that can be easily created and can send messages back to its creator. Creating a worker is as simple as calling the Worker() constructor and specifying a script to be run in the worker thread. */
 interface Worker extends EventTarget, AbstractWorker {
     onmessage: ((this: Worker, ev: MessageEvent) => any) | null;
-    postMessage(message: any, transfer?: Transferable[]): void;
+    postMessage(message: any, transfer: Transferable[]): void;
+    postMessage(message: any, options?: PostMessageOptions): void;
     terminate(): void;
     addEventListener<K extends keyof WorkerEventMap>(type: K, listener: (this: Worker, ev: WorkerEventMap[K]) => any, options?: boolean | AddEventListenerOptions): void;
     addEventListener(type: string, listener: EventListenerOrEventListenerObject, options?: boolean | AddEventListenerOptions): void;

src/server/protocol.ts

@@ -130,7 +130,10 @@ namespace ts.server.protocol {
         GetEditsForFileRename = "getEditsForFileRename",
         /* @internal */
         GetEditsForFileRenameFull = "getEditsForFileRename-full",
-        ConfigurePlugin = "configurePlugin"
+        ConfigurePlugin = "configurePlugin",
+        SelectionRange = "selectionRange",
+        /* @internal */
+        SelectionRangeFull = "selectionRange-full",
 
         // NOTE: If updating this, be sure to also update `allCommandNames` in `harness/unittests/session.ts`.
     }
@@ -1395,6 +1398,24 @@ namespace ts.server.protocol {
     export interface ConfigurePluginResponse extends Response {
     }
 
+    export interface SelectionRangeRequest extends FileRequest {
+        command: CommandTypes.SelectionRange;
+        arguments: SelectionRangeRequestArgs;
+    }
+
+    export interface SelectionRangeRequestArgs extends FileRequestArgs {
+        locations: Location[];
+    }
+
+    export interface SelectionRangeResponse extends Response {
+        body?: SelectionRange[];
+    }
+
+    export interface SelectionRange {
+        textSpan: TextSpan;
+        parent?: SelectionRange;
+    }
+
     /**
      *  Information found in an "open" request.
      */

src/server/session.ts

@@ -1318,11 +1318,11 @@ namespace ts.server {
             this.projectService.openClientFileWithNormalizedPath(fileName, fileContent, scriptKind, /*hasMixedContent*/ false, projectRootPath);
         }
 
-        private getPosition(args: protocol.FileLocationRequestArgs, scriptInfo: ScriptInfo): number {
+        private getPosition(args: protocol.Location & { position?: number }, scriptInfo: ScriptInfo): number {
             return args.position !== undefined ? args.position : scriptInfo.lineOffsetToPosition(args.line, args.offset);
         }
 
-        private getPositionInFile(args: protocol.FileLocationRequestArgs, file: NormalizedPath): number {
+        private getPositionInFile(args: protocol.Location & { position?: number }, file: NormalizedPath): number {
             const scriptInfo = this.projectService.getScriptInfoForNormalizedPath(file)!;
             return this.getPosition(args, scriptInfo);
         }
@@ -2059,6 +2059,28 @@ namespace ts.server {
             this.projectService.configurePlugin(args);
         }
 
+        private getSmartSelectionRange(args: protocol.SelectionRangeRequestArgs, simplifiedResult: boolean) {
+            const { locations } = args;
+            const { file, languageService } = this.getFileAndLanguageServiceForSyntacticOperation(args);
+            const scriptInfo = Debug.assertDefined(this.projectService.getScriptInfo(file));
+
+            return map(locations, location => {
+                const pos = this.getPosition(location, scriptInfo);
+                const selectionRange = languageService.getSmartSelectionRange(file, pos);
+                return simplifiedResult ? this.mapSelectionRange(selectionRange, scriptInfo) : selectionRange;
+            });
+        }
+
+        private mapSelectionRange(selectionRange: SelectionRange, scriptInfo: ScriptInfo): protocol.SelectionRange {
+            const result: protocol.SelectionRange = {
+                textSpan: this.toLocationTextSpan(selectionRange.textSpan, scriptInfo),
+            };
+            if (selectionRange.parent) {
+                result.parent = this.mapSelectionRange(selectionRange.parent, scriptInfo);
+            }
+            return result;
+        }
+
         getCanonicalFileName(fileName: string) {
             const name = this.host.useCaseSensitiveFileNames ? fileName : fileName.toLowerCase();
             return normalizePath(name);
@@ -2414,7 +2436,13 @@ namespace ts.server {
                 this.configurePlugin(request.arguments);
                 this.doOutput(/*info*/ undefined, CommandNames.ConfigurePlugin, request.seq, /*success*/ true);
                 return this.notRequired();
-            }
+            },
+            [CommandNames.SelectionRange]: (request: protocol.SelectionRangeRequest) => {
+                return this.requiredResponse(this.getSmartSelectionRange(request.arguments, /*simplifiedResult*/ true));
+            },
+            [CommandNames.SelectionRangeFull]: (request: protocol.SelectionRangeRequest) => {
+                return this.requiredResponse(this.getSmartSelectionRange(request.arguments, /*simplifiedResult*/ false));
+            },
         });
 
         public addProtocolHandler(command: string, handler: (request: protocol.Request) => HandlerResponse) {

src/services/codefixes/addNameToNamelessParameter.ts

@@ -15,11 +15,11 @@ namespace ts.codefix {
     function makeChange(changeTracker: textChanges.ChangeTracker, sourceFile: SourceFile, pos: number) {
         const token = getTokenAtPosition(sourceFile, pos);
         if (!isIdentifier(token)) {
-            return Debug.fail("add-name-to-nameless-parameter operates on identifiers, but got a " + formatSyntaxKind(token.kind));
+            return Debug.fail("add-name-to-nameless-parameter operates on identifiers, but got a " + Debug.formatSyntaxKind(token.kind));
         }
         const param = token.parent;
         if (!isParameter(param)) {
-            return Debug.fail("Tried to add a parameter name to a non-parameter: " + formatSyntaxKind(token.kind));
+            return Debug.fail("Tried to add a parameter name to a non-parameter: " + Debug.formatSyntaxKind(token.kind));
         }
         const i = param.parent.parameters.indexOf(param);
         Debug.assert(!param.type, "Tried to add a parameter name to a parameter that already had one.");

src/services/completions.ts

@@ -1,5 +1,12 @@
 /* @internal */
 namespace ts.Completions {
+    export enum SortText {
+        LocationPriority = "0",
+        SuggestedClassMembers = "1",
+        GlobalsOrKeywords = "2",
+        AutoImportSuggestions = "3",
+        JavascriptIdentifiers = "4"
+    }
     export type Log = (message: string) => void;
 
     const enum SymbolOriginInfoKind { ThisType, SymbolMemberNoExport, SymbolMemberExport, Export }
@@ -22,6 +29,8 @@ namespace ts.Completions {
      */
     type SymbolOriginInfoMap = (SymbolOriginInfo | undefined)[];
 
+    type SymbolSortTextMap = (SortText | undefined)[];
+
     const enum KeywordCompletionFilters {
         None,                           // No keywords
         All,                            // Every possible keyword (TODO: This is never appropriate)
@@ -78,7 +87,21 @@ namespace ts.Completions {
     }
 
     function completionInfoFromData(sourceFile: SourceFile, typeChecker: TypeChecker, compilerOptions: CompilerOptions, log: Log, completionData: CompletionData, preferences: UserPreferences): CompletionInfo | undefined {
-        const { symbols, completionKind, isInSnippetScope, isNewIdentifierLocation, location, propertyAccessToConvert, keywordFilters, literals, symbolToOriginInfoMap, recommendedCompletion, isJsxInitializer, insideJsDocTagTypeExpression } = completionData;
+        const {
+            symbols,
+            completionKind,
+            isInSnippetScope,
+            isNewIdentifierLocation,
+            location,
+            propertyAccessToConvert,
+            keywordFilters,
+            literals,
+            symbolToOriginInfoMap,
+            recommendedCompletion,
+            isJsxInitializer,
+            insideJsDocTagTypeExpression,
+            symbolToSortTextMap,
+        } = completionData;
 
         if (location && location.parent && isJsxClosingElement(location.parent)) {
             // In the TypeScript JSX element, if such element is not defined. When users query for completion at closing tag,
@@ -93,7 +116,7 @@ namespace ts.Completions {
                 name: tagName.getFullText(sourceFile) + (hasClosingAngleBracket ? "" : ">"),
                 kind: ScriptElementKind.classElement,
                 kindModifiers: undefined,
-                sortText: "0",
+                sortText: SortText.LocationPriority,
             };
             return { isGlobalCompletion: false, isMemberCompletion: true, isNewIdentifierLocation: false, entries: [entry] };
         }
@@ -101,7 +124,22 @@ namespace ts.Completions {
         const entries: CompletionEntry[] = [];
 
         if (isUncheckedFile(sourceFile, compilerOptions)) {
-            const uniqueNames = getCompletionEntriesFromSymbols(symbols, entries, location, sourceFile, typeChecker, compilerOptions.target!, log, completionKind, preferences, propertyAccessToConvert, isJsxInitializer, recommendedCompletion, symbolToOriginInfoMap);
+            const uniqueNames = getCompletionEntriesFromSymbols(
+                symbols,
+                entries,
+                location,
+                sourceFile,
+                typeChecker,
+                compilerOptions.target!,
+                log,
+                completionKind,
+                preferences,
+                propertyAccessToConvert,
+                isJsxInitializer,
+                recommendedCompletion,
+                symbolToOriginInfoMap,
+                symbolToSortTextMap
+            );
             getJSCompletionEntries(sourceFile, location!.pos, uniqueNames, compilerOptions.target!, entries); // TODO: GH#18217
         }
         else {
@@ -109,7 +147,22 @@ namespace ts.Completions {
                 return undefined;
             }
 
-            getCompletionEntriesFromSymbols(symbols, entries, location, sourceFile, typeChecker, compilerOptions.target!, log, completionKind, preferences, propertyAccessToConvert, isJsxInitializer, recommendedCompletion, symbolToOriginInfoMap);
+            getCompletionEntriesFromSymbols(
+                symbols,
+                entries,
+                location,
+                sourceFile,
+                typeChecker,
+                compilerOptions.target!,
+                log,
+                completionKind,
+                preferences,
+                propertyAccessToConvert,
+                isJsxInitializer,
+                recommendedCompletion,
+                symbolToOriginInfoMap,
+                symbolToSortTextMap
+            );
         }
 
         if (keywordFilters !== KeywordCompletionFilters.None) {
@@ -160,7 +213,7 @@ namespace ts.Completions {
                     name: realName,
                     kind: ScriptElementKind.warning,
                     kindModifiers: "",
-                    sortText: "1"
+                    sortText: SortText.JavascriptIdentifiers
                 });
             }
         });
@@ -169,28 +222,23 @@ namespace ts.Completions {
     const completionNameForLiteral = (literal: string | number | PseudoBigInt) =>
         typeof literal === "object" ? pseudoBigIntToString(literal) + "n" : JSON.stringify(literal);
     function createCompletionEntryForLiteral(literal: string | number | PseudoBigInt): CompletionEntry {
-        return { name: completionNameForLiteral(literal), kind: ScriptElementKind.string, kindModifiers: ScriptElementKindModifier.none, sortText: "0" };
+        return { name: completionNameForLiteral(literal), kind: ScriptElementKind.string, kindModifiers: ScriptElementKindModifier.none, sortText: SortText.LocationPriority };
     }
 
     function createCompletionEntry(
         symbol: Symbol,
+        sortText: SortText,
         location: Node | undefined,
         sourceFile: SourceFile,
         typeChecker: TypeChecker,
-        target: ScriptTarget,
-        kind: CompletionKind,
+        name: string,
+        needsConvertPropertyAccess: boolean,
         origin: SymbolOriginInfo | undefined,
         recommendedCompletion: Symbol | undefined,
         propertyAccessToConvert: PropertyAccessExpression | undefined,
         isJsxInitializer: IsJsxInitializer | undefined,
         preferences: UserPreferences,
     ): CompletionEntry | undefined {
-        const info = getCompletionEntryDisplayNameForSymbol(symbol, target, origin, kind);
-        if (!info) {
-            return undefined;
-        }
-        const { name, needsConvertPropertyAccess } = info;
-
         let insertText: string | undefined;
         let replacementSpan: TextSpan | undefined;
         if (origin && origin.kind === SymbolOriginInfoKind.ThisType) {
@@ -230,7 +278,7 @@ namespace ts.Completions {
             name,
             kind: SymbolDisplay.getSymbolKind(typeChecker, symbol, location!), // TODO: GH#18217
             kindModifiers: SymbolDisplay.getSymbolModifiers(symbol),
-            sortText: "0",
+            sortText,
             source: getSourceFromOrigin(origin),
             hasAction: trueOrUndefined(!!origin && originIsExport(origin)),
             isRecommended: trueOrUndefined(isRecommendedCompletionMatch(symbol, recommendedCompletion, typeChecker)),
@@ -266,6 +314,7 @@ namespace ts.Completions {
         isJsxInitializer?: IsJsxInitializer,
         recommendedCompletion?: Symbol,
         symbolToOriginInfoMap?: SymbolOriginInfoMap,
+        symbolToSortTextMap?: SymbolSortTextMap,
     ): Map<true> {
         const start = timestamp();
         // Tracks unique names.
@@ -275,13 +324,30 @@ namespace ts.Completions {
         const uniques = createMap<true>();
         for (const symbol of symbols) {
             const origin = symbolToOriginInfoMap ? symbolToOriginInfoMap[getSymbolId(symbol)] : undefined;
-            const entry = createCompletionEntry(symbol, location, sourceFile, typeChecker, target, kind, origin, recommendedCompletion, propertyAccessToConvert, isJsxInitializer, preferences);
-            if (!entry) {
+            const info = getCompletionEntryDisplayNameForSymbol(symbol, target, origin, kind);
+            if (!info) {
+                continue;
+            }
+            const { name, needsConvertPropertyAccess } = info;
+            if (uniques.has(name)) {
                 continue;
             }
 
-            const { name } = entry;
-            if (uniques.has(name)) {
+            const entry = createCompletionEntry(
+                symbol,
+                symbolToSortTextMap && symbolToSortTextMap[getSymbolId(symbol)] || SortText.LocationPriority,
+                location,
+                sourceFile,
+                typeChecker,
+                name,
+                needsConvertPropertyAccess,
+                origin,
+                recommendedCompletion,
+                propertyAccessToConvert,
+                isJsxInitializer,
+                preferences
+            );
+            if (!entry) {
                 continue;
             }
 
@@ -321,7 +387,7 @@ namespace ts.Completions {
                         name,
                         kindModifiers: ScriptElementKindModifier.none,
                         kind: ScriptElementKind.label,
-                        sortText: "0"
+                        sortText: SortText.LocationPriority
                     });
                 }
             }
@@ -358,7 +424,7 @@ namespace ts.Completions {
         // We don't need to perform character checks here because we're only comparing the
         // name against 'entryName' (which is known to be good), not building a new
         // completion entry.
-        return firstDefined<Symbol, SymbolCompletion>(symbols, (symbol): SymbolCompletion | undefined => { // TODO: Shouldn't need return type annotation (GH#12632)
+        return firstDefined(symbols, (symbol): SymbolCompletion | undefined => {
             const origin = symbolToOriginInfoMap[getSymbolId(symbol)];
             const info = getCompletionEntryDisplayNameForSymbol(symbol, compilerOptions.target!, origin, completionKind);
             return info && info.name === entryId.name && getSourceFromOrigin(origin) === entryId.source
@@ -512,6 +578,7 @@ namespace ts.Completions {
         readonly previousToken: Node | undefined;
         readonly isJsxInitializer: IsJsxInitializer;
         readonly insideJsDocTagTypeExpression: boolean;
+        readonly symbolToSortTextMap: SymbolSortTextMap;
     }
     type Request = { readonly kind: CompletionDataKind.JsDocTagName | CompletionDataKind.JsDocTag } | { readonly kind: CompletionDataKind.JsDocParameterName, tag: JSDocParameterTag };
 
@@ -804,6 +871,7 @@ namespace ts.Completions {
         let keywordFilters = KeywordCompletionFilters.None;
         let symbols: Symbol[] = [];
         const symbolToOriginInfoMap: SymbolOriginInfoMap = [];
+        const symbolToSortTextMap: SymbolSortTextMap = [];
 
         if (isRightOfDot) {
             getTypeScriptMemberSymbols();
@@ -853,7 +921,8 @@ namespace ts.Completions {
             recommendedCompletion,
             previousToken,
             isJsxInitializer,
-            insideJsDocTagTypeExpression
+            insideJsDocTagTypeExpression,
+            symbolToSortTextMap
         };
 
         type JSDocTagWithTypeExpression = JSDocParameterTag | JSDocPropertyTag | JSDocReturnTag | JSDocTypeTag | JSDocTypedefTag;
@@ -1054,6 +1123,12 @@ namespace ts.Completions {
             const symbolMeanings = (isTypeOnly ? SymbolFlags.None : SymbolFlags.Value) | SymbolFlags.Type | SymbolFlags.Namespace | SymbolFlags.Alias;
 
             symbols = Debug.assertEachDefined(typeChecker.getSymbolsInScope(scopeNode, symbolMeanings), "getSymbolsInScope() should all be defined");
+            for (const symbol of symbols) {
+                if (!typeChecker.isArgumentsSymbol(symbol) &&
+                    !some(symbol.declarations, d => d.getSourceFile() === sourceFile)) {
+                    symbolToSortTextMap[getSymbolId(symbol)] = SortText.GlobalsOrKeywords;
+                }
+            }
 
             // Need to insert 'this.' before properties of `this` type, so only do that if `includeInsertTextCompletions`
             if (preferences.includeCompletionsWithInsertText && scopeNode.kind !== SyntaxKind.SourceFile) {
@@ -1062,6 +1137,7 @@ namespace ts.Completions {
                     for (const symbol of getPropertiesForCompletion(thisType, typeChecker)) {
                         symbolToOriginInfoMap[getSymbolId(symbol)] = { kind: SymbolOriginInfoKind.ThisType };
                         symbols.push(symbol);
+                        symbolToSortTextMap[getSymbolId(symbol)] = SortText.SuggestedClassMembers;
                     }
                 }
             }
@@ -1195,6 +1271,7 @@ namespace ts.Completions {
                     // So in `declare namespace foo {} declare module "foo" { export = foo; }`, there will just be the global completion for `foo`.
                     some(resolvedModuleSymbol.declarations, d => !!d.getSourceFile().externalModuleIndicator)) {
                     symbols.push(resolvedModuleSymbol);
+                    symbolToSortTextMap[getSymbolId(resolvedModuleSymbol)] = SortText.AutoImportSuggestions;
                     symbolToOriginInfoMap[getSymbolId(resolvedModuleSymbol)] = { kind: SymbolOriginInfoKind.Export, moduleSymbol, isDefaultExport: false };
                 }
 
@@ -1220,6 +1297,7 @@ namespace ts.Completions {
                     const origin: SymbolOriginInfoExport = { kind: SymbolOriginInfoKind.Export, moduleSymbol, isDefaultExport };
                     if (detailsEntryId || stringContainsCharactersInOrder(getSymbolName(symbol, origin, target).toLowerCase(), tokenTextLowerCase)) {
                         symbols.push(symbol);
+                        symbolToSortTextMap[getSymbolId(symbol)] = SortText.AutoImportSuggestions;
                         symbolToOriginInfoMap[getSymbolId(symbol)] = origin;
                     }
                 }
@@ -1941,7 +2019,7 @@ namespace ts.Completions {
                 name: tokenToString(i)!,
                 kind: ScriptElementKind.keyword,
                 kindModifiers: ScriptElementKindModifier.none,
-                sortText: "0"
+                sortText: SortText.GlobalsOrKeywords
             });
         }
         return res;

src/services/findAllReferences.ts

@@ -635,7 +635,7 @@ namespace ts.FindAllReferences.Core {
                 // Ignore UMD module and global merge
                 if (symbol.flags & SymbolFlags.Transient) return undefined;
                 // Assertions for GH#21814. We should be handling SourceFile symbols in `getReferencedSymbolsForModule` instead of getting here.
-                Debug.fail(`Unexpected symbol at ${Debug.showSyntaxKind(node)}: ${Debug.showSymbol(symbol)}`);
+                Debug.fail(`Unexpected symbol at ${Debug.formatSyntaxKind(node.kind)}: ${Debug.formatSymbol(symbol)}`);
             }
             return isTypeLiteralNode(decl.parent) && isUnionTypeNode(decl.parent.parent)
                 ? checker.getPropertyOfType(checker.getTypeFromTypeNode(decl.parent.parent), symbol.name)

src/services/importTracker.ts

@@ -133,7 +133,7 @@ namespace ts.FindAllReferences {
                             break;
 
                         default:
-                            Debug.assertNever(direct, `Unexpected import kind: ${Debug.showSyntaxKind(direct)}`);
+                            Debug.failBadSyntaxKind(direct, "Unexpected import kind.");
                     }
                 }
             }
@@ -515,7 +515,7 @@ namespace ts.FindAllReferences {
                 const sym = useLhsSymbol ? checker.getSymbolAtLocation(cast(node.left, isPropertyAccessExpression).name) : symbol;
                 // Better detection for GH#20803
                 if (sym && !(checker.getMergedSymbol(sym.parent!).flags & SymbolFlags.Module)) {
-                    Debug.fail(`Special property assignment kind does not have a module as its parent. Assignment is ${Debug.showSymbol(sym)}, parent is ${Debug.showSymbol(sym.parent!)}`);
+                    Debug.fail(`Special property assignment kind does not have a module as its parent. Assignment is ${Debug.formatSymbol(sym)}, parent is ${Debug.formatSymbol(sym.parent!)}`);
                 }
                 return sym && exportInfo(sym, kind);
             }

src/services/services.ts

@@ -173,7 +173,7 @@ namespace ts {
             const textPos = scanner.getTextPos();
             if (textPos <= end) {
                 if (token === SyntaxKind.Identifier) {
-                    Debug.fail(`Did not expect ${Debug.showSyntaxKind(parent)} to have an Identifier in its trivia`);
+                    Debug.fail(`Did not expect ${Debug.formatSyntaxKind(parent.kind)} to have an Identifier in its trivia`);
                 }
                 nodes.push(createNode(token, pos, textPos, parent));
             }
@@ -2080,6 +2080,10 @@ namespace ts {
             };
         }
 
+        function getSmartSelectionRange(fileName: string, position: number): SelectionRange {
+            return SmartSelectionRange.getSmartSelectionRange(position, syntaxTreeCache.getCurrentSourceFile(fileName));
+        }
+
         function getApplicableRefactors(fileName: string, positionOrRange: number | TextRange, preferences: UserPreferences = emptyOptions): ApplicableRefactorInfo[] {
             synchronizeHostData();
             const file = getValidSourceFile(fileName);
@@ -2127,6 +2131,7 @@ namespace ts {
             getBreakpointStatementAtPosition,
             getNavigateToItems,
             getRenameInfo,
+            getSmartSelectionRange,
             findRenameLocations,
             getNavigationBarItems,
             getNavigationTree,

src/services/shims.ts

@@ -165,6 +165,7 @@ namespace ts {
          * { canRename: boolean, localizedErrorMessage: string, displayName: string, fullDisplayName: string, kind: string, kindModifiers: string, triggerSpan: { start; length } }
          */
         getRenameInfo(fileName: string, position: number, options?: RenameInfoOptions): string;
+        getSmartSelectionRange(fileName: string, position: number): string;
 
         /**
          * Returns a JSON-encoded value of the type:
@@ -838,6 +839,13 @@ namespace ts {
             );
         }
 
+        public getSmartSelectionRange(fileName: string, position: number): string {
+            return this.forwardJSONCall(
+                `getSmartSelectionRange('${fileName}', ${position})`,
+                () => this.languageService.getSmartSelectionRange(fileName, position)
+            );
+        }
+
         public findRenameLocations(fileName: string, position: number, findInStrings: boolean, findInComments: boolean, providePrefixAndSuffixTextForRename?: boolean): string {
             return this.forwardJSONCall(
                 `findRenameLocations('${fileName}', ${position}, ${findInStrings}, ${findInComments}, ${providePrefixAndSuffixTextForRename})`,

src/services/signatureHelp.ts

@@ -455,7 +455,7 @@ namespace ts.SignatureHelp {
         for (let n = node; !isSourceFile(n) && (isManuallyInvoked || !isBlock(n)); n = n.parent) {
             // If the node is not a subspan of its parent, this is a big problem.
             // There have been crashes that might be caused by this violation.
-            Debug.assert(rangeContainsRange(n.parent, n), "Not a subspan", () => `Child: ${Debug.showSyntaxKind(n)}, parent: ${Debug.showSyntaxKind(n.parent)}`);
+            Debug.assert(rangeContainsRange(n.parent, n), "Not a subspan", () => `Child: ${Debug.formatSyntaxKind(n.kind)}, parent: ${Debug.formatSyntaxKind(n.parent.kind)}`);
             const argumentInfo = getImmediatelyContainingArgumentOrContextualParameterInfo(n, position, sourceFile, checker);
             if (argumentInfo) {
                 return argumentInfo;

src/services/smartSelection.ts

@@ -0,0 +1,266 @@
+/* @internal */
+namespace ts.SmartSelectionRange {
+    export function getSmartSelectionRange(pos: number, sourceFile: SourceFile): SelectionRange {
+        let selectionRange: SelectionRange = {
+            textSpan: createTextSpanFromBounds(sourceFile.getFullStart(), sourceFile.getEnd())
+        };
+
+        let parentNode: Node = sourceFile;
+        outer: while (true) {
+            const children = getSelectionChildren(parentNode);
+            if (!children.length) break;
+            for (let i = 0; i < children.length; i++) {
+                const prevNode: Node | undefined = children[i - 1];
+                const node: Node = children[i];
+                const nextNode: Node | undefined = children[i + 1];
+                if (node.getStart(sourceFile) > pos) {
+                    break outer;
+                }
+
+                if (positionShouldSnapToNode(pos, node, nextNode)) {
+                    // 1. Blocks are effectively redundant with SyntaxLists.
+                    // 2. TemplateSpans, along with the SyntaxLists containing them, are a somewhat unintuitive grouping
+                    //    of things that should be considered independently.
+                    // 3. A VariableStatement’s children are just a VaraiableDeclarationList and a semicolon.
+                    // 4. A lone VariableDeclaration in a VaraibleDeclaration feels redundant with the VariableStatement.
+                    //
+                    // Dive in without pushing a selection range.
+                    if (isBlock(node)
+                        || isTemplateSpan(node) || isTemplateHead(node)
+                        || prevNode && isTemplateHead(prevNode)
+                        || isVariableDeclarationList(node) && isVariableStatement(parentNode)
+                        || isSyntaxList(node) && isVariableDeclarationList(parentNode)
+                        || isVariableDeclaration(node) && isSyntaxList(parentNode) && children.length === 1) {
+                        parentNode = node;
+                        break;
+                    }
+
+                    // Synthesize a stop for '${ ... }' since '${' and '}' actually belong to siblings.
+                    if (isTemplateSpan(parentNode) && nextNode && isTemplateMiddleOrTemplateTail(nextNode)) {
+                        const start = node.getFullStart() - "${".length;
+                        const end = nextNode.getStart() + "}".length;
+                        pushSelectionRange(start, end);
+                    }
+
+                    // Blocks with braces, brackets, parens, or JSX tags on separate lines should be
+                    // selected from open to close, including whitespace but not including the braces/etc. themselves.
+                    const isBetweenMultiLineBookends = isSyntaxList(node)
+                        && isListOpener(prevNode)
+                        && isListCloser(nextNode)
+                        && !positionsAreOnSameLine(prevNode.getStart(), nextNode.getStart(), sourceFile);
+                    const jsDocCommentStart = hasJSDocNodes(node) && node.jsDoc![0].getStart();
+                    const start = isBetweenMultiLineBookends ? prevNode.getEnd() : node.getStart();
+                    const end = isBetweenMultiLineBookends ? nextNode.getStart() : node.getEnd();
+                    if (isNumber(jsDocCommentStart)) {
+                        pushSelectionRange(jsDocCommentStart, end);
+                    }
+                    pushSelectionRange(start, end);
+
+                    // String literals should have a stop both inside and outside their quotes.
+                    if (isStringLiteral(node) || isTemplateLiteral(node)) {
+                        pushSelectionRange(start + 1, end - 1);
+                    }
+
+                    parentNode = node;
+                    break;
+                }
+            }
+        }
+
+        return selectionRange;
+
+        function pushSelectionRange(start: number, end: number): void {
+            // Skip empty ranges
+            if (start !== end) {
+                // Skip ranges that are identical to the parent
+                const textSpan = createTextSpanFromBounds(start, end);
+                if (!selectionRange || !textSpansEqual(textSpan, selectionRange.textSpan)) {
+                    selectionRange = { textSpan, ...selectionRange && { parent: selectionRange } };
+                }
+            }
+        }
+    }
+
+    /**
+     * Like `ts.positionBelongsToNode`, except positions immediately after nodes
+     * count too, unless that position belongs to the next node. In effect, makes
+     * selections able to snap to preceding tokens when the cursor is on the tail
+     * end of them with only whitespace ahead.
+     * @param pos The position to check.
+     * @param node The candidate node to snap to.
+     * @param nextNode The next sibling node in the tree.
+     * @param sourceFile The source file containing the nodes.
+     */
+    function positionShouldSnapToNode(pos: number, node: Node, nextNode: Node | undefined) {
+        // Can’t use 'ts.positionBelongsToNode()' here because it cleverly accounts
+        // for missing nodes, which can’t really be considered when deciding what
+        // to select.
+        Debug.assert(node.pos <= pos);
+        if (pos < node.end) {
+            return true;
+        }
+        const nodeEnd = node.getEnd();
+        const nextNodeStart = nextNode && nextNode.getStart();
+        if (nodeEnd === pos) {
+            return pos !== nextNodeStart;
+        }
+        return false;
+    }
+
+    const isImport = or(isImportDeclaration, isImportEqualsDeclaration);
+
+    /**
+     * Gets the children of a node to be considered for selection ranging,
+     * transforming them into an artificial tree according to their intuitive
+     * grouping where no grouping actually exists in the parse tree. For example,
+     * top-level imports are grouped into their own SyntaxList so they can be
+     * selected all together, even though in the AST they’re just siblings of each
+     * other as well as of other top-level statements and declarations.
+     */
+    function getSelectionChildren(node: Node): ReadonlyArray<Node> {
+        // Group top-level imports
+        if (isSourceFile(node)) {
+            return groupChildren(node.getChildAt(0).getChildren(), isImport);
+        }
+
+        // Mapped types _look_ like ObjectTypes with a single member,
+        // but in fact don’t contain a SyntaxList or a node containing
+        // the “key/value” pair like ObjectTypes do, but it seems intuitive
+        // that the selection would snap to those points. The philosophy
+        // of choosing a selection range is not so much about what the
+        // syntax currently _is_ as what the syntax might easily become
+        // if the user is making a selection; e.g., we synthesize a selection
+        // around the “key/value” pair not because there’s a node there, but
+        // because it allows the mapped type to become an object type with a
+        // few keystrokes.
+        if (isMappedTypeNode(node)) {
+            const [openBraceToken, ...children] = node.getChildren();
+            const closeBraceToken = Debug.assertDefined(children.pop());
+            Debug.assertEqual(openBraceToken.kind, SyntaxKind.OpenBraceToken);
+            Debug.assertEqual(closeBraceToken.kind, SyntaxKind.CloseBraceToken);
+            // Group `-/+readonly` and `-/+?`
+            const groupedWithPlusMinusTokens = groupChildren(children, child =>
+                child === node.readonlyToken || child.kind === SyntaxKind.ReadonlyKeyword ||
+                child === node.questionToken || child.kind === SyntaxKind.QuestionToken);
+            // Group type parameter with surrounding brackets
+            const groupedWithBrackets = groupChildren(groupedWithPlusMinusTokens, ({ kind }) =>
+                kind === SyntaxKind.OpenBracketToken ||
+                kind === SyntaxKind.TypeParameter ||
+                kind === SyntaxKind.CloseBracketToken
+            );
+            return [
+                openBraceToken,
+                // Pivot on `:`
+                createSyntaxList(splitChildren(groupedWithBrackets, ({ kind }) => kind === SyntaxKind.ColonToken)),
+                closeBraceToken,
+            ];
+        }
+
+        // Group modifiers and property name, then pivot on `:`.
+        if (isPropertySignature(node)) {
+            const children = groupChildren(node.getChildren(), child =>
+                child === node.name || contains(node.modifiers, child));
+            return splitChildren(children, ({ kind }) => kind === SyntaxKind.ColonToken);
+        }
+
+        // Group the parameter name with its `...`, then that group with its `?`, then pivot on `=`.
+        if (isParameter(node)) {
+            const groupedDotDotDotAndName = groupChildren(node.getChildren(), child =>
+                child === node.dotDotDotToken || child === node.name);
+            const groupedWithQuestionToken = groupChildren(groupedDotDotDotAndName, child =>
+                child === groupedDotDotDotAndName[0] || child === node.questionToken);
+            return splitChildren(groupedWithQuestionToken, ({ kind }) => kind === SyntaxKind.EqualsToken);
+        }
+
+        // Pivot on '='
+        if (isBindingElement(node)) {
+            return splitChildren(node.getChildren(), ({ kind }) => kind === SyntaxKind.EqualsToken);
+        }
+
+        return node.getChildren();
+    }
+
+    /**
+     * Groups sibling nodes together into their own SyntaxList if they
+     * a) are adjacent, AND b) match a predicate function.
+     */
+    function groupChildren(children: Node[], groupOn: (child: Node) => boolean): Node[] {
+        const result: Node[] = [];
+        let group: Node[] | undefined;
+        for (const child of children) {
+            if (groupOn(child)) {
+                group = group || [];
+                group.push(child);
+            }
+            else {
+                if (group) {
+                    result.push(createSyntaxList(group));
+                    group = undefined;
+                }
+                result.push(child);
+            }
+        }
+        if (group) {
+            result.push(createSyntaxList(group));
+        }
+
+        return result;
+    }
+
+    /**
+     * Splits sibling nodes into up to four partitions:
+     * 1) everything left of the first node matched by `pivotOn`,
+     * 2) the first node matched by `pivotOn`,
+     * 3) everything right of the first node matched by `pivotOn`,
+     * 4) a trailing semicolon, if `separateTrailingSemicolon` is enabled.
+     * The left and right groups, if not empty, will each be grouped into their own containing SyntaxList.
+     * @param children The sibling nodes to split.
+     * @param pivotOn The predicate function to match the node to be the pivot. The first node that matches
+     * the predicate will be used; any others that may match will be included into the right-hand group.
+     * @param separateTrailingSemicolon If the last token is a semicolon, it will be returned as a separate
+     * child rather than be included in the right-hand group.
+     */
+    function splitChildren(children: Node[], pivotOn: (child: Node) => boolean, separateTrailingSemicolon = true): Node[] {
+        if (children.length < 2) {
+            return children;
+        }
+        const splitTokenIndex = findIndex(children, pivotOn);
+        if (splitTokenIndex === -1) {
+            return children;
+        }
+        const leftChildren = children.slice(0, splitTokenIndex);
+        const splitToken = children[splitTokenIndex];
+        const lastToken = last(children);
+        const separateLastToken = separateTrailingSemicolon && lastToken.kind === SyntaxKind.SemicolonToken;
+        const rightChildren = children.slice(splitTokenIndex + 1, separateLastToken ? children.length - 1 : undefined);
+        const result = compact([
+            leftChildren.length ? createSyntaxList(leftChildren) : undefined,
+            splitToken,
+            rightChildren.length ? createSyntaxList(rightChildren) : undefined,
+        ]);
+        return separateLastToken ? result.concat(lastToken) : result;
+    }
+
+    function createSyntaxList(children: Node[]): SyntaxList {
+        Debug.assertGreaterThanOrEqual(children.length, 1);
+        const syntaxList = createNode(SyntaxKind.SyntaxList, children[0].pos, last(children).end) as SyntaxList;
+        syntaxList._children = children;
+        return syntaxList;
+    }
+
+    function isListOpener(token: Node | undefined): token is Node {
+        const kind = token && token.kind;
+        return kind === SyntaxKind.OpenBraceToken
+            || kind === SyntaxKind.OpenBracketToken
+            || kind === SyntaxKind.OpenParenToken
+            || kind === SyntaxKind.JsxOpeningElement;
+    }
+
+    function isListCloser(token: Node | undefined): token is Node {
+        const kind = token && token.kind;
+        return kind === SyntaxKind.CloseBraceToken
+            || kind === SyntaxKind.CloseBracketToken
+            || kind === SyntaxKind.CloseParenToken
+            || kind === SyntaxKind.JsxClosingElement;
+    }
+}

src/services/stringCompletions.ts

@@ -21,7 +21,17 @@ namespace ts.Completions.StringCompletions {
                 return convertPathCompletions(completion.paths);
             case StringLiteralCompletionKind.Properties: {
                 const entries: CompletionEntry[] = [];
-                getCompletionEntriesFromSymbols(completion.symbols, entries, sourceFile, sourceFile, checker, ScriptTarget.ESNext, log, CompletionKind.String, preferences); // Target will not be used, so arbitrary
+                getCompletionEntriesFromSymbols(
+                    completion.symbols,
+                    entries,
+                    sourceFile,
+                    sourceFile,
+                    checker,
+                    ScriptTarget.ESNext,
+                    log,
+                    CompletionKind.String,
+                    preferences
+                ); // Target will not be used, so arbitrary
                 return { isGlobalCompletion: false, isMemberCompletion: true, isNewIdentifierLocation: completion.hasIndexSignature, entries };
             }
             case StringLiteralCompletionKind.Types: {
@@ -60,7 +70,7 @@ namespace ts.Completions.StringCompletions {
         const isGlobalCompletion = false; // We don't want the editor to offer any other completions, such as snippets, inside a comment.
         const isNewIdentifierLocation = true; // The user may type in a path that doesn't yet exist, creating a "new identifier" with respect to the collection of identifiers the server is aware of.
         const entries = pathCompletions.map(({ name, kind, span, extension }): CompletionEntry =>
-            ({ name, kind, kindModifiers: kindModifiersFromExtension(extension), sortText: "0", replacementSpan: span }));
+            ({ name, kind, kindModifiers: kindModifiersFromExtension(extension), sortText: SortText.LocationPriority, replacementSpan: span }));
         return { isGlobalCompletion, isMemberCompletion: false, isNewIdentifierLocation, entries };
     }
     function kindModifiersFromExtension(extension: Extension | undefined): ScriptElementKindModifier {

src/services/tsconfig.json

@@ -28,6 +28,7 @@
         "patternMatcher.ts",
         "preProcess.ts",
         "rename.ts",
+        "smartSelection.ts",
         "signatureHelp.ts",
         "sourcemaps.ts",
         "suggestionDiagnostics.ts",

src/services/types.ts

@@ -296,6 +296,8 @@ namespace ts {
         getRenameInfo(fileName: string, position: number, options?: RenameInfoOptions): RenameInfo;
         findRenameLocations(fileName: string, position: number, findInStrings: boolean, findInComments: boolean, providePrefixAndSuffixTextForRename?: boolean): ReadonlyArray<RenameLocation> | undefined;
 
+        getSmartSelectionRange(fileName: string, position: number): SelectionRange;
+
         getDefinitionAtPosition(fileName: string, position: number): ReadonlyArray<DefinitionInfo> | undefined;
         getDefinitionAndBoundSpan(fileName: string, position: number): DefinitionInfoAndBoundSpan | undefined;
         getTypeDefinitionAtPosition(fileName: string, position: number): ReadonlyArray<DefinitionInfo> | undefined;
@@ -848,6 +850,11 @@ namespace ts {
         isOptional: boolean;
     }
 
+    export interface SelectionRange {
+        textSpan: TextSpan;
+        parent?: SelectionRange;
+    }
+
     /**
      * Represents a single signature to show in signature help.
      * The id is used for subsequent calls into the language service to ask questions about the

src/testRunner/tsconfig.json

@@ -142,6 +142,7 @@
         "unittests/tsserver/reload.ts",
         "unittests/tsserver/rename.ts",
         "unittests/tsserver/resolutionCache.ts",
+        "unittests/tsserver/smartSelection.ts",
         "unittests/tsserver/session.ts",
         "unittests/tsserver/skipLibCheck.ts",
         "unittests/tsserver/symLinks.ts",

src/testRunner/unittests/config/configurationExtension.ts

@@ -197,13 +197,13 @@ namespace ts {
     const caseSensitiveBasePath = "/dev/";
     const caseSensitiveHost = new fakes.ParseConfigHost(createFileSystem(/*ignoreCase*/ false, caseSensitiveBasePath, "/"));
 
-    function verifyDiagnostics(actual: Diagnostic[], expected: {code: number, category: DiagnosticCategory, messageText: string}[]) {
+    function verifyDiagnostics(actual: Diagnostic[], expected: { code: number; messageText: string; }[]) {
         assert.isTrue(expected.length === actual.length, `Expected error: ${JSON.stringify(expected)}. Actual error: ${JSON.stringify(actual)}.`);
         for (let i = 0; i < actual.length; i++) {
             const actualError = actual[i];
             const expectedError = expected[i];
             assert.equal(actualError.code, expectedError.code, "Error code mismatch");
-            assert.equal(actualError.category, expectedError.category, "Category mismatch");
+            assert.equal(actualError.category, DiagnosticCategory.Error, "Category mismatch"); // Should always be error
             assert.equal(flattenDiagnosticMessageText(actualError.messageText, "\n"), expectedError.messageText);
         }
     }
@@ -246,7 +246,7 @@ namespace ts {
                 });
             }
 
-            function testFailure(name: string, entry: string, expectedDiagnostics: { code: number, category: DiagnosticCategory, messageText: string }[]) {
+            function testFailure(name: string, entry: string, expectedDiagnostics: { code: number; messageText: string; }[]) {
                 it(name, () => {
                     const parsed = getParseCommandLine(entry);
                     verifyDiagnostics(parsed.errors, expectedDiagnostics);
@@ -280,26 +280,22 @@ namespace ts {
                 testFailure("can report errors on circular imports", "circular.json", [
                     {
                         code: 18000,
-                        category: DiagnosticCategory.Error,
                         messageText: `Circularity detected while resolving configuration: ${[combinePaths(basePath, "circular.json"), combinePaths(basePath, "circular2.json"), combinePaths(basePath, "circular.json")].join(" -> ")}`
                     }
                 ]);
 
                 testFailure("can report missing configurations", "missing.json", [{
-                    code: 6096,
-                    category: DiagnosticCategory.Message,
-                    messageText: `File './missing2' does not exist.`
+                    code: 6053,
+                    messageText: `File './missing2' not found.`
                 }]);
 
                 testFailure("can report errors in extended configs", "failure.json", [{
                     code: 6114,
-                    category: DiagnosticCategory.Error,
                     messageText: `Unknown option 'excludes'. Did you mean 'exclude'?`
                 }]);
 
                 testFailure("can error when 'extends' is not a string", "extends.json", [{
                     code: 5024,
-                    category: DiagnosticCategory.Error,
                     messageText: `Compiler option 'extends' requires a value of type string.`
                 }]);
 

src/testRunner/unittests/factory.ts

@@ -1,7 +1,7 @@
 namespace ts {
     describe("unittests:: FactoryAPI", () => {
         function assertSyntaxKind(node: Node, expected: SyntaxKind) {
-            assert.strictEqual(node.kind, expected, `Actual: ${Debug.showSyntaxKind(node)} Expected: ${(ts as any).SyntaxKind[expected]}`);
+            assert.strictEqual(node.kind, expected, `Actual: ${Debug.formatSyntaxKind(node.kind)} Expected: ${Debug.formatSyntaxKind(expected)}`);
         }
         describe("createExportAssignment", () => {
             it("parenthesizes default export if necessary", () => {

src/testRunner/unittests/moduleResolution.ts

@@ -530,7 +530,7 @@ export = C;
         });
     });
 
-    describe("unittests:: moduleResolution:: Files with different casing", () => {
+    describe("unittests:: moduleResolution:: Files with different casing with forceConsistentCasingInFileNames", () => {
         let library: SourceFile;
         function test(files: Map<string>, options: CompilerOptions, currentDirectory: string, useCaseSensitiveFileNames: boolean, rootFiles: string[], diagnosticCodes: number[]): void {
             const getCanonicalFileName = createGetCanonicalFileName(useCaseSensitiveFileNames);
@@ -649,6 +649,22 @@ import b = require("./moduleB");
             });
             test(files, { module: ModuleKind.CommonJS, forceConsistentCasingInFileNames: true }, "/a/B/c", /*useCaseSensitiveFileNames*/ false, ["moduleD.ts"], []);
         });
+
+        it("should succeed when the two files in program differ only in drive letter in their names", () => {
+            const files = createMapFromTemplate({
+                "d:/someFolder/moduleA.ts": `import a = require("D:/someFolder/moduleC")`,
+                "d:/someFolder/moduleB.ts": `import a = require("./moduleC")`,
+                "D:/someFolder/moduleC.ts": "export const x = 10",
+            });
+            test(
+                files,
+                { module: ModuleKind.CommonJS, forceConsistentCasingInFileNames: true },
+                "d:/someFolder",
+                /*useCaseSensitiveFileNames*/ false,
+                ["d:/someFolder/moduleA.ts", "d:/someFolder/moduleB.ts"],
+                []
+            );
+        });
     });
 
     describe("unittests:: moduleResolution:: baseUrl augmented module resolution", () => {

src/testRunner/unittests/tsserver/completions.ts

@@ -36,7 +36,7 @@ namespace ts.projectSystem {
                 kindModifiers: ScriptElementKindModifier.exportedModifier,
                 name: "foo",
                 replacementSpan: undefined,
-                sortText: "0",
+                sortText: Completions.SortText.AutoImportSuggestions,
                 source: "/a",
             };
             assert.deepEqual<protocol.CompletionInfo | undefined>(response, {

src/testRunner/unittests/tsserver/session.ts

@@ -264,6 +264,7 @@ namespace ts.server {
                 CommandNames.OrganizeImportsFull,
                 CommandNames.GetEditsForFileRename,
                 CommandNames.GetEditsForFileRenameFull,
+                CommandNames.SelectionRange,
             ];
 
             it("should not throw when commands are executed with invalid arguments", () => {

src/testRunner/unittests/tsserver/smartSelection.ts

@@ -0,0 +1,66 @@
+namespace ts.projectSystem {
+    function setup(fileName: string, content: string) {
+        const file: File = { path: fileName, content };
+        const host = createServerHost([file, libFile]);
+        const session = createSession(host);
+        openFilesForSession([file], session);
+        return function getSmartSelectionRange(locations: protocol.SelectionRangeRequestArgs["locations"]) {
+            return executeSessionRequest<protocol.SelectionRangeRequest, protocol.SelectionRangeResponse>(
+                session,
+                CommandNames.SelectionRange,
+                { file: fileName, locations });
+        };
+    }
+
+    // More tests in fourslash/smartSelection_*
+    describe("unittests:: tsserver:: smartSelection", () => {
+        it("works for simple JavaScript", () => {
+            const getSmartSelectionRange = setup("/file.js", `
+class Foo {
+    bar(a, b) {
+        if (a === b) {
+            return true;
+        }
+        return false;
+    }
+}`);
+
+            const locations = getSmartSelectionRange([
+                { line: 4, offset: 13 }, // a === b
+            ]);
+
+            assert.deepEqual(locations, [{
+                textSpan: { // a
+                    start: { line: 4, offset: 13 },
+                    end: { line: 4, offset: 14 } },
+                parent: {
+                    textSpan: { // a === b
+                        start: { line: 4, offset: 13 },
+                        end: { line: 4, offset: 20 } },
+                    parent: {
+                        textSpan: { // IfStatement
+                            start: { line: 4, offset: 9 },
+                            end: { line: 6, offset: 10 } },
+                        parent: {
+                            textSpan: { // SyntaxList + whitespace (body of method)
+                                start: { line: 3, offset: 16 },
+                                end: { line: 8, offset: 5 } },
+                            parent: {
+                                textSpan: { // MethodDeclaration
+                                    start: { line: 3, offset: 5 },
+                                    end: { line: 8, offset: 6 } },
+                                parent: {
+                                    textSpan: { // SyntaxList + whitespace (body of class)
+                                        start: { line: 2, offset: 12 },
+                                        end: { line: 9, offset: 1 } },
+                                    parent: {
+                                        textSpan: { // ClassDeclaration
+                                            start: { line: 2, offset: 1 },
+                                            end: { line: 9, offset: 2 } },
+                                        parent: {
+                                            textSpan: { // SourceFile (all text)
+                                                start: { line: 1, offset: 1 },
+                                                end: { line: 9, offset: 2 }, } } } } } } } } }]);
+        });
+    });
+}

tests/baselines/reference/ES5For-of37.js

@@ -0,0 +1,64 @@
+//// [ES5For-of37.ts]
+// https://github.com/microsoft/TypeScript/issues/30083
+
+for (const i of [0, 1, 2, 3, 4]) {
+    try {
+        // Ensure catch binding for the following loop is reset per iteration:
+        for (const j of [1, 2, 3]) {
+            if (i === 2) {
+                throw new Error('ERR');
+            }
+        }
+        console.log(i);
+    } catch (err) {
+        console.log('E %s %s', i, err);
+    }
+}
+
+//// [ES5For-of37.js]
+// https://github.com/microsoft/TypeScript/issues/30083
+var __values = (this && this.__values) || function (o) {
+    var m = typeof Symbol === "function" && o[Symbol.iterator], i = 0;
+    if (m) return m.call(o);
+    return {
+        next: function () {
+            if (o && i >= o.length) o = void 0;
+            return { value: o && o[i++], done: !o };
+        }
+    };
+};
+var e_1, _a, e_2, _b;
+try {
+    for (var _c = __values([0, 1, 2, 3, 4]), _d = _c.next(); !_d.done; _d = _c.next()) {
+        var i = _d.value;
+        try {
+            try {
+                // Ensure catch binding for the following loop is reset per iteration:
+                for (var _e = (e_2 = void 0, __values([1, 2, 3])), _f = _e.next(); !_f.done; _f = _e.next()) {
+                    var j = _f.value;
+                    if (i === 2) {
+                        throw new Error('ERR');
+                    }
+                }
+            }
+            catch (e_2_1) { e_2 = { error: e_2_1 }; }
+            finally {
+                try {
+                    if (_f && !_f.done && (_b = _e["return"])) _b.call(_e);
+                }
+                finally { if (e_2) throw e_2.error; }
+            }
+            console.log(i);
+        }
+        catch (err) {
+            console.log('E %s %s', i, err);
+        }
+    }
+}
+catch (e_1_1) { e_1 = { error: e_1_1 }; }
+finally {
+    try {
+        if (_d && !_d.done && (_a = _c["return"])) _a.call(_c);
+    }
+    finally { if (e_1) throw e_1.error; }
+}

tests/baselines/reference/ES5For-of37.symbols

@@ -0,0 +1,35 @@
+=== tests/cases/conformance/statements/for-ofStatements/ES5For-of37.ts ===
+// https://github.com/microsoft/TypeScript/issues/30083
+
+for (const i of [0, 1, 2, 3, 4]) {
+>i : Symbol(i, Decl(ES5For-of37.ts, 2, 10))
+
+    try {
+        // Ensure catch binding for the following loop is reset per iteration:
+        for (const j of [1, 2, 3]) {
+>j : Symbol(j, Decl(ES5For-of37.ts, 5, 18))
+
+            if (i === 2) {
+>i : Symbol(i, Decl(ES5For-of37.ts, 2, 10))
+
+                throw new Error('ERR');
+>Error : Symbol(Error, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+            }
+        }
+        console.log(i);
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>i : Symbol(i, Decl(ES5For-of37.ts, 2, 10))
+
+    } catch (err) {
+>err : Symbol(err, Decl(ES5For-of37.ts, 11, 13))
+
+        console.log('E %s %s', i, err);
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>i : Symbol(i, Decl(ES5For-of37.ts, 2, 10))
+>err : Symbol(err, Decl(ES5For-of37.ts, 11, 13))
+    }
+}

tests/baselines/reference/ES5For-of37.types

@@ -0,0 +1,52 @@
+=== tests/cases/conformance/statements/for-ofStatements/ES5For-of37.ts ===
+// https://github.com/microsoft/TypeScript/issues/30083
+
+for (const i of [0, 1, 2, 3, 4]) {
+>i : number
+>[0, 1, 2, 3, 4] : number[]
+>0 : 0
+>1 : 1
+>2 : 2
+>3 : 3
+>4 : 4
+
+    try {
+        // Ensure catch binding for the following loop is reset per iteration:
+        for (const j of [1, 2, 3]) {
+>j : number
+>[1, 2, 3] : number[]
+>1 : 1
+>2 : 2
+>3 : 3
+
+            if (i === 2) {
+>i === 2 : boolean
+>i : number
+>2 : 2
+
+                throw new Error('ERR');
+>new Error('ERR') : Error
+>Error : ErrorConstructor
+>'ERR' : "ERR"
+            }
+        }
+        console.log(i);
+>console.log(i) : void
+>console.log : (message?: any, ...optionalParams: any[]) => void
+>console : Console
+>log : (message?: any, ...optionalParams: any[]) => void
+>i : number
+
+    } catch (err) {
+>err : any
+
+        console.log('E %s %s', i, err);
+>console.log('E %s %s', i, err) : void
+>console.log : (message?: any, ...optionalParams: any[]) => void
+>console : Console
+>log : (message?: any, ...optionalParams: any[]) => void
+>'E %s %s' : "E %s %s"
+>i : number
+>err : any
+    }
+}

tests/baselines/reference/ES5For-of7.errors.txt

@@ -10,4 +10,5 @@ tests/cases/conformance/statements/for-ofStatements/ES5For-of7.ts(6,9): error TS
         var x = [w, v];
             ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'any', but here has type 'any[]'.
+!!! related TS6203 tests/cases/conformance/statements/for-ofStatements/ES5For-of7.ts:2:9: 'x' was also declared here.
     }

tests/baselines/reference/FunctionAndModuleWithSameNameAndCommonRoot.errors.txt

@@ -24,6 +24,7 @@ tests/cases/conformance/internalModules/DeclarationMerging/test.ts(2,5): error T
     var fn = A.Point;
         ~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'fn' must be of type '() => { x: number; y: number; }', but here has type 'typeof Point'.
+!!! related TS6203 tests/cases/conformance/internalModules/DeclarationMerging/test.ts:1:5: 'fn' was also declared here.
     
     var cl: { x: number; y: number; }
     var cl = A.Point();
@@ -46,6 +47,7 @@ tests/cases/conformance/internalModules/DeclarationMerging/test.ts(2,5): error T
     var fn = B.Point;  // not expected to be an error. bug 840000: [corelang] Function of fundule not assignalbe as expected
         ~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'fn' must be of type '() => { x: number; y: number; }', but here has type 'typeof Point'.
+!!! related TS6203 tests/cases/conformance/internalModules/DeclarationMerging/test.ts:1:5: 'fn' was also declared here.
     
     var cl: { x: number; y: number; }
     var cl = B.Point();

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -4809,6 +4809,7 @@ declare namespace ts {
         getSignatureHelpItems(fileName: string, position: number, options: SignatureHelpItemsOptions | undefined): SignatureHelpItems | undefined;
         getRenameInfo(fileName: string, position: number, options?: RenameInfoOptions): RenameInfo;
         findRenameLocations(fileName: string, position: number, findInStrings: boolean, findInComments: boolean, providePrefixAndSuffixTextForRename?: boolean): ReadonlyArray<RenameLocation> | undefined;
+        getSmartSelectionRange(fileName: string, position: number): SelectionRange;
         getDefinitionAtPosition(fileName: string, position: number): ReadonlyArray<DefinitionInfo> | undefined;
         getDefinitionAndBoundSpan(fileName: string, position: number): DefinitionInfoAndBoundSpan | undefined;
         getTypeDefinitionAtPosition(fileName: string, position: number): ReadonlyArray<DefinitionInfo> | undefined;
@@ -5253,6 +5254,10 @@ declare namespace ts {
         displayParts: SymbolDisplayPart[];
         isOptional: boolean;
     }
+    interface SelectionRange {
+        textSpan: TextSpan;
+        parent?: SelectionRange;
+    }
     /**
      * Represents a single signature to show in signature help.
      * The id is used for subsequent calls into the language service to ask questions about the
@@ -5800,7 +5805,8 @@ declare namespace ts.server.protocol {
         GetEditsForRefactor = "getEditsForRefactor",
         OrganizeImports = "organizeImports",
         GetEditsForFileRename = "getEditsForFileRename",
-        ConfigurePlugin = "configurePlugin"
+        ConfigurePlugin = "configurePlugin",
+        SelectionRange = "selectionRange",
     }
     /**
      * A TypeScript Server message
@@ -6763,6 +6769,20 @@ declare namespace ts.server.protocol {
     }
     interface ConfigurePluginResponse extends Response {
     }
+    interface SelectionRangeRequest extends FileRequest {
+        command: CommandTypes.SelectionRange;
+        arguments: SelectionRangeRequestArgs;
+    }
+    interface SelectionRangeRequestArgs extends FileRequestArgs {
+        locations: Location[];
+    }
+    interface SelectionRangeResponse extends Response {
+        body?: SelectionRange[];
+    }
+    interface SelectionRange {
+        textSpan: TextSpan;
+        parent?: SelectionRange;
+    }
     /**
      *  Information found in an "open" request.
      */
@@ -9039,6 +9059,8 @@ declare namespace ts.server {
         private getBraceMatching;
         private getDiagnosticsForProject;
         private configurePlugin;
+        private getSmartSelectionRange;
+        private mapSelectionRange;
         getCanonicalFileName(fileName: string): string;
         exit(): void;
         private notRequired;

tests/baselines/reference/api/typescript.d.ts

@@ -4809,6 +4809,7 @@ declare namespace ts {
         getSignatureHelpItems(fileName: string, position: number, options: SignatureHelpItemsOptions | undefined): SignatureHelpItems | undefined;
         getRenameInfo(fileName: string, position: number, options?: RenameInfoOptions): RenameInfo;
         findRenameLocations(fileName: string, position: number, findInStrings: boolean, findInComments: boolean, providePrefixAndSuffixTextForRename?: boolean): ReadonlyArray<RenameLocation> | undefined;
+        getSmartSelectionRange(fileName: string, position: number): SelectionRange;
         getDefinitionAtPosition(fileName: string, position: number): ReadonlyArray<DefinitionInfo> | undefined;
         getDefinitionAndBoundSpan(fileName: string, position: number): DefinitionInfoAndBoundSpan | undefined;
         getTypeDefinitionAtPosition(fileName: string, position: number): ReadonlyArray<DefinitionInfo> | undefined;
@@ -5253,6 +5254,10 @@ declare namespace ts {
         displayParts: SymbolDisplayPart[];
         isOptional: boolean;
     }
+    interface SelectionRange {
+        textSpan: TextSpan;
+        parent?: SelectionRange;
+    }
     /**
      * Represents a single signature to show in signature help.
      * The id is used for subsequent calls into the language service to ask questions about the

tests/baselines/reference/asyncArrowFunction5_es2017.errors.txt

@@ -16,6 +16,7 @@ tests/cases/conformance/async/es2017/asyncArrowFunction/asyncArrowFunction5_es20
 !!! error TS1005: ',' expected.
                              ~~~~~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'Promise' must be of type 'PromiseConstructor', but here has type 'any'.
+!!! related TS6203 /.ts/lib.es2015.promise.d.ts:152:13: 'Promise' was also declared here.
                                     ~
 !!! error TS1005: ',' expected.
                                            ~~

tests/baselines/reference/asyncArrowFunction5_es5.errors.txt

@@ -16,6 +16,7 @@ tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction5_es5.ts(
 !!! error TS1005: ',' expected.
                              ~~~~~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'Promise' must be of type 'PromiseConstructor', but here has type 'any'.
+!!! related TS6203 /.ts/lib.es2015.promise.d.ts:152:13: 'Promise' was also declared here.
                                     ~
 !!! error TS1005: ',' expected.
                                            ~~

tests/baselines/reference/asyncArrowFunction5_es6.errors.txt

@@ -16,6 +16,7 @@ tests/cases/conformance/async/es6/asyncArrowFunction/asyncArrowFunction5_es6.ts(
 !!! error TS1005: ',' expected.
                              ~~~~~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'Promise' must be of type 'PromiseConstructor', but here has type 'any'.
+!!! related TS6203 /.ts/lib.es2015.promise.d.ts:152:13: 'Promise' was also declared here.
                                     ~
 !!! error TS1005: ',' expected.
                                            ~~

tests/baselines/reference/asyncArrowFunction9_es2017.errors.txt

@@ -16,6 +16,7 @@ tests/cases/conformance/async/es2017/asyncArrowFunction/asyncArrowFunction9_es20
 !!! error TS1005: ',' expected.
                                           ~~~~~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'Promise' must be of type 'PromiseConstructor', but here has type 'any'.
+!!! related TS6203 /.ts/lib.es2015.promise.d.ts:152:13: 'Promise' was also declared here.
                                                  ~
 !!! error TS1005: ',' expected.
                                                         ~~

tests/baselines/reference/asyncArrowFunction9_es5.errors.txt

@@ -16,6 +16,7 @@ tests/cases/conformance/async/es5/asyncArrowFunction/asyncArrowFunction9_es5.ts(
 !!! error TS1005: ',' expected.
                                           ~~~~~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'Promise' must be of type 'PromiseConstructor', but here has type 'any'.
+!!! related TS6203 /.ts/lib.es2015.promise.d.ts:152:13: 'Promise' was also declared here.
                                                  ~
 !!! error TS1005: ',' expected.
                                                         ~~

tests/baselines/reference/asyncArrowFunction9_es6.errors.txt

@@ -16,6 +16,7 @@ tests/cases/conformance/async/es6/asyncArrowFunction/asyncArrowFunction9_es6.ts(
 !!! error TS1005: ',' expected.
                                           ~~~~~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'Promise' must be of type 'PromiseConstructor', but here has type 'any'.
+!!! related TS6203 /.ts/lib.es2015.promise.d.ts:152:13: 'Promise' was also declared here.
                                                  ~
 !!! error TS1005: ',' expected.
                                                         ~~

tests/baselines/reference/augmentedTypesVar.errors.txt

@@ -30,6 +30,7 @@ tests/cases/compiler/augmentedTypesVar.ts(31,8): error TS2300: Duplicate identif
     var x3 = () => { } // error
         ~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x3' must be of type 'number', but here has type '() => void'.
+!!! related TS6203 tests/cases/compiler/augmentedTypesVar.ts:9:5: 'x3' was also declared here.
     
     // var then class
     var x4 = 1; // error

tests/baselines/reference/binderUninitializedModuleExportsAssignment.symbols

@@ -0,0 +1,15 @@
+=== tests/cases/conformance/salsa/loop.js ===
+var loop1 = loop2;
+>loop1 : Symbol(loop1, Decl(loop.js, 0, 3))
+>loop2 : Symbol(loop2, Decl(loop.js, 1, 3))
+
+var loop2 = loop1;
+>loop2 : Symbol(loop2, Decl(loop.js, 1, 3))
+>loop1 : Symbol(loop1, Decl(loop.js, 0, 3))
+
+module.exports = loop2;
+>module.exports : Symbol("tests/cases/conformance/salsa/loop", Decl(loop.js, 0, 0))
+>module : Symbol(export=, Decl(loop.js, 1, 18))
+>exports : Symbol(export=, Decl(loop.js, 1, 18))
+>loop2 : Symbol(loop2, Decl(loop.js, 1, 3))
+

tests/baselines/reference/binderUninitializedModuleExportsAssignment.types

@@ -0,0 +1,16 @@
+=== tests/cases/conformance/salsa/loop.js ===
+var loop1 = loop2;
+>loop1 : any
+>loop2 : any
+
+var loop2 = loop1;
+>loop2 : any
+>loop1 : any
+
+module.exports = loop2;
+>module.exports = loop2 : any
+>module.exports : any
+>module : { "tests/cases/conformance/salsa/loop": any; }
+>exports : any
+>loop2 : any
+

tests/baselines/reference/booleanFilterAnyArray.js

@@ -0,0 +1,37 @@
+//// [booleanFilterAnyArray.ts]
+interface Bullean { }
+interface BulleanConstructor {
+    new(v1?: any): Bullean;
+    <T>(v2?: T): v2 is T;
+}
+
+interface Ari<T> {
+    filter<S extends T>(cb1: (value: T) => value is S): T extends any ? Ari<any> : Ari<S>;
+    filter(cb2: (value: T) => unknown): Ari<T>;
+}
+declare var Bullean: BulleanConstructor;
+declare let anys: Ari<any>;
+var xs: Ari<any>;
+var xs = anys.filter(Bullean)
+
+declare let realanys: any[];
+var ys: any[];
+var ys = realanys.filter(Boolean)
+
+var foo = [{ name: 'x' }]
+var foor: Array<{name: string}>
+var foor = foo.filter(x => x.name)
+var foos: Array<boolean>
+var foos = [true, true, false, null].filter((thing): thing is boolean => thing !== null)
+
+
+//// [booleanFilterAnyArray.js]
+var xs;
+var xs = anys.filter(Bullean);
+var ys;
+var ys = realanys.filter(Boolean);
+var foo = [{ name: 'x' }];
+var foor;
+var foor = foo.filter(function (x) { return x.name; });
+var foos;
+var foos = [true, true, false, null].filter(function (thing) { return thing !== null; });

tests/baselines/reference/booleanFilterAnyArray.symbols

@@ -0,0 +1,108 @@
+=== tests/cases/compiler/booleanFilterAnyArray.ts ===
+interface Bullean { }
+>Bullean : Symbol(Bullean, Decl(booleanFilterAnyArray.ts, 0, 0), Decl(booleanFilterAnyArray.ts, 10, 11))
+
+interface BulleanConstructor {
+>BulleanConstructor : Symbol(BulleanConstructor, Decl(booleanFilterAnyArray.ts, 0, 21))
+
+    new(v1?: any): Bullean;
+>v1 : Symbol(v1, Decl(booleanFilterAnyArray.ts, 2, 8))
+>Bullean : Symbol(Bullean, Decl(booleanFilterAnyArray.ts, 0, 0), Decl(booleanFilterAnyArray.ts, 10, 11))
+
+    <T>(v2?: T): v2 is T;
+>T : Symbol(T, Decl(booleanFilterAnyArray.ts, 3, 5))
+>v2 : Symbol(v2, Decl(booleanFilterAnyArray.ts, 3, 8))
+>T : Symbol(T, Decl(booleanFilterAnyArray.ts, 3, 5))
+>v2 : Symbol(v2, Decl(booleanFilterAnyArray.ts, 3, 8))
+>T : Symbol(T, Decl(booleanFilterAnyArray.ts, 3, 5))
+}
+
+interface Ari<T> {
+>Ari : Symbol(Ari, Decl(booleanFilterAnyArray.ts, 4, 1))
+>T : Symbol(T, Decl(booleanFilterAnyArray.ts, 6, 14))
+
+    filter<S extends T>(cb1: (value: T) => value is S): T extends any ? Ari<any> : Ari<S>;
+>filter : Symbol(Ari.filter, Decl(booleanFilterAnyArray.ts, 6, 18), Decl(booleanFilterAnyArray.ts, 7, 90))
+>S : Symbol(S, Decl(booleanFilterAnyArray.ts, 7, 11))
+>T : Symbol(T, Decl(booleanFilterAnyArray.ts, 6, 14))
+>cb1 : Symbol(cb1, Decl(booleanFilterAnyArray.ts, 7, 24))
+>value : Symbol(value, Decl(booleanFilterAnyArray.ts, 7, 30))
+>T : Symbol(T, Decl(booleanFilterAnyArray.ts, 6, 14))
+>value : Symbol(value, Decl(booleanFilterAnyArray.ts, 7, 30))
+>S : Symbol(S, Decl(booleanFilterAnyArray.ts, 7, 11))
+>T : Symbol(T, Decl(booleanFilterAnyArray.ts, 6, 14))
+>Ari : Symbol(Ari, Decl(booleanFilterAnyArray.ts, 4, 1))
+>Ari : Symbol(Ari, Decl(booleanFilterAnyArray.ts, 4, 1))
+>S : Symbol(S, Decl(booleanFilterAnyArray.ts, 7, 11))
+
+    filter(cb2: (value: T) => unknown): Ari<T>;
+>filter : Symbol(Ari.filter, Decl(booleanFilterAnyArray.ts, 6, 18), Decl(booleanFilterAnyArray.ts, 7, 90))
+>cb2 : Symbol(cb2, Decl(booleanFilterAnyArray.ts, 8, 11))
+>value : Symbol(value, Decl(booleanFilterAnyArray.ts, 8, 17))
+>T : Symbol(T, Decl(booleanFilterAnyArray.ts, 6, 14))
+>Ari : Symbol(Ari, Decl(booleanFilterAnyArray.ts, 4, 1))
+>T : Symbol(T, Decl(booleanFilterAnyArray.ts, 6, 14))
+}
+declare var Bullean: BulleanConstructor;
+>Bullean : Symbol(Bullean, Decl(booleanFilterAnyArray.ts, 0, 0), Decl(booleanFilterAnyArray.ts, 10, 11))
+>BulleanConstructor : Symbol(BulleanConstructor, Decl(booleanFilterAnyArray.ts, 0, 21))
+
+declare let anys: Ari<any>;
+>anys : Symbol(anys, Decl(booleanFilterAnyArray.ts, 11, 11))
+>Ari : Symbol(Ari, Decl(booleanFilterAnyArray.ts, 4, 1))
+
+var xs: Ari<any>;
+>xs : Symbol(xs, Decl(booleanFilterAnyArray.ts, 12, 3), Decl(booleanFilterAnyArray.ts, 13, 3))
+>Ari : Symbol(Ari, Decl(booleanFilterAnyArray.ts, 4, 1))
+
+var xs = anys.filter(Bullean)
+>xs : Symbol(xs, Decl(booleanFilterAnyArray.ts, 12, 3), Decl(booleanFilterAnyArray.ts, 13, 3))
+>anys.filter : Symbol(Ari.filter, Decl(booleanFilterAnyArray.ts, 6, 18), Decl(booleanFilterAnyArray.ts, 7, 90))
+>anys : Symbol(anys, Decl(booleanFilterAnyArray.ts, 11, 11))
+>filter : Symbol(Ari.filter, Decl(booleanFilterAnyArray.ts, 6, 18), Decl(booleanFilterAnyArray.ts, 7, 90))
+>Bullean : Symbol(Bullean, Decl(booleanFilterAnyArray.ts, 0, 0), Decl(booleanFilterAnyArray.ts, 10, 11))
+
+declare let realanys: any[];
+>realanys : Symbol(realanys, Decl(booleanFilterAnyArray.ts, 15, 11))
+
+var ys: any[];
+>ys : Symbol(ys, Decl(booleanFilterAnyArray.ts, 16, 3), Decl(booleanFilterAnyArray.ts, 17, 3))
+
+var ys = realanys.filter(Boolean)
+>ys : Symbol(ys, Decl(booleanFilterAnyArray.ts, 16, 3), Decl(booleanFilterAnyArray.ts, 17, 3))
+>realanys.filter : Symbol(Array.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>realanys : Symbol(realanys, Decl(booleanFilterAnyArray.ts, 15, 11))
+>filter : Symbol(Array.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>Boolean : Symbol(Boolean, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+var foo = [{ name: 'x' }]
+>foo : Symbol(foo, Decl(booleanFilterAnyArray.ts, 19, 3))
+>name : Symbol(name, Decl(booleanFilterAnyArray.ts, 19, 12))
+
+var foor: Array<{name: string}>
+>foor : Symbol(foor, Decl(booleanFilterAnyArray.ts, 20, 3), Decl(booleanFilterAnyArray.ts, 21, 3))
+>Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>name : Symbol(name, Decl(booleanFilterAnyArray.ts, 20, 17))
+
+var foor = foo.filter(x => x.name)
+>foor : Symbol(foor, Decl(booleanFilterAnyArray.ts, 20, 3), Decl(booleanFilterAnyArray.ts, 21, 3))
+>foo.filter : Symbol(Array.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>foo : Symbol(foo, Decl(booleanFilterAnyArray.ts, 19, 3))
+>filter : Symbol(Array.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>x : Symbol(x, Decl(booleanFilterAnyArray.ts, 21, 22))
+>x.name : Symbol(name, Decl(booleanFilterAnyArray.ts, 19, 12))
+>x : Symbol(x, Decl(booleanFilterAnyArray.ts, 21, 22))
+>name : Symbol(name, Decl(booleanFilterAnyArray.ts, 19, 12))
+
+var foos: Array<boolean>
+>foos : Symbol(foos, Decl(booleanFilterAnyArray.ts, 22, 3), Decl(booleanFilterAnyArray.ts, 23, 3))
+>Array : Symbol(Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+var foos = [true, true, false, null].filter((thing): thing is boolean => thing !== null)
+>foos : Symbol(foos, Decl(booleanFilterAnyArray.ts, 22, 3), Decl(booleanFilterAnyArray.ts, 23, 3))
+>[true, true, false, null].filter : Symbol(Array.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>filter : Symbol(Array.filter, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+>thing : Symbol(thing, Decl(booleanFilterAnyArray.ts, 23, 45))
+>thing : Symbol(thing, Decl(booleanFilterAnyArray.ts, 23, 45))
+>thing : Symbol(thing, Decl(booleanFilterAnyArray.ts, 23, 45))
+

tests/baselines/reference/booleanFilterAnyArray.types

@@ -0,0 +1,94 @@
+=== tests/cases/compiler/booleanFilterAnyArray.ts ===
+interface Bullean { }
+interface BulleanConstructor {
+    new(v1?: any): Bullean;
+>v1 : any
+
+    <T>(v2?: T): v2 is T;
+>v2 : T
+}
+
+interface Ari<T> {
+    filter<S extends T>(cb1: (value: T) => value is S): T extends any ? Ari<any> : Ari<S>;
+>filter : { <S extends T>(cb1: (value: T) => value is S): T extends any ? Ari<any> : Ari<S>; (cb2: (value: T) => unknown): Ari<T>; }
+>cb1 : (value: T) => value is S
+>value : T
+
+    filter(cb2: (value: T) => unknown): Ari<T>;
+>filter : { <S extends T>(cb1: (value: T) => value is S): T extends any ? Ari<any> : Ari<S>; (cb2: (value: T) => unknown): Ari<T>; }
+>cb2 : (value: T) => unknown
+>value : T
+}
+declare var Bullean: BulleanConstructor;
+>Bullean : BulleanConstructor
+
+declare let anys: Ari<any>;
+>anys : Ari<any>
+
+var xs: Ari<any>;
+>xs : Ari<any>
+
+var xs = anys.filter(Bullean)
+>xs : Ari<any>
+>anys.filter(Bullean) : Ari<any>
+>anys.filter : { <S extends any>(cb1: (value: any) => value is S): Ari<any>; (cb2: (value: any) => unknown): Ari<any>; }
+>anys : Ari<any>
+>filter : { <S extends any>(cb1: (value: any) => value is S): Ari<any>; (cb2: (value: any) => unknown): Ari<any>; }
+>Bullean : BulleanConstructor
+
+declare let realanys: any[];
+>realanys : any[]
+
+var ys: any[];
+>ys : any[]
+
+var ys = realanys.filter(Boolean)
+>ys : any[]
+>realanys.filter(Boolean) : any[]
+>realanys.filter : { <S extends any>(callbackfn: (value: any, index: number, array: any[]) => value is S, thisArg?: any): S[]; (callbackfn: (value: any, index: number, array: any[]) => unknown, thisArg?: any): any[]; }
+>realanys : any[]
+>filter : { <S extends any>(callbackfn: (value: any, index: number, array: any[]) => value is S, thisArg?: any): S[]; (callbackfn: (value: any, index: number, array: any[]) => unknown, thisArg?: any): any[]; }
+>Boolean : BooleanConstructor
+
+var foo = [{ name: 'x' }]
+>foo : { name: string; }[]
+>[{ name: 'x' }] : { name: string; }[]
+>{ name: 'x' } : { name: string; }
+>name : string
+>'x' : "x"
+
+var foor: Array<{name: string}>
+>foor : { name: string; }[]
+>name : string
+
+var foor = foo.filter(x => x.name)
+>foor : { name: string; }[]
+>foo.filter(x => x.name) : { name: string; }[]
+>foo.filter : { <S extends { name: string; }>(callbackfn: (value: { name: string; }, index: number, array: { name: string; }[]) => value is S, thisArg?: any): S[]; (callbackfn: (value: { name: string; }, index: number, array: { name: string; }[]) => unknown, thisArg?: any): { name: string; }[]; }
+>foo : { name: string; }[]
+>filter : { <S extends { name: string; }>(callbackfn: (value: { name: string; }, index: number, array: { name: string; }[]) => value is S, thisArg?: any): S[]; (callbackfn: (value: { name: string; }, index: number, array: { name: string; }[]) => unknown, thisArg?: any): { name: string; }[]; }
+>x => x.name : (x: { name: string; }) => string
+>x : { name: string; }
+>x.name : string
+>x : { name: string; }
+>name : string
+
+var foos: Array<boolean>
+>foos : boolean[]
+
+var foos = [true, true, false, null].filter((thing): thing is boolean => thing !== null)
+>foos : boolean[]
+>[true, true, false, null].filter((thing): thing is boolean => thing !== null) : boolean[]
+>[true, true, false, null].filter : { <S extends boolean>(callbackfn: (value: boolean, index: number, array: boolean[]) => value is S, thisArg?: any): S[]; (callbackfn: (value: boolean, index: number, array: boolean[]) => unknown, thisArg?: any): boolean[]; }
+>[true, true, false, null] : boolean[]
+>true : true
+>true : true
+>false : false
+>null : null
+>filter : { <S extends boolean>(callbackfn: (value: boolean, index: number, array: boolean[]) => value is S, thisArg?: any): S[]; (callbackfn: (value: boolean, index: number, array: boolean[]) => unknown, thisArg?: any): boolean[]; }
+>(thing): thing is boolean => thing !== null : (thing: boolean) => thing is boolean
+>thing : boolean
+>thing !== null : boolean
+>thing : boolean
+>null : null
+

tests/baselines/reference/castingTuple.errors.txt

@@ -71,6 +71,7 @@ tests/cases/conformance/types/tuple/castingTuple.ts(33,1): error TS2304: Cannot
     var array1 = <number[]>numStrTuple;
         ~~~~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'array1' must be of type '{}[]', but here has type 'number[]'.
+!!! related TS6203 tests/cases/conformance/types/tuple/castingTuple.ts:23:5: 'array1' was also declared here.
     t4[2] = 10;
     ~~
 !!! error TS2304: Cannot find name 't4'.

tests/baselines/reference/checkMergedGlobalUMDSymbol.errors.txt

@@ -15,6 +15,7 @@ tests/cases/compiler/global.d.ts(6,16): error TS2403: Subsequent variable declar
       export const THREE: typeof _three;
                    ~~~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'THREE' must be of type 'typeof import("tests/cases/compiler/global")', but here has type 'typeof import("tests/cases/compiler/three")'.
+!!! related TS6203 tests/cases/compiler/global.d.ts:1:1: 'THREE' was also declared here.
     }
     
 ==== tests/cases/compiler/test.ts (0 errors) ====

tests/baselines/reference/classWithDuplicateIdentifier.errors.txt

@@ -14,6 +14,7 @@ tests/cases/compiler/classWithDuplicateIdentifier.ts(11,5): error TS2717: Subseq
 !!! error TS2300: Duplicate identifier 'a'.
         ~
 !!! error TS2717: Subsequent property declarations must have the same type.  Property 'a' must be of type '() => number', but here has type 'number'.
+!!! related TS6203 tests/cases/compiler/classWithDuplicateIdentifier.ts:2:5: 'a' was also declared here.
     }
     class K {
         b: number; // error: duplicate identifier
@@ -30,5 +31,6 @@ tests/cases/compiler/classWithDuplicateIdentifier.ts(11,5): error TS2717: Subseq
 !!! error TS2300: Duplicate identifier 'c'.
         ~
 !!! error TS2717: Subsequent property declarations must have the same type.  Property 'c' must be of type 'number', but here has type 'string'.
+!!! related TS6203 tests/cases/compiler/classWithDuplicateIdentifier.ts:10:5: 'c' was also declared here.
     }
     

tests/baselines/reference/commonJsIsolatedModules.js

@@ -0,0 +1,8 @@
+//// [index.js]
+module.exports = {}
+var x = 1
+
+
+//// [index.js]
+module.exports = {};
+var x = 1;

tests/baselines/reference/commonJsIsolatedModules.symbols

@@ -0,0 +1,9 @@
+=== tests/cases/compiler/index.js ===
+module.exports = {}
+>module.exports : Symbol("tests/cases/compiler/index", Decl(index.js, 0, 0))
+>module : Symbol(module, Decl(index.js, 0, 0))
+>exports : Symbol("tests/cases/compiler/index", Decl(index.js, 0, 0))
+
+var x = 1
+>x : Symbol(x, Decl(index.js, 1, 3))
+

tests/baselines/reference/commonJsIsolatedModules.types

@@ -0,0 +1,12 @@
+=== tests/cases/compiler/index.js ===
+module.exports = {}
+>module.exports = {} : typeof import("tests/cases/compiler/index")
+>module.exports : typeof import("tests/cases/compiler/index")
+>module : { "tests/cases/compiler/index": typeof import("tests/cases/compiler/index"); }
+>exports : typeof import("tests/cases/compiler/index")
+>{} : {}
+
+var x = 1
+>x : number
+>1 : 1
+

tests/baselines/reference/conditionalTypes1.errors.txt

@@ -391,6 +391,7 @@ tests/cases/conformance/types/conditional/conditionalTypes1.ts(288,43): error TS
         var z: T2;  // Error, T2 is distributive, T1 isn't
             ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'z' must be of type 'T1', but here has type 'Foo<T & U>'.
+!!! related TS6203 tests/cases/conformance/types/conditional/conditionalTypes1.ts:262:9: 'z' was also declared here.
     }
     
     function f33<T, U>() {

tests/baselines/reference/declarationsAndAssignments.errors.txt

@@ -97,6 +97,7 @@ tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts(138,9):
         var y: string;
             ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'y' must be of type 'string | number', but here has type 'string'.
+!!! related TS6203 tests/cases/conformance/es6/destructuring/declarationsAndAssignments.ts:56:17: 'y' was also declared here.
     }
     
     function f8() {

tests/baselines/reference/duplicateClassElements.errors.txt

@@ -97,6 +97,7 @@ tests/cases/compiler/duplicateClassElements.ts(41,12): error TS2300: Duplicate i
 !!! error TS2300: Duplicate identifier 'x2'.
                ~~
 !!! error TS2717: Subsequent property declarations must have the same type.  Property 'x2' must be of type 'number', but here has type 'any'.
+!!! related TS6203 tests/cases/compiler/duplicateClassElements.ts:29:9: 'x2' was also declared here.
     
         get z2() {
             ~~

tests/baselines/reference/duplicateIdentifierInCatchBlock.errors.txt

@@ -38,4 +38,5 @@ tests/cases/compiler/duplicateIdentifierInCatchBlock.ts(16,9): error TS2403: Sub
         var p: number; // error
             ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'p' must be of type 'string', but here has type 'number'.
+!!! related TS6203 tests/cases/compiler/duplicateIdentifierInCatchBlock.ts:15:9: 'p' was also declared here.
     }

tests/baselines/reference/duplicateLocalVariable1.errors.txt

@@ -201,6 +201,7 @@ tests/cases/compiler/duplicateLocalVariable1.ts(186,37): error TS2356: An arithm
                 for (var i = 0; i < 14; i++) {
                          ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'i' must be of type 'string', but here has type 'number'.
+!!! related TS6203 tests/cases/compiler/duplicateLocalVariable1.ts:181:22: 'i' was also declared here.
                                 ~~~~~~
 !!! error TS2365: Operator '<' cannot be applied to types 'string' and 'number'.
                                         ~

tests/baselines/reference/duplicateLocalVariable2.errors.txt

@@ -33,6 +33,7 @@ tests/cases/compiler/duplicateLocalVariable2.ts(27,37): error TS2356: An arithme
                 for (var i = 0; i < 14; i++) {
                          ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'i' must be of type 'string', but here has type 'number'.
+!!! related TS6203 tests/cases/compiler/duplicateLocalVariable2.ts:22:22: 'i' was also declared here.
                                 ~~~~~~
 !!! error TS2365: Operator '<' cannot be applied to types 'string' and 'number'.
                                         ~

tests/baselines/reference/duplicateLocalVariable3.errors.txt

@@ -15,4 +15,5 @@ tests/cases/compiler/duplicateLocalVariable3.ts(11,9): error TS2403: Subsequent
         var z = "";
             ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'z' must be of type 'number', but here has type 'string'.
+!!! related TS6203 tests/cases/compiler/duplicateLocalVariable3.ts:10:9: 'z' was also declared here.
     }

tests/baselines/reference/duplicateLocalVariable4.errors.txt

@@ -9,4 +9,5 @@ tests/cases/compiler/duplicateLocalVariable4.ts(6,5): error TS2403: Subsequent v
     var x = E;
     var x = E.a;
         ~
-!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'typeof E', but here has type 'E'.
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'typeof E', but here has type 'E'.
+!!! related TS6203 tests/cases/compiler/duplicateLocalVariable4.ts:5:5: 'x' was also declared here.

tests/baselines/reference/duplicatePackage_relativeImportWithinPackage.trace.json

@@ -2,13 +2,13 @@
     "======== Resolving module 'foo/use' from '/index.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module 'foo/use' from 'node_modules' folder, target file type 'TypeScript'.",
+    "Found 'package.json' at '/node_modules/foo/package.json'.",
     "'package.json' does not have a 'typesVersions' field.",
-    "Found 'package.json' at '/node_modules/foo/package.json'. Package ID is 'foo/use/index.d.ts@1.2.3'.",
     "File '/node_modules/foo/use.ts' does not exist.",
     "File '/node_modules/foo/use.tsx' does not exist.",
     "File '/node_modules/foo/use.d.ts' exist - use it as a name resolution result.",
     "Resolving real path for '/node_modules/foo/use.d.ts', result '/node_modules/foo/use.d.ts'.",
-    "======== Module name 'foo/use' was successfully resolved to '/node_modules/foo/use.d.ts'. ========",
+    "======== Module name 'foo/use' was successfully resolved to '/node_modules/foo/use.d.ts' with Package ID 'foo/use.d.ts@1.2.3'. ========",
     "======== Resolving module 'a' from '/index.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module 'a' from 'node_modules' folder, target file type 'TypeScript'.",
@@ -27,17 +27,14 @@
     "File '/node_modules/foo/index.ts' does not exist.",
     "File '/node_modules/foo/index.tsx' does not exist.",
     "File '/node_modules/foo/index.d.ts' exist - use it as a name resolution result.",
+    "Found 'package.json' at '/node_modules/foo/package.json'.",
     "'package.json' does not have a 'typesVersions' field.",
-    "Found 'package.json' at '/node_modules/foo/package.json'. Package ID is 'foo/index.d.ts@1.2.3'.",
-    "======== Module name './index' was successfully resolved to '/node_modules/foo/index.d.ts'. ========",
+    "======== Module name './index' was successfully resolved to '/node_modules/foo/index.d.ts' with Package ID 'foo/index.d.ts@1.2.3'. ========",
     "======== Resolving module 'foo' from '/node_modules/a/index.d.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module 'foo' from 'node_modules' folder, target file type 'TypeScript'.",
-    "'package.json' does not have a 'typings' field.",
-    "'package.json' does not have a 'types' field.",
-    "'package.json' does not have a 'main' field.",
+    "Found 'package.json' at '/node_modules/a/node_modules/foo/package.json'.",
     "'package.json' does not have a 'typesVersions' field.",
-    "Found 'package.json' at '/node_modules/a/node_modules/foo/package.json'. Package ID is 'foo/index.d.ts@1.2.3'.",
     "File '/node_modules/a/node_modules/foo.ts' does not exist.",
     "File '/node_modules/a/node_modules/foo.tsx' does not exist.",
     "File '/node_modules/a/node_modules/foo.d.ts' does not exist.",
@@ -48,5 +45,5 @@
     "File '/node_modules/a/node_modules/foo/index.tsx' does not exist.",
     "File '/node_modules/a/node_modules/foo/index.d.ts' exist - use it as a name resolution result.",
     "Resolving real path for '/node_modules/a/node_modules/foo/index.d.ts', result '/node_modules/a/node_modules/foo/index.d.ts'.",
-    "======== Module name 'foo' was successfully resolved to '/node_modules/a/node_modules/foo/index.d.ts'. ========"
+    "======== Module name 'foo' was successfully resolved to '/node_modules/a/node_modules/foo/index.d.ts' with Package ID 'foo/index.d.ts@1.2.3'. ========"
 ]

tests/baselines/reference/duplicatePackage_relativeImportWithinPackage_scoped.trace.json

@@ -2,13 +2,13 @@
     "======== Resolving module '@foo/bar/use' from '/index.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module '@foo/bar/use' from 'node_modules' folder, target file type 'TypeScript'.",
+    "Found 'package.json' at '/node_modules/@foo/bar/package.json'.",
     "'package.json' does not have a 'typesVersions' field.",
-    "Found 'package.json' at '/node_modules/@foo/bar/package.json'. Package ID is '@foo/bar/use/index.d.ts@1.2.3'.",
     "File '/node_modules/@foo/bar/use.ts' does not exist.",
     "File '/node_modules/@foo/bar/use.tsx' does not exist.",
     "File '/node_modules/@foo/bar/use.d.ts' exist - use it as a name resolution result.",
     "Resolving real path for '/node_modules/@foo/bar/use.d.ts', result '/node_modules/@foo/bar/use.d.ts'.",
-    "======== Module name '@foo/bar/use' was successfully resolved to '/node_modules/@foo/bar/use.d.ts'. ========",
+    "======== Module name '@foo/bar/use' was successfully resolved to '/node_modules/@foo/bar/use.d.ts' with Package ID '@foo/bar/use.d.ts@1.2.3'. ========",
     "======== Resolving module 'a' from '/index.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module 'a' from 'node_modules' folder, target file type 'TypeScript'.",
@@ -27,17 +27,14 @@
     "File '/node_modules/@foo/bar/index.ts' does not exist.",
     "File '/node_modules/@foo/bar/index.tsx' does not exist.",
     "File '/node_modules/@foo/bar/index.d.ts' exist - use it as a name resolution result.",
+    "Found 'package.json' at '/node_modules/@foo/bar/package.json'.",
     "'package.json' does not have a 'typesVersions' field.",
-    "Found 'package.json' at '/node_modules/@foo/bar/package.json'. Package ID is '@foo/bar/index.d.ts@1.2.3'.",
-    "======== Module name './index' was successfully resolved to '/node_modules/@foo/bar/index.d.ts'. ========",
+    "======== Module name './index' was successfully resolved to '/node_modules/@foo/bar/index.d.ts' with Package ID '@foo/bar/index.d.ts@1.2.3'. ========",
     "======== Resolving module '@foo/bar' from '/node_modules/a/index.d.ts'. ========",
     "Module resolution kind is not specified, using 'NodeJs'.",
     "Loading module '@foo/bar' from 'node_modules' folder, target file type 'TypeScript'.",
-    "'package.json' does not have a 'typings' field.",
-    "'package.json' does not have a 'types' field.",
-    "'package.json' does not have a 'main' field.",
+    "Found 'package.json' at '/node_modules/a/node_modules/@foo/bar/package.json'.",
     "'package.json' does not have a 'typesVersions' field.",
-    "Found 'package.json' at '/node_modules/a/node_modules/@foo/bar/package.json'. Package ID is '@foo/bar/index.d.ts@1.2.3'.",
     "File '/node_modules/a/node_modules/@foo/bar.ts' does not exist.",
     "File '/node_modules/a/node_modules/@foo/bar.tsx' does not exist.",
     "File '/node_modules/a/node_modules/@foo/bar.d.ts' does not exist.",
@@ -48,5 +45,5 @@
     "File '/node_modules/a/node_modules/@foo/bar/index.tsx' does not exist.",
     "File '/node_modules/a/node_modules/@foo/bar/index.d.ts' exist - use it as a name resolution result.",
     "Resolving real path for '/node_modules/a/node_modules/@foo/bar/index.d.ts', result '/node_modules/a/node_modules/@foo/bar/index.d.ts'.",
-    "======== Module name '@foo/bar' was successfully resolved to '/node_modules/a/node_modules/@foo/bar/index.d.ts'. ========"
+    "======== Module name '@foo/bar' was successfully resolved to '/node_modules/a/node_modules/@foo/bar/index.d.ts' with Package ID '@foo/bar/index.d.ts@1.2.3'. ========"
 ]

tests/baselines/reference/duplicateVariablesWithAny.errors.txt

@@ -10,22 +10,26 @@ tests/cases/compiler/duplicateVariablesWithAny.ts(13,9): error TS2403: Subsequen
     var x = 2; //error
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'any', but here has type 'number'.
+!!! related TS6203 tests/cases/compiler/duplicateVariablesWithAny.ts:2:5: 'x' was also declared here.
     
     var y = "";
     var y; //error
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'y' must be of type 'string', but here has type 'any'.
+!!! related TS6203 tests/cases/compiler/duplicateVariablesWithAny.ts:5:5: 'y' was also declared here.
     
     module N {
         var x: any;
         var x = 2; //error
             ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'any', but here has type 'number'.
+!!! related TS6203 tests/cases/compiler/duplicateVariablesWithAny.ts:9:9: 'x' was also declared here.
     
         var y = "";
         var y; //error
             ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'y' must be of type 'string', but here has type 'any'.
+!!! related TS6203 tests/cases/compiler/duplicateVariablesWithAny.ts:12:9: 'y' was also declared here.
     }
     
     var z: any;

tests/baselines/reference/duplicateVarsAcrossFileBoundaries.errors.txt

@@ -12,18 +12,22 @@ tests/cases/compiler/duplicateVarsAcrossFileBoundaries_2.ts(3,5): error TS2403:
     var x = true;
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'number', but here has type 'boolean'.
+!!! related TS6203 tests/cases/compiler/duplicateVarsAcrossFileBoundaries_0.ts:1:5: 'x' was also declared here.
     var z = 3;
     
 ==== tests/cases/compiler/duplicateVarsAcrossFileBoundaries_2.ts (3 errors) ====
     var x = "";
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'number', but here has type 'string'.
+!!! related TS6203 tests/cases/compiler/duplicateVarsAcrossFileBoundaries_0.ts:1:5: 'x' was also declared here.
     var y = 3;
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'y' must be of type 'string', but here has type 'number'.
+!!! related TS6203 tests/cases/compiler/duplicateVarsAcrossFileBoundaries_0.ts:2:5: 'y' was also declared here.
     var z = false;
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'z' must be of type 'number', but here has type 'boolean'.
+!!! related TS6203 tests/cases/compiler/duplicateVarsAcrossFileBoundaries_1.ts:2:5: 'z' was also declared here.
     
 ==== tests/cases/compiler/duplicateVarsAcrossFileBoundaries_3.ts (0 errors) ====
     var x = 0;

tests/baselines/reference/dynamicNamesErrors.errors.txt

@@ -35,6 +35,7 @@ tests/cases/compiler/dynamicNamesErrors.ts(25,1): error TS2322: Type 'T1' is not
         [c1]: string;
         ~~~~
 !!! error TS2717: Subsequent property declarations must have the same type.  Property '[c1]' must be of type 'number', but here has type 'string'.
+!!! related TS6203 tests/cases/compiler/dynamicNamesErrors.ts:18:5: '[c1]' was also declared here.
     }
     
     let t1: T1;

tests/baselines/reference/enumAssignabilityInInheritance.errors.txt

@@ -109,10 +109,12 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssi
     var r4 = foo16(E.A);
         ~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'r4' must be of type 'E', but here has type 'Object'.
+!!! related TS6203 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignabilityInInheritance.ts:22:5: 'r4' was also declared here.
     
     declare function foo17(x: {}): {};
     declare function foo17(x: E): E;
     
     var r4 = foo16(E.A);
         ~~
-!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'r4' must be of type 'E', but here has type 'Object'.
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'r4' must be of type 'E', but here has type 'Object'.
+!!! related TS6203 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/enumAssignabilityInInheritance.ts:22:5: 'r4' was also declared here.

tests/baselines/reference/for-inStatements.errors.txt

@@ -39,6 +39,7 @@ tests/cases/conformance/statements/for-inStatements/for-inStatements.ts(79,15):
             for (var x in this) { }
                      ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'string', but here has type 'Extract<keyof this, string>'.
+!!! related TS6203 tests/cases/conformance/statements/for-inStatements/for-inStatements.ts:31:18: 'x' was also declared here.
             return null;
         }
     
@@ -58,6 +59,7 @@ tests/cases/conformance/statements/for-inStatements/for-inStatements.ts(79,15):
             for (var x in this) { }
                      ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'string', but here has type 'Extract<keyof this, string>'.
+!!! related TS6203 tests/cases/conformance/statements/for-inStatements/for-inStatements.ts:48:18: 'x' was also declared here.
     
             for (var x in super.biz) { }
             for (var x in super.biz()) { }

tests/baselines/reference/for-inStatementsArrayErrors.errors.txt

@@ -29,11 +29,13 @@ tests/cases/conformance/statements/for-inStatements/for-inStatementsArrayErrors.
     for (var i in a ) {
              ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'i' must be of type 'number', but here has type 'string'.
+!!! related TS6203 tests/cases/conformance/statements/for-inStatements/for-inStatementsArrayErrors.ts:11:5: 'i' was also declared here.
     }
     
     var j: any;
     for (var j in a ) {
              ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'j' must be of type 'any', but here has type 'string'.
+!!! related TS6203 tests/cases/conformance/statements/for-inStatements/for-inStatementsArrayErrors.ts:15:5: 'j' was also declared here.
     }
     

tests/baselines/reference/for-inStatementsInvalid.errors.txt

@@ -73,6 +73,7 @@ tests/cases/conformance/statements/for-inStatements/for-inStatementsInvalid.ts(6
             for (var x in this) { }
                      ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'string', but here has type 'Extract<keyof this, string>'.
+!!! related TS6203 tests/cases/conformance/statements/for-inStatements/for-inStatementsInvalid.ts:29:18: 'x' was also declared here.
             return null;
         }
     
@@ -96,6 +97,7 @@ tests/cases/conformance/statements/for-inStatements/for-inStatementsInvalid.ts(6
             for (var x in this) { }
                      ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'string', but here has type 'Extract<keyof this, string>'.
+!!! related TS6203 tests/cases/conformance/statements/for-inStatements/for-inStatementsInvalid.ts:46:18: 'x' was also declared here.
     
             for (var x in super.biz) { }
             for (var x in super.biz()) { }

tests/baselines/reference/forStatementsMultipleInvalidDecl.errors.txt

@@ -47,46 +47,58 @@ tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDec
     for( var a = 1;;){}
              ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'a' must be of type 'any', but here has type 'number'.
+!!! related TS6203 tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDecl.ts:31:10: 'a' was also declared here.
     for( var a = 'a string';;){}
              ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'a' must be of type 'any', but here has type 'string'.
+!!! related TS6203 tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDecl.ts:31:10: 'a' was also declared here.
     for( var a = new C();;){}
              ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'a' must be of type 'any', but here has type 'C'.
+!!! related TS6203 tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDecl.ts:31:10: 'a' was also declared here.
     for( var a = new D<string>();;){}
              ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'a' must be of type 'any', but here has type 'D<string>'.
+!!! related TS6203 tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDecl.ts:31:10: 'a' was also declared here.
     for( var a = M;;){}
              ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'a' must be of type 'any', but here has type 'typeof M'.
+!!! related TS6203 tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDecl.ts:31:10: 'a' was also declared here.
     
     for( var b: I;;){}
     for( var b = new C();;){}
              ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'b' must be of type 'I', but here has type 'C'.
+!!! related TS6203 tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDecl.ts:38:10: 'b' was also declared here.
     for( var b = new C2();;){}
              ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'b' must be of type 'I', but here has type 'C2'.
+!!! related TS6203 tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDecl.ts:38:10: 'b' was also declared here.
     
     for(var f = F;;){}
     for( var f = (x: number) => '';;){}
              ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'f' must be of type '(x: string) => number', but here has type '(x: number) => string'.
+!!! related TS6203 tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDecl.ts:42:9: 'f' was also declared here.
     
     for(var arr: string[];;){}
     for( var arr = [1, 2, 3, 4];;){}
              ~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'arr' must be of type 'string[]', but here has type 'number[]'.
+!!! related TS6203 tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDecl.ts:45:9: 'arr' was also declared here.
     for( var arr = [new C(), new C2(), new D<string>()];;){}
              ~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'arr' must be of type 'string[]', but here has type '(C | D<string>)[]'.
+!!! related TS6203 tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDecl.ts:45:9: 'arr' was also declared here.
     
     for(var arr2 = [new D<string>()];;){}
     for( var arr2 = new Array<D<number>>();;){}
              ~~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'arr2' must be of type 'D<string>[]', but here has type 'D<number>[]'.
+!!! related TS6203 tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDecl.ts:49:9: 'arr2' was also declared here.
     
     for(var m: typeof M;;){}
     for( var m = M.A;;){}
              ~
-!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'm' must be of type 'typeof M', but here has type 'typeof A'.
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'm' must be of type 'typeof M', but here has type 'typeof A'.
+!!! related TS6203 tests/cases/conformance/statements/forStatements/forStatementsMultipleInvalidDecl.ts:52:9: 'm' was also declared here.

tests/baselines/reference/functionArgShadowing.errors.txt

@@ -10,6 +10,7 @@ tests/cases/compiler/functionArgShadowing.ts(10,7): error TS2403: Subsequent var
        var x: B = new B();
            ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'A', but here has type 'B'.
+!!! related TS6203 tests/cases/compiler/functionArgShadowing.ts:3:14: 'x' was also declared here.
          x.bar(); // the property bar does not exist on a value of type A
            ~~~
 !!! error TS2339: Property 'bar' does not exist on type 'A'.
@@ -20,6 +21,7 @@ tests/cases/compiler/functionArgShadowing.ts(10,7): error TS2403: Subsequent var
     		var p: string;
     		    ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'p' must be of type 'number', but here has type 'string'.
+!!! related TS6203 tests/cases/compiler/functionArgShadowing.ts:9:14: 'p' was also declared here.
     
     		var n: number = p;
     	}

tests/baselines/reference/gettersAndSettersErrors.errors.txt

@@ -24,6 +24,7 @@ tests/cases/compiler/gettersAndSettersErrors.ts(12,16): error TS2379: Getter and
 !!! error TS2300: Duplicate identifier 'Foo'.
                ~~~
 !!! error TS2717: Subsequent property declarations must have the same type.  Property 'Foo' must be of type 'string', but here has type 'number'.
+!!! related TS6203 tests/cases/compiler/gettersAndSettersErrors.ts:2:16: 'Foo' was also declared here.
         public get Goo(v:string):string {return null;} // error - getters must not have a parameter
                    ~~~
 !!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.

tests/baselines/reference/identityForSignaturesWithTypeParametersAndAny.errors.txt

@@ -12,18 +12,22 @@ tests/cases/compiler/identityForSignaturesWithTypeParametersAndAny.ts(14,5): err
     var g: <T>(x: any, y: any) => any;
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'g' must be of type '<T, U>(x: T, y: U) => T', but here has type '<T>(x: any, y: any) => any'.
+!!! related TS6203 tests/cases/compiler/identityForSignaturesWithTypeParametersAndAny.ts:4:5: 'g' was also declared here.
     
     var h: <T, U>(x: T, y: U) => T;
     var h: (x: any, y: any) => any;
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'h' must be of type '<T, U>(x: T, y: U) => T', but here has type '(x: any, y: any) => any'.
+!!! related TS6203 tests/cases/compiler/identityForSignaturesWithTypeParametersAndAny.ts:7:5: 'h' was also declared here.
     
     var i: <T, U>(x: T, y: U) => T;
     var i: <T, U>(x: any, y: string) => any;
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'i' must be of type '<T, U>(x: T, y: U) => T', but here has type '<T, U>(x: any, y: string) => any'.
+!!! related TS6203 tests/cases/compiler/identityForSignaturesWithTypeParametersAndAny.ts:10:5: 'i' was also declared here.
     
     var j: <T, U>(x: T, y: U) => T;
     var j: <T, U>(x: any, y: any) => string;
         ~
-!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'j' must be of type '<T, U>(x: T, y: U) => T', but here has type '<T, U>(x: any, y: any) => string'.
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'j' must be of type '<T, U>(x: T, y: U) => T', but here has type '<T, U>(x: any, y: any) => string'.
+!!! related TS6203 tests/cases/compiler/identityForSignaturesWithTypeParametersAndAny.ts:13:5: 'j' was also declared here.

tests/baselines/reference/importHelpersInIsolatedModules.errors.txt

@@ -1,4 +1,4 @@
-tests/cases/compiler/script.ts(1,1): error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+tests/cases/compiler/script.ts(1,1): error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
 
 
 ==== tests/cases/compiler/external.ts (0 errors) ====
@@ -16,7 +16,7 @@ tests/cases/compiler/script.ts(1,1): error TS1208: Cannot compile namespaces whe
 ==== tests/cases/compiler/script.ts (1 errors) ====
     class A { }
     ~~~~~
-!!! error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+!!! error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
     class B extends A { }
     
     declare var dec: any;

tests/baselines/reference/instanceMemberWithComputedPropertyName.js

@@ -0,0 +1,22 @@
+//// [instanceMemberWithComputedPropertyName.ts]
+// https://github.com/microsoft/TypeScript/issues/30953
+const x = 1;
+class C {
+    [x] = true;
+    constructor() {
+        const { a, b } = { a: 1, b: 2 };
+    }
+}
+
+//// [instanceMemberWithComputedPropertyName.js]
+var _a;
+// https://github.com/microsoft/TypeScript/issues/30953
+var x = 1;
+var C = /** @class */ (function () {
+    function C() {
+        this[_a] = true;
+        var _b = { a: 1, b: 2 }, a = _b.a, b = _b.b;
+    }
+    return C;
+}());
+_a = x;

tests/baselines/reference/instanceMemberWithComputedPropertyName.symbols

@@ -0,0 +1,20 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/instanceMemberWithComputedPropertyName.ts ===
+// https://github.com/microsoft/TypeScript/issues/30953
+const x = 1;
+>x : Symbol(x, Decl(instanceMemberWithComputedPropertyName.ts, 1, 5))
+
+class C {
+>C : Symbol(C, Decl(instanceMemberWithComputedPropertyName.ts, 1, 12))
+
+    [x] = true;
+>[x] : Symbol(C[x], Decl(instanceMemberWithComputedPropertyName.ts, 2, 9))
+>x : Symbol(x, Decl(instanceMemberWithComputedPropertyName.ts, 1, 5))
+
+    constructor() {
+        const { a, b } = { a: 1, b: 2 };
+>a : Symbol(a, Decl(instanceMemberWithComputedPropertyName.ts, 5, 15))
+>b : Symbol(b, Decl(instanceMemberWithComputedPropertyName.ts, 5, 18))
+>a : Symbol(a, Decl(instanceMemberWithComputedPropertyName.ts, 5, 26))
+>b : Symbol(b, Decl(instanceMemberWithComputedPropertyName.ts, 5, 32))
+    }
+}

tests/baselines/reference/instanceMemberWithComputedPropertyName.types

@@ -0,0 +1,25 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/instanceMemberWithComputedPropertyName.ts ===
+// https://github.com/microsoft/TypeScript/issues/30953
+const x = 1;
+>x : 1
+>1 : 1
+
+class C {
+>C : C
+
+    [x] = true;
+>[x] : boolean
+>x : 1
+>true : true
+
+    constructor() {
+        const { a, b } = { a: 1, b: 2 };
+>a : number
+>b : number
+>{ a: 1, b: 2 } : { a: number; b: number; }
+>a : number
+>1 : 1
+>b : number
+>2 : 2
+    }
+}

tests/baselines/reference/interfaceDeclaration1.errors.txt

@@ -30,6 +30,7 @@ tests/cases/compiler/interfaceDeclaration1.ts(52,11): error TS2320: Interface 'i
 !!! error TS2300: Duplicate identifier 'item'.
         ~~~~
 !!! error TS2717: Subsequent property declarations must have the same type.  Property 'item' must be of type 'any', but here has type 'number'.
+!!! related TS6203 tests/cases/compiler/interfaceDeclaration1.ts:7:5: 'item' was also declared here.
     }
     
     interface I3 {

tests/baselines/reference/intersectionsOfLargeUnions2.errors.txt

@@ -10,7 +10,7 @@ tests/cases/compiler/intersectionsOfLargeUnions2.ts(31,15): error TS2536: Type '
         interface ElementTagNameMap {
                   ~~~~~~~~~~~~~~~~~
 !!! error TS2300: Duplicate identifier 'ElementTagNameMap'.
-!!! related TS6203 /.ts/lib.dom.d.ts:18109:6: 'ElementTagNameMap' was also declared here.
+!!! related TS6203 /.ts/lib.dom.d.ts:18110:6: 'ElementTagNameMap' was also declared here.
             [index: number]: HTMLElement
         }
     

tests/baselines/reference/invalidMultipleVariableDeclarations.errors.txt

@@ -47,46 +47,58 @@ tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDec
     var a = 1;
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'a' must be of type 'any', but here has type 'number'.
+!!! related TS6203 tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDeclarations.ts:31:5: 'a' was also declared here.
     var a = 'a string';
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'a' must be of type 'any', but here has type 'string'.
+!!! related TS6203 tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDeclarations.ts:31:5: 'a' was also declared here.
     var a = new C();
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'a' must be of type 'any', but here has type 'C'.
+!!! related TS6203 tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDeclarations.ts:31:5: 'a' was also declared here.
     var a = new D<string>();
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'a' must be of type 'any', but here has type 'D<string>'.
+!!! related TS6203 tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDeclarations.ts:31:5: 'a' was also declared here.
     var a = M;
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'a' must be of type 'any', but here has type 'typeof M'.
+!!! related TS6203 tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDeclarations.ts:31:5: 'a' was also declared here.
     
     var b: I;
     var b = new C();
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'b' must be of type 'I', but here has type 'C'.
+!!! related TS6203 tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDeclarations.ts:38:5: 'b' was also declared here.
     var b = new C2();
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'b' must be of type 'I', but here has type 'C2'.
+!!! related TS6203 tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDeclarations.ts:38:5: 'b' was also declared here.
     
     var f = F;
     var f = (x: number) => '';
         ~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'f' must be of type '(x: string) => number', but here has type '(x: number) => string'.
+!!! related TS6203 tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDeclarations.ts:42:5: 'f' was also declared here.
     
     var arr: string[];
     var arr = [1, 2, 3, 4];
         ~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'arr' must be of type 'string[]', but here has type 'number[]'.
+!!! related TS6203 tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDeclarations.ts:45:5: 'arr' was also declared here.
     var arr = [new C(), new C2(), new D<string>()];
         ~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'arr' must be of type 'string[]', but here has type '(C | D<string>)[]'.
+!!! related TS6203 tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDeclarations.ts:45:5: 'arr' was also declared here.
     
     var arr2 = [new D<string>()];
     var arr2 = new Array<D<number>>();
         ~~~~
 !!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'arr2' must be of type 'D<string>[]', but here has type 'D<number>[]'.
+!!! related TS6203 tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDeclarations.ts:49:5: 'arr2' was also declared here.
     
     var m: typeof M;
     var m = M.A;
         ~
-!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'm' must be of type 'typeof M', but here has type 'typeof A'.
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'm' must be of type 'typeof M', but here has type 'typeof A'.
+!!! related TS6203 tests/cases/conformance/statements/VariableStatements/invalidMultipleVariableDeclarations.ts:52:5: 'm' was also declared here.

tests/baselines/reference/isolatedModulesNoExternalModule.errors.txt

@@ -1,7 +1,7 @@
-tests/cases/compiler/file1.ts(1,1): error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+tests/cases/compiler/file1.ts(1,1): error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
 
 
 ==== tests/cases/compiler/file1.ts (1 errors) ====
     var x;
     ~~~
-!!! error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+!!! error TS1208: All files must be modules when the '--isolatedModules' flag is provided.

tests/baselines/reference/isolatedModulesOut.errors.txt

@@ -1,6 +1,6 @@
 error TS5053: Option 'out' cannot be specified with option 'isolatedModules'.
 tests/cases/compiler/file1.ts(1,1): error TS6131: Cannot compile modules using option 'out' unless the '--module' flag is 'amd' or 'system'.
-tests/cases/compiler/file2.ts(1,1): error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+tests/cases/compiler/file2.ts(1,1): error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
 
 
 !!! error TS5053: Option 'out' cannot be specified with option 'isolatedModules'.
@@ -11,4 +11,4 @@ tests/cases/compiler/file2.ts(1,1): error TS1208: Cannot compile namespaces when
 ==== tests/cases/compiler/file2.ts (1 errors) ====
     var y;
     ~~~
-!!! error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+!!! error TS1208: All files must be modules when the '--isolatedModules' flag is provided.

tests/baselines/reference/isolatedModulesPlainFile-AMD.errors.txt

@@ -1,9 +1,9 @@
-tests/cases/compiler/isolatedModulesPlainFile-AMD.ts(1,1): error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+tests/cases/compiler/isolatedModulesPlainFile-AMD.ts(1,1): error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
 
 
 ==== tests/cases/compiler/isolatedModulesPlainFile-AMD.ts (1 errors) ====
     declare function run(a: number): void;
     ~~~~~~~
-!!! error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+!!! error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
     run(1);
     

tests/baselines/reference/isolatedModulesPlainFile-CommonJS.errors.txt

@@ -1,9 +1,9 @@
-tests/cases/compiler/isolatedModulesPlainFile-CommonJS.ts(1,1): error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+tests/cases/compiler/isolatedModulesPlainFile-CommonJS.ts(1,1): error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
 
 
 ==== tests/cases/compiler/isolatedModulesPlainFile-CommonJS.ts (1 errors) ====
     declare function run(a: number): void;
     ~~~~~~~
-!!! error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+!!! error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
     run(1);
     

tests/baselines/reference/isolatedModulesPlainFile-ES6.errors.txt

@@ -1,9 +1,9 @@
-tests/cases/compiler/isolatedModulesPlainFile-ES6.ts(1,1): error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+tests/cases/compiler/isolatedModulesPlainFile-ES6.ts(1,1): error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
 
 
 ==== tests/cases/compiler/isolatedModulesPlainFile-ES6.ts (1 errors) ====
     declare function run(a: number): void;
     ~~~~~~~
-!!! error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+!!! error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
     run(1);
     

tests/baselines/reference/isolatedModulesPlainFile-System.errors.txt

@@ -1,9 +1,9 @@
-tests/cases/compiler/isolatedModulesPlainFile-System.ts(1,1): error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+tests/cases/compiler/isolatedModulesPlainFile-System.ts(1,1): error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
 
 
 ==== tests/cases/compiler/isolatedModulesPlainFile-System.ts (1 errors) ====
     declare function run(a: number): void;
     ~~~~~~~
-!!! error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+!!! error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
     run(1);
     

tests/baselines/reference/isolatedModulesPlainFile-UMD.errors.txt

@@ -1,9 +1,9 @@
-tests/cases/compiler/isolatedModulesPlainFile-UMD.ts(1,1): error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+tests/cases/compiler/isolatedModulesPlainFile-UMD.ts(1,1): error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
 
 
 ==== tests/cases/compiler/isolatedModulesPlainFile-UMD.ts (1 errors) ====
     declare function run(a: number): void;
     ~~~~~~~
-!!! error TS1208: Cannot compile namespaces when the '--isolatedModules' flag is provided.
+!!! error TS1208: All files must be modules when the '--isolatedModules' flag is provided.
     run(1);