diff --git a/scripts/tslint/booleanTriviaRule.ts b/scripts/tslint/booleanTriviaRule.ts
index 189dafac77e..c498131be16 100644
--- a/scripts/tslint/booleanTriviaRule.ts
+++ b/scripts/tslint/booleanTriviaRule.ts
@@ -34,6 +34,7 @@ function walk(ctx: Lint.WalkContext<void>): void {
             switch (methodName) {
                 case "apply":
                 case "assert":
+                case "assertEqual":
                 case "call":
                 case "equal":
                 case "fail":
@@ -69,7 +70,7 @@ function walk(ctx: Lint.WalkContext<void>): void {
 
         const ranges = ts.getTrailingCommentRanges(sourceFile.text, arg.pos) || ts.getLeadingCommentRanges(sourceFile.text, arg.pos);
         if (ranges === undefined || ranges.length !== 1 || ranges[0].kind !== ts.SyntaxKind.MultiLineCommentTrivia) {
-            ctx.addFailureAtNode(arg, "Tag boolean argument with parameter name");
+            ctx.addFailureAtNode(arg, "Tag argument with parameter name");
             return;
         }
 
diff --git a/scripts/tslint/debugAssertRule.ts b/scripts/tslint/debugAssertRule.ts
new file mode 100644
index 00000000000..933b27697b0
--- /dev/null
+++ b/scripts/tslint/debugAssertRule.ts
@@ -0,0 +1,45 @@
+import * as Lint from "tslint/lib";
+import * as ts from "typescript";
+
+export class Rule extends Lint.Rules.AbstractRule {
+    public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
+        return this.applyWithFunction(sourceFile, ctx => walk(ctx));
+    }
+}
+
+function walk(ctx: Lint.WalkContext<void>): void {
+    ts.forEachChild(ctx.sourceFile, function recur(node) {
+        if (ts.isCallExpression(node)) {
+            checkCall(node);
+        }
+        ts.forEachChild(node, recur);
+    });
+
+    function checkCall(node: ts.CallExpression) {
+        if (!isDebugAssert(node.expression) || node.arguments.length < 2) {
+            return;
+        }
+
+        const message = node.arguments[1];
+        if (!ts.isStringLiteral(message)) {
+            ctx.addFailureAtNode(message, "Second argument to 'Debug.assert' should be a string literal.");
+        }
+
+        if (node.arguments.length < 3) {
+            return;
+        }
+
+        const message2 = node.arguments[2];
+        if (!ts.isStringLiteral(message2) && !ts.isArrowFunction(message2)) {
+            ctx.addFailureAtNode(message, "Third argument to 'Debug.assert' should be a string literal or arrow function.");
+        }
+    }
+
+    function isDebugAssert(expr: ts.Node): boolean {
+        return ts.isPropertyAccessExpression(expr) && isName(expr.expression, "Debug") && isName(expr.name, "assert");
+    }
+
+    function isName(expr: ts.Node, text: string): boolean {
+        return ts.isIdentifier(expr) && expr.text === text;
+    }
+}
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 4643ee36685..0fc2b927515 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -1086,7 +1086,10 @@ namespace ts {
                 location = location.parent;
             }
 
-            if (result && nameNotFoundMessage && noUnusedIdentifiers) {
+            // We just climbed up parents looking for the name, meaning that we started in a descendant node of `lastLocation`.
+            // If `result === lastLocation.symbol`, that means that we are somewhere inside `lastLocation` looking up a name, and resolving to `lastLocation` itself.
+            // That means that this is a self-reference of `lastLocation`, and shouldn't count this when considering whether `lastLocation` is used.
+            if (result && nameNotFoundMessage && noUnusedIdentifiers && result !== lastLocation.symbol) {
                 result.isReferenced = true;
             }
 
@@ -2583,10 +2586,8 @@ namespace ts {
                 }
 
                 function createTypeNodeFromObjectType(type: ObjectType): TypeNode {
-                    if (type.objectFlags & ObjectFlags.Mapped) {
-                        if (getConstraintTypeFromMappedType(<MappedType>type).flags & (TypeFlags.TypeParameter | TypeFlags.Index)) {
-                            return createMappedTypeNodeFromType(<MappedType>type);
-                        }
+                    if (isGenericMappedType(type)) {
+                        return createMappedTypeNodeFromType(<MappedType>type);
                     }
 
                     const resolved = resolveStructuredTypeMembers(type);
@@ -3489,11 +3490,9 @@ namespace ts {
                 }
 
                 function writeLiteralType(type: ObjectType, flags: TypeFormatFlags) {
-                    if (type.objectFlags & ObjectFlags.Mapped) {
-                        if (getConstraintTypeFromMappedType(<MappedType>type).flags & (TypeFlags.TypeParameter | TypeFlags.Index)) {
-                            writeMappedType(<MappedType>type);
-                            return;
-                        }
+                    if (isGenericMappedType(type)) {
+                        writeMappedType(<MappedType>type);
+                        return;
                     }
 
                     const resolved = resolveStructuredTypeMembers(type);
@@ -5792,8 +5791,7 @@ namespace ts {
         }
 
         function isGenericMappedType(type: Type) {
-            return getObjectFlags(type) & ObjectFlags.Mapped &&
-                maybeTypeOfKind(getConstraintTypeFromMappedType(<MappedType>type), TypeFlags.TypeVariable | TypeFlags.Index);
+            return getObjectFlags(type) & ObjectFlags.Mapped && isGenericIndexType(getConstraintTypeFromMappedType(<MappedType>type));
         }
 
         function resolveStructuredTypeMembers(type: StructuredType): ResolvedType {
@@ -5905,6 +5903,10 @@ namespace ts {
         }
 
         function getConstraintOfIndexedAccess(type: IndexedAccessType) {
+            const transformed = getTransformedIndexedAccessType(type);
+            if (transformed) {
+                return transformed;
+            }
             const baseObjectType = getBaseConstraintOfType(type.objectType);
             const baseIndexType = getBaseConstraintOfType(type.indexType);
             return baseObjectType || baseIndexType ? getIndexedAccessType(baseObjectType || type.objectType, baseIndexType || type.indexType) : undefined;
@@ -5976,11 +5978,18 @@ namespace ts {
                     return stringType;
                 }
                 if (t.flags & TypeFlags.IndexedAccess) {
+                    const transformed = getTransformedIndexedAccessType(<IndexedAccessType>t);
+                    if (transformed) {
+                        return getBaseConstraint(transformed);
+                    }
                     const baseObjectType = getBaseConstraint((<IndexedAccessType>t).objectType);
                     const baseIndexType = getBaseConstraint((<IndexedAccessType>t).indexType);
                     const baseIndexedAccess = baseObjectType && baseIndexType ? getIndexedAccessType(baseObjectType, baseIndexType) : undefined;
                     return baseIndexedAccess && baseIndexedAccess !== unknownType ? getBaseConstraint(baseIndexedAccess) : undefined;
                 }
+                if (isGenericMappedType(t)) {
+                    return emptyObjectType;
+                }
                 return t;
             }
         }
@@ -7592,36 +7601,89 @@ namespace ts {
         }
 
         function getIndexedAccessForMappedType(type: MappedType, indexType: Type, accessNode?: ElementAccessExpression | IndexedAccessTypeNode) {
-            const accessExpression = accessNode && accessNode.kind === SyntaxKind.ElementAccessExpression ? <ElementAccessExpression>accessNode : undefined;
-            if (accessExpression && isAssignmentTarget(accessExpression) && type.declaration.readonlyToken) {
-                error(accessExpression, Diagnostics.Index_signature_in_type_0_only_permits_reading, typeToString(type));
-                return unknownType;
+            if (accessNode) {
+                // Check if the index type is assignable to 'keyof T' for the object type.
+                if (!isTypeAssignableTo(indexType, getIndexType(type))) {
+                    error(accessNode, Diagnostics.Type_0_cannot_be_used_to_index_type_1, typeToString(indexType), typeToString(type));
+                    return unknownType;
+                }
+                if (accessNode.kind === SyntaxKind.ElementAccessExpression && isAssignmentTarget(accessNode) && type.declaration.readonlyToken) {
+                    error(accessNode, Diagnostics.Index_signature_in_type_0_only_permits_reading, typeToString(type));
+                    return unknownType;
+                }
             }
             const mapper = createTypeMapper([getTypeParameterFromMappedType(type)], [indexType]);
             const templateMapper = type.mapper ? combineTypeMappers(type.mapper, mapper) : mapper;
             return instantiateType(getTemplateTypeFromMappedType(type), templateMapper);
         }
 
-        function getIndexedAccessType(objectType: Type, indexType: Type, accessNode?: ElementAccessExpression | IndexedAccessTypeNode) {
-            // If the index type is generic, if the object type is generic and doesn't originate in an expression,
-            // or if the object type is a mapped type with a generic constraint, we are performing a higher-order
-            // index access where we cannot meaningfully access the properties of the object type. Note that for a
-            // generic T and a non-generic K, we eagerly resolve T[K] if it originates in an expression. This is to
-            // preserve backwards compatibility. For example, an element access 'this["foo"]' has always been resolved
-            // eagerly using the constraint type of 'this' at the given location.
-            if (maybeTypeOfKind(indexType, TypeFlags.TypeVariable | TypeFlags.Index) ||
-                maybeTypeOfKind(objectType, TypeFlags.TypeVariable) && !(accessNode && accessNode.kind === SyntaxKind.ElementAccessExpression) ||
-                isGenericMappedType(objectType)) {
+        function isGenericObjectType(type: Type): boolean {
+            return type.flags & TypeFlags.TypeVariable ? true :
+                getObjectFlags(type) & ObjectFlags.Mapped ? isGenericIndexType(getConstraintTypeFromMappedType(<MappedType>type)) :
+                type.flags & TypeFlags.UnionOrIntersection ? forEach((<UnionOrIntersectionType>type).types, isGenericObjectType) :
+                false;
+        }
+
+        function isGenericIndexType(type: Type): boolean {
+            return type.flags & (TypeFlags.TypeVariable | TypeFlags.Index) ? true :
+                type.flags & TypeFlags.UnionOrIntersection ? forEach((<UnionOrIntersectionType>type).types, isGenericIndexType) :
+                false;
+        }
+
+        // Return true if the given type is a non-generic object type with a string index signature and no
+        // other members.
+        function isStringIndexOnlyType(type: Type) {
+            if (type.flags & TypeFlags.Object && !isGenericMappedType(type)) {
+                const t = resolveStructuredTypeMembers(<ObjectType>type);
+                return t.properties.length === 0 &&
+                    t.callSignatures.length === 0 && t.constructSignatures.length === 0 &&
+                    t.stringIndexInfo && !t.numberIndexInfo;
+            }
+            return false;
+        }
+
+        // Given an indexed access type T[K], if T is an intersection containing one or more generic types and one or
+        // more object types with only a string index signature, e.g. '(U & V & { [x: string]: D })[K]', return a
+        // transformed type of the form '(U & V)[K] | D'. This allows us to properly reason about higher order indexed
+        // access types with default property values as expressed by D.
+        function getTransformedIndexedAccessType(type: IndexedAccessType): Type {
+            const objectType = type.objectType;
+            if (objectType.flags & TypeFlags.Intersection && isGenericObjectType(objectType) && some((<IntersectionType>objectType).types, isStringIndexOnlyType)) {
+                const regularTypes: Type[] = [];
+                const stringIndexTypes: Type[] = [];
+                for (const t of (<IntersectionType>objectType).types) {
+                    if (isStringIndexOnlyType(t)) {
+                        stringIndexTypes.push(getIndexTypeOfType(t, IndexKind.String));
+                    }
+                    else {
+                        regularTypes.push(t);
+                    }
+                }
+                return getUnionType([
+                    getIndexedAccessType(getIntersectionType(regularTypes), type.indexType),
+                    getIntersectionType(stringIndexTypes)
+                ]);
+            }
+            return undefined;
+        }
+
+        function getIndexedAccessType(objectType: Type, indexType: Type, accessNode?: ElementAccessExpression | IndexedAccessTypeNode): Type {
+            // If the object type is a mapped type { [P in K]: E }, where K is generic, we instantiate E using a mapper
+            // that substitutes the index type for P. For example, for an index access { [P in K]: Box<T[P]> }[X], we
+            // construct the type Box<T[X]>.
+            if (isGenericMappedType(objectType)) {
+                return getIndexedAccessForMappedType(<MappedType>objectType, indexType, accessNode);
+            }
+            // Otherwise, if the index type is generic, or if the object type is generic and doesn't originate in an
+            // expression, we are performing a higher-order index access where we cannot meaningfully access the properties
+            // of the object type. Note that for a generic T and a non-generic K, we eagerly resolve T[K] if it originates
+            // in an expression. This is to preserve backwards compatibility. For example, an element access 'this["foo"]'
+            // has always been resolved eagerly using the constraint type of 'this' at the given location.
+            if (isGenericIndexType(indexType) || !(accessNode && accessNode.kind === SyntaxKind.ElementAccessExpression) && isGenericObjectType(objectType)) {
                 if (objectType.flags & TypeFlags.Any) {
                     return objectType;
                 }
-                // If the object type is a mapped type { [P in K]: E }, we instantiate E using a mapper that substitutes
-                // the index type for P. For example, for an index access { [P in K]: Box<T[P]> }[X], we construct the
-                // type Box<T[X]>.
-                if (isGenericMappedType(objectType)) {
-                    return getIndexedAccessForMappedType(<MappedType>objectType, indexType, accessNode);
-                }
-                // Otherwise we defer the operation by creating an indexed access type.
+                // Defer the operation by creating an indexed access type.
                 const id = objectType.id + "," + indexType.id;
                 let type = indexedAccessTypes.get(id);
                 if (!type) {
@@ -8015,7 +8077,7 @@ namespace ts {
 
         function cloneTypeMapper(mapper: TypeMapper): TypeMapper {
             return mapper && isInferenceContext(mapper) ?
-                createInferenceContext(mapper.signature, mapper.flags | InferenceFlags.NoDefault, mapper.inferences) :
+                createInferenceContext(mapper.signature, mapper.flags | InferenceFlags.NoDefault, mapper.compareTypes, mapper.inferences) :
                 mapper;
         }
 
@@ -8456,7 +8518,7 @@ namespace ts {
             ignoreReturnTypes: boolean,
             reportErrors: boolean,
             errorReporter: ErrorReporter,
-            compareTypes: (s: Type, t: Type, reportErrors?: boolean) => Ternary): Ternary {
+            compareTypes: TypeComparer): Ternary {
             // TODO (drosen): De-duplicate code between related functions.
             if (source === target) {
                 return Ternary.True;
@@ -8466,7 +8528,7 @@ namespace ts {
             }
 
             if (source.typeParameters) {
-                source = instantiateSignatureInContextOf(source, target);
+                source = instantiateSignatureInContextOf(source, target, /*contextualMapper*/ undefined, compareTypes);
             }
 
             let result = Ternary.True;
@@ -8879,11 +8941,21 @@ namespace ts {
                     !(target.flags & TypeFlags.Union) &&
                     !isIntersectionConstituent &&
                     source !== globalObjectType &&
-                    getPropertiesOfType(source).length > 0 &&
+                    (getPropertiesOfType(source).length > 0 ||
+                     getSignaturesOfType(source, SignatureKind.Call).length > 0 ||
+                     getSignaturesOfType(source, SignatureKind.Construct).length > 0) &&
                     isWeakType(target) &&
                     !hasCommonProperties(source, target)) {
                     if (reportErrors) {
-                        reportError(Diagnostics.Type_0_has_no_properties_in_common_with_type_1, typeToString(source), typeToString(target));
+                        const calls = getSignaturesOfType(source, SignatureKind.Call);
+                        const constructs = getSignaturesOfType(source, SignatureKind.Construct);
+                        if (calls.length > 0 && isRelatedTo(getReturnTypeOfSignature(calls[0]), target, /*reportErrors*/ false) ||
+                            constructs.length > 0 && isRelatedTo(getReturnTypeOfSignature(constructs[0]), target, /*reportErrors*/ false)) {
+                            reportError(Diagnostics.Value_of_type_0_has_no_properties_in_common_with_type_1_Did_you_mean_to_call_it, typeToString(source), typeToString(target));
+                        }
+                        else {
+                            reportError(Diagnostics.Type_0_has_no_properties_in_common_with_type_1, typeToString(source), typeToString(target));
+                        }
                     }
                     return Ternary.False;
                 }
@@ -9612,6 +9684,11 @@ namespace ts {
                 if (sourceInfo) {
                     return indexInfoRelatedTo(sourceInfo, targetInfo, reportErrors);
                 }
+                if (isGenericMappedType(source)) {
+                    // A generic mapped type { [P in K]: T } is related to an index signature { [x: string]: U }
+                    // if T is related to U.
+                    return kind === IndexKind.String && isRelatedTo(getTemplateTypeFromMappedType(<MappedType>source), targetInfo.type, reportErrors);
+                }
                 if (isObjectLiteralType(source)) {
                     let related = Ternary.True;
                     if (kind === IndexKind.String) {
@@ -10214,13 +10291,14 @@ namespace ts {
             }
         }
 
-        function createInferenceContext(signature: Signature, flags: InferenceFlags, baseInferences?: InferenceInfo[]): InferenceContext {
+        function createInferenceContext(signature: Signature, flags: InferenceFlags, compareTypes?: TypeComparer, baseInferences?: InferenceInfo[]): InferenceContext {
             const inferences = baseInferences ? map(baseInferences, cloneInferenceInfo) : map(signature.typeParameters, createInferenceInfo);
             const context = mapper as InferenceContext;
             context.mappedTypes = signature.typeParameters;
             context.signature = signature;
             context.inferences = inferences;
             context.flags = flags;
+            context.compareTypes = compareTypes || compareTypesAssignable;
             return context;
 
             function mapper(t: Type): Type {
@@ -10323,6 +10401,19 @@ namespace ts {
             }
         }
 
+        function isPossiblyAssignableTo(source: Type, target: Type) {
+            const properties = getPropertiesOfObjectType(target);
+            for (const targetProp of properties) {
+                if (!(targetProp.flags & (SymbolFlags.Optional | SymbolFlags.Prototype))) {
+                    const sourceProp = getPropertyOfObjectType(source, targetProp.escapedName);
+                    if (!sourceProp) {
+                        return false;
+                    }
+                }
+            }
+            return true;
+        }
+
         function inferTypes(inferences: InferenceInfo[], originalSource: Type, originalTarget: Type, priority: InferencePriority = 0) {
             let symbolStack: Symbol[];
             let visited: Map<boolean>;
@@ -10516,10 +10607,14 @@ namespace ts {
                         return;
                     }
                 }
-                inferFromProperties(source, target);
-                inferFromSignatures(source, target, SignatureKind.Call);
-                inferFromSignatures(source, target, SignatureKind.Construct);
-                inferFromIndexTypes(source, target);
+                // Infer from the members of source and target only if the two types are possibly related. We check
+                // in both directions because we may be inferring for a co-variant or a contra-variant position.
+                if (isPossiblyAssignableTo(source, target) || isPossiblyAssignableTo(target, source)) {
+                    inferFromProperties(source, target);
+                    inferFromSignatures(source, target, SignatureKind.Call);
+                    inferFromSignatures(source, target, SignatureKind.Construct);
+                    inferFromIndexTypes(source, target);
+                }
             }
 
             function inferFromProperties(source: Type, target: Type) {
@@ -10651,7 +10746,7 @@ namespace ts {
                 const constraint = getConstraintOfTypeParameter(context.signature.typeParameters[index]);
                 if (constraint) {
                     const instantiatedConstraint = instantiateType(constraint, context);
-                    if (!isTypeAssignableTo(inferredType, getTypeWithThisArgument(instantiatedConstraint, inferredType))) {
+                    if (!context.compareTypes(inferredType, getTypeWithThisArgument(instantiatedConstraint, inferredType))) {
                         inference.inferredType = inferredType = instantiatedConstraint;
                     }
                 }
@@ -10718,17 +10813,6 @@ namespace ts {
             return undefined;
         }
 
-        function getLeftmostIdentifierOrThis(node: Node): Node {
-            switch (node.kind) {
-                case SyntaxKind.Identifier:
-                case SyntaxKind.ThisKeyword:
-                    return node;
-                case SyntaxKind.PropertyAccessExpression:
-                    return getLeftmostIdentifierOrThis((<PropertyAccessExpression>node).expression);
-            }
-            return undefined;
-        }
-
         function getBindingElementNameText(element: BindingElement): string | undefined {
             if (element.parent.kind === SyntaxKind.ObjectBindingPattern) {
                 const name = element.propertyName || element.name;
@@ -14020,11 +14104,8 @@ namespace ts {
          */
         function resolveCustomJsxElementAttributesType(openingLikeElement: JsxOpeningLikeElement,
             shouldIncludeAllStatelessAttributesType: boolean,
-            elementType?: Type,
+            elementType: Type = checkExpression(openingLikeElement.tagName),
             elementClassType?: Type): Type {
-            if (!elementType) {
-                elementType = checkExpression(openingLikeElement.tagName);
-            }
 
             if (elementType.flags & TypeFlags.Union) {
                 const types = (elementType as UnionType).types;
@@ -14158,11 +14239,12 @@ namespace ts {
          */
         function getCustomJsxElementAttributesType(node: JsxOpeningLikeElement, shouldIncludeAllStatelessAttributesType: boolean): Type {
             const links = getNodeLinks(node);
-            if (!links.resolvedJsxElementAttributesType) {
+            const linkLocation = shouldIncludeAllStatelessAttributesType ? "resolvedJsxElementAllAttributesType" : "resolvedJsxElementAttributesType";
+            if (!links[linkLocation]) {
                 const elemClassType = getJsxGlobalElementClassType();
-                return links.resolvedJsxElementAttributesType = resolveCustomJsxElementAttributesType(node, shouldIncludeAllStatelessAttributesType, /*elementType*/ undefined, elemClassType);
+                return links[linkLocation] = resolveCustomJsxElementAttributesType(node, shouldIncludeAllStatelessAttributesType, /*elementType*/ undefined, elemClassType);
             }
-            return links.resolvedJsxElementAttributesType;
+            return links[linkLocation];
         }
 
         /**
@@ -15049,8 +15131,8 @@ namespace ts {
         }
 
         // Instantiate a generic signature in the context of a non-generic signature (section 3.8.5 in TypeScript spec)
-        function instantiateSignatureInContextOf(signature: Signature, contextualSignature: Signature, contextualMapper?: TypeMapper): Signature {
-            const context = createInferenceContext(signature, InferenceFlags.InferUnionTypes);
+        function instantiateSignatureInContextOf(signature: Signature, contextualSignature: Signature, contextualMapper?: TypeMapper, compareTypes?: TypeComparer): Signature {
+            const context = createInferenceContext(signature, InferenceFlags.InferUnionTypes, compareTypes);
             forEachMatchingParameterType(contextualSignature, signature, (source, target) => {
                 // Type parameters from outer context referenced by source type are fixed by instantiation of the source type
                 inferTypes(context.inferences, instantiateType(source, contextualMapper || identityMapper), target);
@@ -16965,8 +17047,13 @@ namespace ts {
             if (operandType === silentNeverType) {
                 return silentNeverType;
             }
-            if (node.operator === SyntaxKind.MinusToken && node.operand.kind === SyntaxKind.NumericLiteral) {
-                return getFreshTypeOfLiteralType(getLiteralType(-(<LiteralExpression>node.operand).text));
+            if (node.operand.kind === SyntaxKind.NumericLiteral) {
+                if (node.operator === SyntaxKind.MinusToken) {
+                    return getFreshTypeOfLiteralType(getLiteralType(-(<LiteralExpression>node.operand).text));
+                }
+                else if (node.operator === SyntaxKind.PlusToken) {
+                    return getFreshTypeOfLiteralType(getLiteralType(+(<LiteralExpression>node.operand).text));
+                }
             }
             switch (node.operator) {
                 case SyntaxKind.PlusToken:
@@ -18419,15 +18506,6 @@ namespace ts {
                 return forEachChild(n, containsSuperCall);
             }
 
-            function markThisReferencesAsErrors(n: Node): void {
-                if (n.kind === SyntaxKind.ThisKeyword) {
-                    error(n, Diagnostics.this_cannot_be_referenced_in_current_location);
-                }
-                else if (n.kind !== SyntaxKind.FunctionExpression && n.kind !== SyntaxKind.FunctionDeclaration) {
-                    forEachChild(n, markThisReferencesAsErrors);
-                }
-            }
-
             function isInstancePropertyWithInitializer(n: Node): boolean {
                 return n.kind === SyntaxKind.PropertyDeclaration &&
                     !(getModifierFlags(n) & ModifierFlags.Static) &&
@@ -18578,7 +18656,17 @@ namespace ts {
                     forEach(node.typeArguments, checkSourceElement);
                     if (produceDiagnostics) {
                         const symbol = getNodeLinks(node).resolvedSymbol;
-                        const typeParameters = symbol.flags & SymbolFlags.TypeAlias ? getSymbolLinks(symbol).typeParameters : (<TypeReference>type).target.localTypeParameters;
+                        if (!symbol) {
+                            // There is no resolved symbol cached if the type resolved to a builtin
+                            // via JSDoc type reference resolution (eg, Boolean became boolean), none
+                            // of which are generic when they have no associated symbol
+                            error(node, Diagnostics.Type_0_is_not_generic, typeToString(type));
+                            return;
+                        }
+                        let typeParameters = symbol.flags & SymbolFlags.TypeAlias && getSymbolLinks(symbol).typeParameters;
+                        if (!typeParameters && getObjectFlags(type) & ObjectFlags.Reference) {
+                            typeParameters = (<TypeReference>type).target.localTypeParameters;
+                        }
                         checkTypeArgumentConstraints(typeParameters, node.typeArguments);
                     }
                 }
@@ -18643,6 +18731,8 @@ namespace ts {
         }
 
         function checkIndexedAccessType(node: IndexedAccessTypeNode) {
+            checkSourceElement(node.objectType);
+            checkSourceElement(node.indexType);
             checkIndexedAccessIndexType(getTypeFromIndexedAccessTypeNode(node), node);
         }
 
diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
index 554b46dcdfe..e82e70dc764 100644
--- a/src/compiler/commandLineParser.ts
+++ b/src/compiler/commandLineParser.ts
@@ -1446,14 +1446,10 @@ namespace ts {
                 }
             }
             else {
-                // If no includes were specified, exclude common package folders and the outDir
-                const specs = includeSpecs ? [] : ["node_modules", "bower_components", "jspm_packages"];
-
                 const outDir = raw["compilerOptions"] && raw["compilerOptions"]["outDir"];
                 if (outDir) {
-                    specs.push(outDir);
+                    excludeSpecs = [outDir];
                 }
-                excludeSpecs = specs;
             }
 
             if (fileNames === undefined && includeSpecs === undefined) {
@@ -2015,23 +2011,13 @@ namespace ts {
     }
 
     function validateSpecs(specs: ReadonlyArray<string>, errors: Push<Diagnostic>, allowTrailingRecursion: boolean, jsonSourceFile: JsonSourceFile, specKey: string) {
-        const validSpecs: string[] = [];
-        for (const spec of specs) {
-            if (!allowTrailingRecursion && invalidTrailingRecursionPattern.test(spec)) {
-                errors.push(createDiagnostic(Diagnostics.File_specification_cannot_end_in_a_recursive_directory_wildcard_Asterisk_Asterisk_Colon_0, spec));
+        return specs.filter(spec => {
+            const diag = specToDiagnostic(spec, allowTrailingRecursion);
+            if (diag !== undefined) {
+                errors.push(createDiagnostic(diag, spec));
             }
-            else if (invalidMultipleRecursionPatterns.test(spec)) {
-                errors.push(createDiagnostic(Diagnostics.File_specification_cannot_contain_multiple_recursive_directory_wildcards_Asterisk_Asterisk_Colon_0, spec));
-            }
-            else if (invalidDotDotAfterRecursiveWildcardPattern.test(spec)) {
-                errors.push(createDiagnostic(Diagnostics.File_specification_cannot_contain_a_parent_directory_that_appears_after_a_recursive_directory_wildcard_Asterisk_Asterisk_Colon_0, spec));
-            }
-            else {
-                validSpecs.push(spec);
-            }
-        }
-
-        return validSpecs;
+            return diag === undefined;
+        });
 
         function createDiagnostic(message: DiagnosticMessage, spec: string): Diagnostic {
             if (jsonSourceFile && jsonSourceFile.jsonObject) {
@@ -2049,6 +2035,18 @@ namespace ts {
         }
     }
 
+    function specToDiagnostic(spec: string, allowTrailingRecursion: boolean): ts.DiagnosticMessage | undefined {
+        if (!allowTrailingRecursion && invalidTrailingRecursionPattern.test(spec)) {
+            return Diagnostics.File_specification_cannot_end_in_a_recursive_directory_wildcard_Asterisk_Asterisk_Colon_0;
+        }
+        else if (invalidMultipleRecursionPatterns.test(spec)) {
+            return Diagnostics.File_specification_cannot_contain_multiple_recursive_directory_wildcards_Asterisk_Asterisk_Colon_0;
+        }
+        else if (invalidDotDotAfterRecursiveWildcardPattern.test(spec)) {
+            return Diagnostics.File_specification_cannot_contain_a_parent_directory_that_appears_after_a_recursive_directory_wildcard_Asterisk_Asterisk_Colon_0;
+        }
+    }
+
     /**
      * Gets directories in a set of include patterns that should be watched for changes.
      */
diff --git a/src/compiler/core.ts b/src/compiler/core.ts
index 728fb433c04..d5c8396d06d 100644
--- a/src/compiler/core.ts
+++ b/src/compiler/core.ts
@@ -11,20 +11,6 @@ namespace ts {
 
 /* @internal */
 namespace ts {
-    /**
-     * Ternary values are defined such that
-     * x & y is False if either x or y is False.
-     * x & y is Maybe if either x or y is Maybe, but neither x or y is False.
-     * x & y is True if both x and y are True.
-     * x | y is False if both x and y are False.
-     * x | y is Maybe if either x or y is Maybe, but neither x or y is True.
-     * x | y is True if either x or y is True.
-     */
-    export const enum Ternary {
-        False = 0,
-        Maybe = 1,
-        True = -1
-    }
 
     // More efficient to create a collator once and use its `compare` than to call `a.localeCompare(b)` many times.
     export const collator: { compare(a: string, b: string): number } = typeof Intl === "object" && typeof Intl.Collator === "function" ? new Intl.Collator(/*locales*/ undefined, { usage: "sort", sensitivity: "accent" }) : undefined;
@@ -375,11 +361,11 @@ namespace ts {
         return false;
     }
 
-    export function filterMutate<T>(array: T[], f: (x: T) => boolean): void {
+    export function filterMutate<T>(array: T[], f: (x: T, i: number, array: T[]) => boolean): void {
         let outIndex = 0;
-        for (const item of array) {
-            if (f(item)) {
-                array[outIndex] = item;
+        for (let i = 0; i < array.length; i++) {
+            if (f(array[i], i, array)) {
+                array[outIndex] = array[i];
                 outIndex++;
             }
         }
@@ -1304,12 +1290,12 @@ namespace ts {
     export function createFileDiagnostic(file: SourceFile, start: number, length: number, message: DiagnosticMessage): Diagnostic {
         const end = start + length;
 
-        Debug.assert(start >= 0, "start must be non-negative, is " + start);
-        Debug.assert(length >= 0, "length must be non-negative, is " + length);
+        Debug.assertGreaterThanOrEqual(start, 0);
+        Debug.assertGreaterThanOrEqual(length, 0);
 
         if (file) {
-            Debug.assert(start <= file.text.length, `start must be within the bounds of the file. ${start} > ${file.text.length}`);
-            Debug.assert(end <= file.text.length, `end must be the bounds of the file. ${end} > ${file.text.length}`);
+            Debug.assertLessThanOrEqual(start, file.text.length);
+            Debug.assertLessThanOrEqual(end, file.text.length);
         }
 
         let text = getLocaleSpecificMessage(message);
@@ -1889,14 +1875,54 @@ namespace ts {
     const reservedCharacterPattern = /[^\w\s\/]/g;
     const wildcardCharCodes = [CharacterCodes.asterisk, CharacterCodes.question];
 
-    /**
-     * Matches any single directory segment unless it is the last segment and a .min.js file
-     * Breakdown:
-     *  [^./]                   # matches everything up to the first . character (excluding directory seperators)
-     *  (\\.(?!min\\.js$))?     # matches . characters but not if they are part of the .min.js file extension
-     */
-    const singleAsteriskRegexFragmentFiles = "([^./]|(\\.(?!min\\.js$))?)*";
-    const singleAsteriskRegexFragmentOther = "[^/]*";
+    /* @internal */
+    export const commonPackageFolders: ReadonlyArray<string> = ["node_modules", "bower_components", "jspm_packages"];
+
+    const implicitExcludePathRegexPattern = `(?!(${commonPackageFolders.join("|")})(/|$))`;
+
+    interface WildcardMatcher {
+        singleAsteriskRegexFragment: string;
+        doubleAsteriskRegexFragment: string;
+        replaceWildcardCharacter: (match: string) => string;
+    }
+
+    const filesMatcher: WildcardMatcher = {
+        /**
+         * Matches any single directory segment unless it is the last segment and a .min.js file
+         * Breakdown:
+         *  [^./]                   # matches everything up to the first . character (excluding directory seperators)
+         *  (\\.(?!min\\.js$))?     # matches . characters but not if they are part of the .min.js file extension
+         */
+        singleAsteriskRegexFragment: "([^./]|(\\.(?!min\\.js$))?)*",
+        /**
+         * Regex for the ** wildcard. Matches any number of subdirectories. When used for including
+         * files or directories, does not match subdirectories that start with a . character
+         */
+        doubleAsteriskRegexFragment: `(/${implicitExcludePathRegexPattern}[^/.][^/]*)*?`,
+        replaceWildcardCharacter: match => replaceWildcardCharacter(match, filesMatcher.singleAsteriskRegexFragment)
+    };
+
+    const directoriesMatcher: WildcardMatcher = {
+        singleAsteriskRegexFragment: "[^/]*",
+        /**
+         * Regex for the ** wildcard. Matches any number of subdirectories. When used for including
+         * files or directories, does not match subdirectories that start with a . character
+         */
+        doubleAsteriskRegexFragment: `(/${implicitExcludePathRegexPattern}[^/.][^/]*)*?`,
+        replaceWildcardCharacter: match => replaceWildcardCharacter(match, directoriesMatcher.singleAsteriskRegexFragment)
+    };
+
+    const excludeMatcher: WildcardMatcher = {
+        singleAsteriskRegexFragment: "[^/]*",
+        doubleAsteriskRegexFragment: "(/.+?)?",
+        replaceWildcardCharacter: match => replaceWildcardCharacter(match, excludeMatcher.singleAsteriskRegexFragment)
+    };
+
+    const wildcardMatchers = {
+        files: filesMatcher,
+        directories: directoriesMatcher,
+        exclude: excludeMatcher
+    };
 
     export function getRegularExpressionForWildcard(specs: ReadonlyArray<string>, basePath: string, usage: "files" | "directories" | "exclude"): string | undefined {
         const patterns = getRegularExpressionsForWildcards(specs, basePath, usage);
@@ -1915,17 +1941,8 @@ namespace ts {
             return undefined;
         }
 
-        const replaceWildcardCharacter = usage === "files" ? replaceWildCardCharacterFiles : replaceWildCardCharacterOther;
-        const singleAsteriskRegexFragment = usage === "files" ? singleAsteriskRegexFragmentFiles : singleAsteriskRegexFragmentOther;
-
-        /**
-         * Regex for the ** wildcard. Matches any number of subdirectories. When used for including
-         * files or directories, does not match subdirectories that start with a . character
-         */
-        const doubleAsteriskRegexFragment = usage === "exclude" ? "(/.+?)?" : "(/[^/.][^/]*)*?";
-
         return flatMap(specs, spec =>
-            spec && getSubPatternFromSpec(spec, basePath, usage, singleAsteriskRegexFragment, doubleAsteriskRegexFragment, replaceWildcardCharacter));
+            spec && getSubPatternFromSpec(spec, basePath, usage, wildcardMatchers[usage]));
     }
 
     /**
@@ -1936,7 +1953,7 @@ namespace ts {
         return !/[.*?]/.test(lastPathComponent);
     }
 
-    function getSubPatternFromSpec(spec: string, basePath: string, usage: "files" | "directories" | "exclude", singleAsteriskRegexFragment: string, doubleAsteriskRegexFragment: string, replaceWildcardCharacter: (match: string) => string): string | undefined {
+    function getSubPatternFromSpec(spec: string, basePath: string, usage: "files" | "directories" | "exclude", { singleAsteriskRegexFragment, doubleAsteriskRegexFragment, replaceWildcardCharacter }: WildcardMatcher): string | undefined {
         let subpattern = "";
         let hasRecursiveDirectoryWildcard = false;
         let hasWrittenComponent = false;
@@ -1975,20 +1992,36 @@ namespace ts {
                 }
 
                 if (usage !== "exclude") {
+                    let componentPattern = "";
                     // The * and ? wildcards should not match directories or files that start with . if they
                     // appear first in a component. Dotted directories and files can be included explicitly
                     // like so: **/.*/.*
                     if (component.charCodeAt(0) === CharacterCodes.asterisk) {
-                        subpattern += "([^./]" + singleAsteriskRegexFragment + ")?";
+                        componentPattern += "([^./]" + singleAsteriskRegexFragment + ")?";
                         component = component.substr(1);
                     }
                     else if (component.charCodeAt(0) === CharacterCodes.question) {
-                        subpattern += "[^./]";
+                        componentPattern += "[^./]";
                         component = component.substr(1);
                     }
-                }
 
-                subpattern += component.replace(reservedCharacterPattern, replaceWildcardCharacter);
+                    componentPattern += component.replace(reservedCharacterPattern, replaceWildcardCharacter);
+
+                    // Patterns should not include subfolders like node_modules unless they are
+                    // explicitly included as part of the path.
+                    //
+                    // As an optimization, if the component pattern is the same as the component,
+                    // then there definitely were no wildcard characters and we do not need to
+                    // add the exclusion pattern.
+                    if (componentPattern !== component) {
+                        subpattern += implicitExcludePathRegexPattern;
+                    }
+
+                    subpattern += componentPattern;
+                }
+                else {
+                    subpattern += component.replace(reservedCharacterPattern, replaceWildcardCharacter);
+                }
             }
 
             hasWrittenComponent = true;
@@ -2002,14 +2035,6 @@ namespace ts {
         return subpattern;
     }
 
-    function replaceWildCardCharacterFiles(match: string) {
-        return replaceWildcardCharacter(match, singleAsteriskRegexFragmentFiles);
-    }
-
-    function replaceWildCardCharacterOther(match: string) {
-        return replaceWildcardCharacter(match, singleAsteriskRegexFragmentOther);
-    }
-
     function replaceWildcardCharacter(match: string, singleAsteriskRegexFragment: string) {
         return match === "*" ? singleAsteriskRegexFragment : match === "?" ? "[^/]" : "\\" + match;
     }
@@ -2364,15 +2389,40 @@ namespace ts {
             return currentAssertionLevel >= level;
         }
 
-        export function assert(expression: boolean, message?: string, verboseDebugInfo?: () => string, stackCrawlMark?: Function): void {
+        export function assert(expression: boolean, message?: string, verboseDebugInfo?: string | (() => string), stackCrawlMark?: Function): void {
             if (!expression) {
                 if (verboseDebugInfo) {
-                    message += "\r\nVerbose Debug Information: " + 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?: Function): void {
             debugger;
             const e = new Error(message ? `Debug Failure. ${message}` : "Debug Failure.");
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 3b4b0ddf667..03164c54ffd 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -1908,6 +1908,10 @@
         "category": "Error",
         "code": 2559
     },
+    "Value of type '{0}' has no properties in common with type '{1}'. Did you mean to call it?": {
+        "category": "Error",
+        "code": 2560
+    },
     "JSX element attributes type '{0}' may not be a union type.": {
         "category": "Error",
         "code": 2600
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index de08b209d3e..4f07331a98e 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -1346,7 +1346,9 @@ namespace ts {
 
             emitExpression(node.left);
             increaseIndentIf(indentBeforeOperator, isCommaOperator ? " " : undefined);
+            emitLeadingCommentsOfPosition(node.operatorToken.pos);
             writeTokenNode(node.operatorToken);
+            emitTrailingCommentsOfPosition(node.operatorToken.end);
             increaseIndentIf(indentAfterOperator, " ");
             emitExpression(node.right);
             decreaseIndentIf(indentBeforeOperator, indentAfterOperator);
diff --git a/src/compiler/moduleNameResolver.ts b/src/compiler/moduleNameResolver.ts
index 513c741ba09..be867db9743 100644
--- a/src/compiler/moduleNameResolver.ts
+++ b/src/compiler/moduleNameResolver.ts
@@ -678,7 +678,7 @@ namespace ts {
         const { resolvedModule, failedLookupLocations } =
             nodeModuleNameResolverWorker(moduleName, initialDir, { moduleResolution: ts.ModuleResolutionKind.NodeJs, allowJs: true }, host, /*cache*/ undefined, /*jsOnly*/ true);
         if (!resolvedModule) {
-            throw new Error(`Could not resolve JS module ${moduleName} starting at ${initialDir}. Looked in: ${failedLookupLocations.join(", ")}`);
+            throw new Error(`Could not resolve JS module '${moduleName}' starting at '${initialDir}'. Looked in: ${failedLookupLocations.join(", ")}`);
         }
         return resolvedModule.resolvedFileName;
     }
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index 34670cd2834..49b682c7302 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -2061,7 +2061,7 @@ namespace ts {
             return <TemplateMiddle | TemplateTail>fragment;
         }
 
-        function parseLiteralLikeNode(kind: SyntaxKind): LiteralLikeNode {
+        function parseLiteralLikeNode(kind: SyntaxKind): LiteralExpression | LiteralLikeNode {
             const node = <LiteralExpression>createNode(kind);
             const text = scanner.getTokenValue();
             node.text = text;
@@ -2611,11 +2611,31 @@ namespace ts {
             return token() === SyntaxKind.DotToken ? undefined : node;
         }
 
-        function parseLiteralTypeNode(): LiteralTypeNode {
-            const node = <LiteralTypeNode>createNode(SyntaxKind.LiteralType);
-            node.literal = parseSimpleUnaryExpression();
-            finishNode(node);
-            return node;
+        function parseLiteralTypeNode(negative?: boolean): LiteralTypeNode {
+            const node = createNode(SyntaxKind.LiteralType) as LiteralTypeNode;
+            let unaryMinusExpression: PrefixUnaryExpression;
+            if (negative) {
+                unaryMinusExpression = createNode(SyntaxKind.PrefixUnaryExpression) as PrefixUnaryExpression;
+                unaryMinusExpression.operator = SyntaxKind.MinusToken;
+                nextToken();
+            }
+            let expression: UnaryExpression;
+            switch (token()) {
+                case SyntaxKind.StringLiteral:
+                case SyntaxKind.NumericLiteral:
+                    expression = parseLiteralLikeNode(token()) as LiteralExpression;
+                    break;
+                case SyntaxKind.TrueKeyword:
+                case SyntaxKind.FalseKeyword:
+                    expression = parseTokenNode();
+            }
+            if (negative) {
+                unaryMinusExpression.operand = expression;
+                finishNode(unaryMinusExpression);
+                expression = unaryMinusExpression;
+            }
+            node.literal = expression;
+            return finishNode(node);
         }
 
         function nextTokenIsNumericLiteral() {
@@ -2650,7 +2670,7 @@ namespace ts {
                 case SyntaxKind.FalseKeyword:
                     return parseLiteralTypeNode();
                 case SyntaxKind.MinusToken:
-                    return lookAhead(nextTokenIsNumericLiteral) ? parseLiteralTypeNode() : parseTypeReference();
+                    return lookAhead(nextTokenIsNumericLiteral) ? parseLiteralTypeNode(/*negative*/ true) : parseTypeReference();
                 case SyntaxKind.VoidKeyword:
                 case SyntaxKind.NullKeyword:
                     return parseTokenNode<TypeNode>();
@@ -2700,6 +2720,7 @@ namespace ts {
                 case SyntaxKind.TrueKeyword:
                 case SyntaxKind.FalseKeyword:
                 case SyntaxKind.ObjectKeyword:
+                case SyntaxKind.AsteriskToken:
                     return true;
                 case SyntaxKind.MinusToken:
                     return lookAhead(nextTokenIsNumericLiteral);
diff --git a/src/compiler/sys.ts b/src/compiler/sys.ts
index 9c6d4bb795d..89cfb074bff 100644
--- a/src/compiler/sys.ts
+++ b/src/compiler/sys.ts
@@ -4,6 +4,18 @@ declare function setTimeout(handler: (...args: any[]) => void, timeout: number):
 declare function clearTimeout(handle: any): void;
 
 namespace ts {
+    /**
+     * Set a high stack trace limit to provide more information in case of an error.
+     * Called for command-line and server use cases.
+     * Not called if TypeScript is used as a library.
+     */
+    /* @internal */
+    export function setStackTraceLimit() {
+        if ((Error as any).stackTraceLimit < 100) { // Also tests that we won't set the property if it doesn't exist.
+            (Error as any).stackTraceLimit = 100;
+        }
+    }
+
     export enum FileWatcherEventKind {
         Created,
         Changed,
diff --git a/src/compiler/transformers/generators.ts b/src/compiler/transformers/generators.ts
index 41edf24fe9e..5e2016ab590 100644
--- a/src/compiler/transformers/generators.ts
+++ b/src/compiler/transformers/generators.ts
@@ -2448,7 +2448,7 @@ namespace ts {
          * @param location An optional source map location for the statement.
          */
         function createInlineBreak(label: Label, location?: TextRange): ReturnStatement {
-            Debug.assert(label > 0, `Invalid label: ${label}`);
+            Debug.assertLessThan(0, label, "Invalid label");
             return setTextRange(
                 createReturn(
                     createArrayLiteral([
diff --git a/src/compiler/tsc.ts b/src/compiler/tsc.ts
index 8cc2e5c5ef6..db25afe45b6 100644
--- a/src/compiler/tsc.ts
+++ b/src/compiler/tsc.ts
@@ -665,6 +665,8 @@ namespace ts {
     }
 }
 
+ts.setStackTraceLimit();
+
 if (ts.Debug.isDebugging) {
     ts.Debug.enableDebugInfo();
 }
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 09f1b5cfcc5..0eb7f03e3ec 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -3067,6 +3067,7 @@ namespace ts {
         hasReportedStatementInAmbientContext?: boolean;  // Cache boolean if we report statements in ambient context
         jsxFlags?: JsxFlags;              // flags for knowing what kind of element/attributes we're dealing with
         resolvedJsxElementAttributesType?: Type;  // resolved element attributes type of a JSX openinglike element
+        resolvedJsxElementAllAttributesType?: Type;  // resolved all element attributes type of a JSX openinglike element
         hasSuperCall?: boolean;           // recorded result when we try to find super-call. We only try to find one if this flag is undefined, indicating that we haven't made an attempt.
         superCall?: ExpressionStatement;  // Cached first super-call found in the constructor. Used in checking whether super is called before this-accessing
         switchTypes?: Type[];             // Cached array of switch case expression types
@@ -3425,11 +3426,29 @@ namespace ts {
         AnyDefault      = 1 << 2,  // Infer anyType for no inferences (otherwise emptyObjectType)
     }
 
+    /**
+     * Ternary values are defined such that
+     * x & y is False if either x or y is False.
+     * x & y is Maybe if either x or y is Maybe, but neither x or y is False.
+     * x & y is True if both x and y are True.
+     * x | y is False if both x and y are False.
+     * x | y is Maybe if either x or y is Maybe, but neither x or y is True.
+     * x | y is True if either x or y is True.
+     */
+    export const enum Ternary {
+        False = 0,
+        Maybe = 1,
+        True = -1
+    }
+
+    export type TypeComparer = (s: Type, t: Type, reportErrors?: boolean) => Ternary;
+
     /* @internal */
     export interface InferenceContext extends TypeMapper {
         signature: Signature;               // Generic signature for which inferences are made
         inferences: InferenceInfo[];        // Inferences made for each type parameter
         flags: InferenceFlags;              // Inference flags
+        compareTypes: TypeComparer;         // Type comparer function
     }
 
     /* @internal */
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 24e0d59318b..76d242e8b08 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -922,21 +922,11 @@ namespace ts {
     }
 
     export function getContainingFunction(node: Node): FunctionLike {
-        while (true) {
-            node = node.parent;
-            if (!node || isFunctionLike(node)) {
-                return <FunctionLike>node;
-            }
-        }
+        return findAncestor(node.parent, isFunctionLike);
     }
 
     export function getContainingClass(node: Node): ClassLikeDeclaration {
-        while (true) {
-            node = node.parent;
-            if (!node || isClassLike(node)) {
-                return <ClassLikeDeclaration>node;
-            }
-        }
+        return findAncestor(node.parent, isClassLike);
     }
 
     export function getThisContainer(node: Node, includeArrowFunctions: boolean): Node {
diff --git a/src/harness/harness.ts b/src/harness/harness.ts
index 55a8f3ebb4d..7122f55cae2 100644
--- a/src/harness/harness.ts
+++ b/src/harness/harness.ts
@@ -420,7 +420,7 @@ namespace Utils {
 
     const maxHarnessFrames = 1;
 
-    export function filterStack(error: Error, stackTraceLimit: number = Infinity) {
+    export function filterStack(error: Error, stackTraceLimit = Infinity) {
         const stack = <string>(<any>error).stack;
         if (stack) {
             const lines = stack.split(/\r\n?|\n/g);
diff --git a/src/harness/harnessLanguageService.ts b/src/harness/harnessLanguageService.ts
index c604b224656..af5a998df99 100644
--- a/src/harness/harnessLanguageService.ts
+++ b/src/harness/harnessLanguageService.ts
@@ -681,11 +681,11 @@ namespace Harness.LanguageService {
         }
 
         info(message: string): void {
-            return this.host.log(message);
+            this.host.log(message);
         }
 
-        msg(message: string) {
-            return this.host.log(message);
+        err(message: string): void {
+            this.host.log(message);
         }
 
         loggingEnabled() {
@@ -700,17 +700,12 @@ namespace Harness.LanguageService {
             return false;
         }
 
-
-        endGroup(): void {
-        }
+        group() { throw ts.notImplemented(); }
 
         perftrc(message: string): void {
             return this.host.log(message);
         }
 
-        startGroup(): void {
-        }
-
         setTimeout(callback: (...args: any[]) => void, ms: number, ...args: any[]): any {
             return setTimeout(callback, ms, args);
         }
@@ -795,7 +790,7 @@ namespace Harness.LanguageService {
                 default:
                     return {
                         module: undefined,
-                        error: "Could not resolve module"
+                        error: new Error("Could not resolve module")
                     };
             }
 
diff --git a/src/harness/unittests/cachingInServerLSHost.ts b/src/harness/unittests/cachingInServerLSHost.ts
index eb2907e89de..92c10c1ff6d 100644
--- a/src/harness/unittests/cachingInServerLSHost.ts
+++ b/src/harness/unittests/cachingInServerLSHost.ts
@@ -52,21 +52,9 @@ namespace ts {
     }
 
     function createProject(rootFile: string, serverHost: server.ServerHost): { project: server.Project, rootScriptInfo: server.ScriptInfo } {
-        const logger: server.Logger = {
-            close: noop,
-            hasLevel: () => false,
-            loggingEnabled: () => false,
-            perftrc: noop,
-            info: noop,
-            startGroup: noop,
-            endGroup: noop,
-            msg: noop,
-            getLogFileName: (): string => undefined
-        };
-
         const svcOpts: server.ProjectServiceOptions = {
             host: serverHost,
-            logger,
+            logger: projectSystem.nullLogger,
             cancellationToken: { isCancellationRequested: () => false },
             useSingleInferredProject: false,
             typingsInstaller: undefined
diff --git a/src/harness/unittests/matchFiles.ts b/src/harness/unittests/matchFiles.ts
index e0454671930..9e2a5883754 100644
--- a/src/harness/unittests/matchFiles.ts
+++ b/src/harness/unittests/matchFiles.ts
@@ -73,6 +73,7 @@ namespace ts {
         "c:/dev/a.d.ts",
         "c:/dev/a.js",
         "c:/dev/b.ts",
+        "c:/dev/x/a.ts",
         "c:/dev/node_modules/a.ts",
         "c:/dev/bower_components/a.ts",
         "c:/dev/jspm_packages/a.ts"
@@ -141,7 +142,8 @@ namespace ts {
                 errors: [],
                 fileNames: [
                     "c:/dev/a.ts",
-                    "c:/dev/b.ts"
+                    "c:/dev/b.ts",
+                    "c:/dev/x/a.ts"
                 ],
                 wildcardDirectories: {
                     "c:/dev": ts.WatchDirectoryFlags.Recursive
@@ -462,7 +464,6 @@ namespace ts {
                 };
                 validateMatches(expected, json, caseInsensitiveHost, caseInsensitiveBasePath);
             });
-
             it("same named declarations are excluded", () => {
                 const json = {
                     include: [
@@ -651,71 +652,127 @@ namespace ts {
                 };
                 validateMatches(expected, json, caseInsensitiveHost, caseInsensitiveBasePath);
             });
-            it("with common package folders and no exclusions", () => {
-                const json = {
-                    include: [
-                        "**/a.ts"
-                    ]
-                };
-                const expected: ts.ParsedCommandLine = {
-                    options: {},
-                    errors: [],
-                    fileNames: [
-                        "c:/dev/a.ts",
-                        "c:/dev/bower_components/a.ts",
-                        "c:/dev/jspm_packages/a.ts",
-                        "c:/dev/node_modules/a.ts"
-                    ],
-                    wildcardDirectories: {
-                        "c:/dev": ts.WatchDirectoryFlags.Recursive
-                    },
-                };
-                validateMatches(expected, json, caseInsensitiveCommonFoldersHost, caseInsensitiveBasePath);
-            });
-            it("with common package folders and exclusions", () => {
-                const json = {
-                    include: [
-                        "**/a.ts"
-                    ],
-                    exclude: [
-                        "a.ts"
-                    ]
-                };
-                const expected: ts.ParsedCommandLine = {
-                    options: {},
-                    errors: [],
-                    fileNames: [
-                        "c:/dev/bower_components/a.ts",
-                        "c:/dev/jspm_packages/a.ts",
-                        "c:/dev/node_modules/a.ts"
-                    ],
-                    wildcardDirectories: {
-                        "c:/dev": ts.WatchDirectoryFlags.Recursive
-                    },
-                };
-                validateMatches(expected, json, caseInsensitiveCommonFoldersHost, caseInsensitiveBasePath);
-            });
-            it("with common package folders and empty exclude", () => {
-                const json = {
-                    include: [
-                        "**/a.ts"
-                    ],
-                    exclude: <string[]>[]
-                };
-                const expected: ts.ParsedCommandLine = {
-                    options: {},
-                    errors: [],
-                    fileNames: [
-                        "c:/dev/a.ts",
-                        "c:/dev/bower_components/a.ts",
-                        "c:/dev/jspm_packages/a.ts",
-                        "c:/dev/node_modules/a.ts"
-                    ],
-                    wildcardDirectories: {
-                        "c:/dev": ts.WatchDirectoryFlags.Recursive
-                    },
-                };
-                validateMatches(expected, json, caseInsensitiveCommonFoldersHost, caseInsensitiveBasePath);
+            describe("with common package folders", () => {
+                it("and no exclusions", () => {
+                    const json = {
+                        include: [
+                            "**/a.ts"
+                        ]
+                    };
+                    const expected: ts.ParsedCommandLine = {
+                        options: {},
+                        errors: [],
+                        fileNames: [
+                            "c:/dev/a.ts",
+                            "c:/dev/x/a.ts"
+                        ],
+                        wildcardDirectories: {
+                            "c:/dev": ts.WatchDirectoryFlags.Recursive
+                        },
+                    };
+                    validateMatches(expected, json, caseInsensitiveCommonFoldersHost, caseInsensitiveBasePath);
+                });
+                it("and exclusions", () => {
+                    const json = {
+                        include: [
+                            "**/?.ts"
+                        ],
+                        exclude: [
+                            "a.ts"
+                        ]
+                    };
+                    const expected: ts.ParsedCommandLine = {
+                        options: {},
+                        errors: [],
+                        fileNames: [
+                            "c:/dev/b.ts",
+                            "c:/dev/x/a.ts"
+                        ],
+                        wildcardDirectories: {
+                            "c:/dev": ts.WatchDirectoryFlags.Recursive
+                        },
+                    };
+                    validateMatches(expected, json, caseInsensitiveCommonFoldersHost, caseInsensitiveBasePath);
+                });
+                it("and empty exclude", () => {
+                    const json = {
+                        include: [
+                            "**/a.ts"
+                        ],
+                        exclude: <string[]>[]
+                    };
+                    const expected: ts.ParsedCommandLine = {
+                        options: {},
+                        errors: [],
+                        fileNames: [
+                            "c:/dev/a.ts",
+                            "c:/dev/x/a.ts"
+                        ],
+                        wildcardDirectories: {
+                            "c:/dev": ts.WatchDirectoryFlags.Recursive
+                        },
+                    };
+                    validateMatches(expected, json, caseInsensitiveCommonFoldersHost, caseInsensitiveBasePath);
+                });
+                it("and explicit recursive include", () => {
+                    const json = {
+                        include: [
+                            "**/a.ts",
+                            "**/node_modules/a.ts"
+                        ]
+                    };
+                    const expected: ts.ParsedCommandLine = {
+                        options: {},
+                        errors: [],
+                        fileNames: [
+                            "c:/dev/a.ts",
+                            "c:/dev/x/a.ts",
+                            "c:/dev/node_modules/a.ts"
+                        ],
+                        wildcardDirectories: {
+                            "c:/dev": ts.WatchDirectoryFlags.Recursive
+                        },
+                    };
+                    validateMatches(expected, json, caseInsensitiveCommonFoldersHost, caseInsensitiveBasePath);
+                });
+                it("and wildcard include", () => {
+                    const json = {
+                        include: [
+                            "*/a.ts"
+                        ]
+                    };
+                    const expected: ts.ParsedCommandLine = {
+                        options: {},
+                        errors: [],
+                        fileNames: [
+                            "c:/dev/x/a.ts"
+                        ],
+                        wildcardDirectories: {
+                            "c:/dev": ts.WatchDirectoryFlags.Recursive
+                        },
+                    };
+                    validateMatches(expected, json, caseInsensitiveCommonFoldersHost, caseInsensitiveBasePath);
+                });
+                it("and explicit wildcard include", () => {
+                    const json = {
+                        include: [
+                            "*/a.ts",
+                            "node_modules/a.ts"
+                        ]
+                    };
+                    const expected: ts.ParsedCommandLine = {
+                        options: {},
+                        errors: [],
+                        fileNames: [
+                            "c:/dev/x/a.ts",
+                            "c:/dev/node_modules/a.ts"
+                        ],
+                        wildcardDirectories: {
+                            "c:/dev": ts.WatchDirectoryFlags.Recursive
+                        },
+                    };
+                    validateMatches(expected, json, caseInsensitiveCommonFoldersHost, caseInsensitiveBasePath);
+                });
             });
             it("exclude .js files when allowJs=false", () => {
                 const json = {
@@ -1066,6 +1123,7 @@ namespace ts {
                 };
                 validateMatches(expected, json, caseInsensitiveHost, caseInsensitiveBasePath);
             });
+
             describe("with trailing recursive directory", () => {
                 it("in includes", () => {
                     const json = {
@@ -1264,6 +1322,7 @@ namespace ts {
                 });
             });
         });
+
         describe("with files or folders that begin with a .", () => {
             it("that are not explicitly included", () => {
                 const json = {
diff --git a/src/harness/unittests/session.ts b/src/harness/unittests/session.ts
index 862ebee4b03..1ce5792a81b 100644
--- a/src/harness/unittests/session.ts
+++ b/src/harness/unittests/session.ts
@@ -28,18 +28,6 @@ namespace ts.server {
         createHash: Harness.LanguageService.mockHash,
     };
 
-    const mockLogger: Logger = {
-        close: noop,
-        hasLevel(): boolean { return false; },
-        loggingEnabled(): boolean { return false; },
-        perftrc: noop,
-        info: noop,
-        startGroup: noop,
-        endGroup: noop,
-        msg: noop,
-        getLogFileName: (): string => undefined
-    };
-
     class TestSession extends Session {
         getProjectService() {
             return this.projectService;
@@ -58,7 +46,7 @@ namespace ts.server {
                 typingsInstaller: undefined,
                 byteLength: Utils.byteLength,
                 hrtime: process.hrtime,
-                logger: mockLogger,
+                logger: projectSystem.nullLogger,
                 canUseEvents: true
             };
             return new TestSession(opts);
@@ -408,7 +396,7 @@ namespace ts.server {
                     typingsInstaller: undefined,
                     byteLength: Utils.byteLength,
                     hrtime: process.hrtime,
-                    logger: mockLogger,
+                    logger: projectSystem.nullLogger,
                     canUseEvents: true
                 });
                 this.addProtocolHandler(this.customHandler, () => {
@@ -475,7 +463,7 @@ namespace ts.server {
                     typingsInstaller: undefined,
                     byteLength: Utils.byteLength,
                     hrtime: process.hrtime,
-                    logger: mockLogger,
+                    logger: projectSystem.nullLogger,
                     canUseEvents: true
                 });
                 this.addProtocolHandler("echo", (req: protocol.Request) => ({
diff --git a/src/harness/unittests/tsserverProjectSystem.ts b/src/harness/unittests/tsserverProjectSystem.ts
index f11900aea11..6c60160740e 100644
--- a/src/harness/unittests/tsserverProjectSystem.ts
+++ b/src/harness/unittests/tsserverProjectSystem.ts
@@ -34,18 +34,17 @@ namespace ts.projectSystem {
     }
 
     export const nullLogger: server.Logger = {
-        close: () => void 0,
-        hasLevel: () => void 0,
+        close: noop,
+        hasLevel: () => false,
         loggingEnabled: () => false,
-        perftrc: () => void 0,
-        info: () => void 0,
-        startGroup: () => void 0,
-        endGroup: () => void 0,
-        msg: () => void 0,
+        perftrc: noop,
+        info: noop,
+        err: noop,
+        group: noop,
         getLogFileName: (): string => undefined
     };
 
-    export const { content: libFileContent } = Harness.getDefaultLibraryFile(Harness.IO);
+    const { content: libFileContent } = Harness.getDefaultLibraryFile(Harness.IO);
     export const libFile: FileOrFolder = {
         path: "/a/lib/lib.d.ts",
         content: libFileContent
@@ -118,7 +117,7 @@ namespace ts.projectSystem {
         return JSON.stringify({ dependencies });
     }
 
-    export function getExecutingFilePathFromLibFile(): string {
+    function getExecutingFilePathFromLibFile(): string {
         return combinePaths(getDirectoryPath(libFile.path), "tsc.js");
     }
 
@@ -130,7 +129,7 @@ namespace ts.projectSystem {
         return map(fileNames, toExternalFile);
     }
 
-    export class TestServerEventManager {
+    class TestServerEventManager {
         public events: server.ProjectServiceEvent[] = [];
 
         handler: server.ProjectServiceEventHandler = (event: server.ProjectServiceEvent) => {
@@ -143,7 +142,7 @@ namespace ts.projectSystem {
         }
     }
 
-    export interface TestServerHostCreationParameters {
+    interface TestServerHostCreationParameters {
         useCaseSensitiveFileNames?: boolean;
         executingFilePath?: string;
         currentDirectory?: string;
@@ -205,7 +204,7 @@ namespace ts.projectSystem {
         return new TestSession(opts);
     }
 
-    export interface CreateProjectServiceParameters {
+    interface CreateProjectServiceParameters {
         cancellationToken?: HostCancellationToken;
         logger?: server.Logger;
         useSingleInferredProject?: boolean;
@@ -253,15 +252,15 @@ namespace ts.projectSystem {
         entries: FSEntry[];
     }
 
-    export function isFolder(s: FSEntry): s is Folder {
+    function isFolder(s: FSEntry): s is Folder {
         return isArray((<Folder>s).entries);
     }
 
-    export function isFile(s: FSEntry): s is File {
+    function isFile(s: FSEntry): s is File {
         return typeof (<File>s).content === "string";
     }
 
-    export function addFolder(fullPath: string, toPath: (s: string) => Path, fs: Map<FSEntry>): Folder {
+    function addFolder(fullPath: string, toPath: (s: string) => Path, fs: Map<FSEntry>): Folder {
         const path = toPath(fullPath);
         if (fs.has(path)) {
             Debug.assert(isFolder(fs.get(path)));
@@ -279,29 +278,29 @@ namespace ts.projectSystem {
         return entry;
     }
 
-    export function checkMapKeys(caption: string, map: Map<any>, expectedKeys: string[]) {
+    function checkMapKeys(caption: string, map: Map<any>, expectedKeys: string[]) {
         assert.equal(map.size, expectedKeys.length, `${caption}: incorrect size of map`);
         for (const name of expectedKeys) {
             assert.isTrue(map.has(name), `${caption} is expected to contain ${name}, actual keys: ${arrayFrom(map.keys())}`);
         }
     }
 
-    export function checkFileNames(caption: string, actualFileNames: string[], expectedFileNames: string[]) {
+    function checkFileNames(caption: string, actualFileNames: string[], expectedFileNames: string[]) {
         assert.equal(actualFileNames.length, expectedFileNames.length, `${caption}: incorrect actual number of files, expected ${JSON.stringify(expectedFileNames)}, got ${actualFileNames}`);
         for (const f of expectedFileNames) {
             assert.isTrue(contains(actualFileNames, f), `${caption}: expected to find ${f} in ${JSON.stringify(actualFileNames)}`);
         }
     }
 
-    export function checkNumberOfConfiguredProjects(projectService: server.ProjectService, expected: number) {
+    function checkNumberOfConfiguredProjects(projectService: server.ProjectService, expected: number) {
         assert.equal(projectService.configuredProjects.length, expected, `expected ${expected} configured project(s)`);
     }
 
-    export function checkNumberOfExternalProjects(projectService: server.ProjectService, expected: number) {
+    function checkNumberOfExternalProjects(projectService: server.ProjectService, expected: number) {
         assert.equal(projectService.externalProjects.length, expected, `expected ${expected} external project(s)`);
     }
 
-    export function checkNumberOfInferredProjects(projectService: server.ProjectService, expected: number) {
+    function checkNumberOfInferredProjects(projectService: server.ProjectService, expected: number) {
         assert.equal(projectService.inferredProjects.length, expected, `expected ${expected} inferred project(s)`);
     }
 
@@ -315,7 +314,7 @@ namespace ts.projectSystem {
         checkMapKeys("watchedFiles", host.watchedFiles, expectedFiles);
     }
 
-    export function checkWatchedDirectories(host: TestServerHost, expectedDirectories: string[]) {
+    function checkWatchedDirectories(host: TestServerHost, expectedDirectories: string[]) {
         checkMapKeys("watchedDirectories", host.watchedDirectories, expectedDirectories);
     }
 
@@ -323,11 +322,11 @@ namespace ts.projectSystem {
         checkFileNames(`${server.ProjectKind[project.projectKind]} project, actual files`, project.getFileNames(), expectedFiles);
     }
 
-    export function checkProjectRootFiles(project: server.Project, expectedFiles: string[]) {
+    function checkProjectRootFiles(project: server.Project, expectedFiles: string[]) {
         checkFileNames(`${server.ProjectKind[project.projectKind]} project, rootFileNames`, project.getRootFiles(), expectedFiles);
     }
 
-    export class Callbacks {
+    class Callbacks {
         private map: TimeOutCallback[] = [];
         private nextId = 1;
 
@@ -363,7 +362,7 @@ namespace ts.projectSystem {
         }
     }
 
-    export type TimeOutCallback = () => any;
+    type TimeOutCallback = () => any;
 
     export class TestServerHost implements server.ServerHost {
         args: string[] = [];
@@ -2332,6 +2331,50 @@ namespace ts.projectSystem {
             const navbar = projectService.externalProjects[0].getLanguageService(/*ensureSynchronized*/ false).getNavigationBarItems(f1.path);
             assert.equal(navbar[0].spans[0].length, f1.content.length);
         });
+
+        it("deleting config file opened from the external project works", () => {
+            const site = {
+                path: "/user/someuser/project/js/site.js",
+                content: ""
+            };
+            const configFile = {
+                path: "/user/someuser/project/tsconfig.json",
+                content: "{}"
+            };
+            const projectFileName = "/user/someuser/project/WebApplication6.csproj";
+            const host = createServerHost([libFile, site, configFile]);
+            const projectService = createProjectService(host);
+
+            const externalProject: protocol.ExternalProject = {
+                projectFileName,
+                rootFiles: [toExternalFile(site.path), toExternalFile(configFile.path)],
+                options: { allowJs: false },
+                typeAcquisition: { "include": [] }
+            };
+
+            projectService.openExternalProjects([externalProject]);
+
+            let knownProjects = projectService.synchronizeProjectList([]);
+            checkNumberOfProjects(projectService, { configuredProjects: 1, externalProjects: 0, inferredProjects: 0 });
+
+            const configProject = projectService.configuredProjects[0];
+            checkProjectActualFiles(configProject, [libFile.path]);
+
+            const diagnostics = configProject.getAllProjectErrors();
+            assert.equal(diagnostics[0].code, Diagnostics.No_inputs_were_found_in_config_file_0_Specified_include_paths_were_1_and_exclude_paths_were_2.code);
+
+            host.reloadFS([libFile, site]);
+            host.triggerFileWatcherCallback(configFile.path, FileWatcherEventKind.Deleted);
+
+            knownProjects = projectService.synchronizeProjectList(map(knownProjects, proj => proj.info));
+            checkNumberOfProjects(projectService, { configuredProjects: 0, externalProjects: 0, inferredProjects: 0 });
+
+            externalProject.rootFiles.length = 1;
+            projectService.openExternalProjects([externalProject]);
+
+            checkNumberOfProjects(projectService, { configuredProjects: 0, externalProjects: 1, inferredProjects: 0 });
+            checkProjectActualFiles(projectService.externalProjects[0], [site.path, libFile.path]);
+        });
     });
 
     describe("Proper errors", () => {
diff --git a/src/lib/es2015.symbol.wellknown.d.ts b/src/lib/es2015.symbol.wellknown.d.ts
index 578cf0acbc2..b7c2610e652 100644
--- a/src/lib/es2015.symbol.wellknown.d.ts
+++ b/src/lib/es2015.symbol.wellknown.d.ts
@@ -110,7 +110,7 @@ interface Map<K, V> {
     readonly [Symbol.toStringTag]: "Map";
 }
 
-interface WeakMap<K extends object, V>{
+interface WeakMap<K extends object, V> {
     readonly [Symbol.toStringTag]: "WeakMap";
 }
 
diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index 4ffdf5d6c5d..554ac337920 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -326,8 +326,8 @@ namespace ts.server {
         typingsInstaller: ITypingsInstaller;
         eventHandler?: ProjectServiceEventHandler;
         throttleWaitMilliseconds?: number;
-        globalPlugins?: string[];
-        pluginProbeLocations?: string[];
+        globalPlugins?: ReadonlyArray<string>;
+        pluginProbeLocations?: ReadonlyArray<string>;
         allowLocalPluginLoads?: boolean;
     }
 
@@ -928,26 +928,24 @@ namespace ts.server {
                 return;
             }
 
-            this.logger.startGroup();
+            this.logger.group(info => {
+                let counter = 0;
+                counter = printProjects(this.externalProjects, info, counter);
+                counter = printProjects(this.configuredProjects, info, counter);
+                printProjects(this.inferredProjects, info, counter);
 
-            let counter = 0;
-            counter = printProjects(this.logger, this.externalProjects, counter);
-            counter = printProjects(this.logger, this.configuredProjects, counter);
-            counter = printProjects(this.logger, this.inferredProjects, counter);
+                info("Open files: ");
+                for (const rootFile of this.openFiles) {
+                    info(`\t${rootFile.fileName}`);
+                }
+            });
 
-            this.logger.info("Open files: ");
-            for (const rootFile of this.openFiles) {
-                this.logger.info(`\t${rootFile.fileName}`);
-            }
-
-            this.logger.endGroup();
-
-            function printProjects(logger: Logger, projects: Project[], counter: number) {
+            function printProjects(projects: Project[], info: (msg: string) => void, counter: number): number {
                 for (const project of projects) {
                     project.updateGraph();
-                    logger.info(`Project '${project.getProjectName()}' (${ProjectKind[project.projectKind]}) ${counter}`);
-                    logger.info(project.filesToString());
-                    logger.info("-----------------------------------------------");
+                    info(`Project '${project.getProjectName()}' (${ProjectKind[project.projectKind]}) ${counter}`);
+                    info(project.filesToString());
+                    info("-----------------------------------------------");
                     counter++;
                 }
                 return counter;
diff --git a/src/server/project.ts b/src/server/project.ts
index 106089fad97..97c8eb706f3 100644
--- a/src/server/project.ts
+++ b/src/server/project.ts
@@ -170,7 +170,8 @@ namespace ts.server {
             log(`Loading ${moduleName} from ${initialDir} (resolved to ${resolvedPath})`);
             const result = host.require(resolvedPath, moduleName);
             if (result.error) {
-                log(`Failed to load module: ${JSON.stringify(result.error)}`);
+                const err = result.error.stack || result.error.message || JSON.stringify(result.error);
+                log(`Failed to load module '${moduleName}': ${err}`);
                 return undefined;
             }
             return result.module;
@@ -362,7 +363,7 @@ namespace ts.server {
             return map(this.program.getSourceFiles(), sourceFile => {
                 const scriptInfo = this.projectService.getScriptInfoForPath(sourceFile.path);
                 if (!scriptInfo) {
-                    Debug.assert(false, `scriptInfo for a file '${sourceFile.fileName}' is missing.`);
+                    Debug.fail(`scriptInfo for a file '${sourceFile.fileName}' is missing.`);
                 }
                 return scriptInfo;
             });
@@ -494,7 +495,7 @@ namespace ts.server {
             this.projectStateVersion++;
         }
 
-        private extractUnresolvedImportsFromSourceFile(file: SourceFile, result: string[]) {
+        private extractUnresolvedImportsFromSourceFile(file: SourceFile, result: Push<string>) {
             const cached = this.cachedUnresolvedImportsPerFile.get(file.path);
             if (cached) {
                 // found cached result - use it and return
@@ -554,7 +555,7 @@ namespace ts.server {
                 for (const sourceFile of this.program.getSourceFiles()) {
                     this.extractUnresolvedImportsFromSourceFile(sourceFile, result);
                 }
-                this.lastCachedUnresolvedImportsList = toSortedArray(result);
+                this.lastCachedUnresolvedImportsList = toDeduplicatedSortedArray(result);
             }
             unresolvedImports = this.lastCachedUnresolvedImportsList;
 
@@ -936,9 +937,9 @@ namespace ts.server {
     export class ConfiguredProject extends Project {
         private typeAcquisition: TypeAcquisition;
         private projectFileWatcher: FileWatcher;
-        private directoryWatcher: FileWatcher;
-        private directoriesWatchedForWildcards: Map<FileWatcher>;
-        private typeRootsWatchers: FileWatcher[];
+        private directoryWatcher: FileWatcher | undefined;
+        private directoriesWatchedForWildcards: Map<FileWatcher> | undefined;
+        private typeRootsWatchers: FileWatcher[] | undefined;
         readonly canonicalConfigFilePath: NormalizedPath;
 
         private plugins: PluginModule[] = [];
@@ -1134,10 +1135,12 @@ namespace ts.server {
                 this.typeRootsWatchers = undefined;
             }
 
-            this.directoriesWatchedForWildcards.forEach(watcher => {
-                watcher.close();
-            });
-            this.directoriesWatchedForWildcards = undefined;
+            if (this.directoriesWatchedForWildcards) {
+                this.directoriesWatchedForWildcards.forEach(watcher => {
+                    watcher.close();
+                });
+                this.directoriesWatchedForWildcards = undefined;
+            }
 
             this.stopWatchingDirectory();
         }
diff --git a/src/server/server.ts b/src/server/server.ts
index 6600b63dcb1..47a858c0efd 100644
--- a/src/server/server.ts
+++ b/src/server/server.ts
@@ -15,8 +15,8 @@ namespace ts.server {
         typingSafeListLocation: string;
         npmLocation: string | undefined;
         telemetryEnabled: boolean;
-        globalPlugins: string[];
-        pluginProbeLocations: string[];
+        globalPlugins: ReadonlyArray<string>;
+        pluginProbeLocations: ReadonlyArray<string>;
         allowLocalPluginLoads: boolean;
     }
 
@@ -116,8 +116,6 @@ namespace ts.server {
         birthtime: Date;
     }
 
-    type RequireResult = { module: {}, error: undefined } | { module: undefined, error: {} };
-
     const readline: {
         createInterface(options: ReadLineOptions): NodeJS.EventEmitter;
     } = require("readline");
@@ -141,8 +139,6 @@ namespace ts.server {
     class Logger implements server.Logger {
         private fd = -1;
         private seq = 0;
-        private inGroup = false;
-        private firstInGroup = true;
 
         constructor(private readonly logFilename: string,
             private readonly traceToConsole: boolean,
@@ -172,22 +168,24 @@ namespace ts.server {
         }
 
         perftrc(s: string) {
-            this.msg(s, Msg.Perf);
+            this.msg(s, "Perf");
         }
 
         info(s: string) {
-            this.msg(s, Msg.Info);
+            this.msg(s, "Info");
         }
 
-        startGroup() {
-            this.inGroup = true;
-            this.firstInGroup = true;
+        err(s: string) {
+            this.msg(s, "Err");
         }
 
-        endGroup() {
-            this.inGroup = false;
+        group(logGroupEntries: (log: (msg: string) => void) => void) {
+            let firstInGroup = false;
+            logGroupEntries(s => {
+                this.msg(s, "Info", /*inGroup*/ true, firstInGroup);
+                firstInGroup = false;
+            });
             this.seq++;
-            this.firstInGroup = true;
         }
 
         loggingEnabled() {
@@ -198,26 +196,32 @@ namespace ts.server {
             return this.loggingEnabled() && this.level >= level;
         }
 
-        msg(s: string, type: Msg.Types = Msg.Err) {
-            if (this.fd >= 0 || this.traceToConsole) {
-                s = `[${nowString()}] ${s}\n`;
+        private msg(s: string, type: string, inGroup = false, firstInGroup = false) {
+            if (!this.canWrite) return;
+
+            s = `[${nowString()}] ${s}\n`;
+            if (!inGroup || firstInGroup) {
                 const prefix = Logger.padStringRight(type + " " + this.seq.toString(), "          ");
-                if (this.firstInGroup) {
-                    s = prefix + s;
-                    this.firstInGroup = false;
-                }
-                if (!this.inGroup) {
-                    this.seq++;
-                    this.firstInGroup = true;
-                }
-                if (this.fd >= 0) {
-                    const buf = new Buffer(s);
-                    // tslint:disable-next-line no-null-keyword
-                    fs.writeSync(this.fd, buf, 0, buf.length, /*position*/ null);
-                }
-                if (this.traceToConsole) {
-                    console.warn(s);
-                }
+                s = prefix + s;
+            }
+            this.write(s);
+            if (!inGroup) {
+                this.seq++;
+            }
+        }
+
+        private get canWrite() {
+            return this.fd >= 0 || this.traceToConsole;
+        }
+
+        private write(s: string) {
+            if (this.fd >= 0) {
+                const buf = new Buffer(s);
+                // tslint:disable-next-line no-null-keyword
+                fs.writeSync(this.fd, buf, 0, buf.length, /*position*/ null);
+            }
+            if (this.traceToConsole) {
+                console.warn(s);
             }
         }
     }
@@ -757,11 +761,21 @@ namespace ts.server {
         validateLocaleAndSetLanguage(localeStr, sys);
     }
 
+    setStackTraceLimit();
+
     const typingSafeListLocation = findArgument(Arguments.TypingSafeListLocation);
     const npmLocation = findArgument(Arguments.NpmLocation);
 
-    const globalPlugins = (findArgument("--globalPlugins") || "").split(",");
-    const pluginProbeLocations = (findArgument("--pluginProbeLocations") || "").split(",");
+    function parseStringArray(argName: string): ReadonlyArray<string> {
+        const arg = findArgument(argName);
+        if (arg === undefined) {
+            return emptyArray;
+        }
+        return arg.split(",").filter(name => name !== "");
+    }
+
+    const globalPlugins = parseStringArray("--globalPlugins");
+    const pluginProbeLocations = parseStringArray("--pluginProbeLocations");
     const allowLocalPluginLoads = hasArgument("--allowLocalPluginLoads");
 
     const useSingleInferredProject = hasArgument("--useSingleInferredProject");
diff --git a/src/server/session.ts b/src/server/session.ts
index 074ba4d6ca1..3c9c1b714de 100644
--- a/src/server/session.ts
+++ b/src/server/session.ts
@@ -163,26 +163,22 @@ namespace ts.server {
      * Scheduling is done via instance of NextStep. If on current step subsequent step was not scheduled - operation is assumed to be completed.
      */
     class MultistepOperation implements NextStep {
-        private requestId: number;
+        private requestId: number | undefined;
         private timerHandle: any;
-        private immediateId: any;
-        private completed = true;
+        private immediateId: number | undefined;
 
         constructor(private readonly operationHost: MultistepOperationHost) {}
 
         public startNew(action: (next: NextStep) => void) {
             this.complete();
             this.requestId = this.operationHost.getCurrentRequestId();
-            this.completed = false;
             this.executeAction(action);
         }
 
         private complete() {
-            if (!this.completed) {
-                if (this.requestId) {
-                    this.operationHost.sendRequestCompletedEvent(this.requestId);
-                }
-                this.completed = true;
+            if (this.requestId !== undefined) {
+                this.operationHost.sendRequestCompletedEvent(this.requestId);
+                this.requestId = undefined;
             }
             this.setTimerHandle(undefined);
             this.setImmediateId(undefined);
@@ -259,8 +255,8 @@ namespace ts.server {
         eventHandler?: ProjectServiceEventHandler;
         throttleWaitMilliseconds?: number;
 
-        globalPlugins?: string[];
-        pluginProbeLocations?: string[];
+        globalPlugins?: ReadonlyArray<string>;
+        pluginProbeLocations?: ReadonlyArray<string>;
         allowLocalPluginLoads?: boolean;
     }
 
@@ -337,7 +333,7 @@ namespace ts.server {
                 case ContextEvent:
                     const { project, fileName } = event.data;
                     this.projectService.logger.info(`got context event, updating diagnostics for ${fileName}`);
-                    this.errorCheck.startNew(next => this.updateErrorCheck(next, [{ fileName, project }], this.changeSeq, (n) => n === this.changeSeq, 100));
+                    this.errorCheck.startNew(next => this.updateErrorCheck(next, [{ fileName, project }], 100));
                     break;
                 case ConfigFileDiagEvent:
                     const { triggerFile, configFileName, diagnostics } = event.data;
@@ -370,7 +366,7 @@ namespace ts.server {
                     msg += "\n" + (<StackTraceError>err).stack;
                 }
             }
-            this.logger.msg(msg, Msg.Err);
+            this.logger.err(msg);
         }
 
         public send(msg: protocol.Message) {
@@ -453,22 +449,23 @@ namespace ts.server {
             }
         }
 
-        private updateProjectStructure(seq: number, matchSeq: (seq: number) => boolean, ms = 1500) {
+        private updateProjectStructure() {
+            const ms = 1500;
+            const seq = this.changeSeq;
             this.host.setTimeout(() => {
-                if (matchSeq(seq)) {
+                if (this.changeSeq === seq) {
                     this.projectService.refreshInferredProjects();
                 }
             }, ms);
         }
 
-        private updateErrorCheck(next: NextStep, checkList: PendingErrorCheck[], seq: number, matchSeq: (seq: number) => boolean, ms = 1500, followMs = 200, requireOpen = true) {
-            if (followMs > ms) {
-                followMs = ms;
-            }
+        private updateErrorCheck(next: NextStep, checkList: PendingErrorCheck[], ms: number, requireOpen = true) {
+            const seq = this.changeSeq;
+            const followMs = Math.min(ms, 200);
 
             let index = 0;
             const checkOne = () => {
-                if (matchSeq(seq)) {
+                if (this.changeSeq === seq) {
                     const checkSpec = checkList[index];
                     index++;
                     if (checkSpec.project.containsFile(checkSpec.fileName, requireOpen)) {
@@ -483,7 +480,7 @@ namespace ts.server {
                 }
             };
 
-            if ((checkList.length > index) && (matchSeq(seq))) {
+            if (checkList.length > index && this.changeSeq === seq) {
                 next.delay(ms, checkOne);
             }
         }
@@ -1262,14 +1259,14 @@ namespace ts.server {
         }
 
         private getDiagnostics(next: NextStep, delay: number, fileNames: string[]): void {
-            const checkList = mapDefined(fileNames, uncheckedFileName => {
+            const checkList = mapDefined<string, PendingErrorCheck>(fileNames, uncheckedFileName => {
                 const fileName = toNormalizedPath(uncheckedFileName);
                 const project = this.projectService.getDefaultProjectForFile(fileName, /*refreshInferredProjects*/ true);
                 return project && { fileName, project };
             });
 
             if (checkList.length > 0) {
-                this.updateErrorCheck(next, checkList, this.changeSeq, (n) => n === this.changeSeq, delay);
+                this.updateErrorCheck(next, checkList, delay);
             }
         }
 
@@ -1283,7 +1280,7 @@ namespace ts.server {
                     scriptInfo.editContent(start, end, args.insertString);
                     this.changeSeq++;
                 }
-                this.updateProjectStructure(this.changeSeq, n => n === this.changeSeq);
+                this.updateProjectStructure();
             }
         }
 
@@ -1638,7 +1635,7 @@ namespace ts.server {
                 const checkList = fileNamesInProject.map(fileName => ({ fileName, project }));
                 // Project level error analysis runs on background files too, therefore
                 // doesn't require the file to be opened
-                this.updateErrorCheck(next, checkList, this.changeSeq, (n) => n === this.changeSeq, delay, 200, /*requireOpen*/ false);
+                this.updateErrorCheck(next, checkList, delay, /*requireOpen*/ false);
             }
         }
 
@@ -1949,7 +1946,7 @@ namespace ts.server {
                 return this.executeWithRequestId(request.seq, () => handler(request));
             }
             else {
-                this.logger.msg(`Unrecognized JSON command: ${JSON.stringify(request)}`, Msg.Err);
+                this.logger.err(`Unrecognized JSON command: ${JSON.stringify(request)}`);
                 this.output(undefined, CommandNames.Unknown, request.seq, `Unrecognized JSON command: ${request.command}`);
                 return { responseRequired: false };
             }
diff --git a/src/server/types.ts b/src/server/types.ts
index 07b94fe827e..4fc4356a4a9 100644
--- a/src/server/types.ts
+++ b/src/server/types.ts
@@ -9,7 +9,7 @@ declare namespace ts.server {
         data: any;
     }
 
-    type RequireResult = { module: {}, error: undefined } | { module: undefined, error: {} };
+    type RequireResult = { module: {}, error: undefined } | { module: undefined, error: { stack?: string, message?: string } };
     export interface ServerHost extends System {
         setTimeout(callback: (...args: any[]) => void, ms: number, ...args: any[]): any;
         clearTimeout(timeoutId: any): void;
diff --git a/src/server/utilities.ts b/src/server/utilities.ts
index fc88f11408a..0d4bc101ff6 100644
--- a/src/server/utilities.ts
+++ b/src/server/utilities.ts
@@ -17,22 +17,11 @@ namespace ts.server {
         loggingEnabled(): boolean;
         perftrc(s: string): void;
         info(s: string): void;
-        startGroup(): void;
-        endGroup(): void;
-        msg(s: string, type?: Msg.Types): void;
+        err(s: string): void;
+        group(logGroupEntries: (log: (msg: string) => void) => void): void;
         getLogFileName(): string;
     }
 
-    export namespace Msg {
-        export type Err = "Err";
-        export const Err: Err = "Err";
-        export type Info = "Info";
-        export const Info: Info = "Info";
-        export type Perf = "Perf";
-        export const Perf: Perf = "Perf";
-        export type Types = Err | Info | Perf;
-    }
-
     function getProjectRootPath(project: Project): Path {
         switch (project.projectKind) {
             case ProjectKind.Configured:
@@ -262,6 +251,15 @@ namespace ts.server {
         return arr as SortedArray<T>;
     }
 
+    export function toDeduplicatedSortedArray(arr: string[]): SortedArray<string> {
+        arr.sort();
+        filterMutate(arr, isNonDuplicateInSortedArray);
+        return arr as SortedArray<string>;
+    }
+    function isNonDuplicateInSortedArray<T>(value: T, index: number, array: T[]) {
+        return index === 0 || value !== array[index - 1];
+    }
+
     export function enumerateInsertsAndDeletes<T>(newItems: SortedReadonlyArray<T>, oldItems: SortedReadonlyArray<T>, inserted: (newItem: T) => void, deleted: (oldItem: T) => void, compare?: Comparer<T>) {
         compare = compare || compareValues;
         let newIndex = 0;
diff --git a/src/services/classifier.ts b/src/services/classifier.ts
index dc5d99bc490..4552d8bf985 100644
--- a/src/services/classifier.ts
+++ b/src/services/classifier.ts
@@ -260,11 +260,11 @@ namespace ts {
                                     templateStack.pop();
                                 }
                                 else {
-                                    Debug.assert(token === SyntaxKind.TemplateMiddle, "Should have been a template middle. Was " + token);
+                                    Debug.assertEqual(token, SyntaxKind.TemplateMiddle, "Should have been a template middle.");
                                 }
                             }
                             else {
-                                Debug.assert(lastTemplateStackToken === SyntaxKind.OpenBraceToken, "Should have been an open brace. Was: " + token);
+                                Debug.assertEqual(lastTemplateStackToken, SyntaxKind.OpenBraceToken, "Should have been an open brace");
                                 templateStack.pop();
                             }
                         }
diff --git a/src/services/completions.ts b/src/services/completions.ts
index b49567ef217..fde07aa78f6 100644
--- a/src/services/completions.ts
+++ b/src/services/completions.ts
@@ -1000,7 +1000,7 @@ namespace ts.Completions {
                     const typeForObject = typeChecker.getTypeAtLocation(objectLikeContainer);
                     if (!typeForObject) return false;
                     // In a binding pattern, get only known properties. Everywhere else we will get all possible properties.
-                    typeMembers = typeChecker.getPropertiesOfType(typeForObject);
+                    typeMembers = typeChecker.getPropertiesOfType(typeForObject).filter((symbol) => !(getDeclarationModifierFlagsFromSymbol(symbol) & ModifierFlags.NonPublicAccessibilityModifier));
                     existingMembers = (<ObjectBindingPattern>objectLikeContainer).elements;
                 }
             }
diff --git a/src/services/formatting/rules.ts b/src/services/formatting/rules.ts
index 15bbf5041d3..2daf8d9d284 100644
--- a/src/services/formatting/rules.ts
+++ b/src/services/formatting/rules.ts
@@ -195,6 +195,7 @@ namespace ts.formatting {
         // Insert space after opening and before closing nonempty parenthesis
         public SpaceAfterOpenParen: Rule;
         public SpaceBeforeCloseParen: Rule;
+        public SpaceBetweenOpenParens: Rule;
         public NoSpaceBetweenParens: Rule;
         public NoSpaceAfterOpenParen: Rule;
         public NoSpaceBeforeCloseParen: Rule;
@@ -457,6 +458,7 @@ namespace ts.formatting {
             // Insert space after opening and before closing nonempty parenthesis
             this.SpaceAfterOpenParen = new Rule(RuleDescriptor.create3(SyntaxKind.OpenParenToken, Shared.TokenRange.Any), RuleOperation.create2(new RuleOperationContext(Rules.IsOptionEnabled("insertSpaceAfterOpeningAndBeforeClosingNonemptyParenthesis"), Rules.IsNonJsxSameLineTokenContext), RuleAction.Space));
             this.SpaceBeforeCloseParen = new Rule(RuleDescriptor.create2(Shared.TokenRange.Any, SyntaxKind.CloseParenToken), RuleOperation.create2(new RuleOperationContext(Rules.IsOptionEnabled("insertSpaceAfterOpeningAndBeforeClosingNonemptyParenthesis"), Rules.IsNonJsxSameLineTokenContext), RuleAction.Space));
+            this.SpaceBetweenOpenParens = new Rule(RuleDescriptor.create1(SyntaxKind.OpenParenToken, SyntaxKind.OpenParenToken), RuleOperation.create2(new RuleOperationContext(Rules.IsOptionEnabled("insertSpaceAfterOpeningAndBeforeClosingNonemptyParenthesis"), Rules.IsNonJsxSameLineTokenContext), RuleAction.Space));
             this.NoSpaceBetweenParens = new Rule(RuleDescriptor.create1(SyntaxKind.OpenParenToken, SyntaxKind.CloseParenToken), RuleOperation.create2(new RuleOperationContext(Rules.IsNonJsxSameLineTokenContext), RuleAction.Delete));
             this.NoSpaceAfterOpenParen = new Rule(RuleDescriptor.create3(SyntaxKind.OpenParenToken, Shared.TokenRange.Any), RuleOperation.create2(new RuleOperationContext(Rules.IsOptionDisabledOrUndefined("insertSpaceAfterOpeningAndBeforeClosingNonemptyParenthesis"), Rules.IsNonJsxSameLineTokenContext), RuleAction.Delete));
             this.NoSpaceBeforeCloseParen = new Rule(RuleDescriptor.create2(Shared.TokenRange.Any, SyntaxKind.CloseParenToken), RuleOperation.create2(new RuleOperationContext(Rules.IsOptionDisabledOrUndefined("insertSpaceAfterOpeningAndBeforeClosingNonemptyParenthesis"), Rules.IsNonJsxSameLineTokenContext), RuleAction.Delete));
@@ -544,7 +546,7 @@ namespace ts.formatting {
                 this.SpaceAfterComma, this.NoSpaceAfterComma,
                 this.SpaceAfterAnonymousFunctionKeyword, this.NoSpaceAfterAnonymousFunctionKeyword,
                 this.SpaceAfterKeywordInControl, this.NoSpaceAfterKeywordInControl,
-                this.SpaceAfterOpenParen, this.SpaceBeforeCloseParen, this.NoSpaceBetweenParens, this.NoSpaceAfterOpenParen, this.NoSpaceBeforeCloseParen,
+                this.SpaceAfterOpenParen, this.SpaceBeforeCloseParen, this.SpaceBetweenOpenParens, this.NoSpaceBetweenParens, this.NoSpaceAfterOpenParen, this.NoSpaceBeforeCloseParen,
                 this.SpaceAfterOpenBracket, this.SpaceBeforeCloseBracket, this.NoSpaceBetweenBrackets, this.NoSpaceAfterOpenBracket, this.NoSpaceBeforeCloseBracket,
                 this.SpaceAfterOpenBrace, this.SpaceBeforeCloseBrace, this.NoSpaceBetweenEmptyBraceBrackets, this.NoSpaceAfterOpenBrace, this.NoSpaceBeforeCloseBrace,
                 this.SpaceAfterTemplateHeadAndMiddle, this.SpaceBeforeTemplateMiddleAndTail, this.NoSpaceAfterTemplateHeadAndMiddle, this.NoSpaceBeforeTemplateMiddleAndTail,
diff --git a/src/services/jsTyping.ts b/src/services/jsTyping.ts
index 4de7bb3191d..5e7b7d424f8 100644
--- a/src/services/jsTyping.ts
+++ b/src/services/jsTyping.ts
@@ -35,7 +35,7 @@ namespace ts.JsTyping {
         "crypto", "stream", "util", "assert", "tty", "domain",
         "constants", "process", "v8", "timers", "console"];
 
-    const nodeCoreModules = arrayToMap(<string[]>nodeCoreModuleList, x => x);
+    const nodeCoreModules = arrayToSet(nodeCoreModuleList);
 
     /**
      * A map of loose file names to library names that we are confident require typings
diff --git a/src/services/services.ts b/src/services/services.ts
index 6a171ad9166..874c2feb107 100644
--- a/src/services/services.ts
+++ b/src/services/services.ts
@@ -1258,7 +1258,7 @@ namespace ts {
                         // We do not support the scenario where a host can modify a registered
                         // file's script kind, i.e. in one project some file is treated as ".ts"
                         // and in another as ".js"
-                        Debug.assert(hostFileInformation.scriptKind === oldSourceFile.scriptKind, "Registered script kind (" + oldSourceFile.scriptKind + ") should match new script kind (" + hostFileInformation.scriptKind + ") for file: " + path);
+                        Debug.assertEqual(hostFileInformation.scriptKind, oldSourceFile.scriptKind, "Registered script kind should match new script kind.", path);
 
                         return documentRegistry.updateDocumentWithKey(fileName, path, newSettings, documentRegistryBucketKey, hostFileInformation.scriptSnapshot, hostFileInformation.version, hostFileInformation.scriptKind);
                     }
diff --git a/src/services/signatureHelp.ts b/src/services/signatureHelp.ts
index f008c829116..2976b0d28ee 100644
--- a/src/services/signatureHelp.ts
+++ b/src/services/signatureHelp.ts
@@ -136,7 +136,9 @@ namespace ts.SignatureHelp {
 
             const kind = invocation.typeArguments && invocation.typeArguments.pos === list.pos ? ArgumentListKind.TypeArguments : ArgumentListKind.CallArguments;
             const argumentCount = getArgumentCount(list);
-            Debug.assert(argumentIndex === 0 || argumentIndex < argumentCount, `argumentCount < argumentIndex, ${argumentCount} < ${argumentIndex}`);
+            if (argumentIndex !== 0) {
+                Debug.assertLessThan(argumentIndex, argumentCount);
+            }
             const argumentsSpan = getApplicableSpanForArguments(list, sourceFile);
             return { kind, invocation, argumentsSpan, argumentIndex, argumentCount };
         }
@@ -270,7 +272,9 @@ namespace ts.SignatureHelp {
             ? 1
             : (<TemplateExpression>tagExpression.template).templateSpans.length + 1;
 
-        Debug.assert(argumentIndex === 0 || argumentIndex < argumentCount, `argumentCount < argumentIndex, ${argumentCount} < ${argumentIndex}`);
+        if (argumentIndex !== 0) {
+            Debug.assertLessThan(argumentIndex, argumentCount);
+        }
         return {
             kind: ArgumentListKind.TaggedTemplateArguments,
             invocation: tagExpression,
@@ -402,7 +406,9 @@ namespace ts.SignatureHelp {
             };
         });
 
-        Debug.assert(argumentIndex === 0 || argumentIndex < argumentCount, `argumentCount < argumentIndex, ${argumentCount} < ${argumentIndex}`);
+        if (argumentIndex !== 0) {
+            Debug.assertLessThan(argumentIndex, argumentCount);
+        }
 
         const selectedItemIndex = candidates.indexOf(resolvedSignature);
         Debug.assert(selectedItemIndex !== -1); // If candidates is non-empty it should always include bestSignature. We check for an empty candidates before calling this function.
diff --git a/src/services/transpile.ts b/src/services/transpile.ts
index 561c188c6cd..79a69b886d9 100644
--- a/src/services/transpile.ts
+++ b/src/services/transpile.ts
@@ -78,11 +78,11 @@ namespace ts {
             getSourceFile: (fileName) => fileName === normalizePath(inputFileName) ? sourceFile : undefined,
             writeFile: (name, text) => {
                 if (fileExtensionIs(name, ".map")) {
-                    Debug.assert(sourceMapText === undefined, `Unexpected multiple source map outputs for the file '${name}'`);
+                    Debug.assertEqual(sourceMapText, undefined, "Unexpected multiple source map outputs, file:", name);
                     sourceMapText = text;
                 }
                 else {
-                    Debug.assert(outputText === undefined, `Unexpected multiple outputs for the file: '${name}'`);
+                    Debug.assertEqual(outputText, undefined, "Unexpected multiple outputs, file:", name);
                     outputText = text;
                 }
             },
diff --git a/tests/baselines/reference/anyIndexedAccessArrayNoException.errors.txt b/tests/baselines/reference/anyIndexedAccessArrayNoException.errors.txt
index e207468122b..01c5bd6b2e2 100644
--- a/tests/baselines/reference/anyIndexedAccessArrayNoException.errors.txt
+++ b/tests/baselines/reference/anyIndexedAccessArrayNoException.errors.txt
@@ -1,8 +1,11 @@
+tests/cases/compiler/anyIndexedAccessArrayNoException.ts(1,12): error TS1122: A tuple type element list cannot be empty.
 tests/cases/compiler/anyIndexedAccessArrayNoException.ts(1,12): error TS2538: Type '[]' cannot be used as an index type.
 
 
-==== tests/cases/compiler/anyIndexedAccessArrayNoException.ts (1 errors) ====
+==== tests/cases/compiler/anyIndexedAccessArrayNoException.ts (2 errors) ====
     var x: any[[]];
                ~~
+!!! error TS1122: A tuple type element list cannot be empty.
+               ~~
 !!! error TS2538: Type '[]' cannot be used as an index type.
     
\ No newline at end of file
diff --git a/tests/baselines/reference/checkTypePredicateForRedundantProperties.errors.txt b/tests/baselines/reference/checkTypePredicateForRedundantProperties.errors.txt
new file mode 100644
index 00000000000..a5cb9b0a098
--- /dev/null
+++ b/tests/baselines/reference/checkTypePredicateForRedundantProperties.errors.txt
@@ -0,0 +1,13 @@
+tests/cases/compiler/checkTypePredicateForRedundantProperties.ts(1,35): error TS2300: Duplicate identifier 'a'.
+tests/cases/compiler/checkTypePredicateForRedundantProperties.ts(1,46): error TS2300: Duplicate identifier 'a'.
+
+
+==== tests/cases/compiler/checkTypePredicateForRedundantProperties.ts (2 errors) ====
+    function addProp2(x: any): x is { a: string; a: string; } {
+                                      ~
+!!! error TS2300: Duplicate identifier 'a'.
+                                                 ~
+!!! error TS2300: Duplicate identifier 'a'.
+        return true;
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/checkTypePredicateForRedundantProperties.js b/tests/baselines/reference/checkTypePredicateForRedundantProperties.js
new file mode 100644
index 00000000000..8f7be2bfbbc
--- /dev/null
+++ b/tests/baselines/reference/checkTypePredicateForRedundantProperties.js
@@ -0,0 +1,10 @@
+//// [checkTypePredicateForRedundantProperties.ts]
+function addProp2(x: any): x is { a: string; a: string; } {
+    return true;
+}
+
+
+//// [checkTypePredicateForRedundantProperties.js]
+function addProp2(x) {
+    return true;
+}
diff --git a/tests/baselines/reference/commentOnBinaryOperator1.js b/tests/baselines/reference/commentOnBinaryOperator1.js
new file mode 100644
index 00000000000..daad6f5bdde
--- /dev/null
+++ b/tests/baselines/reference/commentOnBinaryOperator1.js
@@ -0,0 +1,25 @@
+//// [commentOnBinaryOperator1.ts]
+var a = 'some'
+    // comment
+    + 'text';
+
+var b = 'some'
+    /* comment */
+    + 'text';
+
+var c = 'some'
+    /* comment */
+    + /*comment1*/
+    'text';
+
+//// [commentOnBinaryOperator1.js]
+var a = 'some'
+    // comment
+    + 'text';
+var b = 'some'
+    /* comment */
+    + 'text';
+var c = 'some'
+    /* comment */
+    +/*comment1*/ 
+        'text';
diff --git a/tests/baselines/reference/commentOnBinaryOperator1.symbols b/tests/baselines/reference/commentOnBinaryOperator1.symbols
new file mode 100644
index 00000000000..db92e4e4fc5
--- /dev/null
+++ b/tests/baselines/reference/commentOnBinaryOperator1.symbols
@@ -0,0 +1,19 @@
+=== tests/cases/compiler/commentOnBinaryOperator1.ts ===
+var a = 'some'
+>a : Symbol(a, Decl(commentOnBinaryOperator1.ts, 0, 3))
+
+    // comment
+    + 'text';
+
+var b = 'some'
+>b : Symbol(b, Decl(commentOnBinaryOperator1.ts, 4, 3))
+
+    /* comment */
+    + 'text';
+
+var c = 'some'
+>c : Symbol(c, Decl(commentOnBinaryOperator1.ts, 8, 3))
+
+    /* comment */
+    + /*comment1*/
+    'text';
diff --git a/tests/baselines/reference/commentOnBinaryOperator1.types b/tests/baselines/reference/commentOnBinaryOperator1.types
new file mode 100644
index 00000000000..59724d42f51
--- /dev/null
+++ b/tests/baselines/reference/commentOnBinaryOperator1.types
@@ -0,0 +1,29 @@
+=== tests/cases/compiler/commentOnBinaryOperator1.ts ===
+var a = 'some'
+>a : string
+>'some'    // comment    + 'text' : string
+>'some' : "some"
+
+    // comment
+    + 'text';
+>'text' : "text"
+
+var b = 'some'
+>b : string
+>'some'    /* comment */    + 'text' : string
+>'some' : "some"
+
+    /* comment */
+    + 'text';
+>'text' : "text"
+
+var c = 'some'
+>c : string
+>'some'    /* comment */    + /*comment1*/    'text' : string
+>'some' : "some"
+
+    /* comment */
+    + /*comment1*/
+    'text';
+>'text' : "text"
+
diff --git a/tests/baselines/reference/commentOnBinaryOperator2.js b/tests/baselines/reference/commentOnBinaryOperator2.js
new file mode 100644
index 00000000000..5d87ddccbef
--- /dev/null
+++ b/tests/baselines/reference/commentOnBinaryOperator2.js
@@ -0,0 +1,22 @@
+//// [commentOnBinaryOperator2.ts]
+var a = 'some'
+    // comment
+    + 'text';
+
+var b = 'some'
+    /* comment */
+    + 'text';
+
+var c = 'some'
+    /* comment */
+    + /*comment1*/
+    'text';
+
+//// [commentOnBinaryOperator2.js]
+var a = 'some'
+    + 'text';
+var b = 'some'
+    + 'text';
+var c = 'some'
+    +
+        'text';
diff --git a/tests/baselines/reference/commentOnBinaryOperator2.symbols b/tests/baselines/reference/commentOnBinaryOperator2.symbols
new file mode 100644
index 00000000000..10a0e94dd36
--- /dev/null
+++ b/tests/baselines/reference/commentOnBinaryOperator2.symbols
@@ -0,0 +1,19 @@
+=== tests/cases/compiler/commentOnBinaryOperator2.ts ===
+var a = 'some'
+>a : Symbol(a, Decl(commentOnBinaryOperator2.ts, 0, 3))
+
+    // comment
+    + 'text';
+
+var b = 'some'
+>b : Symbol(b, Decl(commentOnBinaryOperator2.ts, 4, 3))
+
+    /* comment */
+    + 'text';
+
+var c = 'some'
+>c : Symbol(c, Decl(commentOnBinaryOperator2.ts, 8, 3))
+
+    /* comment */
+    + /*comment1*/
+    'text';
diff --git a/tests/baselines/reference/commentOnBinaryOperator2.types b/tests/baselines/reference/commentOnBinaryOperator2.types
new file mode 100644
index 00000000000..411c8c69b8a
--- /dev/null
+++ b/tests/baselines/reference/commentOnBinaryOperator2.types
@@ -0,0 +1,29 @@
+=== tests/cases/compiler/commentOnBinaryOperator2.ts ===
+var a = 'some'
+>a : string
+>'some'    // comment    + 'text' : string
+>'some' : "some"
+
+    // comment
+    + 'text';
+>'text' : "text"
+
+var b = 'some'
+>b : string
+>'some'    /* comment */    + 'text' : string
+>'some' : "some"
+
+    /* comment */
+    + 'text';
+>'text' : "text"
+
+var c = 'some'
+>c : string
+>'some'    /* comment */    + /*comment1*/    'text' : string
+>'some' : "some"
+
+    /* comment */
+    + /*comment1*/
+    'text';
+>'text' : "text"
+
diff --git a/tests/baselines/reference/commentsArgumentsOfCallExpression2.js b/tests/baselines/reference/commentsArgumentsOfCallExpression2.js
index a7065410ff4..e05256b86b6 100644
--- a/tests/baselines/reference/commentsArgumentsOfCallExpression2.js
+++ b/tests/baselines/reference/commentsArgumentsOfCallExpression2.js
@@ -14,7 +14,7 @@ foo(
 function foo(/*c1*/ x, /*d1*/ y, /*e1*/ w) { }
 var a, b;
 foo(/*c2*/ 1, /*d2*/ 1 + 2, /*e1*/ a + b);
-foo(/*c3*/ function () { }, /*d2*/ function () { }, /*e2*/ a + b);
+foo(/*c3*/ function () { }, /*d2*/ function () { }, /*e2*/ a +/*e3*/  b);
 foo(/*c3*/ function () { }, /*d3*/ function () { }, /*e3*/ (a + b));
 foo(
 /*c4*/ function () { }, 
diff --git a/tests/baselines/reference/deferredLookupTypeResolution.js b/tests/baselines/reference/deferredLookupTypeResolution.js
new file mode 100644
index 00000000000..5f8edd63e57
--- /dev/null
+++ b/tests/baselines/reference/deferredLookupTypeResolution.js
@@ -0,0 +1,64 @@
+//// [deferredLookupTypeResolution.ts]
+// Repro from #17456
+
+type StringContains<S extends string, L extends string> = (
+    { [K in S]:      'true' } &
+    { [key: string]: 'false' }
+  )[L]
+
+type ObjectHasKey<O, L extends string> = StringContains<keyof O, L>
+
+type First<T> = ObjectHasKey<T, '0'>;  // Should be deferred
+
+type T1 = ObjectHasKey<{ a: string }, 'a'>;  // 'true'
+type T2 = ObjectHasKey<{ a: string }, 'b'>;  // 'false'
+
+// Verify that mapped type isn't eagerly resolved in type-to-string operation
+
+declare function f1<A extends string, B extends string>(a: A, b: B): { [P in A | B]: any };
+
+function f2<A extends string>(a: A) {
+    return f1(a, 'x');
+}
+
+function f3(x: 'a' | 'b') {
+    return f2(x);
+}
+
+
+//// [deferredLookupTypeResolution.js]
+"use strict";
+// Repro from #17456
+function f2(a) {
+    return f1(a, 'x');
+}
+function f3(x) {
+    return f2(x);
+}
+
+
+//// [deferredLookupTypeResolution.d.ts]
+declare type StringContains<S extends string, L extends string> = ({
+    [K in S]: 'true';
+} & {
+    [key: string]: 'false';
+})[L];
+declare type ObjectHasKey<O, L extends string> = StringContains<keyof O, L>;
+declare type First<T> = ObjectHasKey<T, '0'>;
+declare type T1 = ObjectHasKey<{
+    a: string;
+}, 'a'>;
+declare type T2 = ObjectHasKey<{
+    a: string;
+}, 'b'>;
+declare function f1<A extends string, B extends string>(a: A, b: B): {
+    [P in A | B]: any;
+};
+declare function f2<A extends string>(a: A): {
+    [P in A | "x"]: any;
+};
+declare function f3(x: 'a' | 'b'): {
+    a: any;
+    b: any;
+    x: any;
+};
diff --git a/tests/baselines/reference/deferredLookupTypeResolution.symbols b/tests/baselines/reference/deferredLookupTypeResolution.symbols
new file mode 100644
index 00000000000..022dc3cc2f4
--- /dev/null
+++ b/tests/baselines/reference/deferredLookupTypeResolution.symbols
@@ -0,0 +1,76 @@
+=== tests/cases/compiler/deferredLookupTypeResolution.ts ===
+// Repro from #17456
+
+type StringContains<S extends string, L extends string> = (
+>StringContains : Symbol(StringContains, Decl(deferredLookupTypeResolution.ts, 0, 0))
+>S : Symbol(S, Decl(deferredLookupTypeResolution.ts, 2, 20))
+>L : Symbol(L, Decl(deferredLookupTypeResolution.ts, 2, 37))
+
+    { [K in S]:      'true' } &
+>K : Symbol(K, Decl(deferredLookupTypeResolution.ts, 3, 7))
+>S : Symbol(S, Decl(deferredLookupTypeResolution.ts, 2, 20))
+
+    { [key: string]: 'false' }
+>key : Symbol(key, Decl(deferredLookupTypeResolution.ts, 4, 7))
+
+  )[L]
+>L : Symbol(L, Decl(deferredLookupTypeResolution.ts, 2, 37))
+
+type ObjectHasKey<O, L extends string> = StringContains<keyof O, L>
+>ObjectHasKey : Symbol(ObjectHasKey, Decl(deferredLookupTypeResolution.ts, 5, 6))
+>O : Symbol(O, Decl(deferredLookupTypeResolution.ts, 7, 18))
+>L : Symbol(L, Decl(deferredLookupTypeResolution.ts, 7, 20))
+>StringContains : Symbol(StringContains, Decl(deferredLookupTypeResolution.ts, 0, 0))
+>O : Symbol(O, Decl(deferredLookupTypeResolution.ts, 7, 18))
+>L : Symbol(L, Decl(deferredLookupTypeResolution.ts, 7, 20))
+
+type First<T> = ObjectHasKey<T, '0'>;  // Should be deferred
+>First : Symbol(First, Decl(deferredLookupTypeResolution.ts, 7, 67))
+>T : Symbol(T, Decl(deferredLookupTypeResolution.ts, 9, 11))
+>ObjectHasKey : Symbol(ObjectHasKey, Decl(deferredLookupTypeResolution.ts, 5, 6))
+>T : Symbol(T, Decl(deferredLookupTypeResolution.ts, 9, 11))
+
+type T1 = ObjectHasKey<{ a: string }, 'a'>;  // 'true'
+>T1 : Symbol(T1, Decl(deferredLookupTypeResolution.ts, 9, 37))
+>ObjectHasKey : Symbol(ObjectHasKey, Decl(deferredLookupTypeResolution.ts, 5, 6))
+>a : Symbol(a, Decl(deferredLookupTypeResolution.ts, 11, 24))
+
+type T2 = ObjectHasKey<{ a: string }, 'b'>;  // 'false'
+>T2 : Symbol(T2, Decl(deferredLookupTypeResolution.ts, 11, 43))
+>ObjectHasKey : Symbol(ObjectHasKey, Decl(deferredLookupTypeResolution.ts, 5, 6))
+>a : Symbol(a, Decl(deferredLookupTypeResolution.ts, 12, 24))
+
+// Verify that mapped type isn't eagerly resolved in type-to-string operation
+
+declare function f1<A extends string, B extends string>(a: A, b: B): { [P in A | B]: any };
+>f1 : Symbol(f1, Decl(deferredLookupTypeResolution.ts, 12, 43))
+>A : Symbol(A, Decl(deferredLookupTypeResolution.ts, 16, 20))
+>B : Symbol(B, Decl(deferredLookupTypeResolution.ts, 16, 37))
+>a : Symbol(a, Decl(deferredLookupTypeResolution.ts, 16, 56))
+>A : Symbol(A, Decl(deferredLookupTypeResolution.ts, 16, 20))
+>b : Symbol(b, Decl(deferredLookupTypeResolution.ts, 16, 61))
+>B : Symbol(B, Decl(deferredLookupTypeResolution.ts, 16, 37))
+>P : Symbol(P, Decl(deferredLookupTypeResolution.ts, 16, 72))
+>A : Symbol(A, Decl(deferredLookupTypeResolution.ts, 16, 20))
+>B : Symbol(B, Decl(deferredLookupTypeResolution.ts, 16, 37))
+
+function f2<A extends string>(a: A) {
+>f2 : Symbol(f2, Decl(deferredLookupTypeResolution.ts, 16, 91))
+>A : Symbol(A, Decl(deferredLookupTypeResolution.ts, 18, 12))
+>a : Symbol(a, Decl(deferredLookupTypeResolution.ts, 18, 30))
+>A : Symbol(A, Decl(deferredLookupTypeResolution.ts, 18, 12))
+
+    return f1(a, 'x');
+>f1 : Symbol(f1, Decl(deferredLookupTypeResolution.ts, 12, 43))
+>a : Symbol(a, Decl(deferredLookupTypeResolution.ts, 18, 30))
+}
+
+function f3(x: 'a' | 'b') {
+>f3 : Symbol(f3, Decl(deferredLookupTypeResolution.ts, 20, 1))
+>x : Symbol(x, Decl(deferredLookupTypeResolution.ts, 22, 12))
+
+    return f2(x);
+>f2 : Symbol(f2, Decl(deferredLookupTypeResolution.ts, 16, 91))
+>x : Symbol(x, Decl(deferredLookupTypeResolution.ts, 22, 12))
+}
+
diff --git a/tests/baselines/reference/deferredLookupTypeResolution.types b/tests/baselines/reference/deferredLookupTypeResolution.types
new file mode 100644
index 00000000000..d9486d30b07
--- /dev/null
+++ b/tests/baselines/reference/deferredLookupTypeResolution.types
@@ -0,0 +1,79 @@
+=== tests/cases/compiler/deferredLookupTypeResolution.ts ===
+// Repro from #17456
+
+type StringContains<S extends string, L extends string> = (
+>StringContains : ({ [K in S]: "true"; } & { [key: string]: "false"; })[L]
+>S : S
+>L : L
+
+    { [K in S]:      'true' } &
+>K : K
+>S : S
+
+    { [key: string]: 'false' }
+>key : string
+
+  )[L]
+>L : L
+
+type ObjectHasKey<O, L extends string> = StringContains<keyof O, L>
+>ObjectHasKey : ({ [K in S]: "true"; } & { [key: string]: "false"; })[L]
+>O : O
+>L : L
+>StringContains : ({ [K in S]: "true"; } & { [key: string]: "false"; })[L]
+>O : O
+>L : L
+
+type First<T> = ObjectHasKey<T, '0'>;  // Should be deferred
+>First : ({ [K in S]: "true"; } & { [key: string]: "false"; })["0"]
+>T : T
+>ObjectHasKey : ({ [K in S]: "true"; } & { [key: string]: "false"; })[L]
+>T : T
+
+type T1 = ObjectHasKey<{ a: string }, 'a'>;  // 'true'
+>T1 : "true"
+>ObjectHasKey : ({ [K in S]: "true"; } & { [key: string]: "false"; })[L]
+>a : string
+
+type T2 = ObjectHasKey<{ a: string }, 'b'>;  // 'false'
+>T2 : "false"
+>ObjectHasKey : ({ [K in S]: "true"; } & { [key: string]: "false"; })[L]
+>a : string
+
+// Verify that mapped type isn't eagerly resolved in type-to-string operation
+
+declare function f1<A extends string, B extends string>(a: A, b: B): { [P in A | B]: any };
+>f1 : <A extends string, B extends string>(a: A, b: B) => { [P in A | B]: any; }
+>A : A
+>B : B
+>a : A
+>A : A
+>b : B
+>B : B
+>P : P
+>A : A
+>B : B
+
+function f2<A extends string>(a: A) {
+>f2 : <A extends string>(a: A) => { [P in A | B]: any; }
+>A : A
+>a : A
+>A : A
+
+    return f1(a, 'x');
+>f1(a, 'x') : { [P in A | B]: any; }
+>f1 : <A extends string, B extends string>(a: A, b: B) => { [P in A | B]: any; }
+>a : A
+>'x' : "x"
+}
+
+function f3(x: 'a' | 'b') {
+>f3 : (x: "a" | "b") => { a: any; b: any; x: any; }
+>x : "a" | "b"
+
+    return f2(x);
+>f2(x) : { a: any; b: any; x: any; }
+>f2 : <A extends string>(a: A) => { [P in A | B]: any; }
+>x : "a" | "b"
+}
+
diff --git a/tests/baselines/reference/deferredLookupTypeResolution2.errors.txt b/tests/baselines/reference/deferredLookupTypeResolution2.errors.txt
new file mode 100644
index 00000000000..f6bbe72f1a6
--- /dev/null
+++ b/tests/baselines/reference/deferredLookupTypeResolution2.errors.txt
@@ -0,0 +1,31 @@
+tests/cases/compiler/deferredLookupTypeResolution2.ts(14,13): error TS2536: Type '({ [K in S]: "true"; } & { [key: string]: "false"; })["1"]' cannot be used to index type '{ true: "true"; }'.
+tests/cases/compiler/deferredLookupTypeResolution2.ts(19,21): error TS2536: Type '({ true: "otherwise"; } & { [k: string]: "true"; })[({ [K in S]: "true"; } & { [key: string]: "false"; })["1"]]' cannot be used to index type '{ true: "true"; }'.
+
+
+==== tests/cases/compiler/deferredLookupTypeResolution2.ts (2 errors) ====
+    // Repro from #17456
+    
+    type StringContains<S extends string, L extends string> = ({ [K in S]: 'true' } & { [key: string]: 'false'})[L];
+    
+    type ObjectHasKey<O, L extends string> = StringContains<keyof O, L>;
+    
+    type A<T> = ObjectHasKey<T, '0'>;
+    
+    type B = ObjectHasKey<[string, number], '1'>;  // "true"
+    type C = ObjectHasKey<[string, number], '2'>;  // "false"
+    type D = A<[string]>;  // "true"
+    
+    // Error, "false" not handled
+    type E<T> = { true: 'true' }[ObjectHasKey<T, '1'>];
+                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2536: Type '({ [K in S]: "true"; } & { [key: string]: "false"; })["1"]' cannot be used to index type '{ true: "true"; }'.
+    
+    type Juxtapose<T> = ({ true: 'otherwise' } & { [k: string]: 'true' })[ObjectHasKey<T, '1'>];
+    
+    // Error, "otherwise" is missing
+    type DeepError<T> = { true: 'true' }[Juxtapose<T>];
+                        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2536: Type '({ true: "otherwise"; } & { [k: string]: "true"; })[({ [K in S]: "true"; } & { [key: string]: "false"; })["1"]]' cannot be used to index type '{ true: "true"; }'.
+    
+    type DeepOK<T> = { true: 'true', otherwise: 'false' }[Juxtapose<T>];
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/deferredLookupTypeResolution2.js b/tests/baselines/reference/deferredLookupTypeResolution2.js
new file mode 100644
index 00000000000..97289f47f9c
--- /dev/null
+++ b/tests/baselines/reference/deferredLookupTypeResolution2.js
@@ -0,0 +1,55 @@
+//// [deferredLookupTypeResolution2.ts]
+// Repro from #17456
+
+type StringContains<S extends string, L extends string> = ({ [K in S]: 'true' } & { [key: string]: 'false'})[L];
+
+type ObjectHasKey<O, L extends string> = StringContains<keyof O, L>;
+
+type A<T> = ObjectHasKey<T, '0'>;
+
+type B = ObjectHasKey<[string, number], '1'>;  // "true"
+type C = ObjectHasKey<[string, number], '2'>;  // "false"
+type D = A<[string]>;  // "true"
+
+// Error, "false" not handled
+type E<T> = { true: 'true' }[ObjectHasKey<T, '1'>];
+
+type Juxtapose<T> = ({ true: 'otherwise' } & { [k: string]: 'true' })[ObjectHasKey<T, '1'>];
+
+// Error, "otherwise" is missing
+type DeepError<T> = { true: 'true' }[Juxtapose<T>];
+
+type DeepOK<T> = { true: 'true', otherwise: 'false' }[Juxtapose<T>];
+
+
+//// [deferredLookupTypeResolution2.js]
+"use strict";
+// Repro from #17456
+
+
+//// [deferredLookupTypeResolution2.d.ts]
+declare type StringContains<S extends string, L extends string> = ({
+    [K in S]: 'true';
+} & {
+    [key: string]: 'false';
+})[L];
+declare type ObjectHasKey<O, L extends string> = StringContains<keyof O, L>;
+declare type A<T> = ObjectHasKey<T, '0'>;
+declare type B = ObjectHasKey<[string, number], '1'>;
+declare type C = ObjectHasKey<[string, number], '2'>;
+declare type D = A<[string]>;
+declare type E<T> = {
+    true: 'true';
+}[ObjectHasKey<T, '1'>];
+declare type Juxtapose<T> = ({
+    true: 'otherwise';
+} & {
+    [k: string]: 'true';
+})[ObjectHasKey<T, '1'>];
+declare type DeepError<T> = {
+    true: 'true';
+}[Juxtapose<T>];
+declare type DeepOK<T> = {
+    true: 'true';
+    otherwise: 'false';
+}[Juxtapose<T>];
diff --git a/tests/baselines/reference/doNotInferUnrelatedTypes.js b/tests/baselines/reference/doNotInferUnrelatedTypes.js
new file mode 100644
index 00000000000..cff708cec89
--- /dev/null
+++ b/tests/baselines/reference/doNotInferUnrelatedTypes.js
@@ -0,0 +1,11 @@
+//// [doNotInferUnrelatedTypes.ts]
+// #16709
+declare function dearray<T>(ara: ReadonlyArray<T>): T;
+type LiteralType = "foo" | "bar";
+declare var alt: Array<LiteralType>;
+
+let foo: LiteralType = dearray(alt);
+
+
+//// [doNotInferUnrelatedTypes.js]
+var foo = dearray(alt);
diff --git a/tests/baselines/reference/doNotInferUnrelatedTypes.symbols b/tests/baselines/reference/doNotInferUnrelatedTypes.symbols
new file mode 100644
index 00000000000..ce7351cf78f
--- /dev/null
+++ b/tests/baselines/reference/doNotInferUnrelatedTypes.symbols
@@ -0,0 +1,24 @@
+=== tests/cases/compiler/doNotInferUnrelatedTypes.ts ===
+// #16709
+declare function dearray<T>(ara: ReadonlyArray<T>): T;
+>dearray : Symbol(dearray, Decl(doNotInferUnrelatedTypes.ts, 0, 0))
+>T : Symbol(T, Decl(doNotInferUnrelatedTypes.ts, 1, 25))
+>ara : Symbol(ara, Decl(doNotInferUnrelatedTypes.ts, 1, 28))
+>ReadonlyArray : Symbol(ReadonlyArray, Decl(lib.d.ts, --, --))
+>T : Symbol(T, Decl(doNotInferUnrelatedTypes.ts, 1, 25))
+>T : Symbol(T, Decl(doNotInferUnrelatedTypes.ts, 1, 25))
+
+type LiteralType = "foo" | "bar";
+>LiteralType : Symbol(LiteralType, Decl(doNotInferUnrelatedTypes.ts, 1, 54))
+
+declare var alt: Array<LiteralType>;
+>alt : Symbol(alt, Decl(doNotInferUnrelatedTypes.ts, 3, 11))
+>Array : Symbol(Array, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>LiteralType : Symbol(LiteralType, Decl(doNotInferUnrelatedTypes.ts, 1, 54))
+
+let foo: LiteralType = dearray(alt);
+>foo : Symbol(foo, Decl(doNotInferUnrelatedTypes.ts, 5, 3))
+>LiteralType : Symbol(LiteralType, Decl(doNotInferUnrelatedTypes.ts, 1, 54))
+>dearray : Symbol(dearray, Decl(doNotInferUnrelatedTypes.ts, 0, 0))
+>alt : Symbol(alt, Decl(doNotInferUnrelatedTypes.ts, 3, 11))
+
diff --git a/tests/baselines/reference/doNotInferUnrelatedTypes.types b/tests/baselines/reference/doNotInferUnrelatedTypes.types
new file mode 100644
index 00000000000..5068c04ab1b
--- /dev/null
+++ b/tests/baselines/reference/doNotInferUnrelatedTypes.types
@@ -0,0 +1,25 @@
+=== tests/cases/compiler/doNotInferUnrelatedTypes.ts ===
+// #16709
+declare function dearray<T>(ara: ReadonlyArray<T>): T;
+>dearray : <T>(ara: ReadonlyArray<T>) => T
+>T : T
+>ara : ReadonlyArray<T>
+>ReadonlyArray : ReadonlyArray<T>
+>T : T
+>T : T
+
+type LiteralType = "foo" | "bar";
+>LiteralType : LiteralType
+
+declare var alt: Array<LiteralType>;
+>alt : LiteralType[]
+>Array : T[]
+>LiteralType : LiteralType
+
+let foo: LiteralType = dearray(alt);
+>foo : LiteralType
+>LiteralType : LiteralType
+>dearray(alt) : LiteralType
+>dearray : <T>(ara: ReadonlyArray<T>) => T
+>alt : LiteralType[]
+
diff --git a/tests/baselines/reference/emitExponentiationOperator3.types b/tests/baselines/reference/emitExponentiationOperator3.types
index 2fe95d4db8f..666d46dca39 100644
--- a/tests/baselines/reference/emitExponentiationOperator3.types
+++ b/tests/baselines/reference/emitExponentiationOperator3.types
@@ -113,32 +113,32 @@ var temp = 10;
 
 (+3) ** temp++;
 >(+3) ** temp++ : number
->(+3) : number
->+3 : number
+>(+3) : 3
+>+3 : 3
 >3 : 3
 >temp++ : number
 >temp : number
 
 (+3) ** temp--;
 >(+3) ** temp-- : number
->(+3) : number
->+3 : number
+>(+3) : 3
+>+3 : 3
 >3 : 3
 >temp-- : number
 >temp : number
 
 (+3) ** ++temp;
 >(+3) ** ++temp : number
->(+3) : number
->+3 : number
+>(+3) : 3
+>+3 : 3
 >3 : 3
 >++temp : number
 >temp : number
 
 (+3) ** --temp;
 >(+3) ** --temp : number
->(+3) : number
->+3 : number
+>(+3) : 3
+>+3 : 3
 >3 : 3
 >--temp : number
 >temp : number
@@ -185,8 +185,8 @@ var temp = 10;
 
 (+3) ** temp++ ** 2;
 >(+3) ** temp++ ** 2 : number
->(+3) : number
->+3 : number
+>(+3) : 3
+>+3 : 3
 >3 : 3
 >temp++ ** 2 : number
 >temp++ : number
@@ -195,8 +195,8 @@ var temp = 10;
 
 (+3) ** temp-- ** 2;
 >(+3) ** temp-- ** 2 : number
->(+3) : number
->+3 : number
+>(+3) : 3
+>+3 : 3
 >3 : 3
 >temp-- ** 2 : number
 >temp-- : number
@@ -205,8 +205,8 @@ var temp = 10;
 
 (+3) ** ++temp ** 2;
 >(+3) ** ++temp ** 2 : number
->(+3) : number
->+3 : number
+>(+3) : 3
+>+3 : 3
 >3 : 3
 >++temp ** 2 : number
 >++temp : number
@@ -215,8 +215,8 @@ var temp = 10;
 
 (+3) ** --temp ** 2;
 >(+3) ** --temp ** 2 : number
->(+3) : number
->+3 : number
+>(+3) : 3
+>+3 : 3
 >3 : 3
 >--temp ** 2 : number
 >--temp : number
diff --git a/tests/baselines/reference/enumClassification.types b/tests/baselines/reference/enumClassification.types
index d0581c7fcae..73c8041a6b7 100644
--- a/tests/baselines/reference/enumClassification.types
+++ b/tests/baselines/reference/enumClassification.types
@@ -131,7 +131,7 @@ enum E11 {
 
     A = +0,
 >A : E11
->+0 : number
+>+0 : 0
 >0 : 0
 
     B,
diff --git a/tests/baselines/reference/expressionTypeNodeShouldError.errors.txt b/tests/baselines/reference/expressionTypeNodeShouldError.errors.txt
new file mode 100644
index 00000000000..86a592779ca
--- /dev/null
+++ b/tests/baselines/reference/expressionTypeNodeShouldError.errors.txt
@@ -0,0 +1,90 @@
+tests/cases/compiler/base.d.ts(1,23): error TS1005: ',' expected.
+tests/cases/compiler/base.d.ts(1,34): error TS1005: '=' expected.
+tests/cases/compiler/boolean.ts(7,23): error TS1005: ',' expected.
+tests/cases/compiler/boolean.ts(7,24): error TS1134: Variable declaration expected.
+tests/cases/compiler/boolean.ts(11,16): error TS2304: Cannot find name 'document'.
+tests/cases/compiler/boolean.ts(12,22): error TS1005: ';' expected.
+tests/cases/compiler/number.ts(7,26): error TS1005: ',' expected.
+tests/cases/compiler/number.ts(7,27): error TS1134: Variable declaration expected.
+tests/cases/compiler/number.ts(11,16): error TS2304: Cannot find name 'document'.
+tests/cases/compiler/number.ts(12,20): error TS1005: ';' expected.
+tests/cases/compiler/string.ts(7,20): error TS1005: ',' expected.
+tests/cases/compiler/string.ts(7,21): error TS1134: Variable declaration expected.
+tests/cases/compiler/string.ts(11,15): error TS2304: Cannot find name 'document'.
+tests/cases/compiler/string.ts(12,19): error TS1005: ';' expected.
+
+
+==== tests/cases/compiler/base.d.ts (2 errors) ====
+    declare const x: "foo".charCodeAt(0);
+                          ~
+!!! error TS1005: ',' expected.
+                                     ~
+!!! error TS1005: '=' expected.
+    
+==== tests/cases/compiler/string.ts (4 errors) ====
+    interface String {
+        typeof<T>(x: T): T;
+    }
+    
+    class C {
+        foo() {
+            const x: "".typeof(this.foo);
+                       ~
+!!! error TS1005: ',' expected.
+                        ~~~~~~
+!!! error TS1134: Variable declaration expected.
+        }
+    }
+    
+    const nodes = document.getElementsByTagName("li");
+                  ~~~~~~~~
+!!! error TS2304: Cannot find name 'document'.
+    type ItemType = "".typeof(nodes.item(0));
+                      ~
+!!! error TS1005: ';' expected.
+    
+==== tests/cases/compiler/number.ts (4 errors) ====
+    interface Number {
+        typeof<T>(x: T): T;
+    }
+    
+    class C2 {
+        foo() {
+            const x: 3.141592.typeof(this.foo);
+                             ~
+!!! error TS1005: ',' expected.
+                              ~~~~~~
+!!! error TS1134: Variable declaration expected.
+        }
+    }
+    
+    const nodes2 = document.getElementsByTagName("li");
+                   ~~~~~~~~
+!!! error TS2304: Cannot find name 'document'.
+    type ItemType2 = 4..typeof(nodes.item(0));
+                       ~
+!!! error TS1005: ';' expected.
+    
+==== tests/cases/compiler/boolean.ts (4 errors) ====
+    interface Boolean {
+        typeof<T>(x: T): T;
+    }
+    
+    class C3 {
+        foo() {
+            const x: false.typeof(this.foo);
+                          ~
+!!! error TS1005: ',' expected.
+                           ~~~~~~
+!!! error TS1134: Variable declaration expected.
+        }
+    }
+    
+    const nodes3 = document.getElementsByTagName("li");
+                   ~~~~~~~~
+!!! error TS2304: Cannot find name 'document'.
+    type ItemType3 = true.typeof(nodes.item(0));
+                         ~
+!!! error TS1005: ';' expected.
+    
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/expressionTypeNodeShouldError.js b/tests/baselines/reference/expressionTypeNodeShouldError.js
new file mode 100644
index 00000000000..80f9f82145a
--- /dev/null
+++ b/tests/baselines/reference/expressionTypeNodeShouldError.js
@@ -0,0 +1,85 @@
+//// [tests/cases/compiler/expressionTypeNodeShouldError.ts] ////
+
+//// [base.d.ts]
+declare const x: "foo".charCodeAt(0);
+
+//// [string.ts]
+interface String {
+    typeof<T>(x: T): T;
+}
+
+class C {
+    foo() {
+        const x: "".typeof(this.foo);
+    }
+}
+
+const nodes = document.getElementsByTagName("li");
+type ItemType = "".typeof(nodes.item(0));
+
+//// [number.ts]
+interface Number {
+    typeof<T>(x: T): T;
+}
+
+class C2 {
+    foo() {
+        const x: 3.141592.typeof(this.foo);
+    }
+}
+
+const nodes2 = document.getElementsByTagName("li");
+type ItemType2 = 4..typeof(nodes.item(0));
+
+//// [boolean.ts]
+interface Boolean {
+    typeof<T>(x: T): T;
+}
+
+class C3 {
+    foo() {
+        const x: false.typeof(this.foo);
+    }
+}
+
+const nodes3 = document.getElementsByTagName("li");
+type ItemType3 = true.typeof(nodes.item(0));
+
+
+
+//// [string.js]
+var C = (function () {
+    function C() {
+    }
+    C.prototype.foo = function () {
+        var x;
+        typeof (this.foo);
+    };
+    return C;
+}());
+var nodes = document.getElementsByTagName("li");
+typeof (nodes.item(0));
+//// [number.js]
+var C2 = (function () {
+    function C2() {
+    }
+    C2.prototype.foo = function () {
+        var x;
+        typeof (this.foo);
+    };
+    return C2;
+}());
+var nodes2 = document.getElementsByTagName("li");
+typeof (nodes.item(0));
+//// [boolean.js]
+var C3 = (function () {
+    function C3() {
+    }
+    C3.prototype.foo = function () {
+        var x;
+        typeof (this.foo);
+    };
+    return C3;
+}());
+var nodes3 = document.getElementsByTagName("li");
+typeof (nodes.item(0));
diff --git a/tests/baselines/reference/indexSignatureAndMappedType.errors.txt b/tests/baselines/reference/indexSignatureAndMappedType.errors.txt
new file mode 100644
index 00000000000..623fcd11bd0
--- /dev/null
+++ b/tests/baselines/reference/indexSignatureAndMappedType.errors.txt
@@ -0,0 +1,47 @@
+tests/cases/compiler/indexSignatureAndMappedType.ts(6,5): error TS2322: Type '{ [key: string]: T; }' is not assignable to type 'Record<K, T>'.
+tests/cases/compiler/indexSignatureAndMappedType.ts(15,5): error TS2322: Type 'Record<K, U>' is not assignable to type '{ [key: string]: T; }'.
+  Type 'U' is not assignable to type 'T'.
+tests/cases/compiler/indexSignatureAndMappedType.ts(16,5): error TS2322: Type '{ [key: string]: T; }' is not assignable to type 'Record<K, U>'.
+
+
+==== tests/cases/compiler/indexSignatureAndMappedType.ts (3 errors) ====
+    // A mapped type { [P in K]: X }, where K is a generic type, is related to
+    // { [key: string]: Y } if X is related to Y.
+    
+    function f1<T, K extends string>(x: { [key: string]: T }, y: Record<K, T>) {
+        x = y;
+        y = x;  // Error
+        ~
+!!! error TS2322: Type '{ [key: string]: T; }' is not assignable to type 'Record<K, T>'.
+    }
+    
+    function f2<T>(x: { [key: string]: T }, y: Record<string, T>) {
+        x = y;
+        y = x;
+    }
+    
+    function f3<T, U, K extends string>(x: { [key: string]: T }, y: Record<K, U>) {
+        x = y;  // Error
+        ~
+!!! error TS2322: Type 'Record<K, U>' is not assignable to type '{ [key: string]: T; }'.
+!!! error TS2322:   Type 'U' is not assignable to type 'T'.
+        y = x;  // Error
+        ~
+!!! error TS2322: Type '{ [key: string]: T; }' is not assignable to type 'Record<K, U>'.
+    }
+    
+    // Repro from #14548
+    
+    type Dictionary = {
+        [key: string]: string;
+    };
+    
+    interface IBaseEntity {
+        name: string;
+        properties: Dictionary;
+    }
+    
+    interface IEntity<T extends string> extends IBaseEntity {
+        properties: Record<T, string>;
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/indexSignatureAndMappedType.js b/tests/baselines/reference/indexSignatureAndMappedType.js
new file mode 100644
index 00000000000..be58286fb46
--- /dev/null
+++ b/tests/baselines/reference/indexSignatureAndMappedType.js
@@ -0,0 +1,73 @@
+//// [indexSignatureAndMappedType.ts]
+// A mapped type { [P in K]: X }, where K is a generic type, is related to
+// { [key: string]: Y } if X is related to Y.
+
+function f1<T, K extends string>(x: { [key: string]: T }, y: Record<K, T>) {
+    x = y;
+    y = x;  // Error
+}
+
+function f2<T>(x: { [key: string]: T }, y: Record<string, T>) {
+    x = y;
+    y = x;
+}
+
+function f3<T, U, K extends string>(x: { [key: string]: T }, y: Record<K, U>) {
+    x = y;  // Error
+    y = x;  // Error
+}
+
+// Repro from #14548
+
+type Dictionary = {
+    [key: string]: string;
+};
+
+interface IBaseEntity {
+    name: string;
+    properties: Dictionary;
+}
+
+interface IEntity<T extends string> extends IBaseEntity {
+    properties: Record<T, string>;
+}
+
+
+//// [indexSignatureAndMappedType.js]
+"use strict";
+// A mapped type { [P in K]: X }, where K is a generic type, is related to
+// { [key: string]: Y } if X is related to Y.
+function f1(x, y) {
+    x = y;
+    y = x; // Error
+}
+function f2(x, y) {
+    x = y;
+    y = x;
+}
+function f3(x, y) {
+    x = y; // Error
+    y = x; // Error
+}
+
+
+//// [indexSignatureAndMappedType.d.ts]
+declare function f1<T, K extends string>(x: {
+    [key: string]: T;
+}, y: Record<K, T>): void;
+declare function f2<T>(x: {
+    [key: string]: T;
+}, y: Record<string, T>): void;
+declare function f3<T, U, K extends string>(x: {
+    [key: string]: T;
+}, y: Record<K, U>): void;
+declare type Dictionary = {
+    [key: string]: string;
+};
+interface IBaseEntity {
+    name: string;
+    properties: Dictionary;
+}
+interface IEntity<T extends string> extends IBaseEntity {
+    properties: Record<T, string>;
+}
diff --git a/tests/baselines/reference/jsdocTypeGenericInstantiationAttempt.symbols b/tests/baselines/reference/jsdocTypeGenericInstantiationAttempt.symbols
new file mode 100644
index 00000000000..1b17b09fce2
--- /dev/null
+++ b/tests/baselines/reference/jsdocTypeGenericInstantiationAttempt.symbols
@@ -0,0 +1,12 @@
+=== tests/cases/compiler/index.js ===
+/**
+ * @param {Array<*>} list
+ */
+function thing(list) {
+>thing : Symbol(thing, Decl(index.js, 0, 0))
+>list : Symbol(list, Decl(index.js, 3, 15))
+
+    return list;
+>list : Symbol(list, Decl(index.js, 3, 15))
+}
+
diff --git a/tests/baselines/reference/jsdocTypeGenericInstantiationAttempt.types b/tests/baselines/reference/jsdocTypeGenericInstantiationAttempt.types
new file mode 100644
index 00000000000..50231c9d868
--- /dev/null
+++ b/tests/baselines/reference/jsdocTypeGenericInstantiationAttempt.types
@@ -0,0 +1,12 @@
+=== tests/cases/compiler/index.js ===
+/**
+ * @param {Array<*>} list
+ */
+function thing(list) {
+>thing : (list: any[]) => any[]
+>list : any[]
+
+    return list;
+>list : any[]
+}
+
diff --git a/tests/baselines/reference/jsdocTypeNongenericInstantiationAttempt.errors.txt b/tests/baselines/reference/jsdocTypeNongenericInstantiationAttempt.errors.txt
new file mode 100644
index 00000000000..645eca539f4
--- /dev/null
+++ b/tests/baselines/reference/jsdocTypeNongenericInstantiationAttempt.errors.txt
@@ -0,0 +1,97 @@
+tests/cases/compiler/index.js(2,19): error TS2315: Type 'boolean' is not generic.
+tests/cases/compiler/index2.js(2,19): error TS2315: Type 'void' is not generic.
+tests/cases/compiler/index3.js(2,19): error TS2315: Type 'undefined' is not generic.
+tests/cases/compiler/index4.js(2,19): error TS2315: Type 'Function' is not generic.
+tests/cases/compiler/index5.js(2,19): error TS2315: Type 'string' is not generic.
+tests/cases/compiler/index6.js(2,19): error TS2315: Type 'number' is not generic.
+tests/cases/compiler/index7.js(2,19): error TS2315: Type 'any' is not generic.
+tests/cases/compiler/index8.js(4,12): error TS2304: Cannot find name 'fn'.
+tests/cases/compiler/index8.js(4,15): error TS2304: Cannot find name 'T'.
+
+
+==== tests/cases/compiler/index.js (1 errors) ====
+    /**
+     * @param {<T>(m: Boolean<T>) => string} somebody
+                      ~~~~~~~~~~
+!!! error TS2315: Type 'boolean' is not generic.
+     */
+    function sayHello(somebody) {
+        return 'Hello ' + somebody;
+    }
+    
+==== tests/cases/compiler/index2.js (1 errors) ====
+    /**
+     * @param {<T>(m: Void<T>) => string} somebody
+                      ~~~~~~~
+!!! error TS2315: Type 'void' is not generic.
+     */
+    function sayHello2(somebody) {
+        return 'Hello ' + somebody;
+    }
+    
+    
+==== tests/cases/compiler/index3.js (1 errors) ====
+    /**
+     * @param {<T>(m: Undefined<T>) => string} somebody
+                      ~~~~~~~~~~~~
+!!! error TS2315: Type 'undefined' is not generic.
+     */
+    function sayHello3(somebody) {
+        return 'Hello ' + somebody;
+    }
+    
+    
+==== tests/cases/compiler/index4.js (1 errors) ====
+    /**
+     * @param {<T>(m: Function<T>) => string} somebody
+                      ~~~~~~~~~~~
+!!! error TS2315: Type 'Function' is not generic.
+     */
+    function sayHello4(somebody) {
+        return 'Hello ' + somebody;
+    }
+    
+    
+==== tests/cases/compiler/index5.js (1 errors) ====
+    /**
+     * @param {<T>(m: String<T>) => string} somebody
+                      ~~~~~~~~~
+!!! error TS2315: Type 'string' is not generic.
+     */
+    function sayHello5(somebody) {
+        return 'Hello ' + somebody;
+    }
+    
+    
+==== tests/cases/compiler/index6.js (1 errors) ====
+    /**
+     * @param {<T>(m: Number<T>) => string} somebody
+                      ~~~~~~~~~
+!!! error TS2315: Type 'number' is not generic.
+     */
+    function sayHello6(somebody) {
+        return 'Hello ' + somebody;
+    }
+    
+    
+==== tests/cases/compiler/index7.js (1 errors) ====
+    /**
+     * @param {<T>(m: Object<T>) => string} somebody
+                      ~~~~~~~~~
+!!! error TS2315: Type 'any' is not generic.
+     */
+    function sayHello7(somebody) {
+        return 'Hello ' + somebody;
+    }
+    
+==== tests/cases/compiler/index8.js (2 errors) ====
+    function fn() {}
+    
+    /**
+     * @param {fn<T>} somebody
+               ~~
+!!! error TS2304: Cannot find name 'fn'.
+                  ~
+!!! error TS2304: Cannot find name 'T'.
+     */
+    function sayHello8(somebody) { }
\ No newline at end of file
diff --git a/tests/baselines/reference/jsdocTypeTagCast.js b/tests/baselines/reference/jsdocTypeTagCast.js
index c2df50cd6dd..ffe59d0138d 100644
--- a/tests/baselines/reference/jsdocTypeTagCast.js
+++ b/tests/baselines/reference/jsdocTypeTagCast.js
@@ -97,7 +97,7 @@ var a;
 /** @type {string} */
 var s;
 var a = ("" + 4);
-var s = "" + (4);
+var s = "" +/** @type {*} */  (4);
 var SomeBase = (function () {
     function SomeBase() {
         this.p = 42;
@@ -128,19 +128,19 @@ var someBase = new SomeBase();
 var someDerived = new SomeDerived();
 var someOther = new SomeOther();
 var someFakeClass = new SomeFakeClass();
-someBase = (someDerived);
-someBase = (someBase);
-someBase = (someOther); // Error
-someDerived = (someDerived);
-someDerived = (someBase);
-someDerived = (someOther); // Error
-someOther = (someDerived); // Error
-someOther = (someBase); // Error
-someOther = (someOther);
+someBase =/** @type {SomeBase} */  (someDerived);
+someBase =/** @type {SomeBase} */  (someBase);
+someBase =/** @type {SomeBase} */  (someOther); // Error
+someDerived =/** @type {SomeDerived} */  (someDerived);
+someDerived =/** @type {SomeDerived} */  (someBase);
+someDerived =/** @type {SomeDerived} */  (someOther); // Error
+someOther =/** @type {SomeOther} */  (someDerived); // Error
+someOther =/** @type {SomeOther} */  (someBase); // Error
+someOther =/** @type {SomeOther} */  (someOther);
 someFakeClass = someBase;
 someFakeClass = someDerived;
 someBase = someFakeClass; // Error
-someBase = (someFakeClass);
+someBase =/** @type {SomeBase} */  (someFakeClass);
 // Type assertion cannot be a type-predicate type
 /** @type {number | string} */
 var numOrStr;
diff --git a/tests/baselines/reference/keyofAndIndexedAccessErrors.errors.txt b/tests/baselines/reference/keyofAndIndexedAccessErrors.errors.txt
index 1e88e2abc43..0634c3419e0 100644
--- a/tests/baselines/reference/keyofAndIndexedAccessErrors.errors.txt
+++ b/tests/baselines/reference/keyofAndIndexedAccessErrors.errors.txt
@@ -15,6 +15,7 @@ tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts(35,21): error
 tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts(36,21): error TS2538: Type 'boolean' cannot be used as an index type.
 tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts(41,31): error TS2538: Type 'boolean' cannot be used as an index type.
 tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts(46,16): error TS2538: Type 'boolean' cannot be used as an index type.
+tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts(49,12): error TS1122: A tuple type element list cannot be empty.
 tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts(63,33): error TS2345: Argument of type '"size"' is not assignable to parameter of type '"name" | "width" | "height" | "visible"'.
 tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts(64,33): error TS2345: Argument of type '"name" | "size"' is not assignable to parameter of type '"name" | "width" | "height" | "visible"'.
   Type '"size"' is not assignable to type '"name" | "width" | "height" | "visible"'.
@@ -28,7 +29,7 @@ tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts(76,5): error
 tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts(77,5): error TS2322: Type 'keyof (T & U)' is not assignable to type 'keyof (T | U)'.
 
 
-==== tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts (24 errors) ====
+==== tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts (25 errors) ====
     class Shape {
         name: string;
         width: number;
@@ -112,6 +113,8 @@ tests/cases/conformance/types/keyof/keyofAndIndexedAccessErrors.ts(77,5): error
     
     type T60 = {}["toString"];
     type T61 = []["toString"];
+               ~~
+!!! error TS1122: A tuple type element list cannot be empty.
     
     declare let cond: boolean;
     
diff --git a/tests/baselines/reference/mappedTypeErrors2.errors.txt b/tests/baselines/reference/mappedTypeErrors2.errors.txt
new file mode 100644
index 00000000000..18bc7cc7239
--- /dev/null
+++ b/tests/baselines/reference/mappedTypeErrors2.errors.txt
@@ -0,0 +1,35 @@
+tests/cases/conformance/types/mapped/mappedTypeErrors2.ts(9,30): error TS2536: Type 'K' cannot be used to index type 'T1<K>'.
+tests/cases/conformance/types/mapped/mappedTypeErrors2.ts(13,30): error TS2536: Type 'K' cannot be used to index type 'T3'.
+tests/cases/conformance/types/mapped/mappedTypeErrors2.ts(15,47): error TS2536: Type 'S' cannot be used to index type 'AB'.
+tests/cases/conformance/types/mapped/mappedTypeErrors2.ts(17,49): error TS2536: Type 'L' cannot be used to index type '{ [key in AB[S]]: true; }'.
+
+
+==== tests/cases/conformance/types/mapped/mappedTypeErrors2.ts (4 errors) ====
+    // Repros from #17238
+    
+    type AB = {
+        a: 'a'
+        b: 'a'
+    };
+    
+    type T1<K extends keyof AB> = { [key in AB[K]]: true };
+    type T2<K extends 'a'|'b'> = T1<K>[K]; // Error
+                                 ~~~~~~~~
+!!! error TS2536: Type 'K' cannot be used to index type 'T1<K>'.
+    
+    type R = AB[keyof AB]; // "a"
+    type T3 = { [key in R]: true };
+    type T4<K extends 'a'|'b'> = T3[K] // Error
+                                 ~~~~~
+!!! error TS2536: Type 'K' cannot be used to index type 'T3'.
+    
+    type T5<S extends 'a'|'b'|'extra'> = {[key in AB[S]]: true}[S]; // Error
+                                                  ~~~~~
+!!! error TS2536: Type 'S' cannot be used to index type 'AB'.
+    
+    type T6<S extends 'a'|'b', L extends 'a'|'b'> = {[key in AB[S]]: true}[L]; // Error
+                                                    ~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2536: Type 'L' cannot be used to index type '{ [key in AB[S]]: true; }'.
+    
+    type T7<S extends 'a'|'b', L extends 'a'> = {[key in AB[S]]: true}[L];
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/mappedTypeErrors2.js b/tests/baselines/reference/mappedTypeErrors2.js
new file mode 100644
index 00000000000..d9fc6b0bc72
--- /dev/null
+++ b/tests/baselines/reference/mappedTypeErrors2.js
@@ -0,0 +1,49 @@
+//// [mappedTypeErrors2.ts]
+// Repros from #17238
+
+type AB = {
+    a: 'a'
+    b: 'a'
+};
+
+type T1<K extends keyof AB> = { [key in AB[K]]: true };
+type T2<K extends 'a'|'b'> = T1<K>[K]; // Error
+
+type R = AB[keyof AB]; // "a"
+type T3 = { [key in R]: true };
+type T4<K extends 'a'|'b'> = T3[K] // Error
+
+type T5<S extends 'a'|'b'|'extra'> = {[key in AB[S]]: true}[S]; // Error
+
+type T6<S extends 'a'|'b', L extends 'a'|'b'> = {[key in AB[S]]: true}[L]; // Error
+
+type T7<S extends 'a'|'b', L extends 'a'> = {[key in AB[S]]: true}[L];
+
+
+//// [mappedTypeErrors2.js]
+// Repros from #17238
+
+
+//// [mappedTypeErrors2.d.ts]
+declare type AB = {
+    a: 'a';
+    b: 'a';
+};
+declare type T1<K extends keyof AB> = {
+    [key in AB[K]]: true;
+};
+declare type T2<K extends 'a' | 'b'> = T1<K>[K];
+declare type R = AB[keyof AB];
+declare type T3 = {
+    [key in R]: true;
+};
+declare type T4<K extends 'a' | 'b'> = T3[K];
+declare type T5<S extends 'a' | 'b' | 'extra'> = {
+    [key in AB[S]]: true;
+}[S];
+declare type T6<S extends 'a' | 'b', L extends 'a' | 'b'> = {
+    [key in AB[S]]: true;
+}[L];
+declare type T7<S extends 'a' | 'b', L extends 'a'> = {
+    [key in AB[S]]: true;
+}[L];
diff --git a/tests/baselines/reference/noUnusedLocals_selfReference.errors.txt b/tests/baselines/reference/noUnusedLocals_selfReference.errors.txt
new file mode 100644
index 00000000000..af40081e71c
--- /dev/null
+++ b/tests/baselines/reference/noUnusedLocals_selfReference.errors.txt
@@ -0,0 +1,28 @@
+tests/cases/compiler/noUnusedLocals_selfReference.ts(3,10): error TS6133: 'f' is declared but never used.
+tests/cases/compiler/noUnusedLocals_selfReference.ts(4,7): error TS6133: 'C' is declared but never used.
+tests/cases/compiler/noUnusedLocals_selfReference.ts(7,6): error TS6133: 'E' is declared but never used.
+
+
+==== tests/cases/compiler/noUnusedLocals_selfReference.ts (3 errors) ====
+    export {}; // Make this a module scope, so these are local variables.
+    
+    function f() { f; }
+             ~
+!!! error TS6133: 'f' is declared but never used.
+    class C {
+          ~
+!!! error TS6133: 'C' is declared but never used.
+        m() { C; }
+    }
+    enum E { A = 0, B = E.A }
+         ~
+!!! error TS6133: 'E' is declared but never used.
+    
+    // Does not detect mutual recursion.
+    function g() { D; }
+    class D { m() { g; } }
+    
+    // Does not work on private methods.
+    class P { private m() { this.m; } }
+    P;
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/noUnusedLocals_selfReference.js b/tests/baselines/reference/noUnusedLocals_selfReference.js
new file mode 100644
index 00000000000..74a39923d57
--- /dev/null
+++ b/tests/baselines/reference/noUnusedLocals_selfReference.js
@@ -0,0 +1,49 @@
+//// [noUnusedLocals_selfReference.ts]
+export {}; // Make this a module scope, so these are local variables.
+
+function f() { f; }
+class C {
+    m() { C; }
+}
+enum E { A = 0, B = E.A }
+
+// Does not detect mutual recursion.
+function g() { D; }
+class D { m() { g; } }
+
+// Does not work on private methods.
+class P { private m() { this.m; } }
+P;
+
+
+//// [noUnusedLocals_selfReference.js]
+"use strict";
+exports.__esModule = true;
+function f() { f; }
+var C = (function () {
+    function C() {
+    }
+    C.prototype.m = function () { C; };
+    return C;
+}());
+var E;
+(function (E) {
+    E[E["A"] = 0] = "A";
+    E[E["B"] = 0] = "B";
+})(E || (E = {}));
+// Does not detect mutual recursion.
+function g() { D; }
+var D = (function () {
+    function D() {
+    }
+    D.prototype.m = function () { g; };
+    return D;
+}());
+// Does not work on private methods.
+var P = (function () {
+    function P() {
+    }
+    P.prototype.m = function () { this.m; };
+    return P;
+}());
+P;
diff --git a/tests/baselines/reference/parser15.4.4.14-9-2.js b/tests/baselines/reference/parser15.4.4.14-9-2.js
index 0f533cd9a26..e24da870d3e 100644
--- a/tests/baselines/reference/parser15.4.4.14-9-2.js
+++ b/tests/baselines/reference/parser15.4.4.14-9-2.js
@@ -41,9 +41,9 @@ function testcase() {
     var one = 1;
     var _float = -(4 / 3);
     var a = new Array(false, undefined, null, "0", obj, -1.3333333333333, "str", -0, true, +0, one, 1, 0, false, _float, -(4 / 3));
-    if (a.indexOf(-(4 / 3)) === 14 &&
-        a.indexOf(0) === 7 &&
-        a.indexOf(-0) === 7 &&
+    if (a.indexOf(-(4 / 3)) === 14 &&// a[14]=_float===-(4/3)
+        a.indexOf(0) === 7 &&// a[7] = +0, 0===+0
+        a.indexOf(-0) === 7 &&// a[7] = +0, -0===+0
         a.indexOf(1) === 10) {
         return true;
     }
diff --git a/tests/baselines/reference/parserGreaterThanTokenAmbiguity10.js b/tests/baselines/reference/parserGreaterThanTokenAmbiguity10.js
index 862722b1a73..7ff9e380dcf 100644
--- a/tests/baselines/reference/parserGreaterThanTokenAmbiguity10.js
+++ b/tests/baselines/reference/parserGreaterThanTokenAmbiguity10.js
@@ -6,5 +6,6 @@
 
 //// [parserGreaterThanTokenAmbiguity10.js]
 1
-    >>>
+    // before
+    >>>// after
         2;
diff --git a/tests/baselines/reference/parserGreaterThanTokenAmbiguity15.js b/tests/baselines/reference/parserGreaterThanTokenAmbiguity15.js
index b6f905e12e7..03e6211ae15 100644
--- a/tests/baselines/reference/parserGreaterThanTokenAmbiguity15.js
+++ b/tests/baselines/reference/parserGreaterThanTokenAmbiguity15.js
@@ -6,5 +6,6 @@
 
 //// [parserGreaterThanTokenAmbiguity15.js]
 1
-    >>=
+    // before
+    >>=// after
         2;
diff --git a/tests/baselines/reference/parserGreaterThanTokenAmbiguity20.js b/tests/baselines/reference/parserGreaterThanTokenAmbiguity20.js
index 01d1d6401f2..ba5e380043d 100644
--- a/tests/baselines/reference/parserGreaterThanTokenAmbiguity20.js
+++ b/tests/baselines/reference/parserGreaterThanTokenAmbiguity20.js
@@ -6,5 +6,6 @@
 
 //// [parserGreaterThanTokenAmbiguity20.js]
 1
-    >>>=
+    // Before
+    >>>=// after
         2;
diff --git a/tests/baselines/reference/parserGreaterThanTokenAmbiguity5.js b/tests/baselines/reference/parserGreaterThanTokenAmbiguity5.js
index c65b76f504a..e240746caa4 100644
--- a/tests/baselines/reference/parserGreaterThanTokenAmbiguity5.js
+++ b/tests/baselines/reference/parserGreaterThanTokenAmbiguity5.js
@@ -6,5 +6,6 @@
 
 //// [parserGreaterThanTokenAmbiguity5.js]
 1
-    >>
+    // before
+    >>// after
         2;
diff --git a/tests/baselines/reference/prefixedNumberLiteralAssignToNumberLiteralType.js b/tests/baselines/reference/prefixedNumberLiteralAssignToNumberLiteralType.js
new file mode 100644
index 00000000000..63f1f42d101
--- /dev/null
+++ b/tests/baselines/reference/prefixedNumberLiteralAssignToNumberLiteralType.js
@@ -0,0 +1,8 @@
+//// [prefixedNumberLiteralAssignToNumberLiteralType.ts]
+let x: 1 = +1;
+
+let y: -1 = -1;
+
+//// [prefixedNumberLiteralAssignToNumberLiteralType.js]
+var x = +1;
+var y = -1;
diff --git a/tests/baselines/reference/prefixedNumberLiteralAssignToNumberLiteralType.symbols b/tests/baselines/reference/prefixedNumberLiteralAssignToNumberLiteralType.symbols
new file mode 100644
index 00000000000..4ab5d371e8a
--- /dev/null
+++ b/tests/baselines/reference/prefixedNumberLiteralAssignToNumberLiteralType.symbols
@@ -0,0 +1,7 @@
+=== tests/cases/compiler/prefixedNumberLiteralAssignToNumberLiteralType.ts ===
+let x: 1 = +1;
+>x : Symbol(x, Decl(prefixedNumberLiteralAssignToNumberLiteralType.ts, 0, 3))
+
+let y: -1 = -1;
+>y : Symbol(y, Decl(prefixedNumberLiteralAssignToNumberLiteralType.ts, 2, 3))
+
diff --git a/tests/baselines/reference/prefixedNumberLiteralAssignToNumberLiteralType.types b/tests/baselines/reference/prefixedNumberLiteralAssignToNumberLiteralType.types
new file mode 100644
index 00000000000..93bd5cc6274
--- /dev/null
+++ b/tests/baselines/reference/prefixedNumberLiteralAssignToNumberLiteralType.types
@@ -0,0 +1,13 @@
+=== tests/cases/compiler/prefixedNumberLiteralAssignToNumberLiteralType.ts ===
+let x: 1 = +1;
+>x : 1
+>+1 : 1
+>1 : 1
+
+let y: -1 = -1;
+>y : -1
+>-1 : -1
+>1 : 1
+>-1 : -1
+>1 : 1
+
diff --git a/tests/baselines/reference/project/nodeModulesMaxDepthExceeded/amd/nodeModulesMaxDepthExceeded.errors.txt b/tests/baselines/reference/project/nodeModulesMaxDepthExceeded/amd/nodeModulesMaxDepthExceeded.errors.txt
index a1b170ce665..bd2dd6231f3 100644
--- a/tests/baselines/reference/project/nodeModulesMaxDepthExceeded/amd/nodeModulesMaxDepthExceeded.errors.txt
+++ b/tests/baselines/reference/project/nodeModulesMaxDepthExceeded/amd/nodeModulesMaxDepthExceeded.errors.txt
@@ -9,7 +9,7 @@ maxDepthExceeded/root.ts(4,4): error TS2540: Cannot assign to 'rel' because it i
         "maxNodeModuleJsDepth": 1, // Note: Module m1 is already included as a root file
         "outDir": "built"
       },
-      "include": ["**/*"],
+      "include": ["**/*", "node_modules/**/*"],
       "exclude": ["node_modules/m2/**/*"]
     }
     
diff --git a/tests/baselines/reference/project/nodeModulesMaxDepthExceeded/node/nodeModulesMaxDepthExceeded.errors.txt b/tests/baselines/reference/project/nodeModulesMaxDepthExceeded/node/nodeModulesMaxDepthExceeded.errors.txt
index a1b170ce665..bd2dd6231f3 100644
--- a/tests/baselines/reference/project/nodeModulesMaxDepthExceeded/node/nodeModulesMaxDepthExceeded.errors.txt
+++ b/tests/baselines/reference/project/nodeModulesMaxDepthExceeded/node/nodeModulesMaxDepthExceeded.errors.txt
@@ -9,7 +9,7 @@ maxDepthExceeded/root.ts(4,4): error TS2540: Cannot assign to 'rel' because it i
         "maxNodeModuleJsDepth": 1, // Note: Module m1 is already included as a root file
         "outDir": "built"
       },
-      "include": ["**/*"],
+      "include": ["**/*", "node_modules/**/*"],
       "exclude": ["node_modules/m2/**/*"]
     }
     
diff --git a/tests/baselines/reference/signatureInstantiationWithRecursiveConstraints.js b/tests/baselines/reference/signatureInstantiationWithRecursiveConstraints.js
new file mode 100644
index 00000000000..0be7fa1444d
--- /dev/null
+++ b/tests/baselines/reference/signatureInstantiationWithRecursiveConstraints.js
@@ -0,0 +1,30 @@
+//// [signatureInstantiationWithRecursiveConstraints.ts]
+// Repro from #17148
+
+class Foo {
+  myFunc<T extends Foo>(arg: T) {}
+}
+
+class Bar {
+  myFunc<T extends Bar>(arg: T) {}
+}
+
+const myVar: Foo = new Bar();
+
+
+//// [signatureInstantiationWithRecursiveConstraints.js]
+"use strict";
+// Repro from #17148
+var Foo = (function () {
+    function Foo() {
+    }
+    Foo.prototype.myFunc = function (arg) { };
+    return Foo;
+}());
+var Bar = (function () {
+    function Bar() {
+    }
+    Bar.prototype.myFunc = function (arg) { };
+    return Bar;
+}());
+var myVar = new Bar();
diff --git a/tests/baselines/reference/signatureInstantiationWithRecursiveConstraints.symbols b/tests/baselines/reference/signatureInstantiationWithRecursiveConstraints.symbols
new file mode 100644
index 00000000000..ebc1b625d9e
--- /dev/null
+++ b/tests/baselines/reference/signatureInstantiationWithRecursiveConstraints.symbols
@@ -0,0 +1,30 @@
+=== tests/cases/compiler/signatureInstantiationWithRecursiveConstraints.ts ===
+// Repro from #17148
+
+class Foo {
+>Foo : Symbol(Foo, Decl(signatureInstantiationWithRecursiveConstraints.ts, 0, 0))
+
+  myFunc<T extends Foo>(arg: T) {}
+>myFunc : Symbol(Foo.myFunc, Decl(signatureInstantiationWithRecursiveConstraints.ts, 2, 11))
+>T : Symbol(T, Decl(signatureInstantiationWithRecursiveConstraints.ts, 3, 9))
+>Foo : Symbol(Foo, Decl(signatureInstantiationWithRecursiveConstraints.ts, 0, 0))
+>arg : Symbol(arg, Decl(signatureInstantiationWithRecursiveConstraints.ts, 3, 24))
+>T : Symbol(T, Decl(signatureInstantiationWithRecursiveConstraints.ts, 3, 9))
+}
+
+class Bar {
+>Bar : Symbol(Bar, Decl(signatureInstantiationWithRecursiveConstraints.ts, 4, 1))
+
+  myFunc<T extends Bar>(arg: T) {}
+>myFunc : Symbol(Bar.myFunc, Decl(signatureInstantiationWithRecursiveConstraints.ts, 6, 11))
+>T : Symbol(T, Decl(signatureInstantiationWithRecursiveConstraints.ts, 7, 9))
+>Bar : Symbol(Bar, Decl(signatureInstantiationWithRecursiveConstraints.ts, 4, 1))
+>arg : Symbol(arg, Decl(signatureInstantiationWithRecursiveConstraints.ts, 7, 24))
+>T : Symbol(T, Decl(signatureInstantiationWithRecursiveConstraints.ts, 7, 9))
+}
+
+const myVar: Foo = new Bar();
+>myVar : Symbol(myVar, Decl(signatureInstantiationWithRecursiveConstraints.ts, 10, 5))
+>Foo : Symbol(Foo, Decl(signatureInstantiationWithRecursiveConstraints.ts, 0, 0))
+>Bar : Symbol(Bar, Decl(signatureInstantiationWithRecursiveConstraints.ts, 4, 1))
+
diff --git a/tests/baselines/reference/signatureInstantiationWithRecursiveConstraints.types b/tests/baselines/reference/signatureInstantiationWithRecursiveConstraints.types
new file mode 100644
index 00000000000..2368835be08
--- /dev/null
+++ b/tests/baselines/reference/signatureInstantiationWithRecursiveConstraints.types
@@ -0,0 +1,31 @@
+=== tests/cases/compiler/signatureInstantiationWithRecursiveConstraints.ts ===
+// Repro from #17148
+
+class Foo {
+>Foo : Foo
+
+  myFunc<T extends Foo>(arg: T) {}
+>myFunc : <T extends Foo>(arg: T) => void
+>T : T
+>Foo : Foo
+>arg : T
+>T : T
+}
+
+class Bar {
+>Bar : Bar
+
+  myFunc<T extends Bar>(arg: T) {}
+>myFunc : <T extends Bar>(arg: T) => void
+>T : T
+>Bar : Bar
+>arg : T
+>T : T
+}
+
+const myVar: Foo = new Bar();
+>myVar : Foo
+>Foo : Foo
+>new Bar() : Bar
+>Bar : typeof Bar
+
diff --git a/tests/baselines/reference/typeGuardsInConditionalExpression.js b/tests/baselines/reference/typeGuardsInConditionalExpression.js
index 9aade91612a..8be83a887b1 100644
--- a/tests/baselines/reference/typeGuardsInConditionalExpression.js
+++ b/tests/baselines/reference/typeGuardsInConditionalExpression.js
@@ -138,7 +138,7 @@ function foo8(x) {
     var b;
     return typeof x === "string"
         ? x === "hello"
-        : ((b = x) &&
+        : ((b = x) &&//  number | boolean
             (typeof x === "boolean"
                 ? x // boolean
                 : x == 10)); // boolean
diff --git a/tests/baselines/reference/unaryPlus.types b/tests/baselines/reference/unaryPlus.types
index 8f92b51a159..9bd741f2ad1 100644
--- a/tests/baselines/reference/unaryPlus.types
+++ b/tests/baselines/reference/unaryPlus.types
@@ -2,7 +2,7 @@
 // allowed per spec
 var a = +1;
 >a : number
->+1 : number
+>+1 : 1
 >1 : 1
 
 var b = +(<any>"");
diff --git a/tests/baselines/reference/unusedLocalsAndParametersTypeAliases2.errors.txt b/tests/baselines/reference/unusedLocalsAndParametersTypeAliases2.errors.txt
index 528ca9f9e73..e5c6f476480 100644
--- a/tests/baselines/reference/unusedLocalsAndParametersTypeAliases2.errors.txt
+++ b/tests/baselines/reference/unusedLocalsAndParametersTypeAliases2.errors.txt
@@ -1,8 +1,9 @@
 tests/cases/compiler/unusedLocalsAndParametersTypeAliases2.ts(2,6): error TS6133: 'handler1' is declared but never used.
+tests/cases/compiler/unusedLocalsAndParametersTypeAliases2.ts(5,10): error TS6133: 'foo' is declared but never used.
 tests/cases/compiler/unusedLocalsAndParametersTypeAliases2.ts(6,10): error TS6133: 'handler2' is declared but never used.
 
 
-==== tests/cases/compiler/unusedLocalsAndParametersTypeAliases2.ts (2 errors) ====
+==== tests/cases/compiler/unusedLocalsAndParametersTypeAliases2.ts (3 errors) ====
     // unused
     type handler1 = () => void;
          ~~~~~~~~
@@ -10,6 +11,8 @@ tests/cases/compiler/unusedLocalsAndParametersTypeAliases2.ts(6,10): error TS613
     
     
     function foo() {
+             ~~~
+!!! error TS6133: 'foo' is declared but never used.
         type handler2 = () => void;
              ~~~~~~~~
 !!! error TS6133: 'handler2' is declared but never used.
diff --git a/tests/baselines/reference/weakType.errors.txt b/tests/baselines/reference/weakType.errors.txt
index 441ef70ac16..ffc1d237593 100644
--- a/tests/baselines/reference/weakType.errors.txt
+++ b/tests/baselines/reference/weakType.errors.txt
@@ -1,14 +1,17 @@
-tests/cases/compiler/weakType.ts(16,13): error TS2559: Type '12' has no properties in common with type 'Settings'.
-tests/cases/compiler/weakType.ts(17,13): error TS2559: Type '"completely wrong"' has no properties in common with type 'Settings'.
-tests/cases/compiler/weakType.ts(18,13): error TS2559: Type 'false' has no properties in common with type 'Settings'.
-tests/cases/compiler/weakType.ts(35,18): error TS2559: Type '{ error?: number; }' has no properties in common with type 'ChangeOptions'.
-tests/cases/compiler/weakType.ts(60,5): error TS2322: Type '{ properties: { wrong: string; }; }' is not assignable to type 'Weak & Spoiler'.
+tests/cases/compiler/weakType.ts(15,13): error TS2560: Value of type '() => { timeout: number; }' has no properties in common with type 'Settings'. Did you mean to call it?
+tests/cases/compiler/weakType.ts(16,13): error TS2560: Value of type '() => { timeout: number; }' has no properties in common with type 'Settings'. Did you mean to call it?
+tests/cases/compiler/weakType.ts(17,13): error TS2560: Value of type 'CtorOnly' has no properties in common with type 'Settings'. Did you mean to call it?
+tests/cases/compiler/weakType.ts(18,13): error TS2559: Type '12' has no properties in common with type 'Settings'.
+tests/cases/compiler/weakType.ts(19,13): error TS2559: Type '"completely wrong"' has no properties in common with type 'Settings'.
+tests/cases/compiler/weakType.ts(20,13): error TS2559: Type 'false' has no properties in common with type 'Settings'.
+tests/cases/compiler/weakType.ts(37,18): error TS2559: Type '{ error?: number; }' has no properties in common with type 'ChangeOptions'.
+tests/cases/compiler/weakType.ts(62,5): error TS2322: Type '{ properties: { wrong: string; }; }' is not assignable to type 'Weak & Spoiler'.
   Type '{ properties: { wrong: string; }; }' is not assignable to type 'Weak'.
     Types of property 'properties' are incompatible.
       Type '{ wrong: string; }' has no properties in common with type '{ b?: number; }'.
 
 
-==== tests/cases/compiler/weakType.ts (5 errors) ====
+==== tests/cases/compiler/weakType.ts (8 errors) ====
     interface Settings {
         timeout?: number;
         onError?(): void;
@@ -17,13 +20,21 @@ tests/cases/compiler/weakType.ts(60,5): error TS2322: Type '{ properties: { wron
     function getDefaultSettings() {
         return { timeout: 1000 };
     }
+    interface CtorOnly {
+        new(s: string): { timeout: 1000 }
+    }
     
     function doSomething(settings: Settings) { /* ... */ }
     // forgot to call `getDefaultSettings`
-    // but it is not caught because we don't check for call signatures
     doSomething(getDefaultSettings);
-    // same for arrow expressions:
-    doSomething(() => { });
+                ~~~~~~~~~~~~~~~~~~
+!!! error TS2560: Value of type '() => { timeout: number; }' has no properties in common with type 'Settings'. Did you mean to call it?
+    doSomething(() => ({ timeout: 1000 }));
+                ~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2560: Value of type '() => { timeout: number; }' has no properties in common with type 'Settings'. Did you mean to call it?
+    doSomething(null as CtorOnly);
+                ~~~~~~~~~~~~~~~~
+!!! error TS2560: Value of type 'CtorOnly' has no properties in common with type 'Settings'. Did you mean to call it?
     doSomething(12);
                 ~~
 !!! error TS2559: Type '12' has no properties in common with type 'Settings'.
@@ -82,4 +93,5 @@ tests/cases/compiler/weakType.ts(60,5): error TS2322: Type '{ properties: { wron
 !!! error TS2322:   Type '{ properties: { wrong: string; }; }' is not assignable to type 'Weak'.
 !!! error TS2322:     Types of property 'properties' are incompatible.
 !!! error TS2322:       Type '{ wrong: string; }' has no properties in common with type '{ b?: number; }'.
+    
     
\ No newline at end of file
diff --git a/tests/baselines/reference/weakType.js b/tests/baselines/reference/weakType.js
index 5637271ccec..2a1dc4ca0e4 100644
--- a/tests/baselines/reference/weakType.js
+++ b/tests/baselines/reference/weakType.js
@@ -7,13 +7,15 @@ interface Settings {
 function getDefaultSettings() {
     return { timeout: 1000 };
 }
+interface CtorOnly {
+    new(s: string): { timeout: 1000 }
+}
 
 function doSomething(settings: Settings) { /* ... */ }
 // forgot to call `getDefaultSettings`
-// but it is not caught because we don't check for call signatures
 doSomething(getDefaultSettings);
-// same for arrow expressions:
-doSomething(() => { });
+doSomething(() => ({ timeout: 1000 }));
+doSomething(null as CtorOnly);
 doSomething(12);
 doSomething('completely wrong');
 doSomething(false);
@@ -59,6 +61,7 @@ declare let unknown: {
     }
 }
 let weak: Weak & Spoiler = unknown
+
 
 
 //// [weakType.js]
@@ -67,10 +70,9 @@ function getDefaultSettings() {
 }
 function doSomething(settings) { }
 // forgot to call `getDefaultSettings`
-// but it is not caught because we don't check for call signatures
 doSomething(getDefaultSettings);
-// same for arrow expressions:
-doSomething(function () { });
+doSomething(function () { return ({ timeout: 1000 }); });
+doSomething(null);
 doSomething(12);
 doSomething('completely wrong');
 doSomething(false);
diff --git a/tests/cases/compiler/checkTypePredicateForRedundantProperties.ts b/tests/cases/compiler/checkTypePredicateForRedundantProperties.ts
new file mode 100644
index 00000000000..35222f1e9db
--- /dev/null
+++ b/tests/cases/compiler/checkTypePredicateForRedundantProperties.ts
@@ -0,0 +1,3 @@
+function addProp2(x: any): x is { a: string; a: string; } {
+    return true;
+}
diff --git a/tests/cases/compiler/commentOnBinaryOperator1.ts b/tests/cases/compiler/commentOnBinaryOperator1.ts
new file mode 100644
index 00000000000..29de3410c32
--- /dev/null
+++ b/tests/cases/compiler/commentOnBinaryOperator1.ts
@@ -0,0 +1,12 @@
+var a = 'some'
+    // comment
+    + 'text';
+
+var b = 'some'
+    /* comment */
+    + 'text';
+
+var c = 'some'
+    /* comment */
+    + /*comment1*/
+    'text';
\ No newline at end of file
diff --git a/tests/cases/compiler/commentOnBinaryOperator2.ts b/tests/cases/compiler/commentOnBinaryOperator2.ts
new file mode 100644
index 00000000000..023655e16c0
--- /dev/null
+++ b/tests/cases/compiler/commentOnBinaryOperator2.ts
@@ -0,0 +1,13 @@
+// @removeComments: true
+var a = 'some'
+    // comment
+    + 'text';
+
+var b = 'some'
+    /* comment */
+    + 'text';
+
+var c = 'some'
+    /* comment */
+    + /*comment1*/
+    'text';
\ No newline at end of file
diff --git a/tests/cases/compiler/deferredLookupTypeResolution.ts b/tests/cases/compiler/deferredLookupTypeResolution.ts
new file mode 100644
index 00000000000..6c9853266ad
--- /dev/null
+++ b/tests/cases/compiler/deferredLookupTypeResolution.ts
@@ -0,0 +1,28 @@
+// @strict: true
+// @declaration: true
+
+// Repro from #17456
+
+type StringContains<S extends string, L extends string> = (
+    { [K in S]:      'true' } &
+    { [key: string]: 'false' }
+  )[L]
+
+type ObjectHasKey<O, L extends string> = StringContains<keyof O, L>
+
+type First<T> = ObjectHasKey<T, '0'>;  // Should be deferred
+
+type T1 = ObjectHasKey<{ a: string }, 'a'>;  // 'true'
+type T2 = ObjectHasKey<{ a: string }, 'b'>;  // 'false'
+
+// Verify that mapped type isn't eagerly resolved in type-to-string operation
+
+declare function f1<A extends string, B extends string>(a: A, b: B): { [P in A | B]: any };
+
+function f2<A extends string>(a: A) {
+    return f1(a, 'x');
+}
+
+function f3(x: 'a' | 'b') {
+    return f2(x);
+}
diff --git a/tests/cases/compiler/deferredLookupTypeResolution2.ts b/tests/cases/compiler/deferredLookupTypeResolution2.ts
new file mode 100644
index 00000000000..4aa18c092ba
--- /dev/null
+++ b/tests/cases/compiler/deferredLookupTypeResolution2.ts
@@ -0,0 +1,24 @@
+// @strict: true
+// @declaration: true
+
+// Repro from #17456
+
+type StringContains<S extends string, L extends string> = ({ [K in S]: 'true' } & { [key: string]: 'false'})[L];
+
+type ObjectHasKey<O, L extends string> = StringContains<keyof O, L>;
+
+type A<T> = ObjectHasKey<T, '0'>;
+
+type B = ObjectHasKey<[string, number], '1'>;  // "true"
+type C = ObjectHasKey<[string, number], '2'>;  // "false"
+type D = A<[string]>;  // "true"
+
+// Error, "false" not handled
+type E<T> = { true: 'true' }[ObjectHasKey<T, '1'>];
+
+type Juxtapose<T> = ({ true: 'otherwise' } & { [k: string]: 'true' })[ObjectHasKey<T, '1'>];
+
+// Error, "otherwise" is missing
+type DeepError<T> = { true: 'true' }[Juxtapose<T>];
+
+type DeepOK<T> = { true: 'true', otherwise: 'false' }[Juxtapose<T>];
diff --git a/tests/cases/compiler/doNotInferUnrelatedTypes.ts b/tests/cases/compiler/doNotInferUnrelatedTypes.ts
new file mode 100644
index 00000000000..08a7d793430
--- /dev/null
+++ b/tests/cases/compiler/doNotInferUnrelatedTypes.ts
@@ -0,0 +1,6 @@
+// #16709
+declare function dearray<T>(ara: ReadonlyArray<T>): T;
+type LiteralType = "foo" | "bar";
+declare var alt: Array<LiteralType>;
+
+let foo: LiteralType = dearray(alt);
diff --git a/tests/cases/compiler/expressionTypeNodeShouldError.ts b/tests/cases/compiler/expressionTypeNodeShouldError.ts
new file mode 100644
index 00000000000..0f6463f454b
--- /dev/null
+++ b/tests/cases/compiler/expressionTypeNodeShouldError.ts
@@ -0,0 +1,45 @@
+// @Filename: base.d.ts
+declare const x: "foo".charCodeAt(0);
+
+// @filename: string.ts
+interface String {
+    typeof<T>(x: T): T;
+}
+
+class C {
+    foo() {
+        const x: "".typeof(this.foo);
+    }
+}
+
+const nodes = document.getElementsByTagName("li");
+type ItemType = "".typeof(nodes.item(0));
+
+// @filename: number.ts
+interface Number {
+    typeof<T>(x: T): T;
+}
+
+class C2 {
+    foo() {
+        const x: 3.141592.typeof(this.foo);
+    }
+}
+
+const nodes2 = document.getElementsByTagName("li");
+type ItemType2 = 4..typeof(nodes.item(0));
+
+// @filename: boolean.ts
+interface Boolean {
+    typeof<T>(x: T): T;
+}
+
+class C3 {
+    foo() {
+        const x: false.typeof(this.foo);
+    }
+}
+
+const nodes3 = document.getElementsByTagName("li");
+type ItemType3 = true.typeof(nodes.item(0));
+
diff --git a/tests/cases/compiler/indexSignatureAndMappedType.ts b/tests/cases/compiler/indexSignatureAndMappedType.ts
new file mode 100644
index 00000000000..b5f9e8a0030
--- /dev/null
+++ b/tests/cases/compiler/indexSignatureAndMappedType.ts
@@ -0,0 +1,35 @@
+// @strict: true
+// @declaration: true
+
+// A mapped type { [P in K]: X }, where K is a generic type, is related to
+// { [key: string]: Y } if X is related to Y.
+
+function f1<T, K extends string>(x: { [key: string]: T }, y: Record<K, T>) {
+    x = y;
+    y = x;  // Error
+}
+
+function f2<T>(x: { [key: string]: T }, y: Record<string, T>) {
+    x = y;
+    y = x;
+}
+
+function f3<T, U, K extends string>(x: { [key: string]: T }, y: Record<K, U>) {
+    x = y;  // Error
+    y = x;  // Error
+}
+
+// Repro from #14548
+
+type Dictionary = {
+    [key: string]: string;
+};
+
+interface IBaseEntity {
+    name: string;
+    properties: Dictionary;
+}
+
+interface IEntity<T extends string> extends IBaseEntity {
+    properties: Record<T, string>;
+}
diff --git a/tests/cases/compiler/jsdocTypeGenericInstantiationAttempt.ts b/tests/cases/compiler/jsdocTypeGenericInstantiationAttempt.ts
new file mode 100644
index 00000000000..f7a694f6124
--- /dev/null
+++ b/tests/cases/compiler/jsdocTypeGenericInstantiationAttempt.ts
@@ -0,0 +1,10 @@
+// @allowJs: true
+// @noEmit: true
+// @checkJs: true
+// @filename: index.js
+/**
+ * @param {Array<*>} list
+ */
+function thing(list) {
+    return list;
+}
diff --git a/tests/cases/compiler/jsdocTypeNongenericInstantiationAttempt.ts b/tests/cases/compiler/jsdocTypeNongenericInstantiationAttempt.ts
new file mode 100644
index 00000000000..bf05c7f6de7
--- /dev/null
+++ b/tests/cases/compiler/jsdocTypeNongenericInstantiationAttempt.ts
@@ -0,0 +1,71 @@
+// @allowJs: true
+// @noEmit: true
+// @checkJs: true
+// @filename: index.js
+/**
+ * @param {<T>(m: Boolean<T>) => string} somebody
+ */
+function sayHello(somebody) {
+    return 'Hello ' + somebody;
+}
+
+// @filename: index2.js
+/**
+ * @param {<T>(m: Void<T>) => string} somebody
+ */
+function sayHello2(somebody) {
+    return 'Hello ' + somebody;
+}
+
+
+// @filename: index3.js
+/**
+ * @param {<T>(m: Undefined<T>) => string} somebody
+ */
+function sayHello3(somebody) {
+    return 'Hello ' + somebody;
+}
+
+
+// @filename: index4.js
+/**
+ * @param {<T>(m: Function<T>) => string} somebody
+ */
+function sayHello4(somebody) {
+    return 'Hello ' + somebody;
+}
+
+
+// @filename: index5.js
+/**
+ * @param {<T>(m: String<T>) => string} somebody
+ */
+function sayHello5(somebody) {
+    return 'Hello ' + somebody;
+}
+
+
+// @filename: index6.js
+/**
+ * @param {<T>(m: Number<T>) => string} somebody
+ */
+function sayHello6(somebody) {
+    return 'Hello ' + somebody;
+}
+
+
+// @filename: index7.js
+/**
+ * @param {<T>(m: Object<T>) => string} somebody
+ */
+function sayHello7(somebody) {
+    return 'Hello ' + somebody;
+}
+
+// @filename: index8.js
+function fn() {}
+
+/**
+ * @param {fn<T>} somebody
+ */
+function sayHello8(somebody) { }
\ No newline at end of file
diff --git a/tests/cases/compiler/noUnusedLocals_selfReference.ts b/tests/cases/compiler/noUnusedLocals_selfReference.ts
new file mode 100644
index 00000000000..8eb528743c0
--- /dev/null
+++ b/tests/cases/compiler/noUnusedLocals_selfReference.ts
@@ -0,0 +1,17 @@
+// @noUnusedLocals: true
+
+export {}; // Make this a module scope, so these are local variables.
+
+function f() { f; }
+class C {
+    m() { C; }
+}
+enum E { A = 0, B = E.A }
+
+// Does not detect mutual recursion.
+function g() { D; }
+class D { m() { g; } }
+
+// Does not work on private methods.
+class P { private m() { this.m; } }
+P;
diff --git a/tests/cases/compiler/prefixedNumberLiteralAssignToNumberLiteralType.ts b/tests/cases/compiler/prefixedNumberLiteralAssignToNumberLiteralType.ts
new file mode 100644
index 00000000000..6c2afbba2bd
--- /dev/null
+++ b/tests/cases/compiler/prefixedNumberLiteralAssignToNumberLiteralType.ts
@@ -0,0 +1,3 @@
+let x: 1 = +1;
+
+let y: -1 = -1;
\ No newline at end of file
diff --git a/tests/cases/compiler/signatureInstantiationWithRecursiveConstraints.ts b/tests/cases/compiler/signatureInstantiationWithRecursiveConstraints.ts
new file mode 100644
index 00000000000..4f25446aad8
--- /dev/null
+++ b/tests/cases/compiler/signatureInstantiationWithRecursiveConstraints.ts
@@ -0,0 +1,13 @@
+// @strict: true
+
+// Repro from #17148
+
+class Foo {
+  myFunc<T extends Foo>(arg: T) {}
+}
+
+class Bar {
+  myFunc<T extends Bar>(arg: T) {}
+}
+
+const myVar: Foo = new Bar();
diff --git a/tests/cases/compiler/weakType.ts b/tests/cases/compiler/weakType.ts
index ffe51205e53..08c9d95e672 100644
--- a/tests/cases/compiler/weakType.ts
+++ b/tests/cases/compiler/weakType.ts
@@ -6,13 +6,15 @@ interface Settings {
 function getDefaultSettings() {
     return { timeout: 1000 };
 }
+interface CtorOnly {
+    new(s: string): { timeout: 1000 }
+}
 
 function doSomething(settings: Settings) { /* ... */ }
 // forgot to call `getDefaultSettings`
-// but it is not caught because we don't check for call signatures
 doSomething(getDefaultSettings);
-// same for arrow expressions:
-doSomething(() => { });
+doSomething(() => ({ timeout: 1000 }));
+doSomething(null as CtorOnly);
 doSomething(12);
 doSomething('completely wrong');
 doSomething(false);
@@ -58,3 +60,4 @@ declare let unknown: {
     }
 }
 let weak: Weak & Spoiler = unknown
+
diff --git a/tests/cases/conformance/types/mapped/mappedTypeErrors2.ts b/tests/cases/conformance/types/mapped/mappedTypeErrors2.ts
new file mode 100644
index 00000000000..100a93eb159
--- /dev/null
+++ b/tests/cases/conformance/types/mapped/mappedTypeErrors2.ts
@@ -0,0 +1,22 @@
+// @strictNullChecks: true
+// @declaration: true
+
+// Repros from #17238
+
+type AB = {
+    a: 'a'
+    b: 'a'
+};
+
+type T1<K extends keyof AB> = { [key in AB[K]]: true };
+type T2<K extends 'a'|'b'> = T1<K>[K]; // Error
+
+type R = AB[keyof AB]; // "a"
+type T3 = { [key in R]: true };
+type T4<K extends 'a'|'b'> = T3[K] // Error
+
+type T5<S extends 'a'|'b'|'extra'> = {[key in AB[S]]: true}[S]; // Error
+
+type T6<S extends 'a'|'b', L extends 'a'|'b'> = {[key in AB[S]]: true}[L]; // Error
+
+type T7<S extends 'a'|'b', L extends 'a'> = {[key in AB[S]]: true}[L];
diff --git a/tests/cases/fourslash/completionListInObjectBindingPattern14.ts b/tests/cases/fourslash/completionListInObjectBindingPattern14.ts
new file mode 100644
index 00000000000..425813a5543
--- /dev/null
+++ b/tests/cases/fourslash/completionListInObjectBindingPattern14.ts
@@ -0,0 +1,9 @@
+/// <reference path="fourslash.ts"/>
+
+////const { b/**/ } = new class {
+////    private ab;
+////    protected bc;
+////}
+
+goTo.marker();
+verify.completionListIsEmpty();
diff --git a/tests/cases/fourslash/formattingSpaceBetweenParent.ts b/tests/cases/fourslash/formattingSpaceBetweenParent.ts
new file mode 100644
index 00000000000..60ec632f59c
--- /dev/null
+++ b/tests/cases/fourslash/formattingSpaceBetweenParent.ts
@@ -0,0 +1,14 @@
+/// <reference path='fourslash.ts' />
+
+/////*1*/foo(() => 1);
+/////*2*/foo(1);
+/////*3*/if((true)){}
+
+format.setOption("InsertSpaceAfterOpeningAndBeforeClosingNonemptyParenthesis", true);
+format.document();
+goTo.marker("1");
+verify.currentLineContentIs("foo( () => 1 );");
+goTo.marker("2");
+verify.currentLineContentIs("foo( 1 );");
+goTo.marker("3");
+verify.currentLineContentIs("if ( ( true ) ) { }");
diff --git a/tests/cases/projects/NodeModulesSearch/maxDepthExceeded/tsconfig.json b/tests/cases/projects/NodeModulesSearch/maxDepthExceeded/tsconfig.json
index 52633bb5a98..b2ee28482ba 100644
--- a/tests/cases/projects/NodeModulesSearch/maxDepthExceeded/tsconfig.json
+++ b/tests/cases/projects/NodeModulesSearch/maxDepthExceeded/tsconfig.json
@@ -4,6 +4,6 @@
     "maxNodeModuleJsDepth": 1, // Note: Module m1 is already included as a root file
     "outDir": "built"
   },
-  "include": ["**/*"],
+  "include": ["**/*", "node_modules/**/*"],
   "exclude": ["node_modules/m2/**/*"]
 }
diff --git a/tests/webTestServer.ts b/tests/webTestServer.ts
index abfd71a8fff..20228f9a741 100644
--- a/tests/webTestServer.ts
+++ b/tests/webTestServer.ts
@@ -125,22 +125,6 @@ function dir(dirPath: string, spec?: string, options?: any) {
     }
 }
 
-// fs.rmdirSync won't delete directories with files in it
-function deleteFolderRecursive(dirPath: string) {
-    if (fs.existsSync(dirPath)) {
-        fs.readdirSync(dirPath).forEach((file) => {
-            const curPath = path.join(dirPath, file);
-            if (fs.statSync(curPath).isDirectory()) { // recurse
-                deleteFolderRecursive(curPath);
-            }
-            else { // delete file
-                fs.unlinkSync(curPath);
-            }
-        });
-        fs.rmdirSync(dirPath);
-    }
-};
-
 function writeFile(path: string, data: any) {
     ensureDirectoriesExist(getDirectoryPath(path));
     fs.writeFileSync(path, data);
diff --git a/tslint.json b/tslint.json
index bcd4dfa2223..de60ad7683a 100644
--- a/tslint.json
+++ b/tslint.json
@@ -7,6 +7,7 @@
             "check-space"
         ],
         "curly":[true, "ignore-same-line"],
+        "debug-assert": true,
         "indent": [true,
             "spaces"
         ],