Merge remote-tracking branch 'tsupstream/master'

src/compiler/checker.ts

@@ -1439,9 +1439,8 @@ namespace ts {
              // May be an untyped module. If so, ignore resolutionDiagnostic.
             if (!isRelative && resolvedModule && !extensionIsTypeScript(resolvedModule.extension)) {
                 if (isForAugmentation) {
-                    Debug.assert(!!moduleNotFoundError);
                     const diag = Diagnostics.Invalid_module_name_in_augmentation_Module_0_resolves_to_an_untyped_module_at_1_which_cannot_be_augmented;
-                    error(errorNode, diag, moduleName, resolvedModule.resolvedFileName);
+                    error(errorNode, diag, moduleReference, resolvedModule.resolvedFileName);
                 }
                 else if (compilerOptions.noImplicitAny && moduleNotFoundError) {
                     error(errorNode,
@@ -1742,7 +1741,19 @@ namespace ts {
         }
 
         function getAccessibleSymbolChain(symbol: Symbol, enclosingDeclaration: Node, meaning: SymbolFlags, useOnlyExternalAliasing: boolean): Symbol[] {
-            function getAccessibleSymbolChainFromSymbolTable(symbols: SymbolTable): Symbol[] {
+            function getAccessibleSymbolChainFromSymbolTable(symbols: SymbolTable) {
+                return getAccessibleSymbolChainFromSymbolTableWorker(symbols, []);
+            }
+
+            function getAccessibleSymbolChainFromSymbolTableWorker(symbols: SymbolTable, visitedSymbolTables: SymbolTable[]): Symbol[] {
+                if (contains(visitedSymbolTables, symbols)) {
+                    return undefined;
+                }
+                visitedSymbolTables.push(symbols);
+                const result = trySymbolTable(symbols);
+                visitedSymbolTables.pop();
+                return result;
+
                 function canQualifySymbol(symbolFromSymbolTable: Symbol, meaning: SymbolFlags) {
                     // If the symbol is equivalent and doesn't need further qualification, this symbol is accessible
                     if (!needsQualification(symbolFromSymbolTable, enclosingDeclaration, meaning)) {
@@ -1764,34 +1775,36 @@ namespace ts {
                     }
                 }
 
-                // If symbol is directly available by its name in the symbol table
-                if (isAccessible(symbols[symbol.name])) {
-                    return [symbol];
-                }
+                function trySymbolTable(symbols: SymbolTable) {
+                    // If symbol is directly available by its name in the symbol table
+                    if (isAccessible(symbols[symbol.name])) {
+                        return [symbol];
+                    }
 
-                // Check if symbol is any of the alias
-                return forEachProperty(symbols, symbolFromSymbolTable => {
-                    if (symbolFromSymbolTable.flags & SymbolFlags.Alias
-                        && symbolFromSymbolTable.name !== "export="
-                        && !getDeclarationOfKind(symbolFromSymbolTable, SyntaxKind.ExportSpecifier)) {
-                        if (!useOnlyExternalAliasing || // We can use any type of alias to get the name
-                            // Is this external alias, then use it to name
-                            ts.forEach(symbolFromSymbolTable.declarations, isExternalModuleImportEqualsDeclaration)) {
+                    // Check if symbol is any of the alias
+                    return forEachProperty(symbols, symbolFromSymbolTable => {
+                        if (symbolFromSymbolTable.flags & SymbolFlags.Alias
+                            && symbolFromSymbolTable.name !== "export="
+                            && !getDeclarationOfKind(symbolFromSymbolTable, SyntaxKind.ExportSpecifier)) {
+                            if (!useOnlyExternalAliasing || // We can use any type of alias to get the name
+                                // Is this external alias, then use it to name
+                                ts.forEach(symbolFromSymbolTable.declarations, isExternalModuleImportEqualsDeclaration)) {
 
-                            const resolvedImportedSymbol = resolveAlias(symbolFromSymbolTable);
-                            if (isAccessible(symbolFromSymbolTable, resolveAlias(symbolFromSymbolTable))) {
-                                return [symbolFromSymbolTable];
-                            }
+                                const resolvedImportedSymbol = resolveAlias(symbolFromSymbolTable);
+                                if (isAccessible(symbolFromSymbolTable, resolveAlias(symbolFromSymbolTable))) {
+                                    return [symbolFromSymbolTable];
+                                }
 
-                            // Look in the exported members, if we can find accessibleSymbolChain, symbol is accessible using this chain
-                            // but only if the symbolFromSymbolTable can be qualified
-                            const accessibleSymbolsFromExports = resolvedImportedSymbol.exports ? getAccessibleSymbolChainFromSymbolTable(resolvedImportedSymbol.exports) : undefined;
-                            if (accessibleSymbolsFromExports && canQualifySymbol(symbolFromSymbolTable, getQualifiedLeftMeaning(meaning))) {
-                                return [symbolFromSymbolTable].concat(accessibleSymbolsFromExports);
+                                // Look in the exported members, if we can find accessibleSymbolChain, symbol is accessible using this chain
+                                // but only if the symbolFromSymbolTable can be qualified
+                                const accessibleSymbolsFromExports = resolvedImportedSymbol.exports ? getAccessibleSymbolChainFromSymbolTableWorker(resolvedImportedSymbol.exports, visitedSymbolTables) : undefined;
+                                if (accessibleSymbolsFromExports && canQualifySymbol(symbolFromSymbolTable, getQualifiedLeftMeaning(meaning))) {
+                                    return [symbolFromSymbolTable].concat(accessibleSymbolsFromExports);
+                                }
                             }
                         }
-                    }
-                });
+                    });
+                }
             }
 
             if (symbol) {
@@ -2673,7 +2686,7 @@ namespace ts {
                 }
                 Debug.assert(bindingElement.kind === SyntaxKind.BindingElement);
                 if (bindingElement.propertyName) {
-                    writer.writeSymbol(getTextOfNode(bindingElement.propertyName), bindingElement.symbol);
+                    writer.writeProperty(getTextOfNode(bindingElement.propertyName));
                     writePunctuation(writer, SyntaxKind.ColonToken);
                     writeSpace(writer);
                 }
@@ -3472,20 +3485,7 @@ namespace ts {
                 }
 
                 if (!popTypeResolution()) {
-                    if ((<VariableLikeDeclaration>symbol.valueDeclaration).type) {
-                        // Variable has type annotation that circularly references the variable itself
-                        type = unknownType;
-                        error(symbol.valueDeclaration, Diagnostics._0_is_referenced_directly_or_indirectly_in_its_own_type_annotation,
-                            symbolToString(symbol));
-                    }
-                    else {
-                        // Variable has initializer that circularly references the variable itself
-                        type = anyType;
-                        if (compilerOptions.noImplicitAny) {
-                            error(symbol.valueDeclaration, Diagnostics._0_implicitly_has_type_any_because_it_does_not_have_a_type_annotation_and_is_referenced_directly_or_indirectly_in_its_own_initializer,
-                                symbolToString(symbol));
-                        }
-                    }
+                    type = reportCircularityError(symbol);
                 }
                 links.type = type;
             }
@@ -3619,11 +3619,33 @@ namespace ts {
         function getTypeOfInstantiatedSymbol(symbol: Symbol): Type {
             const links = getSymbolLinks(symbol);
             if (!links.type) {
-                links.type = instantiateType(getTypeOfSymbol(links.target), links.mapper);
+                if (!pushTypeResolution(symbol, TypeSystemPropertyName.Type)) {
+                    return unknownType;
+                }
+                let type = instantiateType(getTypeOfSymbol(links.target), links.mapper);
+                if (!popTypeResolution()) {
+                    type = reportCircularityError(symbol);
+                }
+                links.type = type;
             }
             return links.type;
         }
 
+        function reportCircularityError(symbol: Symbol) {
+            // Check if variable has type annotation that circularly references the variable itself
+            if ((<VariableLikeDeclaration>symbol.valueDeclaration).type) {
+                error(symbol.valueDeclaration, Diagnostics._0_is_referenced_directly_or_indirectly_in_its_own_type_annotation,
+                    symbolToString(symbol));
+                return unknownType;
+            }
+            // Otherwise variable has initializer that circularly references the variable itself
+            if (compilerOptions.noImplicitAny) {
+                error(symbol.valueDeclaration, Diagnostics._0_implicitly_has_type_any_because_it_does_not_have_a_type_annotation_and_is_referenced_directly_or_indirectly_in_its_own_initializer,
+                    symbolToString(symbol));
+            }
+            return anyType;
+        }
+
         function getTypeOfSymbol(symbol: Symbol): Type {
             if (symbol.flags & SymbolFlags.Instantiated) {
                 return getTypeOfInstantiatedSymbol(symbol);
@@ -4512,18 +4534,17 @@ namespace ts {
             // Resolve upfront such that recursive references see an empty object type.
             setStructuredTypeMembers(type, emptySymbols, emptyArray, emptyArray, undefined, undefined);
             // In { [P in K]: T }, we refer to P as the type parameter type, K as the constraint type,
-            // and T as the template type. If K is of the form 'keyof S', the mapped type and S are
-            // homomorphic and we copy property modifiers from corresponding properties in S.
+            // and T as the template type.
             const typeParameter = getTypeParameterFromMappedType(type);
             const constraintType = getConstraintTypeFromMappedType(type);
-            const homomorphicType = getHomomorphicTypeFromMappedType(type);
             const templateType = getTemplateTypeFromMappedType(type);
+            const modifiersType = getModifiersTypeFromMappedType(type);
             const templateReadonly = !!type.declaration.readonlyToken;
             const templateOptional = !!type.declaration.questionToken;
             // First, if the constraint type is a type parameter, obtain the base constraint. Then,
             // if the key type is a 'keyof X', obtain 'keyof C' where C is the base constraint of X.
             // Finally, iterate over the constituents of the resulting iteration type.
-            const keyType = constraintType.flags & TypeFlags.TypeParameter ? getApparentType(constraintType) : constraintType;
+            const keyType = constraintType.flags & TypeFlags.TypeVariable ? getApparentType(constraintType) : constraintType;
             const iterationType = keyType.flags & TypeFlags.Index ? getIndexType(getApparentType((<IndexType>keyType).type)) : keyType;
             forEachType(iterationType, t => {
                 // Create a mapper from T to the current iteration type constituent. Then, if the
@@ -4536,11 +4557,11 @@ namespace ts {
                 // Otherwise, for type string create a string index signature.
                 if (t.flags & TypeFlags.StringLiteral) {
                     const propName = (<LiteralType>t).text;
-                    const homomorphicProp = homomorphicType && getPropertyOfType(homomorphicType, propName);
-                    const isOptional = templateOptional || !!(homomorphicProp && homomorphicProp.flags & SymbolFlags.Optional);
+                    const modifiersProp = getPropertyOfType(modifiersType, propName);
+                    const isOptional = templateOptional || !!(modifiersProp && modifiersProp.flags & SymbolFlags.Optional);
                     const prop = <TransientSymbol>createSymbol(SymbolFlags.Property | SymbolFlags.Transient | (isOptional ? SymbolFlags.Optional : 0), propName);
                     prop.type = propType;
-                    prop.isReadonly = templateReadonly || homomorphicProp && isReadonlySymbol(homomorphicProp);
+                    prop.isReadonly = templateReadonly || modifiersProp && isReadonlySymbol(modifiersProp);
                     members[propName] = prop;
                 }
                 else if (t.flags & TypeFlags.String) {
@@ -4567,9 +4588,26 @@ namespace ts {
                     unknownType);
         }
 
-        function getHomomorphicTypeFromMappedType(type: MappedType) {
-            const constraint = getConstraintDeclaration(getTypeParameterFromMappedType(type));
-            return constraint.kind === SyntaxKind.TypeOperator ? instantiateType(getTypeFromTypeNode((<TypeOperatorNode>constraint).type), type.mapper || identityMapper) : undefined;
+        function getModifiersTypeFromMappedType(type: MappedType) {
+            if (!type.modifiersType) {
+                const constraintDeclaration = type.declaration.typeParameter.constraint;
+                if (constraintDeclaration.kind === SyntaxKind.TypeOperator) {
+                    // If the constraint declaration is a 'keyof T' node, the modifiers type is T. We check
+                    // AST nodes here because, when T is a non-generic type, the logic below eagerly resolves
+                    // 'keyof T' to a literal union type and we can't recover T from that type.
+                    type.modifiersType = instantiateType(getTypeFromTypeNode((<TypeOperatorNode>constraintDeclaration).type), type.mapper || identityMapper);
+                }
+                else {
+                    // Otherwise, get the declared constraint type, and if the constraint type is a type parameter,
+                    // get the constraint of that type parameter. If the resulting type is an indexed type 'keyof T',
+                    // the modifiers type is T. Otherwise, the modifiers type is {}.
+                    const declaredType = <MappedType>getTypeFromMappedTypeNode(type.declaration);
+                    const constraint = getConstraintTypeFromMappedType(declaredType);
+                    const extendedConstraint = constraint.flags & TypeFlags.TypeParameter ? getConstraintOfTypeParameter(<TypeParameter>constraint) : constraint;
+                    type.modifiersType = extendedConstraint.flags & TypeFlags.Index ? instantiateType((<IndexType>extendedConstraint).type, type.mapper || identityMapper) : emptyObjectType;
+                }
+            }
+            return type.modifiersType;
         }
 
         function getErasedTemplateTypeFromMappedType(type: MappedType) {
@@ -4579,7 +4617,7 @@ namespace ts {
         function isGenericMappedType(type: Type) {
             if (getObjectFlags(type) & ObjectFlags.Mapped) {
                 const constraintType = getConstraintTypeFromMappedType(<MappedType>type);
-                return !!(constraintType.flags & (TypeFlags.TypeParameter | TypeFlags.Index));
+                return maybeTypeOfKind(constraintType, TypeFlags.TypeVariable | TypeFlags.Index);
             }
             return false;
         }
@@ -4667,33 +4705,24 @@ namespace ts {
          * The apparent type of a type parameter is the base constraint instantiated with the type parameter
          * as the type argument for the 'this' type.
          */
-        function getApparentTypeOfTypeParameter(type: TypeParameter) {
+        function getApparentTypeOfTypeVariable(type: TypeVariable) {
             if (!type.resolvedApparentType) {
-                let constraintType = getConstraintOfTypeParameter(type);
+                let constraintType = getConstraintOfTypeVariable(type);
                 while (constraintType && constraintType.flags & TypeFlags.TypeParameter) {
-                    constraintType = getConstraintOfTypeParameter(<TypeParameter>constraintType);
+                    constraintType = getConstraintOfTypeVariable(<TypeVariable>constraintType);
                 }
                 type.resolvedApparentType = getTypeWithThisArgument(constraintType || emptyObjectType, type);
             }
             return type.resolvedApparentType;
         }
 
-        /**
-         * The apparent type of an indexed access T[K] is the type of T's string index signature, if any.
-         */
-        function getApparentTypeOfIndexedAccess(type: IndexedAccessType) {
-            return getIndexTypeOfType(getApparentType(type.objectType), IndexKind.String) || type;
-        }
-
         /**
          * For a type parameter, return the base constraint of the type parameter. For the string, number,
          * boolean, and symbol primitive types, return the corresponding object types. Otherwise return the
          * type itself. Note that the apparent type of a union type is the union type itself.
          */
         function getApparentType(type: Type): Type {
-            const t = type.flags & TypeFlags.TypeParameter ? getApparentTypeOfTypeParameter(<TypeParameter>type) :
-                type.flags & TypeFlags.IndexedAccess ? getApparentTypeOfIndexedAccess(<IndexedAccessType>type) :
-                type;
+            const t = type.flags & TypeFlags.TypeVariable ? getApparentTypeOfTypeVariable(<TypeVariable>type) : type;
             return t.flags & TypeFlags.StringLike ? globalStringType :
                 t.flags & TypeFlags.NumberLike ? globalNumberType :
                 t.flags & TypeFlags.BooleanLike ? globalBooleanType :
@@ -5279,6 +5308,12 @@ namespace ts {
             return typeParameter.constraint === noConstraintType ? undefined : typeParameter.constraint;
         }
 
+        function getConstraintOfTypeVariable(type: TypeVariable): Type {
+            return type.flags & TypeFlags.TypeParameter ? getConstraintOfTypeParameter(<TypeParameter>type) :
+                type.flags & TypeFlags.IndexedAccess ? (<IndexedAccessType>type).constraint :
+                undefined;
+        }
+
         function getParentSymbolOfTypeParameter(typeParameter: TypeParameter): Symbol {
             return getSymbolOfNode(getDeclarationOfKind(typeParameter.symbol, SyntaxKind.TypeParameter).parent);
         }
@@ -5912,7 +5947,7 @@ namespace ts {
             return links.resolvedType;
         }
 
-        function getIndexTypeForTypeVariable(type: TypeVariable) {
+        function getIndexTypeForGenericType(type: TypeVariable | UnionOrIntersectionType) {
             if (!type.resolvedIndexType) {
                 type.resolvedIndexType = <IndexType>createType(TypeFlags.Index);
                 type.resolvedIndexType.type = type;
@@ -5931,7 +5966,7 @@ namespace ts {
         }
 
         function getIndexType(type: Type): Type {
-            return type.flags & TypeFlags.TypeVariable ? getIndexTypeForTypeVariable(<TypeVariable>type) :
+            return maybeTypeOfKind(type, TypeFlags.TypeVariable) ? getIndexTypeForGenericType(<TypeVariable | UnionOrIntersectionType>type) :
                 getObjectFlags(type) & ObjectFlags.Mapped ? getConstraintTypeFromMappedType(<MappedType>type) :
                 type.flags & TypeFlags.Any || getIndexInfoOfType(type, IndexKind.String) ? stringType :
                 getLiteralTypeFromPropertyNames(type);
@@ -5954,6 +5989,24 @@ namespace ts {
             const type = <IndexedAccessType>createType(TypeFlags.IndexedAccess);
             type.objectType = objectType;
             type.indexType = indexType;
+            // We eagerly compute the constraint of the indexed access type such that circularity
+            // errors are immediately caught and reported. For example, class C { x: this["x"] }
+            // becomes an error only when the constraint is eagerly computed.
+            if (type.objectType.flags & TypeFlags.StructuredType) {
+                // The constraint of T[K], where T is an object, union, or intersection type,
+                // is the type of the string index signature of T, if any.
+                type.constraint = getIndexTypeOfType(type.objectType, IndexKind.String);
+            }
+            else if (type.objectType.flags & TypeFlags.TypeVariable) {
+                // The constraint of T[K], where T is a type variable, is A[K], where A is the
+                // apparent type of T.
+                const apparentType = getApparentTypeOfTypeVariable(<TypeVariable>type.objectType);
+                if (apparentType !== emptyObjectType) {
+                    type.constraint = isTypeOfKind((<IndexedAccessType>type).indexType, TypeFlags.StringLike) ?
+                        getIndexedAccessType(apparentType, (<IndexedAccessType>type).indexType) :
+                        getIndexTypeOfType(apparentType, IndexKind.String);
+                }
+            }
             return type;
         }
 
@@ -6032,14 +6085,19 @@ namespace ts {
         }
 
         function getIndexedAccessType(objectType: Type, indexType: Type, accessNode?: ElementAccessExpression | IndexedAccessTypeNode) {
-            if (indexType.flags & TypeFlags.TypeVariable ||
-                objectType.flags & TypeFlags.TypeVariable && indexType.flags & TypeFlags.Index ||
+            // 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)) {
-                // If the object type is a type variable (a type parameter or another indexed access type), if the
-                // index type is a type variable or an index type, 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. In those cases, we first check that the index type is
-                // assignable to 'keyof T' for the object type.
+                if (objectType.flags & TypeFlags.Any) {
+                    return objectType;
+                }
+                // We first check that the index type is assignable to 'keyof T' for the object type.
                 if (accessNode) {
                     if (!isTypeAssignableTo(indexType, getIndexType(objectType))) {
                         error(accessNode, Diagnostics.Type_0_cannot_be_used_to_index_type_1, typeToString(indexType), typeToString(objectType));
@@ -6056,6 +6114,7 @@ namespace ts {
                 const id = objectType.id + "," + indexType.id;
                 return indexedAccessTypes[id] || (indexedAccessTypes[id] = createIndexedAccessType(objectType, indexType));
             }
+            // In the following we resolve T[K] to the type of the property in T selected by K.
             const apparentObjectType = getApparentType(objectType);
             if (indexType.flags & TypeFlags.Union && !(indexType.flags & TypeFlags.Primitive)) {
                 const propTypes: Type[] = [];
@@ -6539,7 +6598,7 @@ namespace ts {
             // union type A | undefined, we produce { [P in keyof A]: X } | undefined.
             const constraintType = getConstraintTypeFromMappedType(type);
             if (constraintType.flags & TypeFlags.Index) {
-                const typeVariable = <TypeParameter>(<IndexType>constraintType).type;
+                const typeVariable = (<IndexType>constraintType).type;
                 const mappedTypeVariable = instantiateType(typeVariable, mapper);
                 if (typeVariable !== mappedTypeVariable) {
                     return mapType(mappedTypeVariable, t => {
@@ -7162,6 +7221,25 @@ namespace ts {
                 }
             }
 
+            function isUnionOrIntersectionTypeWithoutNullableConstituents(type: Type): boolean {
+                if (!(type.flags & TypeFlags.UnionOrIntersection)) {
+                    return false;
+                }
+                // at this point we know that this is union or intersection type possibly with nullable constituents.
+                // check if we still will have compound type if we ignore nullable components.
+                let seenNonNullable = false;
+                for (const t of (<UnionOrIntersectionType>type).types) {
+                    if (t.flags & TypeFlags.Nullable) {
+                        continue;
+                    }
+                    if (seenNonNullable) {
+                        return true;
+                    }
+                    seenNonNullable = true;
+                }
+                return false;
+            }
+
             // Compare two types and return
             // Ternary.True if they are related with no assumptions,
             // Ternary.Maybe if they are related with assumptions of other relationships, or
@@ -7194,7 +7272,7 @@ namespace ts {
                     // and intersection types are further deconstructed on the target side, we don't want to
                     // make the check again (as it might fail for a partial target type). Therefore we obtain
                     // the regular source type and proceed with that.
-                    if (target.flags & TypeFlags.UnionOrIntersection) {
+                    if (isUnionOrIntersectionTypeWithoutNullableConstituents(target)) {
                         source = getRegularTypeOfObjectLiteral(source);
                     }
                 }
@@ -7243,8 +7321,7 @@ namespace ts {
                         return result;
                     }
                 }
-
-                if (target.flags & TypeFlags.TypeParameter) {
+                else if (target.flags & TypeFlags.TypeParameter) {
                     // A source type { [P in keyof T]: X } is related to a target type T if X is related to T[P].
                     if (getObjectFlags(source) & ObjectFlags.Mapped && getConstraintTypeFromMappedType(<MappedType>source) === getIndexType(target)) {
                         if (!(<MappedType>source).declaration.questionToken) {
@@ -7273,10 +7350,10 @@ namespace ts {
                             return result;
                         }
                     }
-                    // Given a type parameter T with a constraint C, a type S is assignable to
+                    // Given a type variable T with a constraint C, a type S is assignable to
                     // keyof T if S is assignable to keyof C.
-                    if ((<IndexType>target).type.flags & TypeFlags.TypeParameter) {
-                        const constraint = getConstraintOfTypeParameter(<TypeParameter>(<IndexType>target).type);
+                    if ((<IndexType>target).type.flags & TypeFlags.TypeVariable) {
+                        const constraint = getConstraintOfTypeVariable(<TypeVariable>(<IndexType>target).type);
                         if (constraint) {
                             if (result = isRelatedTo(source, getIndexType(constraint), reportErrors)) {
                                 return result;
@@ -7292,6 +7369,14 @@ namespace ts {
                             return result;
                         }
                     }
+                    // A type S is related to a type T[K] if S is related to A[K], where K is string-like and
+                    // A is the apparent type of S.
+                    if ((<IndexedAccessType>target).constraint) {
+                        if (result = isRelatedTo(source, (<IndexedAccessType>target).constraint, reportErrors)) {
+                            errorInfo = saveErrorInfo;
+                            return result;
+                        }
+                    }
                 }
 
                 if (source.flags & TypeFlags.TypeParameter) {
@@ -7300,6 +7385,7 @@ namespace ts {
                         const indexedAccessType = getIndexedAccessType(source, getTypeParameterFromMappedType(<MappedType>target));
                         const templateType = getTemplateTypeFromMappedType(<MappedType>target);
                         if (result = isRelatedTo(indexedAccessType, templateType, reportErrors)) {
+                            errorInfo = saveErrorInfo;
                             return result;
                         }
                     }
@@ -7321,6 +7407,16 @@ namespace ts {
                         }
                     }
                 }
+                else if (source.flags & TypeFlags.IndexedAccess) {
+                    // A type S[K] is related to a type T if A[K] is related to T, where K is string-like and
+                    // A is the apparent type of S.
+                    if ((<IndexedAccessType>source).constraint) {
+                        if (result = isRelatedTo((<IndexedAccessType>source).constraint, target, reportErrors)) {
+                            errorInfo = saveErrorInfo;
+                            return result;
+                        }
+                    }
+                }
                 else {
                     if (getObjectFlags(source) & ObjectFlags.Reference && getObjectFlags(target) & ObjectFlags.Reference && (<TypeReference>source).target === (<TypeReference>target).target) {
                         // We have type references to same target type, see if relationship holds for all type arguments
@@ -8708,12 +8804,15 @@ namespace ts {
                     if (constraintType.flags & TypeFlags.Index) {
                         // We're inferring from some source type S to a homomorphic mapped type { [P in keyof T]: X },
                         // where T is a type variable. Use inferTypeForHomomorphicMappedType to infer a suitable source
-                        // type and then infer from that type to T.
+                        // type and then make a secondary inference from that type to T. We make a secondary inference
+                        // such that direct inferences to T get priority over inferences to Partial<T>, for example.
                         const index = indexOf(typeVariables, (<IndexType>constraintType).type);
                         if (index >= 0 && !typeInferences[index].isFixed) {
                             const inferredType = inferTypeForHomomorphicMappedType(source, <MappedType>target);
                             if (inferredType) {
+                                inferiority++;
                                 inferFromTypes(inferredType, typeVariables[index]);
+                                inferiority--;
                             }
                         }
                         return;
@@ -10404,6 +10503,29 @@ namespace ts {
             return baseConstructorType === nullWideningType;
         }
 
+        function checkThisBeforeSuper(node: Node, container: Node, diagnosticMessage: DiagnosticMessage) {
+            const containingClassDecl = <ClassDeclaration>container.parent;
+            const baseTypeNode = getClassExtendsHeritageClauseElement(containingClassDecl);
+
+            // If a containing class does not have extends clause or the class extends null
+            // skip checking whether super statement is called before "this" accessing.
+            if (baseTypeNode && !classDeclarationExtendsNull(containingClassDecl)) {
+                const superCall = getSuperCallInConstructor(<ConstructorDeclaration>container);
+
+                // We should give an error in the following cases:
+                //      - No super-call
+                //      - "this" is accessing before super-call.
+                //          i.e super(this)
+                //              this.x; super();
+                // We want to make sure that super-call is done before accessing "this" so that
+                // "this" is not accessed as a parameter of the super-call.
+                if (!superCall || superCall.end > node.pos) {
+                    // In ES6, super inside constructor of class-declaration has to precede "this" accessing
+                    error(node, diagnosticMessage);
+                }
+            }
+        }
+
         function checkThisExpression(node: Node): Type {
             // Stop at the first arrow function so that we can
             // tell whether 'this' needs to be captured.
@@ -10411,26 +10533,7 @@ namespace ts {
             let needToCaptureLexicalThis = false;
 
             if (container.kind === SyntaxKind.Constructor) {
-                const containingClassDecl = <ClassDeclaration>container.parent;
-                const baseTypeNode = getClassExtendsHeritageClauseElement(containingClassDecl);
-
-                // If a containing class does not have extends clause or the class extends null
-                // skip checking whether super statement is called before "this" accessing.
-                if (baseTypeNode && !classDeclarationExtendsNull(containingClassDecl)) {
-                    const superCall = getSuperCallInConstructor(<ConstructorDeclaration>container);
-
-                    // We should give an error in the following cases:
-                    //      - No super-call
-                    //      - "this" is accessing before super-call.
-                    //          i.e super(this)
-                    //              this.x; super();
-                    // We want to make sure that super-call is done before accessing "this" so that
-                    // "this" is not accessed as a parameter of the super-call.
-                    if (!superCall || superCall.end > node.pos) {
-                        // In ES6, super inside constructor of class-declaration has to precede "this" accessing
-                        error(node, Diagnostics.super_must_be_called_before_accessing_this_in_the_constructor_of_a_derived_class);
-                    }
-                }
+                checkThisBeforeSuper(node, container, Diagnostics.super_must_be_called_before_accessing_this_in_the_constructor_of_a_derived_class);
             }
 
             // Now skip arrow functions to get the "real" owner of 'this'.
@@ -10578,6 +10681,10 @@ namespace ts {
                 return unknownType;
             }
 
+            if (!isCallExpression && container.kind === SyntaxKind.Constructor) {
+                checkThisBeforeSuper(node, container, Diagnostics.super_must_be_called_before_accessing_a_property_of_super_in_the_constructor_of_a_derived_class);
+            }
+
             if ((getModifierFlags(container) & ModifierFlags.Static) || isCallExpression) {
                 nodeCheckFlag = NodeCheckFlags.SuperStatic;
             }
@@ -11243,13 +11350,7 @@ namespace ts {
         }
 
         function checkSpreadExpression(node: SpreadElement, contextualMapper?: TypeMapper): Type {
-            // It is usually not safe to call checkExpressionCached if we can be contextually typing.
-            // You can tell that we are contextually typing because of the contextualMapper parameter.
-            // While it is true that a spread element can have a contextual type, it does not do anything
-            // with this type. It is neither affected by it, nor does it propagate it to its operand.
-            // So the fact that contextualMapper is passed is not important, because the operand of a spread
-            // element is not contextually typed.
-            const arrayOrIterableType = checkExpressionCached(node.expression, contextualMapper);
+            const arrayOrIterableType = checkExpression(node.expression, contextualMapper);
             return checkIteratedTypeOrElementType(arrayOrIterableType, node.expression, /*allowStringInput*/ false);
         }
 
@@ -11539,8 +11640,11 @@ namespace ts {
                 if (propertiesArray.length > 0) {
                     spread = getSpreadType(spread, createObjectLiteralType(), /*isFromObjectLiteral*/ true);
                 }
-                spread.flags |= propagatedFlags;
-                spread.symbol = node.symbol;
+                if (spread.flags & TypeFlags.Object) {
+                    // only set the symbol and flags if this is a (fresh) object type
+                    spread.flags |= propagatedFlags;
+                    spread.symbol = node.symbol;
+                }
                 return spread;
             }
 
@@ -13466,13 +13570,14 @@ namespace ts {
                 const containingClass = getContainingClass(node);
                 if (containingClass) {
                     const containingType = getTypeOfNode(containingClass);
-                    const baseTypes = getBaseTypes(<InterfaceType>containingType);
-                    if (baseTypes.length) {
+                    let baseTypes = getBaseTypes(containingType as InterfaceType);
+                    while (baseTypes.length) {
                         const baseType = baseTypes[0];
                         if (modifiers & ModifierFlags.Protected &&
                             baseType.symbol === declaration.parent.symbol) {
                             return true;
                         }
+                        baseTypes = getBaseTypes(baseType as InterfaceType);
                     }
                 }
                 if (modifiers & ModifierFlags.Private) {
@@ -14980,8 +15085,8 @@ namespace ts {
 
         function isLiteralContextualType(contextualType: Type) {
             if (contextualType) {
-                if (contextualType.flags & TypeFlags.TypeParameter) {
-                    const apparentType = getApparentTypeOfTypeParameter(<TypeParameter>contextualType);
+                if (contextualType.flags & TypeFlags.TypeVariable) {
+                    const apparentType = getApparentTypeOfTypeVariable(<TypeVariable>contextualType);
                     // If the type parameter is constrained to the base primitive type we're checking for,
                     // consider this a literal context. For example, given a type parameter 'T extends string',
                     // this causes us to infer string literal types for T.
@@ -15816,7 +15921,7 @@ namespace ts {
             checkSourceElement(node.type);
             const type = <MappedType>getTypeFromMappedTypeNode(node);
             const constraintType = getConstraintTypeFromMappedType(type);
-            const keyType = constraintType.flags & TypeFlags.TypeParameter ? getApparentTypeOfTypeParameter(<TypeParameter>constraintType) : constraintType;
+            const keyType = constraintType.flags & TypeFlags.TypeVariable ? getApparentTypeOfTypeVariable(<TypeVariable>constraintType) : constraintType;
             checkTypeAssignableTo(keyType, stringType, node.typeParameter.constraint);
         }
 
@@ -16198,7 +16303,7 @@ namespace ts {
                 return undefined;
             }
 
-            const onfulfilledParameterType = getTypeWithFacts(getUnionType(map(thenSignatures, getTypeOfFirstParameterOfSignature)), TypeFacts.NEUndefined);
+            const onfulfilledParameterType = getTypeWithFacts(getUnionType(map(thenSignatures, getTypeOfFirstParameterOfSignature)), TypeFacts.NEUndefinedOrNull);
             if (isTypeAny(onfulfilledParameterType)) {
                 return undefined;
             }
@@ -16481,6 +16586,10 @@ namespace ts {
             }
         }
 
+        function getParameterTypeNodeForDecoratorCheck(node: ParameterDeclaration): TypeNode {
+            return node.dotDotDotToken ? getRestParameterElementType(node.type) : node.type;
+        }
+
         /** Check the decorators of a node */
         function checkDecorators(node: Node): void {
             if (!node.decorators) {
@@ -16512,7 +16621,7 @@ namespace ts {
                         const constructor = getFirstConstructorWithBody(<ClassDeclaration>node);
                         if (constructor) {
                             for (const parameter of constructor.parameters) {
-                                markTypeNodeAsReferenced(parameter.type);
+                                markTypeNodeAsReferenced(getParameterTypeNodeForDecoratorCheck(parameter));
                             }
                         }
                         break;
@@ -16521,15 +16630,17 @@ namespace ts {
                     case SyntaxKind.GetAccessor:
                     case SyntaxKind.SetAccessor:
                         for (const parameter of (<FunctionLikeDeclaration>node).parameters) {
-                            markTypeNodeAsReferenced(parameter.type);
+                            markTypeNodeAsReferenced(getParameterTypeNodeForDecoratorCheck(parameter));
                         }
 
                         markTypeNodeAsReferenced((<FunctionLikeDeclaration>node).type);
                         break;
 
                     case SyntaxKind.PropertyDeclaration:
+                        markTypeNodeAsReferenced(getParameterTypeNodeForDecoratorCheck(<ParameterDeclaration>node));
+                        break;
                     case SyntaxKind.Parameter:
-                        markTypeNodeAsReferenced((<PropertyDeclaration | ParameterDeclaration>node).type);
+                        markTypeNodeAsReferenced((<PropertyDeclaration>node).type);
                         break;
                 }
             }
@@ -16692,6 +16803,14 @@ namespace ts {
             }
         }
 
+        function isRemovedPropertyFromObjectSpread(node: Node) {
+            if (isBindingElement(node) && isObjectBindingPattern(node.parent)) {
+                const lastElement = lastOrUndefined(node.parent.elements);
+                return lastElement !== node && !!lastElement.dotDotDotToken;
+            }
+            return false;
+        }
+
         function errorUnusedLocal(node: Node, name: string) {
             if (isIdentifierThatStartsWithUnderScore(node)) {
                 const declaration = getRootDeclaration(node.parent);
@@ -16701,7 +16820,10 @@ namespace ts {
                     return;
                 }
             }
-            error(node, Diagnostics._0_is_declared_but_never_used, name);
+
+            if (!isRemovedPropertyFromObjectSpread(node.kind === SyntaxKind.Identifier ? node.parent : node)) {
+                error(node, Diagnostics._0_is_declared_but_never_used, name);
+            }
         }
 
         function parameterNameStartsWithUnderscore(parameterName: DeclarationName) {
@@ -17989,7 +18111,7 @@ namespace ts {
 
             const baseTypeNode = getClassExtendsHeritageClauseElement(node);
             if (baseTypeNode) {
-                if (languageVersion < ScriptTarget.ES2015) {
+                if (languageVersion < ScriptTarget.ES2015 && !isInAmbientContext(node)) {
                     checkExternalEmitHelpers(baseTypeNode.parent, ExternalEmitHelpers.Extends);
                 }
 

src/compiler/commandLineParser.ts

@@ -549,14 +549,7 @@ namespace ts {
 
     /* @internal */
     export function parseCustomTypeOption(opt: CommandLineOptionOfCustomType, value: string, errors: Diagnostic[]) {
-        const key = trimString((value || "")).toLowerCase();
-        const map = opt.type;
-        if (key in map) {
-            return map[key];
-        }
-        else {
-            errors.push(createCompilerDiagnosticForInvalidCustomType(opt));
-        }
+        return convertJsonOptionOfCustomType(opt, trimString(value || ""), errors);
     }
 
     /* @internal */
@@ -848,7 +841,7 @@ namespace ts {
       * @param basePath A root directory to resolve relative path entries in the config
       *    file to. e.g. outDir
       */
-    export function parseJsonConfigFileContent(json: any, host: ParseConfigHost, basePath: string, existingOptions: CompilerOptions = {}, configFileName?: string, resolutionStack: Path[] = []): ParsedCommandLine {
+    export function parseJsonConfigFileContent(json: any, host: ParseConfigHost, basePath: string, existingOptions: CompilerOptions = {}, configFileName?: string, resolutionStack: Path[] = [], extraFileExtensions: FileExtensionInfo[] = []): ParsedCommandLine {
         const errors: Diagnostic[] = [];
         const getCanonicalFileName = createGetCanonicalFileName(host.useCaseSensitiveFileNames);
         const resolvedPath = toPath(configFileName || "", basePath, getCanonicalFileName);
@@ -988,7 +981,7 @@ namespace ts {
                 includeSpecs = ["**/*"];
             }
 
-            const result = matchFileNames(fileNames, includeSpecs, excludeSpecs, basePath, options, host, errors);
+            const result = matchFileNames(fileNames, includeSpecs, excludeSpecs, basePath, options, host, errors, extraFileExtensions);
 
             if (result.fileNames.length === 0 && !hasProperty(json, "files") && resolutionStack.length === 0) {
                 errors.push(
@@ -1192,7 +1185,7 @@ namespace ts {
      * @param host The host used to resolve files and directories.
      * @param errors An array for diagnostic reporting.
      */
-    function matchFileNames(fileNames: string[], include: string[], exclude: string[], basePath: string, options: CompilerOptions, host: ParseConfigHost, errors: Diagnostic[]): ExpandResult {
+    function matchFileNames(fileNames: string[], include: string[], exclude: string[], basePath: string, options: CompilerOptions, host: ParseConfigHost, errors: Diagnostic[], extraFileExtensions: FileExtensionInfo[]): ExpandResult {
         basePath = normalizePath(basePath);
 
         // The exclude spec list is converted into a regular expression, which allows us to quickly
@@ -1226,7 +1219,7 @@ namespace ts {
 
         // Rather than requery this for each file and filespec, we query the supported extensions
         // once and store it on the expansion context.
-        const supportedExtensions = getSupportedExtensions(options);
+        const supportedExtensions = getSupportedExtensions(options, extraFileExtensions);
 
         // Literal files are always included verbatim. An "include" or "exclude" specification cannot
         // remove a literal file.

src/compiler/comments.ts

@@ -156,6 +156,9 @@ namespace ts {
 
             if (!skipTrailingComments) {
                 emitLeadingComments(detachedRange.end, /*isEmittedNode*/ true);
+                if (hasWrittenComment && !writer.isAtStartOfLine()) {
+                    writer.writeLine();
+                }
             }
 
             if (extendedDiagnostics) {

src/compiler/core.ts

@@ -863,24 +863,6 @@ namespace ts {
         return result;
     }
 
-    /**
-     * Reduce the properties defined on a map-like (but not from its prototype chain).
-     *
-     * NOTE: This is intended for use with MapLike<T> objects. For Map<T> objects, use
-     *       reduceProperties instead as it offers better performance.
-     *
-     * @param map The map-like to reduce
-     * @param callback An aggregation function that is called for each entry in the map
-     * @param initial The initial value for the reduction.
-     */
-    export function reduceOwnProperties<T, U>(map: MapLike<T>, callback: (aggregate: U, value: T, key: string) => U, initial: U): U {
-        let result = initial;
-        for (const key in map) if (hasOwnProperty.call(map, key)) {
-            result = callback(result, map[key], String(key));
-        }
-        return result;
-    }
-
     /**
      * Performs a shallow equality comparison of the contents of two map-likes.
      *
@@ -1942,8 +1924,18 @@ namespace ts {
     export const supportedJavascriptExtensions = [".js", ".jsx"];
     const allSupportedExtensions = supportedTypeScriptExtensions.concat(supportedJavascriptExtensions);
 
-    export function getSupportedExtensions(options?: CompilerOptions): string[] {
-        return options && options.allowJs ? allSupportedExtensions : supportedTypeScriptExtensions;
+    export function getSupportedExtensions(options?: CompilerOptions, extraFileExtensions?: FileExtensionInfo[]): string[] {
+        const needAllExtensions = options && options.allowJs;
+        if (!extraFileExtensions || extraFileExtensions.length === 0) {
+            return needAllExtensions ? allSupportedExtensions : supportedTypeScriptExtensions;
+        }
+        const extensions = (needAllExtensions ? allSupportedExtensions : supportedTypeScriptExtensions).slice(0);
+        for (const extInfo of extraFileExtensions) {
+            if (needAllExtensions || extInfo.scriptKind === ScriptKind.TS) {
+                extensions.push(extInfo.extension);
+            }
+        }
+        return extensions;
     }
 
     export function hasJavaScriptFileExtension(fileName: string) {
@@ -1954,10 +1946,10 @@ namespace ts {
         return forEach(supportedTypeScriptExtensions, extension => fileExtensionIs(fileName, extension));
     }
 
-    export function isSupportedSourceFileName(fileName: string, compilerOptions?: CompilerOptions) {
+    export function isSupportedSourceFileName(fileName: string, compilerOptions?: CompilerOptions, extraFileExtensions?: FileExtensionInfo[]) {
         if (!fileName) { return false; }
 
-        for (const extension of getSupportedExtensions(compilerOptions)) {
+        for (const extension of getSupportedExtensions(compilerOptions, extraFileExtensions)) {
             if (fileExtensionIs(fileName, extension)) {
                 return true;
             }

src/compiler/declarationEmitter.ts

@@ -194,6 +194,7 @@ namespace ts {
             writer.writeSpace = writer.write;
             writer.writeStringLiteral = writer.writeLiteral;
             writer.writeParameter = writer.write;
+            writer.writeProperty = writer.write;
             writer.writeSymbol = writer.write;
             setWriter(writer);
         }

src/compiler/diagnosticMessages.json

@@ -3165,6 +3165,10 @@
         "category": "Error",
         "code": 17010
     },
+    "'super' must be called before accessing a property of 'super' in the constructor of a derived class.": {
+        "category": "Error",
+        "code": 17011
+    },
 
     "Circularity detected while resolving configuration: {0}": {
         "category": "Error",

src/compiler/parser.ts

@@ -6337,7 +6337,7 @@ namespace ts {
                                 break;
                             case SyntaxKind.AsteriskToken:
                                 const asterisk = scanner.getTokenText();
-                                if (state === JSDocState.SawAsterisk) {
+                                if (state === JSDocState.SawAsterisk || state === JSDocState.SavingComments) {
                                     // If we've already seen an asterisk, then we can no longer parse a tag on this line
                                     state = JSDocState.SavingComments;
                                     pushComment(asterisk);
@@ -6358,7 +6358,10 @@ namespace ts {
                             case SyntaxKind.WhitespaceTrivia:
                                 // only collect whitespace if we're already saving comments or have just crossed the comment indent margin
                                 const whitespace = scanner.getTokenText();
-                                if (state === JSDocState.SavingComments || margin !== undefined && indent + whitespace.length > margin) {
+                                if (state === JSDocState.SavingComments) {
+                                    comments.push(whitespace);
+                                }
+                                else if (margin !== undefined && indent + whitespace.length > margin) {
                                     comments.push(whitespace.slice(margin - indent - 1));
                                 }
                                 indent += whitespace.length;
@@ -6366,6 +6369,8 @@ namespace ts {
                             case SyntaxKind.EndOfFileToken:
                                 break;
                             default:
+                                // anything other than whitespace or asterisk at the beginning of the line starts the comment text
+                                state = JSDocState.SavingComments;
                                 pushComment(scanner.getTokenText());
                                 break;
                         }

src/compiler/sourcemap.ts

@@ -427,7 +427,7 @@ namespace ts {
 
             encodeLastRecordedSourceMapSpan();
 
-            return stringify({
+            return JSON.stringify({
                 version: 3,
                 file: sourceMapData.sourceMapFile,
                 sourceRoot: sourceMapData.sourceMapSourceRoot,

src/compiler/transformers/es2015.ts

@@ -2286,14 +2286,19 @@ namespace ts {
                 }
             }
 
+            startLexicalEnvironment();
             let loopBody = visitNode(node.statement, visitor, isStatement);
+            const lexicalEnvironment = endLexicalEnvironment();
 
             const currentState = convertedLoopState;
             convertedLoopState = outerConvertedLoopState;
 
-            if (loopOutParameters.length) {
+            if (loopOutParameters.length || lexicalEnvironment) {
                 const statements = isBlock(loopBody) ? (<Block>loopBody).statements.slice() : [loopBody];
-                copyOutParameters(loopOutParameters, CopyDirection.ToOutParameter, statements);
+                if (loopOutParameters.length) {
+                    copyOutParameters(loopOutParameters, CopyDirection.ToOutParameter, statements);
+                }
+                addRange(statements, lexicalEnvironment)
                 loopBody = createBlock(statements, /*location*/ undefined, /*multiline*/ true);
             }
 
@@ -2837,7 +2842,6 @@ namespace ts {
                 //      _super.call(this, a)
                 //      _super.m.call(this, a)
                 //      _super.prototype.m.call(this, a)
-
                 resultingCall = createFunctionCall(
                     visitNode(target, visitor, isExpression),
                     visitNode(thisArg, visitor, isExpression),

src/compiler/transformers/module/system.ts

@@ -101,20 +101,21 @@ namespace ts {
             // So the helper will be emit at the correct position instead of at the top of the source-file
             const moduleName = tryGetModuleNameFromFile(node, host, compilerOptions);
             const dependencies = createArrayLiteral(map(dependencyGroups, dependencyGroup => dependencyGroup.name));
-            const updated = updateSourceFileNode(
-                node,
-                createNodeArray([
-                    createStatement(
-                        createCall(
-                            createPropertyAccess(createIdentifier("System"), "register"),
+            const updated = setEmitFlags(
+                updateSourceFileNode(
+                    node,
+                    createNodeArray([
+                        createStatement(
+                            createCall(
+                                createPropertyAccess(createIdentifier("System"), "register"),
                             /*typeArguments*/ undefined,
-                            moduleName
-                                ? [moduleName, dependencies, moduleBodyFunction]
-                                : [dependencies, moduleBodyFunction]
+                                moduleName
+                                    ? [moduleName, dependencies, moduleBodyFunction]
+                                    : [dependencies, moduleBodyFunction]
+                            )
                         )
-                    )
-                ], node.statements)
-            );
+                    ], node.statements)
+                ), EmitFlags.NoTrailingComments);
 
             if (!(compilerOptions.outFile || compilerOptions.out)) {
                 moveEmitHelpers(updated, moduleBodyBlock, helper => !helper.scoped);

src/compiler/transformers/ts.ts

@@ -1223,11 +1223,12 @@ namespace ts {
             }
 
             const { firstAccessor, secondAccessor, setAccessor } = getAllAccessorDeclarations(node.members, accessor);
-            if (accessor !== firstAccessor) {
+            const firstAccessorWithDecorators = firstAccessor.decorators ? firstAccessor : secondAccessor && secondAccessor.decorators ? secondAccessor : undefined;
+            if (!firstAccessorWithDecorators || accessor !== firstAccessorWithDecorators) {
                 return undefined;
             }
 
-            const decorators = firstAccessor.decorators || (secondAccessor && secondAccessor.decorators);
+            const decorators = firstAccessorWithDecorators.decorators;
             const parameters = getDecoratorsOfParameters(setAccessor);
             if (!decorators && !parameters) {
                 return undefined;
@@ -1276,7 +1277,7 @@ namespace ts {
          * @param node The declaration node.
          * @param allDecorators An object containing all of the decorators for the declaration.
          */
-        function transformAllDecoratorsOfDeclaration(node: Declaration, allDecorators: AllDecorators) {
+        function transformAllDecoratorsOfDeclaration(node: Declaration, container: ClassLikeDeclaration, allDecorators: AllDecorators) {
             if (!allDecorators) {
                 return undefined;
             }
@@ -1284,7 +1285,7 @@ namespace ts {
             const decoratorExpressions: Expression[] = [];
             addRange(decoratorExpressions, map(allDecorators.decorators, transformDecorator));
             addRange(decoratorExpressions, flatMap(allDecorators.parameters, transformDecoratorsOfParameter));
-            addTypeMetadata(node, decoratorExpressions);
+            addTypeMetadata(node, container, decoratorExpressions);
             return decoratorExpressions;
         }
 
@@ -1333,7 +1334,7 @@ namespace ts {
          */
         function generateClassElementDecorationExpression(node: ClassExpression | ClassDeclaration, member: ClassElement) {
             const allDecorators = getAllDecoratorsOfClassElement(node, member);
-            const decoratorExpressions = transformAllDecoratorsOfDeclaration(member, allDecorators);
+            const decoratorExpressions = transformAllDecoratorsOfDeclaration(member, node, allDecorators);
             if (!decoratorExpressions) {
                 return undefined;
             }
@@ -1414,7 +1415,7 @@ namespace ts {
          */
         function generateConstructorDecorationExpression(node: ClassExpression | ClassDeclaration) {
             const allDecorators = getAllDecoratorsOfConstructor(node);
-            const decoratorExpressions = transformAllDecoratorsOfDeclaration(node, allDecorators);
+            const decoratorExpressions = transformAllDecoratorsOfDeclaration(node, node, allDecorators);
             if (!decoratorExpressions) {
                 return undefined;
             }
@@ -1467,22 +1468,22 @@ namespace ts {
          * @param node The declaration node.
          * @param decoratorExpressions The destination array to which to add new decorator expressions.
          */
-        function addTypeMetadata(node: Declaration, decoratorExpressions: Expression[]) {
+        function addTypeMetadata(node: Declaration, container: ClassLikeDeclaration, decoratorExpressions: Expression[]) {
             if (USE_NEW_TYPE_METADATA_FORMAT) {
-                addNewTypeMetadata(node, decoratorExpressions);
+                addNewTypeMetadata(node, container, decoratorExpressions);
             }
             else {
-                addOldTypeMetadata(node, decoratorExpressions);
+                addOldTypeMetadata(node, container, decoratorExpressions);
             }
         }
 
-        function addOldTypeMetadata(node: Declaration, decoratorExpressions: Expression[]) {
+        function addOldTypeMetadata(node: Declaration, container: ClassLikeDeclaration, decoratorExpressions: Expression[]) {
             if (compilerOptions.emitDecoratorMetadata) {
                 if (shouldAddTypeMetadata(node)) {
                     decoratorExpressions.push(createMetadataHelper(context, "design:type", serializeTypeOfNode(node)));
                 }
                 if (shouldAddParamTypesMetadata(node)) {
-                    decoratorExpressions.push(createMetadataHelper(context, "design:paramtypes", serializeParameterTypesOfNode(node)));
+                    decoratorExpressions.push(createMetadataHelper(context, "design:paramtypes", serializeParameterTypesOfNode(node, container)));
                 }
                 if (shouldAddReturnTypeMetadata(node)) {
                     decoratorExpressions.push(createMetadataHelper(context, "design:returntype", serializeReturnTypeOfNode(node)));
@@ -1490,14 +1491,14 @@ namespace ts {
             }
         }
 
-        function addNewTypeMetadata(node: Declaration, decoratorExpressions: Expression[]) {
+        function addNewTypeMetadata(node: Declaration, container: ClassLikeDeclaration, decoratorExpressions: Expression[]) {
             if (compilerOptions.emitDecoratorMetadata) {
                 let properties: ObjectLiteralElementLike[];
                 if (shouldAddTypeMetadata(node)) {
                     (properties || (properties = [])).push(createPropertyAssignment("type", createArrowFunction(/*modifiers*/ undefined, /*typeParameters*/ undefined, [], /*type*/ undefined, createToken(SyntaxKind.EqualsGreaterThanToken), serializeTypeOfNode(node))));
                 }
                 if (shouldAddParamTypesMetadata(node)) {
-                    (properties || (properties = [])).push(createPropertyAssignment("paramTypes", createArrowFunction(/*modifiers*/ undefined, /*typeParameters*/ undefined, [], /*type*/ undefined, createToken(SyntaxKind.EqualsGreaterThanToken), serializeParameterTypesOfNode(node))));
+                    (properties || (properties = [])).push(createPropertyAssignment("paramTypes", createArrowFunction(/*modifiers*/ undefined, /*typeParameters*/ undefined, [], /*type*/ undefined, createToken(SyntaxKind.EqualsGreaterThanToken), serializeParameterTypesOfNode(node, container))));
                 }
                 if (shouldAddReturnTypeMetadata(node)) {
                     (properties || (properties = [])).push(createPropertyAssignment("returnType", createArrowFunction(/*modifiers*/ undefined, /*typeParameters*/ undefined, [], /*type*/ undefined, createToken(SyntaxKind.EqualsGreaterThanToken), serializeReturnTypeOfNode(node))));
@@ -1542,12 +1543,16 @@ namespace ts {
          * @param node The node to test.
          */
         function shouldAddParamTypesMetadata(node: Declaration): boolean {
-            const kind = node.kind;
-            return kind === SyntaxKind.ClassDeclaration
-                || kind === SyntaxKind.ClassExpression
-                || kind === SyntaxKind.MethodDeclaration
-                || kind === SyntaxKind.GetAccessor
-                || kind === SyntaxKind.SetAccessor;
+            switch (node.kind) {
+                case SyntaxKind.ClassDeclaration:
+                case SyntaxKind.ClassExpression:
+                    return getFirstConstructorWithBody(<ClassLikeDeclaration>node) !== undefined;
+                case SyntaxKind.MethodDeclaration:
+                case SyntaxKind.GetAccessor:
+                case SyntaxKind.SetAccessor:
+                    return true;
+            }
+            return false;
         }
 
         /**
@@ -1572,30 +1577,12 @@ namespace ts {
             }
         }
 
-        /**
-         * Gets the most likely element type for a TypeNode. This is not an exhaustive test
-         * as it assumes a rest argument can only be an array type (either T[], or Array<T>).
-         *
-         * @param node The type node.
-         */
-        function getRestParameterElementType(node: TypeNode) {
-            if (node && node.kind === SyntaxKind.ArrayType) {
-                return (<ArrayTypeNode>node).elementType;
-            }
-            else if (node && node.kind === SyntaxKind.TypeReference) {
-                return singleOrUndefined((<TypeReferenceNode>node).typeArguments);
-            }
-            else {
-                return undefined;
-            }
-        }
-
         /**
          * Serializes the types of the parameters of a node for use with decorator type metadata.
          *
          * @param node The node that should have its parameter types serialized.
          */
-        function serializeParameterTypesOfNode(node: Node): Expression {
+        function serializeParameterTypesOfNode(node: Node, container: ClassLikeDeclaration): Expression {
             const valueDeclaration =
                 isClassLike(node)
                     ? getFirstConstructorWithBody(node)
@@ -1605,7 +1592,7 @@ namespace ts {
 
             const expressions: Expression[] = [];
             if (valueDeclaration) {
-                const parameters = valueDeclaration.parameters;
+                const parameters = getParametersOfDecoratedDeclaration(valueDeclaration, container);
                 const numParameters = parameters.length;
                 for (let i = 0; i < numParameters; i++) {
                     const parameter = parameters[i];
@@ -1624,6 +1611,16 @@ namespace ts {
             return createArrayLiteral(expressions);
         }
 
+        function getParametersOfDecoratedDeclaration(node: FunctionLikeDeclaration, container: ClassLikeDeclaration) {
+            if (container && node.kind === SyntaxKind.GetAccessor) {
+                const { setAccessor } = getAllAccessorDeclarations(container.members, <AccessorDeclaration>node);
+                if (setAccessor) {
+                    return setAccessor.parameters;
+                }
+            }
+            return node.parameters;
+        }
+
         /**
          * Serializes the return type of a node for use with decorator type metadata.
          *

src/compiler/tsconfig.json

@@ -11,7 +11,8 @@
         "stripInternal": true,
         "target": "es5",
         "noUnusedLocals": true,
-        "noUnusedParameters": true
+        "noUnusedParameters": true,
+        "types": [ ]
     },
     "files": [
         "core.ts",

src/compiler/types.ts

@@ -2407,6 +2407,7 @@ namespace ts {
         writeSpace(text: string): void;
         writeStringLiteral(text: string): void;
         writeParameter(text: string): void;
+        writeProperty(text: string): void;
         writeSymbol(text: string, symbol: Symbol): void;
         writeLine(): void;
         increaseIndent(): void;
@@ -2908,6 +2909,8 @@ namespace ts {
         /* @internal */
         resolvedProperties: SymbolTable;  // Cache of resolved properties
         /* @internal */
+        resolvedIndexType: IndexType;
+        /* @internal */
         couldContainTypeVariables: boolean;
     }
 
@@ -2930,6 +2933,7 @@ namespace ts {
         typeParameter?: TypeParameter;
         constraintType?: Type;
         templateType?: Type;
+        modifiersType?: Type;
         mapper?: TypeMapper;  // Instantiation mapper
     }
 
@@ -2965,6 +2969,8 @@ namespace ts {
     }
 
     export interface TypeVariable extends Type {
+        /* @internal */
+        resolvedApparentType: Type;
         /* @internal */
         resolvedIndexType: IndexType;
     }
@@ -2977,8 +2983,6 @@ namespace ts {
         /* @internal */
         mapper?: TypeMapper;     // Instantiation mapper
         /* @internal */
-        resolvedApparentType: Type;
-        /* @internal */
         isThisType?: boolean;
     }
 
@@ -2987,11 +2991,12 @@ namespace ts {
     export interface IndexedAccessType extends TypeVariable {
         objectType: Type;
         indexType: Type;
+        constraint?: Type;
     }
 
     // keyof T types (TypeFlags.Index)
     export interface IndexType extends Type {
-        type: TypeVariable;
+        type: TypeVariable | UnionOrIntersectionType;
     }
 
     export const enum SignatureKind {
@@ -3083,6 +3088,12 @@ namespace ts {
         ThisProperty
     }
 
+    export interface FileExtensionInfo {
+        extension: string;
+        scriptKind: ScriptKind;
+        isMixedContent: boolean;
+    }
+
     export interface DiagnosticMessage {
         key: string;
         category: DiagnosticCategory;

src/compiler/utilities.ts

@@ -43,6 +43,7 @@ namespace ts {
                 writeSpace: writeText,
                 writeStringLiteral: writeText,
                 writeParameter: writeText,
+                writeProperty: writeText,
                 writeSymbol: writeText,
 
                 // Completely ignore indentation for string writers.  And map newlines to
@@ -802,6 +803,23 @@ namespace ts {
         }
     }
 
+    /**
+     * Gets the most likely element type for a TypeNode. This is not an exhaustive test
+     * as it assumes a rest argument can only be an array type (either T[], or Array<T>).
+     *
+     * @param node The type node.
+     */
+    export function getRestParameterElementType(node: TypeNode) {
+        if (node && node.kind === SyntaxKind.ArrayType) {
+            return (<ArrayTypeNode>node).elementType;
+        }
+        else if (node && node.kind === SyntaxKind.TypeReference) {
+            return singleOrUndefined((<TypeReferenceNode>node).typeArguments);
+        }
+        else {
+            return undefined;
+        }
+    }
 
     export function isVariableLike(node: Node): node is VariableLikeDeclaration {
         if (node) {
@@ -3188,55 +3206,6 @@ namespace ts {
         return output;
     }
 
-    /**
-     * Serialize an object graph into a JSON string. This is intended only for use on an acyclic graph
-     * as the fallback implementation does not check for circular references by default.
-     */
-    export const stringify: (value: any) => string = typeof JSON !== "undefined" && JSON.stringify
-        ? JSON.stringify
-        : stringifyFallback;
-
-    /**
-     * Serialize an object graph into a JSON string.
-     */
-    function stringifyFallback(value: any): string {
-        // JSON.stringify returns `undefined` here, instead of the string "undefined".
-        return value === undefined ? undefined : stringifyValue(value);
-    }
-
-    function stringifyValue(value: any): string {
-        return typeof value === "string" ? `"${escapeString(value)}"`
-            : typeof value === "number" ? isFinite(value) ? String(value) : "null"
-                : typeof value === "boolean" ? value ? "true" : "false"
-                    : typeof value === "object" && value ? isArray(value) ? cycleCheck(stringifyArray, value) : cycleCheck(stringifyObject, value)
-                        : /*fallback*/ "null";
-    }
-
-    function cycleCheck(cb: (value: any) => string, value: any) {
-        Debug.assert(!value.hasOwnProperty("__cycle"), "Converting circular structure to JSON");
-        value.__cycle = true;
-        const result = cb(value);
-        delete value.__cycle;
-        return result;
-    }
-
-    function stringifyArray(value: any) {
-        return `[${reduceLeft(value, stringifyElement, "")}]`;
-    }
-
-    function stringifyElement(memo: string, value: any) {
-        return (memo ? memo + "," : memo) + stringifyValue(value);
-    }
-
-    function stringifyObject(value: any) {
-        return `{${reduceOwnProperties(value, stringifyProperty, "")}}`;
-    }
-
-    function stringifyProperty(memo: string, value: any, key: string) {
-        return value === undefined || typeof value === "function" || key === "__cycle" ? memo
-            : (memo ? memo + "," : memo) + `"${escapeString(key)}":${stringifyValue(value)}`;
-    }
-
     const base64Digits = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
 
     /**

src/harness/fourslash.ts

@@ -607,23 +607,13 @@ namespace FourSlash {
             });
         }
 
-        public verifyMemberListContains(symbol: string, text?: string, documentation?: string, kind?: string) {
-            const members = this.getMemberListAtCaret();
-            if (members) {
-                this.assertItemInCompletionList(members.entries, symbol, text, documentation, kind);
-            }
-            else {
-                this.raiseError("Expected a member list, but none was provided");
-            }
-        }
-
-        public verifyMemberListCount(expectedCount: number, negative: boolean) {
+        public verifyCompletionListCount(expectedCount: number, negative: boolean) {
             if (expectedCount === 0 && negative) {
-                this.verifyMemberListIsEmpty(/*negative*/ false);
+                this.verifyCompletionListIsEmpty(/*negative*/ false);
                 return;
             }
 
-            const members = this.getMemberListAtCaret();
+            const members = this.getCompletionListAtCaret();
 
             if (members) {
                 const match = members.entries.length === expectedCount;
@@ -637,13 +627,6 @@ namespace FourSlash {
             }
         }
 
-        public verifyMemberListDoesNotContain(symbol: string) {
-            const members = this.getMemberListAtCaret();
-            if (members && members.entries.filter(e => e.name === symbol).length !== 0) {
-                this.raiseError(`Member list did contain ${symbol}`);
-            }
-        }
-
         public verifyCompletionListItemsCountIsGreaterThan(count: number, negative: boolean) {
             const completions = this.getCompletionListAtCaret();
             const itemsCount = completions.entries.length;
@@ -685,16 +668,6 @@ namespace FourSlash {
             }
         }
 
-        public verifyMemberListIsEmpty(negative: boolean) {
-            const members = this.getMemberListAtCaret();
-            if ((!members || members.entries.length === 0) && negative) {
-                this.raiseError("Member list is empty at Caret");
-            }
-            else if ((members && members.entries.length !== 0) && !negative) {
-                this.raiseError(`Member list is not empty at Caret:\nMember List contains: ${stringify(members.entries.map(e => e.name))}`);
-            }
-        }
-
         public verifyCompletionListIsEmpty(negative: boolean) {
             const completions = this.getCompletionListAtCaret();
             if ((!completions || completions.entries.length === 0) && negative) {
@@ -892,10 +865,6 @@ namespace FourSlash {
             this.raiseError(`verifyReferencesAtPositionListContains failed - could not find the item: ${stringify(missingItem)} in the returned list: (${stringify(references)})`);
         }
 
-        private getMemberListAtCaret() {
-            return this.languageService.getCompletionsAtPosition(this.activeFile.fileName, this.currentCaretPosition);
-        }
-
         private getCompletionListAtCaret() {
             return this.languageService.getCompletionsAtPosition(this.activeFile.fileName, this.currentCaretPosition);
         }
@@ -1353,11 +1322,6 @@ namespace FourSlash {
             Harness.IO.log(stringify(sigHelp));
         }
 
-        public printMemberListMembers() {
-            const members = this.getMemberListAtCaret();
-            this.printMembersOrCompletions(members);
-        }
-
         public printCompletionListMembers() {
             const completions = this.getCompletionListAtCaret();
             this.printMembersOrCompletions(completions);
@@ -3061,19 +3025,8 @@ namespace FourSlashInterface {
             }
         }
 
-        // Verifies the member list contains the specified symbol. The
-        // member list is brought up if necessary
-        public memberListContains(symbol: string, text?: string, documentation?: string, kind?: string) {
-            if (this.negative) {
-                this.state.verifyMemberListDoesNotContain(symbol);
-            }
-            else {
-                this.state.verifyMemberListContains(symbol, text, documentation, kind);
-            }
-        }
-
-        public memberListCount(expectedCount: number) {
-            this.state.verifyMemberListCount(expectedCount, this.negative);
+        public completionListCount(expectedCount: number) {
+            this.state.verifyCompletionListCount(expectedCount, this.negative);
         }
 
         // Verifies the completion list contains the specified symbol. The
@@ -3109,10 +3062,6 @@ namespace FourSlashInterface {
             this.state.verifyCompletionListAllowsNewIdentifier(this.negative);
         }
 
-        public memberListIsEmpty() {
-            this.state.verifyMemberListIsEmpty(this.negative);
-        }
-
         public signatureHelpPresent() {
             this.state.verifySignatureHelpPresent(!this.negative);
         }
@@ -3514,10 +3463,6 @@ namespace FourSlashInterface {
             this.state.printCurrentSignatureHelp();
         }
 
-        public printMemberListMembers() {
-            this.state.printMemberListMembers();
-        }
-
         public printCompletionListMembers() {
             this.state.printCompletionListMembers();
         }

src/harness/unittests/textStorage.ts

@@ -0,0 +1,70 @@
+/// <reference path="../harness.ts" />
+/// <reference path="../../server/scriptVersionCache.ts"/>
+/// <reference path="./tsserverProjectSystem.ts" />
+
+namespace ts.textStorage {
+    describe("Text storage", () => {
+        const f = {
+            path: "/a/app.ts",
+            content: `
+                let x = 1;
+                let y = 2;
+                function bar(a: number) {
+                    return a + 1;
+                }`
+        };
+
+        it("text based storage should be have exactly the same as script version cache", () => {
+
+            const host = ts.projectSystem.createServerHost([f]);
+
+            const ts1 = new server.TextStorage(host, server.asNormalizedPath(f.path));
+            const ts2 = new server.TextStorage(host, server.asNormalizedPath(f.path));
+
+            ts1.useScriptVersionCache();
+            ts2.useText();
+
+            const lineMap = computeLineStarts(f.content);
+
+            for (let line = 0; line < lineMap.length; line++) {
+                const start = lineMap[line];
+                const end = line === lineMap.length - 1 ? f.path.length : lineMap[line + 1];
+
+                for (let offset = 0; offset < end - start; offset++) {
+                    const pos1 = ts1.lineOffsetToPosition(line + 1, offset + 1);
+                    const pos2 = ts2.lineOffsetToPosition(line + 1, offset + 1);
+                    assert.isTrue(pos1 === pos2, `lineOffsetToPosition ${line + 1}-${offset + 1}: expected ${pos1} to equal ${pos2}`);
+                }
+
+                const {start: start1, length: length1 } = ts1.lineToTextSpan(line);
+                const {start: start2, length: length2 } = ts2.lineToTextSpan(line);
+                assert.isTrue(start1 === start2, `lineToTextSpan ${line}::start:: expected ${start1} to equal ${start2}`);
+                assert.isTrue(length1 === length2, `lineToTextSpan ${line}::length:: expected ${length1} to equal ${length2}`);
+            }
+
+            for (let pos = 0; pos < f.content.length; pos++) {
+                const { line: line1, offset: offset1 } = ts1.positionToLineOffset(pos);
+                const { line: line2, offset: offset2 } = ts2.positionToLineOffset(pos);
+                assert.isTrue(line1 === line2, `positionToLineOffset ${pos}::line:: expected ${line1} to equal ${line2}`);
+                assert.isTrue(offset1 === offset2, `positionToLineOffset ${pos}::offset:: expected ${offset1} to equal ${offset2}`);
+            }
+        });
+
+        it("should switch to script version cache if necessary", () => {
+            const host = ts.projectSystem.createServerHost([f]);
+            const ts1 = new server.TextStorage(host, server.asNormalizedPath(f.path));
+
+            ts1.getSnapshot();
+            assert.isTrue(!ts1.hasScriptVersionCache(), "should not have script version cache - 1");
+
+            ts1.edit(0, 5, "   ");
+            assert.isTrue(ts1.hasScriptVersionCache(), "have script version cache - 1");
+
+            ts1.useText();
+            assert.isTrue(!ts1.hasScriptVersionCache(), "should not have script version cache - 2");
+
+            ts1.getLineInfo(0);
+            assert.isTrue(ts1.hasScriptVersionCache(), "have script version cache - 2");
+        })
+    });
+}

src/harness/unittests/tsserverProjectSystem.ts

@@ -140,7 +140,6 @@ namespace ts.projectSystem {
     export interface TestServerHostCreationParameters {
         useCaseSensitiveFileNames?: boolean;
         executingFilePath?: string;
-        libFile?: FileOrFolder;
         currentDirectory?: string;
     }
 
@@ -727,6 +726,66 @@ namespace ts.projectSystem {
             checkNumberOfInferredProjects(projectService, 1);
         });
 
+        it("remove not-listed external projects", () => {
+            const f1 = {
+                path: "/a/app.ts",
+                content: "let x = 1"
+            };
+            const f2 = {
+                path: "/b/app.ts",
+                content: "let x = 1"
+            };
+            const f3 = {
+                path: "/c/app.ts",
+                content: "let x = 1"
+            };
+            const makeProject = (f:  FileOrFolder) => ({ projectFileName: f.path + ".csproj", rootFiles: [toExternalFile(f.path)], options: {} });
+            const p1 = makeProject(f1);
+            const p2 = makeProject(f2);
+            const p3 = makeProject(f3);
+
+            const host = createServerHost([f1, f2, f3]);
+            const session = createSession(host);
+
+            session.executeCommand(<protocol.OpenExternalProjectsRequest>{
+                seq: 1,
+                type: "request",
+                command: "openExternalProjects",
+                arguments: { projects: [p1, p2] }
+            });
+
+            const projectService = session.getProjectService();
+            checkNumberOfProjects(projectService, { externalProjects: 2 });
+            assert.equal(projectService.externalProjects[0].getProjectName(), p1.projectFileName);
+            assert.equal(projectService.externalProjects[1].getProjectName(), p2.projectFileName);
+
+            session.executeCommand(<protocol.OpenExternalProjectsRequest>{
+                seq: 2,
+                type: "request",
+                command: "openExternalProjects",
+                arguments: { projects: [p1, p3] }
+            });
+            checkNumberOfProjects(projectService, { externalProjects: 2 });
+            assert.equal(projectService.externalProjects[0].getProjectName(), p1.projectFileName);
+            assert.equal(projectService.externalProjects[1].getProjectName(), p3.projectFileName);
+
+            session.executeCommand(<protocol.OpenExternalProjectsRequest>{
+                seq: 3,
+                type: "request",
+                command: "openExternalProjects",
+                arguments: { projects: [] }
+            });
+            checkNumberOfProjects(projectService, { externalProjects: 0 });
+
+            session.executeCommand(<protocol.OpenExternalProjectsRequest>{
+                seq: 3,
+                type: "request",
+                command: "openExternalProjects",
+                arguments: { projects: [p2] }
+            });
+            assert.equal(projectService.externalProjects[0].getProjectName(), p2.projectFileName);
+        });
+
         it("handle recreated files correctly", () => {
             const configFile: FileOrFolder = {
                 path: "/a/b/tsconfig.json",
@@ -1085,6 +1144,69 @@ namespace ts.projectSystem {
             checkNumberOfProjects(projectService, {});
         });
 
+        it("reload regular file after closing", () => {
+            const f1 = {
+                path: "/a/b/app.ts",
+                content: "x."
+            };
+            const f2 = {
+                path: "/a/b/lib.ts",
+                content: "let x: number;"
+            };
+
+            const host = createServerHost([f1, f2, libFile]);
+            const service = createProjectService(host);
+            service.openExternalProject({ projectFileName: "/a/b/project", rootFiles: toExternalFiles([f1.path, f2.path]), options: {} })
+
+            service.openClientFile(f1.path);
+            service.openClientFile(f2.path, "let x: string");
+
+            service.checkNumberOfProjects({ externalProjects: 1 });
+            checkProjectActualFiles(service.externalProjects[0], [f1.path, f2.path, libFile.path]);
+
+            const completions1 = service.externalProjects[0].getLanguageService().getCompletionsAtPosition(f1.path, 2);
+            // should contain completions for string
+            assert.isTrue(completions1.entries.some(e => e.name === "charAt"), "should contain 'charAt'");
+            assert.isFalse(completions1.entries.some(e => e.name === "toExponential"), "should not contain 'toExponential'");
+
+            service.closeClientFile(f2.path);
+            const completions2 = service.externalProjects[0].getLanguageService().getCompletionsAtPosition(f1.path, 2);
+            // should contain completions for string
+            assert.isFalse(completions2.entries.some(e => e.name === "charAt"), "should not contain 'charAt'");
+            assert.isTrue(completions2.entries.some(e => e.name === "toExponential"), "should contain 'toExponential'");
+        });
+
+        it("clear mixed content file after closing", () => {
+            const f1 = {
+                path: "/a/b/app.ts",
+                content: " "
+            };
+            const f2 = {
+                path: "/a/b/lib.html",
+                content: "<html/>"
+            };
+
+            const host = createServerHost([f1, f2, libFile]);
+            const service = createProjectService(host);
+            service.openExternalProject({ projectFileName: "/a/b/project", rootFiles: [{ fileName: f1.path }, { fileName: f2.path, hasMixedContent: true }], options: {} })
+
+            service.openClientFile(f1.path);
+            service.openClientFile(f2.path, "let somelongname: string");
+
+            service.checkNumberOfProjects({ externalProjects: 1 });
+            checkProjectActualFiles(service.externalProjects[0], [f1.path, f2.path, libFile.path]);
+
+            const completions1 = service.externalProjects[0].getLanguageService().getCompletionsAtPosition(f1.path, 0);
+            assert.isTrue(completions1.entries.some(e => e.name === "somelongname"), "should contain 'somelongname'");
+
+            service.closeClientFile(f2.path);
+            const completions2 = service.externalProjects[0].getLanguageService().getCompletionsAtPosition(f1.path, 0);
+            assert.isFalse(completions2.entries.some(e => e.name === "somelongname"), "should not contain 'somelongname'");
+            const sf2 = service.externalProjects[0].getLanguageService().getProgram().getSourceFile(f2.path);
+            assert.equal(sf2.text, "");
+        });
+
+
         it("external project with included config file opened after configured project", () => {
             const file1 = {
                 path: "/a/b/f1.ts",
@@ -1116,6 +1238,7 @@ namespace ts.projectSystem {
             projectService.closeExternalProject(externalProjectName);
             checkNumberOfProjects(projectService, { configuredProjects: 0 });
         });
+
         it("external project with included config file opened after configured project and then closed", () => {
             const file1 = {
                 path: "/a/b/f1.ts",
@@ -1469,6 +1592,67 @@ namespace ts.projectSystem {
             checkProjectActualFiles(projectService.inferredProjects[1], [file2.path]);
         });
 
+        it("tsconfig script block support", () => {
+            const file1 = {
+                path: "/a/b/f1.ts",
+                content: ` `
+            };
+            const file2 = {
+                path: "/a/b/f2.html",
+                content: `var hello = "hello";`
+            };
+            const config = {
+                path: "/a/b/tsconfig.json",
+                content: JSON.stringify({ compilerOptions: { allowJs: true } })
+            };
+            const host = createServerHost([file1, file2, config]);
+            const session = createSession(host);
+            openFilesForSession([file1], session);
+            const projectService = session.getProjectService();
+
+            // HTML file will not be included in any projects yet
+            checkNumberOfProjects(projectService, { configuredProjects: 1 });
+            checkProjectActualFiles(projectService.configuredProjects[0], [file1.path]);
+
+            // Specify .html extension as mixed content
+            const extraFileExtensions = [{ extension: ".html", scriptKind: ScriptKind.JS, isMixedContent: true }];
+            const configureHostRequest = makeSessionRequest<protocol.ConfigureRequestArguments>(CommandNames.Configure, { extraFileExtensions });
+            session.executeCommand(configureHostRequest).response;
+
+             // HTML file still not included in the project as it is closed
+            checkNumberOfProjects(projectService, { configuredProjects: 1 });
+            checkProjectActualFiles(projectService.configuredProjects[0], [file1.path]);
+
+            // Open HTML file
+            projectService.applyChangesInOpenFiles(
+                /*openFiles*/[{ fileName: file2.path, hasMixedContent: true, scriptKind: ScriptKind.JS, content: `var hello = "hello";` }],
+                /*changedFiles*/undefined,
+                /*closedFiles*/undefined);
+
+            // Now HTML file is included in the project
+            checkNumberOfProjects(projectService, { configuredProjects: 1 });
+            checkProjectActualFiles(projectService.configuredProjects[0], [file1.path, file2.path]);
+
+            // Check identifiers defined in HTML content are available in .ts file
+            const project = projectService.configuredProjects[0];
+            let completions = project.getLanguageService().getCompletionsAtPosition(file1.path, 1);
+            assert(completions && completions.entries[0].name === "hello", `expected entry hello to be in completion list`);
+
+            // Close HTML file
+            projectService.applyChangesInOpenFiles(
+                /*openFiles*/undefined,
+                /*changedFiles*/undefined,
+                /*closedFiles*/[file2.path]);
+
+            // HTML file is still included in project
+            checkNumberOfProjects(projectService, { configuredProjects: 1 });
+            checkProjectActualFiles(projectService.configuredProjects[0], [file1.path, file2.path]);
+
+            // Check identifiers defined in HTML content are not available in .ts file
+            completions = project.getLanguageService().getCompletionsAtPosition(file1.path, 5);
+            assert(completions && completions.entries[0].name !== "hello", `unexpected hello entry in completion list`);
+        });
+
         it("project structure update is deferred if files are not added\removed", () => {
             const file1 = {
                 path: "/a/b/f1.ts",
@@ -1514,7 +1698,7 @@ namespace ts.projectSystem {
             const project = projectService.externalProjects[0];
 
             const scriptInfo = project.getScriptInfo(file1.path);
-            const snap = scriptInfo.snap();
+            const snap = scriptInfo.getSnapshot();
             const actualText = snap.getText(0, snap.getLength());
             assert.equal(actualText, "", `expected content to be empty string, got "${actualText}"`);
 
@@ -1527,7 +1711,7 @@ namespace ts.projectSystem {
             projectService.closeClientFile(file1.path);
 
             const scriptInfo2 = project.getScriptInfo(file1.path);
-            const snap2 = scriptInfo2.snap();
+            const snap2 = scriptInfo2.getSnapshot();
             const actualText2 = snap2.getText(0, snap.getLength());
             assert.equal(actualText2, "", `expected content to be empty string, got "${actualText2}"`);
         });
@@ -1614,6 +1798,49 @@ namespace ts.projectSystem {
             checkNumberOfProjects(projectService, { configuredProjects: 0 });
         });
 
+        it("language service disabled state is updated in external projects", () => {
+            debugger
+            const f1 = {
+                path: "/a/app.js",
+                content: "var x = 1"
+            };
+            const f2 = {
+                path: "/a/largefile.js",
+                content: ""
+            };
+            const host = createServerHost([f1, f2]);
+            const originalGetFileSize = host.getFileSize;
+            host.getFileSize = (filePath: string) =>
+                filePath === f2.path ? server.maxProgramSizeForNonTsFiles + 1 : originalGetFileSize.call(host, filePath);
+
+            const service = createProjectService(host);
+            const projectFileName = "/a/proj.csproj";
+
+            service.openExternalProject({
+                projectFileName,
+                rootFiles: toExternalFiles([f1.path, f2.path]),
+                options: {}
+            });
+            service.checkNumberOfProjects({ externalProjects: 1 });
+            assert.isFalse(service.externalProjects[0].languageServiceEnabled, "language service should be disabled - 1");
+
+            service.openExternalProject({
+                projectFileName,
+                rootFiles: toExternalFiles([f1.path]),
+                options: {}
+            });
+            service.checkNumberOfProjects({ externalProjects: 1 });
+            assert.isTrue(service.externalProjects[0].languageServiceEnabled, "language service should be enabled");
+
+            service.openExternalProject({
+                projectFileName,
+                rootFiles: toExternalFiles([f1.path, f2.path]),
+                options: {}
+            });
+            service.checkNumberOfProjects({ externalProjects: 1 });
+            assert.isFalse(service.externalProjects[0].languageServiceEnabled, "language service should be disabled - 2");
+        });
+
         it("language service disabled events are triggered", () => {
             const f1 = {
                 path: "/a/app.js",
@@ -2225,13 +2452,13 @@ namespace ts.projectSystem {
             p.updateGraph();
 
             const scriptInfo = p.getScriptInfo(f.path);
-            checkSnapLength(scriptInfo.snap(), f.content.length);
+            checkSnapLength(scriptInfo.getSnapshot(), f.content.length);
 
             // open project and replace its content with empty string
             projectService.openClientFile(f.path, "");
-            checkSnapLength(scriptInfo.snap(), 0);
+            checkSnapLength(scriptInfo.getSnapshot(), 0);
         });
-        function checkSnapLength(snap: server.LineIndexSnapshot, expectedLength: number) {
+        function checkSnapLength(snap: IScriptSnapshot, expectedLength: number) {
             assert.equal(snap.getLength(), expectedLength, "Incorrect snapshot size");
         }
     });
@@ -2384,7 +2611,6 @@ namespace ts.projectSystem {
             const cwd = {
                 path: "/a/c"
             };
-            debugger;
             const host = createServerHost([f1, config, node, cwd], { currentDirectory: cwd.path });
             const projectService = createProjectService(host);
             projectService.openClientFile(f1.path);
@@ -2655,7 +2881,7 @@ namespace ts.projectSystem {
 
             // verify content
             const projectServiice = session.getProjectService();
-            const snap1 = projectServiice.getScriptInfo(f1.path).snap();
+            const snap1 = projectServiice.getScriptInfo(f1.path).getSnapshot();
             assert.equal(snap1.getText(0, snap1.getLength()), tmp.content, "content should be equal to the content of temp file");
 
             // reload from original file file
@@ -2667,7 +2893,7 @@ namespace ts.projectSystem {
             });
 
             // verify content
-            const snap2 = projectServiice.getScriptInfo(f1.path).snap();
+            const snap2 = projectServiice.getScriptInfo(f1.path).getSnapshot();
             assert.equal(snap2.getText(0, snap2.getLength()), f1.content, "content should be equal to the content of original file");
 
         });

src/lib/es2016.array.include.d.ts

@@ -7,6 +7,15 @@ interface Array<T> {
     includes(searchElement: T, fromIndex?: number): boolean;
 }
 
+interface ReadonlyArray<T> {
+    /**
+      * Determines whether an array includes a certain element, returning true or false as appropriate.
+      * @param searchElement The element to search for.
+      * @param fromIndex The position in this array at which to begin searching for searchElement.
+      */
+    includes(searchElement: T, fromIndex?: number): boolean;
+}
+
 interface Int8Array {
     /**
       * Determines whether an array includes a certain element, returning true or false as appropriate.

src/server/builder.ts

@@ -75,17 +75,32 @@ namespace ts.server {
         getFilesAffectedBy(scriptInfo: ScriptInfo): string[];
         onProjectUpdateGraph(): void;
         emitFile(scriptInfo: ScriptInfo, writeFile: (path: string, data: string, writeByteOrderMark?: boolean) => void): boolean;
+        clear(): void;
     }
 
     abstract class AbstractBuilder<T extends BuilderFileInfo> implements Builder {
 
-        private fileInfos = createFileMap<T>();
+        /**
+         * stores set of files from the project.
+         * NOTE: this field is created on demand and should not be accessed directly.
+         * Use 'getFileInfos' instead.
+         */
+        private fileInfos_doNotAccessDirectly: FileMap<T>;
 
         constructor(public readonly project: Project, private ctor: { new (scriptInfo: ScriptInfo, project: Project): T }) {
         }
 
+        private getFileInfos() {
+            return this.fileInfos_doNotAccessDirectly || (this.fileInfos_doNotAccessDirectly = createFileMap<T>());
+        }
+
+        public clear() {
+            // drop the existing list - it will be re-created as necessary
+            this.fileInfos_doNotAccessDirectly = undefined;
+        }
+
         protected getFileInfo(path: Path): T {
-            return this.fileInfos.get(path);
+            return this.getFileInfos().get(path);
         }
 
         protected getOrCreateFileInfo(path: Path): T {
@@ -99,19 +114,19 @@ namespace ts.server {
         }
 
         protected getFileInfoPaths(): Path[] {
-            return this.fileInfos.getKeys();
+            return this.getFileInfos().getKeys();
         }
 
         protected setFileInfo(path: Path, info: T) {
-            this.fileInfos.set(path, info);
+            this.getFileInfos().set(path, info);
         }
 
         protected removeFileInfo(path: Path) {
-            this.fileInfos.remove(path);
+            this.getFileInfos().remove(path);
         }
 
         protected forEachFileInfo(action: (fileInfo: T) => any) {
-            this.fileInfos.forEachValue((_path, value) => action(value));
+            this.getFileInfos().forEachValue((_path, value) => action(value));
         }
 
         abstract getFilesAffectedBy(scriptInfo: ScriptInfo): string[];
@@ -231,6 +246,11 @@ namespace ts.server {
 
         private projectVersionForDependencyGraph: string;
 
+        public clear() {
+            this.projectVersionForDependencyGraph = undefined;
+            super.clear();
+        }
+
         private getReferencedFileInfos(fileInfo: ModuleBuilderFileInfo): ModuleBuilderFileInfo[] {
             if (!fileInfo.isExternalModuleOrHasOnlyAmbientExternalModules()) {
                 return [];

src/server/editorServices.ts

@@ -108,6 +108,7 @@ namespace ts.server {
     export interface HostConfiguration {
         formatCodeOptions: FormatCodeSettings;
         hostInfo: string;
+        extraFileExtensions?: FileExtensionInfo[];
     }
 
     interface ConfigFileConversionResult {
@@ -125,20 +126,23 @@ namespace ts.server {
     }
 
     export interface OpenConfiguredProjectResult {
-        configFileName?: string;
+        configFileName?: NormalizedPath;
         configFileErrors?: Diagnostic[];
     }
 
     interface FilePropertyReader<T> {
         getFileName(f: T): string;
         getScriptKind(f: T): ScriptKind;
-        hasMixedContent(f: T): boolean;
+        hasMixedContent(f: T, extraFileExtensions: FileExtensionInfo[]): boolean;
     }
 
     const fileNamePropertyReader: FilePropertyReader<string> = {
         getFileName: x => x,
         getScriptKind: _ => undefined,
-        hasMixedContent: _ => false
+        hasMixedContent: (fileName, extraFileExtensions) => {
+            const mixedContentExtensions = ts.map(ts.filter(extraFileExtensions, item => item.isMixedContent), item => item.extension);
+            return forEach(mixedContentExtensions, extension => fileExtensionIs(fileName, extension))
+        }
     };
 
     const externalFilePropertyReader: FilePropertyReader<protocol.ExternalFile> = {
@@ -282,7 +286,8 @@ namespace ts.server {
 
             this.hostConfiguration = {
                 formatCodeOptions: getDefaultFormatCodeSettings(this.host),
-                hostInfo: "Unknown host"
+                hostInfo: "Unknown host",
+                extraFileExtensions: []
             };
 
             this.documentRegistry = createDocumentRegistry(host.useCaseSensitiveFileNames, host.getCurrentDirectory());
@@ -424,7 +429,7 @@ namespace ts.server {
                 this.handleDeletedFile(info);
             }
             else {
-                if (info && (!info.isOpen)) {
+                if (info && (!info.isScriptOpen())) {
                     // file has been changed which might affect the set of referenced files in projects that include 
                     // this file and set of inferred projects
                     info.reloadFromFile();
@@ -440,7 +445,7 @@ namespace ts.server {
 
             // TODO: handle isOpen = true case
 
-            if (!info.isOpen) {
+            if (!info.isScriptOpen()) {
                 this.filenameToScriptInfo.remove(info.path);
                 this.lastDeletedFile = info;
 
@@ -486,7 +491,7 @@ namespace ts.server {
             // If a change was made inside "folder/file", node will trigger the callback twice:
             // one with the fileName being "folder/file", and the other one with "folder".
             // We don't respond to the second one.
-            if (fileName && !ts.isSupportedSourceFileName(fileName, project.getCompilerOptions())) {
+            if (fileName && !ts.isSupportedSourceFileName(fileName, project.getCompilerOptions(), this.hostConfiguration.extraFileExtensions)) {
                 return;
             }
 
@@ -634,15 +639,17 @@ namespace ts.server {
             // Closing file should trigger re-reading the file content from disk. This is
             // because the user may chose to discard the buffer content before saving
             // to the disk, and the server's version of the file can be out of sync.
-            info.reloadFromFile();
+            info.close();
 
             removeItemFromSet(this.openFiles, info);
-            info.isOpen = false;
 
             // collect all projects that should be removed
             let projectsToRemove: Project[];
             for (const p of info.containingProjects) {
                 if (p.projectKind === ProjectKind.Configured) {
+                    if (info.hasMixedContent) {
+                        info.registerFileUpdate();
+                    }
                     // last open file in configured project - close it
                     if ((<ConfiguredProject>p).deleteOpenRef() === 0) {
                         (projectsToRemove || (projectsToRemove = [])).push(p);
@@ -652,6 +659,13 @@ namespace ts.server {
                     // open file in inferred project
                     (projectsToRemove || (projectsToRemove = [])).push(p);
                 }
+
+                if (!p.languageServiceEnabled) {
+                    // if project language service is disabled then we create a program only for open files.
+                    // this means that project should be marked as dirty to force rebuilding of the program
+                    // on the next request
+                    p.markAsDirty();
+                }
             }
             if (projectsToRemove) {
                 for (const project of projectsToRemove) {
@@ -811,7 +825,9 @@ namespace ts.server {
                 this.host,
                 getDirectoryPath(configFilename),
                 /*existingOptions*/ {},
-                configFilename);
+                configFilename,
+                /*resolutionStack*/ [],
+                this.hostConfiguration.extraFileExtensions);
 
             if (parsedCommandLine.errors.length) {
                 errors = concatenate(errors, parsedCommandLine.errors);
@@ -915,7 +931,7 @@ namespace ts.server {
             for (const f of files) {
                 const rootFilename = propertyReader.getFileName(f);
                 const scriptKind = propertyReader.getScriptKind(f);
-                const hasMixedContent = propertyReader.hasMixedContent(f);
+                const hasMixedContent = propertyReader.hasMixedContent(f, this.hostConfiguration.extraFileExtensions);
                 if (this.host.fileExists(rootFilename)) {
                     const info = this.getOrCreateScriptInfoForNormalizedPath(toNormalizedPath(rootFilename), /*openedByClient*/ clientFileName == rootFilename, /*fileContent*/ undefined, scriptKind, hasMixedContent);
                     project.addRoot(info);
@@ -961,7 +977,7 @@ namespace ts.server {
                     rootFilesChanged = true;
                     if (!scriptInfo) {
                         const scriptKind = propertyReader.getScriptKind(f);
-                        const hasMixedContent = propertyReader.hasMixedContent(f);
+                        const hasMixedContent = propertyReader.hasMixedContent(f, this.hostConfiguration.extraFileExtensions);
                         scriptInfo = this.getOrCreateScriptInfoForNormalizedPath(normalizedPath, /*openedByClient*/ false, /*fileContent*/ undefined, scriptKind, hasMixedContent);
                     }
                 }
@@ -989,7 +1005,7 @@ namespace ts.server {
                 }
                 if (toAdd) {
                     for (const f of toAdd) {
-                        if (f.isOpen && isRootFileInInferredProject(f)) {
+                        if (f.isScriptOpen() && isRootFileInInferredProject(f)) {
                             // if file is already root in some inferred project 
                             // - remove the file from that project and delete the project if necessary
                             const inferredProject = f.containingProjects[0];
@@ -1043,9 +1059,7 @@ namespace ts.server {
                 project.stopWatchingDirectory();
             }
             else {
-                if (!project.languageServiceEnabled) {
-                    project.enableLanguageService();
-                }
+                project.enableLanguageService();
                 this.watchConfigDirectoryForProject(project, projectOptions);
                 this.updateNonInferredProject(project, projectOptions.files, fileNamePropertyReader, projectOptions.compilerOptions, projectOptions.typeAcquisition, projectOptions.compileOnSave, configFileErrors);
             }
@@ -1089,32 +1103,34 @@ namespace ts.server {
         getOrCreateScriptInfoForNormalizedPath(fileName: NormalizedPath, openedByClient: boolean, fileContent?: string, scriptKind?: ScriptKind, hasMixedContent?: boolean) {
             let info = this.getScriptInfoForNormalizedPath(fileName);
             if (!info) {
-                let content: string;
-                if (this.host.fileExists(fileName)) {
-                    // by default pick whatever content was supplied as the argument
-                    // if argument was not given - then for mixed content files assume that its content is empty string
-                    content = fileContent || (hasMixedContent ? "" : this.host.readFile(fileName));
-                }
-                if (!content) {
-                    if (openedByClient) {
-                        content = "";
-                    }
-                }
-                if (content !== undefined) {
-                    info = new ScriptInfo(this.host, fileName, content, scriptKind, openedByClient, hasMixedContent);
-                    // do not watch files with mixed content - server doesn't know how to interpret it
+                if (openedByClient || this.host.fileExists(fileName)) {
+                    info = new ScriptInfo(this.host, fileName, scriptKind, hasMixedContent);
+
                     this.filenameToScriptInfo.set(info.path, info);
-                    if (!info.isOpen && !hasMixedContent) {
-                        info.setWatcher(this.host.watchFile(fileName, _ => this.onSourceFileChanged(fileName)));
+
+                    if (openedByClient) {
+                        if (fileContent === undefined) {
+                            // if file is opened by client and its content is not specified - use file text
+                            fileContent = this.host.readFile(fileName) || "";
+                        }
+                    }
+                    else {
+                        // do not watch files with mixed content - server doesn't know how to interpret it
+                        if (!hasMixedContent) {
+                            info.setWatcher(this.host.watchFile(fileName, _ => this.onSourceFileChanged(fileName)));
+                        }
                     }
                 }
             }
             if (info) {
-                if (fileContent !== undefined) {
-                    info.reload(fileContent);
+                if (openedByClient && !info.isScriptOpen()) {
+                    info.open(fileContent);
+                    if (hasMixedContent) {
+                        info.registerFileUpdate();
+                    }
                 }
-                if (openedByClient) {
-                    info.isOpen = true;
+                else if (fileContent !== undefined) {
+                    info.reload(fileContent);
                 }
             }
             return info;
@@ -1146,6 +1162,10 @@ namespace ts.server {
                     mergeMaps(this.hostConfiguration.formatCodeOptions, convertFormatOptions(args.formatOptions));
                     this.logger.info("Format host information updated");
                 }
+                if (args.extraFileExtensions) {
+                    this.hostConfiguration.extraFileExtensions = args.extraFileExtensions;
+                    this.logger.info("Host file extension mappings updated");
+                }
             }
         }
 
@@ -1211,9 +1231,22 @@ namespace ts.server {
         }
 
         openClientFileWithNormalizedPath(fileName: NormalizedPath, fileContent?: string, scriptKind?: ScriptKind, hasMixedContent?: boolean): OpenConfiguredProjectResult {
-            const { configFileName = undefined, configFileErrors = undefined }: OpenConfiguredProjectResult = this.findContainingExternalProject(fileName)
-                ? {}
-                : this.openOrUpdateConfiguredProjectForFile(fileName);
+            let configFileName: NormalizedPath;
+            let configFileErrors: Diagnostic[];
+
+            let project: ConfiguredProject | ExternalProject = this.findContainingExternalProject(fileName);
+            if (!project) {
+                ({ configFileName, configFileErrors } = this.openOrUpdateConfiguredProjectForFile(fileName));
+                if (configFileName) {
+                    project = this.findConfiguredProjectByProjectName(configFileName);
+                }
+            }
+            if (project && !project.languageServiceEnabled) {
+                // if project language service is disabled then we create a program only for open files.
+                // this means that project should be marked as dirty to force rebuilding of the program
+                // on the next request
+                project.markAsDirty();
+            }
 
             // at this point if file is the part of some configured/external project then this project should be created
             const info = this.getOrCreateScriptInfoForNormalizedPath(fileName, /*openedByClient*/ true, fileContent, scriptKind, hasMixedContent);
@@ -1230,7 +1263,6 @@ namespace ts.server {
             const info = this.getScriptInfoForNormalizedPath(toNormalizedPath(uncheckedFileName));
             if (info) {
                 this.closeOpenFile(info);
-                info.isOpen = false;
             }
             this.printProjects();
         }
@@ -1255,7 +1287,7 @@ namespace ts.server {
             if (openFiles) {
                 for (const file of openFiles) {
                     const scriptInfo = this.getScriptInfo(file.fileName);
-                    Debug.assert(!scriptInfo || !scriptInfo.isOpen);
+                    Debug.assert(!scriptInfo || !scriptInfo.isScriptOpen());
                     const normalizedPath = scriptInfo ? scriptInfo.fileName : toNormalizedPath(file.fileName);
                     this.openClientFileWithNormalizedPath(normalizedPath, file.content, tryConvertScriptKindName(file.scriptKind), file.hasMixedContent);
                 }
@@ -1327,7 +1359,28 @@ namespace ts.server {
             }
         }
 
-        openExternalProject(proj: protocol.ExternalProject): void {
+        openExternalProjects(projects: protocol.ExternalProject[]): void {
+            // record project list before the update
+            const projectsToClose = arrayToMap(this.externalProjects, p => p.getProjectName(), _ => true);
+            for (const externalProjectName in this.externalProjectToConfiguredProjectMap) {
+                projectsToClose[externalProjectName] = true;
+            }
+
+            for (const externalProject of projects) {
+                this.openExternalProject(externalProject, /*suppressRefreshOfInferredProjects*/ true);
+                // delete project that is present in input list
+                delete projectsToClose[externalProject.projectFileName];
+            }
+
+            // close projects that were missing in the input list
+            for (const externalProjectName in projectsToClose) {
+                this.closeExternalProject(externalProjectName, /*suppressRefresh*/ true)
+            }
+
+            this.refreshInferredProjects();
+        }
+
+        openExternalProject(proj: protocol.ExternalProject, suppressRefreshOfInferredProjects = false): void {
             // typingOptions has been deprecated and is only supported for backward compatibility
             // purposes. It should be removed in future releases - use typeAcquisition instead.
             if (proj.typingOptions && !proj.typeAcquisition) {
@@ -1357,8 +1410,15 @@ namespace ts.server {
             let exisingConfigFiles: string[];
             if (externalProject) {
                 if (!tsConfigFiles) {
+                    const compilerOptions = convertCompilerOptions(proj.options);
+                    if (this.exceededTotalSizeLimitForNonTsFiles(compilerOptions, proj.rootFiles, externalFilePropertyReader)) {
+                        externalProject.disableLanguageService();
+                    }
+                    else {
+                        externalProject.enableLanguageService();
+                    }
                     // external project already exists and not config files were added - update the project and return;
-                    this.updateNonInferredProject(externalProject, proj.rootFiles, externalFilePropertyReader, convertCompilerOptions(proj.options), proj.typeAcquisition, proj.options.compileOnSave, /*configFileErrors*/ undefined);
+                    this.updateNonInferredProject(externalProject, proj.rootFiles, externalFilePropertyReader, compilerOptions, proj.typeAcquisition, proj.options.compileOnSave, /*configFileErrors*/ undefined);
                     return;
                 }
                 // some config files were added to external project (that previously were not there)
@@ -1420,7 +1480,9 @@ namespace ts.server {
                 delete this.externalProjectToConfiguredProjectMap[proj.projectFileName];
                 this.createAndAddExternalProject(proj.projectFileName, rootFiles, proj.options, proj.typeAcquisition);
             }
-            this.refreshInferredProjects();
+            if (!suppressRefreshOfInferredProjects) {
+                this.refreshInferredProjects();
+            }
         }
     }
 }

src/server/lsHost.ts

@@ -169,7 +169,7 @@ namespace ts.server {
         getScriptSnapshot(filename: string): ts.IScriptSnapshot {
             const scriptInfo = this.project.getScriptInfoLSHost(filename);
             if (scriptInfo) {
-                return scriptInfo.snap();
+                return scriptInfo.getSnapshot();
             }
         }
 

src/server/project.ts

@@ -1,4 +1,4 @@
-/// <reference path="..\services\services.ts" />
+/// <reference path="..\services\services.ts" />
 /// <reference path="utilities.ts"/>
 /// <reference path="scriptInfo.ts"/>
 /// <reference path="lsHost.ts"/>
@@ -90,87 +90,6 @@ namespace ts.server {
         }
     }
 
-    const emptyResult: any[] = [];
-    const getEmptyResult = () => emptyResult;
-    const getUndefined = () => <any>undefined;
-    const emptyEncodedSemanticClassifications = { spans: emptyResult, endOfLineState: EndOfLineState.None };
-
-    export function createNoSemanticFeaturesWrapper(realLanguageService: LanguageService): LanguageService {
-        return {
-            cleanupSemanticCache: noop,
-            getSyntacticDiagnostics: (fileName) =>
-                fileName ? realLanguageService.getSyntacticDiagnostics(fileName) : emptyResult,
-            getSemanticDiagnostics: getEmptyResult,
-            getCompilerOptionsDiagnostics: () =>
-                realLanguageService.getCompilerOptionsDiagnostics(),
-            getSyntacticClassifications: (fileName, span) =>
-                realLanguageService.getSyntacticClassifications(fileName, span),
-            getEncodedSyntacticClassifications: (fileName, span) =>
-                realLanguageService.getEncodedSyntacticClassifications(fileName, span),
-            getSemanticClassifications: getEmptyResult,
-            getEncodedSemanticClassifications: () =>
-                emptyEncodedSemanticClassifications,
-            getCompletionsAtPosition: getUndefined,
-            findReferences: getEmptyResult,
-            getCompletionEntryDetails: getUndefined,
-            getQuickInfoAtPosition: getUndefined,
-            findRenameLocations: getEmptyResult,
-            getNameOrDottedNameSpan: (fileName, startPos, endPos) =>
-                realLanguageService.getNameOrDottedNameSpan(fileName, startPos, endPos),
-            getBreakpointStatementAtPosition: (fileName, position) =>
-                realLanguageService.getBreakpointStatementAtPosition(fileName, position),
-            getBraceMatchingAtPosition: (fileName, position) =>
-                realLanguageService.getBraceMatchingAtPosition(fileName, position),
-            getSignatureHelpItems: getUndefined,
-            getDefinitionAtPosition: getEmptyResult,
-            getRenameInfo: () => ({
-                canRename: false,
-                localizedErrorMessage: getLocaleSpecificMessage(Diagnostics.Language_service_is_disabled),
-                displayName: undefined,
-                fullDisplayName: undefined,
-                kind: undefined,
-                kindModifiers: undefined,
-                triggerSpan: undefined
-            }),
-            getTypeDefinitionAtPosition: getUndefined,
-            getReferencesAtPosition: getEmptyResult,
-            getDocumentHighlights: getEmptyResult,
-            getOccurrencesAtPosition: getEmptyResult,
-            getNavigateToItems: getEmptyResult,
-            getNavigationBarItems: fileName =>
-                realLanguageService.getNavigationBarItems(fileName),
-            getNavigationTree: fileName =>
-                realLanguageService.getNavigationTree(fileName),
-            getOutliningSpans: fileName =>
-                realLanguageService.getOutliningSpans(fileName),
-            getTodoComments: getEmptyResult,
-            getIndentationAtPosition: (fileName, position, options) =>
-                realLanguageService.getIndentationAtPosition(fileName, position, options),
-            getFormattingEditsForRange: (fileName, start, end, options) =>
-                realLanguageService.getFormattingEditsForRange(fileName, start, end, options),
-            getFormattingEditsForDocument: (fileName, options) =>
-                realLanguageService.getFormattingEditsForDocument(fileName, options),
-            getFormattingEditsAfterKeystroke: (fileName, position, key, options) =>
-                realLanguageService.getFormattingEditsAfterKeystroke(fileName, position, key, options),
-            getDocCommentTemplateAtPosition: (fileName, position) =>
-                realLanguageService.getDocCommentTemplateAtPosition(fileName, position),
-            isValidBraceCompletionAtPosition: (fileName, position, openingBrace) =>
-                realLanguageService.isValidBraceCompletionAtPosition(fileName, position, openingBrace),
-            getEmitOutput: getUndefined,
-            getProgram: () =>
-                realLanguageService.getProgram(),
-            getNonBoundSourceFile: fileName =>
-                realLanguageService.getNonBoundSourceFile(fileName),
-            dispose: () =>
-                realLanguageService.dispose(),
-            getCompletionEntrySymbol: getUndefined,
-            getImplementationAtPosition: getEmptyResult,
-            getSourceFile: fileName =>
-                realLanguageService.getSourceFile(fileName),
-            getCodeFixesAtPosition: getEmptyResult
-        };
-    }
-
     export abstract class Project {
         private rootFiles: ScriptInfo[] = [];
         private rootFilesMap: FileMap<ScriptInfo> = createFileMap<ScriptInfo>();
@@ -181,12 +100,14 @@ namespace ts.server {
         private lastCachedUnresolvedImportsList: SortedReadonlyArray<string>;
 
         private readonly languageService: LanguageService;
-        // wrapper over the real language service that will suppress all semantic operations
-        private readonly noSemanticFeaturesLanguageService: LanguageService;
 
         public languageServiceEnabled = true;
 
         builder: Builder;
+        /**
+         * Set of files names that were updated since the last call to getChangesSinceVersion.
+         */
+        private updatedFileNames: Map<string>;
         /**
          * Set of files that was returned from the last call to getChangesSinceVersion.
          */
@@ -254,7 +175,6 @@ namespace ts.server {
             this.lsHost.setCompilationSettings(this.compilerOptions);
 
             this.languageService = ts.createLanguageService(this.lsHost, this.documentRegistry);
-            this.noSemanticFeaturesLanguageService = createNoSemanticFeaturesWrapper(this.languageService);
 
             if (!languageServiceEnabled) {
                 this.disableLanguageService();
@@ -278,9 +198,7 @@ namespace ts.server {
             if (ensureSynchronized) {
                 this.updateGraph();
             }
-            return this.languageServiceEnabled
-                ? this.languageService
-                : this.noSemanticFeaturesLanguageService;
+            return this.languageService;
         }
 
         getCompileOnSaveAffectedFileList(scriptInfo: ScriptInfo): string[] {
@@ -369,7 +287,10 @@ namespace ts.server {
             const result: string[] = [];
             if (this.rootFiles) {
                 for (const f of this.rootFiles) {
-                    result.push(f.fileName);
+                    if (this.languageServiceEnabled || f.isScriptOpen()) {
+                        // if language service is disabled - process only files that are open
+                        result.push(f.fileName);
+                    }
                 }
                 if (this.typingFiles) {
                     for (const f of this.typingFiles) {
@@ -385,6 +306,10 @@ namespace ts.server {
         }
 
         getScriptInfos() {
+            if (!this.languageServiceEnabled) {
+                // if language service is not enabled - return just root files
+                return this.rootFiles;
+            }
             return map(this.program.getSourceFiles(), sourceFile => {
                 const scriptInfo = this.projectService.getScriptInfoForPath(sourceFile.path);
                 if (!scriptInfo) {
@@ -448,7 +373,7 @@ namespace ts.server {
 
         containsFile(filename: NormalizedPath, requireOpen?: boolean) {
             const info = this.projectService.getScriptInfoForNormalizedPath(filename);
-            if (info && (info.isOpen || !requireOpen)) {
+            if (info && (info.isScriptOpen() || !requireOpen)) {
                 return this.containsScriptInfo(info);
             }
         }
@@ -480,6 +405,10 @@ namespace ts.server {
             this.markAsDirty();
         }
 
+        registerFileUpdate(fileName: string) {
+            (this.updatedFileNames || (this.updatedFileNames = createMap<string>()))[fileName] = fileName;
+        }
+
         markAsDirty() {
             this.projectStateVersion++;
         }
@@ -521,10 +450,6 @@ namespace ts.server {
          * @returns: true if set of files in the project stays the same and false - otherwise.
          */
         updateGraph(): boolean {
-            if (!this.languageServiceEnabled) {
-                return true;
-            }
-
             this.lsHost.startRecordingFilesWithChangedResolutions();
 
             let hasChanges = this.updateGraphWorker();
@@ -556,6 +481,16 @@ namespace ts.server {
             if (this.setTypings(cachedTypings)) {
                 hasChanges = this.updateGraphWorker() || hasChanges;
             }
+
+            // update builder only if language service is enabled
+            // otherwise tell it to drop its internal state
+            if (this.languageServiceEnabled) {
+                this.builder.onProjectUpdateGraph();
+            }
+            else {
+                this.builder.clear();
+            }
+
             if (hasChanges) {
                 this.projectStructureVersion++;
             }
@@ -594,7 +529,6 @@ namespace ts.server {
                     }
                 }
             }
-            this.builder.onProjectUpdateGraph();
             return hasChanges;
         }
 
@@ -665,12 +599,15 @@ namespace ts.server {
                 projectName: this.getProjectName(),
                 version: this.projectStructureVersion,
                 isInferred: this.projectKind === ProjectKind.Inferred,
-                options: this.getCompilerOptions()
+                options: this.getCompilerOptions(),
+                languageServiceDisabled: !this.languageServiceEnabled
             };
+            const updatedFileNames = this.updatedFileNames;
+            this.updatedFileNames = undefined;
             // check if requested version is the same that we have reported last time
             if (this.lastReportedFileNames && lastKnownVersion === this.lastReportedVersion) {
-                // if current structure version is the same - return info witout any changes
-                if (this.projectStructureVersion == this.lastReportedVersion) {
+                // if current structure version is the same - return info without any changes
+                if (this.projectStructureVersion == this.lastReportedVersion && !updatedFileNames) {
                     return { info, projectErrors: this.projectErrors };
                 }
                 // compute and return the difference
@@ -679,6 +616,7 @@ namespace ts.server {
 
                 const added: string[] = [];
                 const removed: string[] = [];
+                const updated: string[] = getOwnKeys(updatedFileNames);
                 for (const id in currentFiles) {
                     if (!hasProperty(lastReportedFileNames, id)) {
                         added.push(id);
@@ -691,7 +629,7 @@ namespace ts.server {
                 }
                 this.lastReportedFileNames = currentFiles;
                 this.lastReportedVersion = this.projectStructureVersion;
-                return { info, changes: { added, removed }, projectErrors: this.projectErrors };
+                return { info, changes: { added, removed, updated }, projectErrors: this.projectErrors };
             }
             else {
                 // unknown version - return everything

src/server/protocol.ts

@@ -1,4 +1,4 @@
-/**
+/**
   * Declaration module describing the TypeScript Server protocol
   */
 namespace ts.server.protocol {
@@ -904,6 +904,11 @@ namespace ts.server.protocol {
          * Current set of compiler options for project
          */
         options: ts.CompilerOptions;
+
+        /**
+         * true if project language service is disabled
+         */
+        languageServiceDisabled: boolean;
     }
 
     /**
@@ -918,6 +923,10 @@ namespace ts.server.protocol {
          * List of removed files
          */
         removed: string[];
+        /**
+         * List of updated files
+         */
+        updated: string[];
     }
 
     /**
@@ -990,6 +999,11 @@ namespace ts.server.protocol {
          * The format options to use during formatting and other code editing features.
          */
         formatOptions?: FormatCodeSettings;
+
+        /**
+         * The host's additional supported file extensions
+         */
+        extraFileExtensions?: FileExtensionInfo[];
     }
 
     /**

src/server/scriptInfo.ts

@@ -2,6 +2,161 @@
 
 namespace ts.server {
 
+    /* @internal */
+    export class TextStorage {
+        private svc: ScriptVersionCache | undefined;
+        private svcVersion = 0;
+
+        private text: string;
+        private lineMap: number[];
+        private textVersion = 0;
+
+        constructor(private readonly host: ServerHost, private readonly fileName: NormalizedPath) {
+        }
+
+        public getVersion() {
+            return this.svc
+                ? `SVC-${this.svcVersion}-${this.svc.getSnapshot().version}`
+                : `Text-${this.textVersion}`;
+        }
+
+        public hasScriptVersionCache() {
+            return this.svc !== undefined;
+        }
+
+        public useScriptVersionCache(newText?: string) {
+            this.switchToScriptVersionCache(newText);
+        }
+
+        public useText(newText?: string) {
+            this.svc = undefined;
+            this.setText(newText);
+        }
+
+        public edit(start: number, end: number, newText: string) {
+            this.switchToScriptVersionCache().edit(start, end - start, newText);
+        }
+
+        public reload(text: string) {
+            if (this.svc) {
+                this.svc.reload(text);
+            }
+            else {
+                this.setText(text);
+            }
+        }
+
+        public reloadFromFile(tempFileName?: string) {
+            if (this.svc || (tempFileName !== this.fileName)) {
+                this.reload(this.getFileText(tempFileName))
+            }
+            else {
+                this.setText(undefined);
+            }
+        }
+
+        public getSnapshot(): IScriptSnapshot {
+            return this.svc
+                ? this.svc.getSnapshot()
+                : ScriptSnapshot.fromString(this.getOrLoadText());
+        }
+
+        public getLineInfo(line: number) {
+            return this.switchToScriptVersionCache().getSnapshot().index.lineNumberToInfo(line);
+        }
+        /**
+         *  @param line 0 based index
+         */
+        lineToTextSpan(line: number) {
+            if (!this.svc) {
+                const lineMap = this.getLineMap();
+                const start = lineMap[line]; // -1 since line is 1-based
+                const end = line + 1 < lineMap.length ? lineMap[line + 1] : this.text.length;
+                return ts.createTextSpanFromBounds(start, end);
+            }
+            const index = this.svc.getSnapshot().index;
+            const lineInfo = index.lineNumberToInfo(line + 1);
+            let len: number;
+            if (lineInfo.leaf) {
+                len = lineInfo.leaf.text.length;
+            }
+            else {
+                const nextLineInfo = index.lineNumberToInfo(line + 2);
+                len = nextLineInfo.offset - lineInfo.offset;
+            }
+            return ts.createTextSpan(lineInfo.offset, len);
+        }
+
+        /**
+         * @param line 1 based index
+         * @param offset 1 based index
+         */
+        lineOffsetToPosition(line: number, offset: number): number {
+            if (!this.svc) {
+                return computePositionOfLineAndCharacter(this.getLineMap(), line - 1, offset - 1);
+            }
+            const index = this.svc.getSnapshot().index;
+
+            const lineInfo = index.lineNumberToInfo(line);
+            // TODO: assert this offset is actually on the line
+            return (lineInfo.offset + offset - 1);
+        }
+
+        /**
+         * @param line 1-based index
+         * @param offset 1-based index
+         */
+        positionToLineOffset(position: number): ILineInfo {
+            if (!this.svc) {
+                const { line, character } = computeLineAndCharacterOfPosition(this.getLineMap(), position);
+                return { line: line + 1, offset: character + 1 };
+            }
+            const index = this.svc.getSnapshot().index;
+            const lineOffset = index.charOffsetToLineNumberAndPos(position);
+            return { line: lineOffset.line, offset: lineOffset.offset + 1 };
+        }
+
+        private getFileText(tempFileName?: string) {
+            return this.host.readFile(tempFileName || this.fileName) || "";
+        }
+
+        private ensureNoScriptVersionCache() {
+            Debug.assert(!this.svc, "ScriptVersionCache should not be set");
+        }
+
+        private switchToScriptVersionCache(newText?: string): ScriptVersionCache {
+            if (!this.svc) {
+                this.svc = ScriptVersionCache.fromString(this.host, newText !== undefined ? newText : this.getOrLoadText());
+                this.svcVersion++;
+                this.text = undefined;
+            }
+            return this.svc;
+        }
+
+        private getOrLoadText() {
+            this.ensureNoScriptVersionCache();
+            if (this.text === undefined) {
+                this.setText(this.getFileText());
+            }
+            return this.text;
+        }
+
+        private getLineMap() {
+            this.ensureNoScriptVersionCache();
+            return this.lineMap || (this.lineMap = computeLineStarts(this.getOrLoadText()));
+        }
+
+        private setText(newText: string) {
+            this.ensureNoScriptVersionCache();
+            if (newText === undefined || this.text !== newText) {
+                this.text = newText;
+                this.lineMap = undefined;
+                this.textVersion++;
+            }
+        }
+    }
+
+
     export class ScriptInfo {
         /**
          * All projects that include this file
@@ -11,24 +166,46 @@ namespace ts.server {
         readonly path: Path;
 
         private fileWatcher: FileWatcher;
-        private svc: ScriptVersionCache;
+        private textStorage: TextStorage;
+
+        private isOpen: boolean;
 
-        // TODO: allow to update hasMixedContent from the outside
         constructor(
             private readonly host: ServerHost,
             readonly fileName: NormalizedPath,
-            content: string,
             readonly scriptKind: ScriptKind,
-            public isOpen = false,
             public hasMixedContent = false) {
 
             this.path = toPath(fileName, host.getCurrentDirectory(), createGetCanonicalFileName(host.useCaseSensitiveFileNames));
-            this.svc = ScriptVersionCache.fromString(host, content);
+            this.textStorage = new TextStorage(host, fileName);
+            if (hasMixedContent) {
+                this.textStorage.reload("");
+            }
             this.scriptKind = scriptKind
                 ? scriptKind
                 : getScriptKindFromFileName(fileName);
         }
 
+        public isScriptOpen() {
+            return this.isOpen;
+        }
+
+        public open(newText: string) {
+            this.isOpen = true;
+            this.textStorage.useScriptVersionCache(newText);
+            this.markContainingProjectsAsDirty();
+        }
+
+        public close() {
+            this.isOpen = false;
+            this.textStorage.useText(this.hasMixedContent ? "" : undefined);
+            this.markContainingProjectsAsDirty();
+        }
+
+        public getSnapshot() {
+            return this.textStorage.getSnapshot();
+        }
+
         getFormatCodeSettings() {
             return this.formatCodeSettings;
         }
@@ -90,6 +267,12 @@ namespace ts.server {
             return this.containingProjects[0];
         }
 
+        registerFileUpdate(): void {
+            for (const p of this.containingProjects) {
+                p.registerFileUpdate(this.path);
+            }
+        }
+
         setFormatOptions(formatSettings: FormatCodeSettings): void {
             if (formatSettings) {
                 if (!this.formatCodeSettings) {
@@ -112,16 +295,16 @@ namespace ts.server {
         }
 
         getLatestVersion() {
-            return this.svc.latestVersion().toString();
+            return this.textStorage.getVersion();
         }
 
         reload(script: string) {
-            this.svc.reload(script);
+            this.textStorage.reload(script);
             this.markContainingProjectsAsDirty();
         }
 
         saveTo(fileName: string) {
-            const snap = this.snap();
+            const snap = this.textStorage.getSnapshot();
             this.host.writeFile(fileName, snap.getText(0, snap.getLength()));
         }
 
@@ -130,22 +313,17 @@ namespace ts.server {
                 this.reload("");
             }
             else {
-                this.svc.reloadFromFile(tempFileName || this.fileName);
+                this.textStorage.reloadFromFile(tempFileName);
                 this.markContainingProjectsAsDirty();
             }
         }
 
-        snap() {
-            return this.svc.getSnapshot();
-        }
-
         getLineInfo(line: number) {
-            const snap = this.snap();
-            return snap.index.lineNumberToInfo(line);
+            return this.textStorage.getLineInfo(line);
         }
 
         editContent(start: number, end: number, newText: string): void {
-            this.svc.edit(start, end - start, newText);
+            this.textStorage.edit(start, end, newText);
             this.markContainingProjectsAsDirty();
         }
 
@@ -159,17 +337,7 @@ namespace ts.server {
          *  @param line 1 based index
          */
         lineToTextSpan(line: number) {
-            const index = this.snap().index;
-            const lineInfo = index.lineNumberToInfo(line + 1);
-            let len: number;
-            if (lineInfo.leaf) {
-                len = lineInfo.leaf.text.length;
-            }
-            else {
-                const nextLineInfo = index.lineNumberToInfo(line + 2);
-                len = nextLineInfo.offset - lineInfo.offset;
-            }
-            return ts.createTextSpan(lineInfo.offset, len);
+            return this.textStorage.lineToTextSpan(line);
         }
 
         /**
@@ -177,11 +345,7 @@ namespace ts.server {
          * @param offset 1 based index
          */
         lineOffsetToPosition(line: number, offset: number): number {
-            const index = this.snap().index;
-
-            const lineInfo = index.lineNumberToInfo(line);
-            // TODO: assert this offset is actually on the line
-            return (lineInfo.offset + offset - 1);
+            return this.textStorage.lineOffsetToPosition(line, offset);
         }
 
         /**
@@ -189,9 +353,7 @@ namespace ts.server {
          * @param offset 1-based index
          */
         positionToLineOffset(position: number): ILineInfo {
-            const index = this.snap().index;
-            const lineOffset = index.charOffsetToLineNumberAndPos(position);
-            return { line: lineOffset.line, offset: lineOffset.offset + 1 };
+            return this.textStorage.positionToLineOffset(position);
         }
     }
 }

src/server/scriptVersionCache.ts

@@ -438,8 +438,9 @@ namespace ts.server {
             }
         }
         getChangeRange(oldSnapshot: ts.IScriptSnapshot): ts.TextChangeRange {
-            const oldSnap = <LineIndexSnapshot>oldSnapshot;
-            return this.getTextChangeRangeSinceVersion(oldSnap.version);
+            if (oldSnapshot instanceof LineIndexSnapshot) {
+                return this.getTextChangeRangeSinceVersion(oldSnapshot.version);
+            }
         }
     }
 

src/server/server.ts

@@ -20,34 +20,41 @@ namespace ts.server {
     } = require("os");
 
     function getGlobalTypingsCacheLocation() {
-        let basePath: string;
         switch (process.platform) {
-            case "win32":
-                basePath = process.env.LOCALAPPDATA ||
+            case "win32": {
+                const basePath = process.env.LOCALAPPDATA ||
                     process.env.APPDATA ||
                     (os.homedir && os.homedir()) ||
                     process.env.USERPROFILE ||
                     (process.env.HOMEDRIVE && process.env.HOMEPATH && normalizeSlashes(process.env.HOMEDRIVE + process.env.HOMEPATH)) ||
                     os.tmpdir();
-                break;
-            case "linux":
-            case "android":
-                basePath = (os.homedir && os.homedir()) ||
-                    process.env.HOME ||
-                    ((process.env.LOGNAME || process.env.USER) && `/home/${process.env.LOGNAME || process.env.USER}`) ||
-                    os.tmpdir();
-                break;
+                return combinePaths(normalizeSlashes(basePath), "Microsoft/TypeScript");
+            }
             case "darwin":
-                const homeDir = (os.homedir && os.homedir()) ||
-                        process.env.HOME ||
-                        ((process.env.LOGNAME || process.env.USER) && `/Users/${process.env.LOGNAME || process.env.USER}`) ||
-                        os.tmpdir();
-                basePath = combinePaths(homeDir, "Library/Application Support/");
-                break;
+            case "linux":
+            case "android": {
+                const cacheLocation = getNonWindowsCacheLocation(process.platform === "darwin");
+                return combinePaths(cacheLocation, "typescript");
+            }
+            default:
+                Debug.fail(`unsupported platform '${process.platform}'`);
+                return;
         }
+    }
 
-        Debug.assert(basePath !== undefined);
-        return combinePaths(normalizeSlashes(basePath), "Microsoft/TypeScript");
+    function getNonWindowsCacheLocation(platformIsDarwin: boolean) {
+        if (process.env.XDG_CACHE_HOME) {
+            return process.env.XDG_CACHE_HOME;
+        }
+        const usersDir = platformIsDarwin ? "Users" : "home"
+        const homePath = (os.homedir && os.homedir()) ||
+            process.env.HOME ||
+            ((process.env.LOGNAME || process.env.USER) && `/${usersDir}/${process.env.LOGNAME || process.env.USER}`) ||
+            os.tmpdir();
+        const cacheFolder = platformIsDarwin
+            ? "Library/Caches"
+            : ".cache"
+        return combinePaths(normalizeSlashes(homePath), cacheFolder);
     }
 
     interface NodeChildProcess {

src/server/session.ts

@@ -709,7 +709,7 @@ namespace ts.server {
                 const displayString = ts.displayPartsToString(nameInfo.displayParts);
                 const nameSpan = nameInfo.textSpan;
                 const nameColStart = scriptInfo.positionToLineOffset(nameSpan.start).offset;
-                const nameText = scriptInfo.snap().getText(nameSpan.start, ts.textSpanEnd(nameSpan));
+                const nameText = scriptInfo.getSnapshot().getText(nameSpan.start, ts.textSpanEnd(nameSpan));
                 const refs = combineProjectOutput<protocol.ReferencesResponseItem>(
                     projects,
                     (project: Project) => {
@@ -722,7 +722,7 @@ namespace ts.server {
                             const refScriptInfo = project.getScriptInfo(ref.fileName);
                             const start = refScriptInfo.positionToLineOffset(ref.textSpan.start);
                             const refLineSpan = refScriptInfo.lineToTextSpan(start.line - 1);
-                            const lineText = refScriptInfo.snap().getText(refLineSpan.start, ts.textSpanEnd(refLineSpan)).replace(/\r|\n/g, "");
+                            const lineText = refScriptInfo.getSnapshot().getText(refLineSpan.start, ts.textSpanEnd(refLineSpan)).replace(/\r|\n/g, "");
                             return {
                                 file: ref.fileName,
                                 start: start,
@@ -1026,6 +1026,9 @@ namespace ts.server {
             if (!project) {
                 Errors.ThrowNoProject();
             }
+            if (!project.languageServiceEnabled) {
+                return false;
+            }
             const scriptInfo = project.getScriptInfo(file);
             return project.builder.emitFile(scriptInfo, (path, data, writeByteOrderMark) => this.host.writeFile(path, data, writeByteOrderMark));
         }
@@ -1326,7 +1329,7 @@ namespace ts.server {
                     highPriorityFiles.push(fileNameInProject);
                 else {
                     const info = this.projectService.getScriptInfo(fileNameInProject);
-                    if (!info.isOpen) {
+                    if (!info.isScriptOpen()) {
                         if (fileNameInProject.indexOf(".d.ts") > 0)
                             veryLowPriorityFiles.push(fileNameInProject);
                         else
@@ -1365,14 +1368,12 @@ namespace ts.server {
 
         private handlers = createMap<(request: protocol.Request) => { response?: any, responseRequired?: boolean }>({
             [CommandNames.OpenExternalProject]: (request: protocol.OpenExternalProjectRequest) => {
-                this.projectService.openExternalProject(request.arguments);
+                this.projectService.openExternalProject(request.arguments, /*suppressRefreshOfInferredProjects*/ false);
                 // TODO: report errors
                 return this.requiredResponse(true);
             },
             [CommandNames.OpenExternalProjects]: (request: protocol.OpenExternalProjectsRequest) => {
-                for (const proj of request.arguments.projects) {
-                    this.projectService.openExternalProject(proj);
-                }
+                this.projectService.openExternalProjects(request.arguments.projects);
                 // TODO: report errors
                 return this.requiredResponse(true);
             },

src/server/utilities.ts

@@ -1,4 +1,4 @@
-/// <reference path="types.d.ts" />
+/// <reference path="types.d.ts" />
 /// <reference path="shared.ts" />
 
 namespace ts.server {

src/services/jsDoc.ts

@@ -1,4 +1,4 @@
-/* @internal */
+/* @internal */
 namespace ts.JsDoc {
     const jsDocTagNames = [
         "augments",
@@ -23,6 +23,7 @@ namespace ts.JsDoc {
         "lends",
         "link",
         "memberOf",
+        "method",
         "name",
         "namespace",
         "param",
@@ -166,6 +167,7 @@ namespace ts.JsDoc {
         const lineStart = sourceFile.getLineStarts()[posLineAndChar.line];
 
         const indentationStr = sourceFile.text.substr(lineStart, posLineAndChar.character);
+        const isJavaScriptFile = hasJavaScriptFileExtension(sourceFile.fileName);
 
         let docParams = "";
         for (let i = 0, numParams = parameters.length; i < numParams; i++) {
@@ -173,8 +175,12 @@ namespace ts.JsDoc {
             const paramName = currentName.kind === SyntaxKind.Identifier ?
                 (<Identifier>currentName).text :
                 "param" + i;
-
-            docParams += `${indentationStr} * @param ${paramName}${newLine}`;
+            if (isJavaScriptFile) {
+                docParams += `${indentationStr} * @param {any} ${paramName}${newLine}`;
+            }
+            else {
+                docParams += `${indentationStr} * @param ${paramName}${newLine}`;
+            }
         }
 
         // A doc comment consists of the following

src/services/services.ts

@@ -1725,7 +1725,7 @@ namespace ts {
             const sourceFile = syntaxTreeCache.getCurrentSourceFile(fileName);
 
             // Check if in a context where we don't want to perform any insertion
-            if (isInString(sourceFile, position) || isInComment(sourceFile, position)) {
+            if (isInString(sourceFile, position)) {
                 return false;
             }
 

src/services/types.ts

@@ -91,7 +91,9 @@ namespace ts {
             }
 
             public getText(start: number, end: number): string {
-                return this.text.substring(start, end);
+                return start === 0 && end === this.text.length
+                    ? this.text
+                    : this.text.substring(start, end);
             }
 
             public getLength(): number {

src/services/utilities.ts

@@ -1137,6 +1137,7 @@ namespace ts {
             writeSpace: text => writeKind(text, SymbolDisplayPartKind.space),
             writeStringLiteral: text => writeKind(text, SymbolDisplayPartKind.stringLiteral),
             writeParameter: text => writeKind(text, SymbolDisplayPartKind.parameterName),
+            writeProperty: text => writeKind(text, SymbolDisplayPartKind.propertyName),
             writeSymbol,
             writeLine,
             increaseIndent: () => { indent++; },