Merge branch 'master' into implicitlyExcludeNodeModules

Author: rbuckton

src/compiler/checker.ts

@@ -5788,8 +5788,7 @@ namespace ts {
         }
 
         function isGenericMappedType(type: Type) {
-            return getObjectFlags(type) & ObjectFlags.Mapped &&
-                maybeTypeOfKind(getConstraintTypeFromMappedType(<MappedType>type), TypeFlags.TypeVariable | TypeFlags.Index);
+            return getObjectFlags(type) & ObjectFlags.Mapped && isGenericIndexType(getConstraintTypeFromMappedType(<MappedType>type));
         }
 
         function resolveStructuredTypeMembers(type: StructuredType): ResolvedType {
@@ -5901,6 +5900,10 @@ namespace ts {
         }
 
         function getConstraintOfIndexedAccess(type: IndexedAccessType) {
+            const transformed = getTransformedIndexedAccessType(type);
+            if (transformed) {
+                return transformed;
+            }
             const baseObjectType = getBaseConstraintOfType(type.objectType);
             const baseIndexType = getBaseConstraintOfType(type.indexType);
             return baseObjectType || baseIndexType ? getIndexedAccessType(baseObjectType || type.objectType, baseIndexType || type.indexType) : undefined;
@@ -5972,11 +5975,18 @@ namespace ts {
                     return stringType;
                 }
                 if (t.flags & TypeFlags.IndexedAccess) {
+                    const transformed = getTransformedIndexedAccessType(<IndexedAccessType>t);
+                    if (transformed) {
+                        return getBaseConstraint(transformed);
+                    }
                     const baseObjectType = getBaseConstraint((<IndexedAccessType>t).objectType);
                     const baseIndexType = getBaseConstraint((<IndexedAccessType>t).indexType);
                     const baseIndexedAccess = baseObjectType && baseIndexType ? getIndexedAccessType(baseObjectType, baseIndexType) : undefined;
                     return baseIndexedAccess && baseIndexedAccess !== unknownType ? getBaseConstraint(baseIndexedAccess) : undefined;
                 }
+                if (isGenericMappedType(t)) {
+                    return emptyObjectType;
+                }
                 return t;
             }
         }
@@ -7604,26 +7614,73 @@ namespace ts {
             return instantiateType(getTemplateTypeFromMappedType(type), templateMapper);
         }
 
-        function getIndexedAccessType(objectType: Type, indexType: Type, accessNode?: ElementAccessExpression | IndexedAccessTypeNode) {
-            // If the index type is generic, if the object type is generic and doesn't originate in an expression,
-            // or if the object type is a mapped type with a generic constraint, we are performing a higher-order
-            // index access where we cannot meaningfully access the properties of the object type. Note that for a
-            // generic T and a non-generic K, we eagerly resolve T[K] if it originates in an expression. This is to
-            // preserve backwards compatibility. For example, an element access 'this["foo"]' has always been resolved
-            // eagerly using the constraint type of 'this' at the given location.
-            if (maybeTypeOfKind(indexType, TypeFlags.TypeVariable | TypeFlags.Index) ||
-                maybeTypeOfKind(objectType, TypeFlags.TypeVariable) && !(accessNode && accessNode.kind === SyntaxKind.ElementAccessExpression) ||
-                isGenericMappedType(objectType)) {
+        function isGenericObjectType(type: Type): boolean {
+            return type.flags & TypeFlags.TypeVariable ? true :
+                getObjectFlags(type) & ObjectFlags.Mapped ? isGenericIndexType(getConstraintTypeFromMappedType(<MappedType>type)) :
+                type.flags & TypeFlags.UnionOrIntersection ? forEach((<UnionOrIntersectionType>type).types, isGenericObjectType) :
+                false;
+        }
+
+        function isGenericIndexType(type: Type): boolean {
+            return type.flags & (TypeFlags.TypeVariable | TypeFlags.Index) ? true :
+                type.flags & TypeFlags.UnionOrIntersection ? forEach((<UnionOrIntersectionType>type).types, isGenericIndexType) :
+                false;
+        }
+
+        // Return true if the given type is a non-generic object type with a string index signature and no
+        // other members.
+        function isStringIndexOnlyType(type: Type) {
+            if (type.flags & TypeFlags.Object && !isGenericMappedType(type)) {
+                const t = resolveStructuredTypeMembers(<ObjectType>type);
+                return t.properties.length === 0 &&
+                    t.callSignatures.length === 0 && t.constructSignatures.length === 0 &&
+                    t.stringIndexInfo && !t.numberIndexInfo;
+            }
+            return false;
+        }
+
+        // Given an indexed access type T[K], if T is an intersection containing one or more generic types and one or
+        // more object types with only a string index signature, e.g. '(U & V & { [x: string]: D })[K]', return a
+        // transformed type of the form '(U & V)[K] | D'. This allows us to properly reason about higher order indexed
+        // access types with default property values as expressed by D.
+        function getTransformedIndexedAccessType(type: IndexedAccessType): Type {
+            const objectType = type.objectType;
+            if (objectType.flags & TypeFlags.Intersection && isGenericObjectType(objectType) && some((<IntersectionType>objectType).types, isStringIndexOnlyType)) {
+                const regularTypes: Type[] = [];
+                const stringIndexTypes: Type[] = [];
+                for (const t of (<IntersectionType>objectType).types) {
+                    if (isStringIndexOnlyType(t)) {
+                        stringIndexTypes.push(getIndexTypeOfType(t, IndexKind.String));
+                    }
+                    else {
+                        regularTypes.push(t);
+                    }
+                }
+                return getUnionType([
+                    getIndexedAccessType(getIntersectionType(regularTypes), type.indexType),
+                    getIntersectionType(stringIndexTypes)
+                ]);
+            }
+            return undefined;
+        }
+
+        function getIndexedAccessType(objectType: Type, indexType: Type, accessNode?: ElementAccessExpression | IndexedAccessTypeNode): Type {
+            // If the object type is a mapped type { [P in K]: E }, where K is generic, we instantiate E using a mapper
+            // that substitutes the index type for P. For example, for an index access { [P in K]: Box<T[P]> }[X], we
+            // construct the type Box<T[X]>.
+            if (isGenericMappedType(objectType)) {
+                return getIndexedAccessForMappedType(<MappedType>objectType, indexType, accessNode);
+            }
+            // Otherwise, if the index type is generic, or if the object type is generic and doesn't originate in an
+            // expression, we are performing a higher-order index access where we cannot meaningfully access the properties
+            // of the object type. Note that for a generic T and a non-generic K, we eagerly resolve T[K] if it originates
+            // in an expression. This is to preserve backwards compatibility. For example, an element access 'this["foo"]'
+            // has always been resolved eagerly using the constraint type of 'this' at the given location.
+            if (isGenericIndexType(indexType) || !(accessNode && accessNode.kind === SyntaxKind.ElementAccessExpression) && isGenericObjectType(objectType)) {
                 if (objectType.flags & TypeFlags.Any) {
                     return objectType;
                 }
-                // If the object type is a mapped type { [P in K]: E }, we instantiate E using a mapper that substitutes
-                // the index type for P. For example, for an index access { [P in K]: Box<T[P]> }[X], we construct the
-                // type Box<T[X]>.
-                if (isGenericMappedType(objectType)) {
-                    return getIndexedAccessForMappedType(<MappedType>objectType, indexType, accessNode);
-                }
-                // Otherwise we defer the operation by creating an indexed access type.
+                // Defer the operation by creating an indexed access type.
                 const id = objectType.id + "," + indexType.id;
                 let type = indexedAccessTypes.get(id);
                 if (!type) {
@@ -8017,7 +8074,7 @@ namespace ts {
 
         function cloneTypeMapper(mapper: TypeMapper): TypeMapper {
             return mapper && isInferenceContext(mapper) ?
-                createInferenceContext(mapper.signature, mapper.flags | InferenceFlags.NoDefault, mapper.inferences) :
+                createInferenceContext(mapper.signature, mapper.flags | InferenceFlags.NoDefault, mapper.compareTypes, mapper.inferences) :
                 mapper;
         }
 
@@ -8458,7 +8515,7 @@ namespace ts {
             ignoreReturnTypes: boolean,
             reportErrors: boolean,
             errorReporter: ErrorReporter,
-            compareTypes: (s: Type, t: Type, reportErrors?: boolean) => Ternary): Ternary {
+            compareTypes: TypeComparer): Ternary {
             // TODO (drosen): De-duplicate code between related functions.
             if (source === target) {
                 return Ternary.True;
@@ -8468,7 +8525,7 @@ namespace ts {
             }
 
             if (source.typeParameters) {
-                source = instantiateSignatureInContextOf(source, target);
+                source = instantiateSignatureInContextOf(source, target, /*contextualMapper*/ undefined, compareTypes);
             }
 
             let result = Ternary.True;
@@ -9614,6 +9671,11 @@ namespace ts {
                 if (sourceInfo) {
                     return indexInfoRelatedTo(sourceInfo, targetInfo, reportErrors);
                 }
+                if (isGenericMappedType(source)) {
+                    // A generic mapped type { [P in K]: T } is related to an index signature { [x: string]: U }
+                    // if T is related to U.
+                    return kind === IndexKind.String && isRelatedTo(getTemplateTypeFromMappedType(<MappedType>source), targetInfo.type, reportErrors);
+                }
                 if (isObjectLiteralType(source)) {
                     let related = Ternary.True;
                     if (kind === IndexKind.String) {
@@ -10216,13 +10278,14 @@ namespace ts {
             }
         }
 
-        function createInferenceContext(signature: Signature, flags: InferenceFlags, baseInferences?: InferenceInfo[]): InferenceContext {
+        function createInferenceContext(signature: Signature, flags: InferenceFlags, compareTypes?: TypeComparer, baseInferences?: InferenceInfo[]): InferenceContext {
             const inferences = baseInferences ? map(baseInferences, cloneInferenceInfo) : map(signature.typeParameters, createInferenceInfo);
             const context = mapper as InferenceContext;
             context.mappedTypes = signature.typeParameters;
             context.signature = signature;
             context.inferences = inferences;
             context.flags = flags;
+            context.compareTypes = compareTypes || compareTypesAssignable;
             return context;
 
             function mapper(t: Type): Type {
@@ -10325,6 +10388,19 @@ namespace ts {
             }
         }
 
+        function isPossiblyAssignableTo(source: Type, target: Type) {
+            const properties = getPropertiesOfObjectType(target);
+            for (const targetProp of properties) {
+                if (!(targetProp.flags & (SymbolFlags.Optional | SymbolFlags.Prototype))) {
+                    const sourceProp = getPropertyOfObjectType(source, targetProp.escapedName);
+                    if (!sourceProp) {
+                        return false;
+                    }
+                }
+            }
+            return true;
+        }
+
         function inferTypes(inferences: InferenceInfo[], originalSource: Type, originalTarget: Type, priority: InferencePriority = 0) {
             let symbolStack: Symbol[];
             let visited: Map<boolean>;
@@ -10518,10 +10594,14 @@ namespace ts {
                         return;
                     }
                 }
-                inferFromProperties(source, target);
-                inferFromSignatures(source, target, SignatureKind.Call);
-                inferFromSignatures(source, target, SignatureKind.Construct);
-                inferFromIndexTypes(source, target);
+                // Infer from the members of source and target only if the two types are possibly related. We check
+                // in both directions because we may be inferring for a co-variant or a contra-variant position.
+                if (isPossiblyAssignableTo(source, target) || isPossiblyAssignableTo(target, source)) {
+                    inferFromProperties(source, target);
+                    inferFromSignatures(source, target, SignatureKind.Call);
+                    inferFromSignatures(source, target, SignatureKind.Construct);
+                    inferFromIndexTypes(source, target);
+                }
             }
 
             function inferFromProperties(source: Type, target: Type) {
@@ -10653,7 +10733,7 @@ namespace ts {
                 const constraint = getConstraintOfTypeParameter(context.signature.typeParameters[index]);
                 if (constraint) {
                     const instantiatedConstraint = instantiateType(constraint, context);
-                    if (!isTypeAssignableTo(inferredType, getTypeWithThisArgument(instantiatedConstraint, inferredType))) {
+                    if (!context.compareTypes(inferredType, getTypeWithThisArgument(instantiatedConstraint, inferredType))) {
                         inference.inferredType = inferredType = instantiatedConstraint;
                     }
                 }
@@ -15054,8 +15134,8 @@ namespace ts {
         }
 
         // Instantiate a generic signature in the context of a non-generic signature (section 3.8.5 in TypeScript spec)
-        function instantiateSignatureInContextOf(signature: Signature, contextualSignature: Signature, contextualMapper?: TypeMapper): Signature {
-            const context = createInferenceContext(signature, InferenceFlags.InferUnionTypes);
+        function instantiateSignatureInContextOf(signature: Signature, contextualSignature: Signature, contextualMapper?: TypeMapper, compareTypes?: TypeComparer): Signature {
+            const context = createInferenceContext(signature, InferenceFlags.InferUnionTypes, compareTypes);
             forEachMatchingParameterType(contextualSignature, signature, (source, target) => {
                 // Type parameters from outer context referenced by source type are fixed by instantiation of the source type
                 inferTypes(context.inferences, instantiateType(source, contextualMapper || identityMapper), target);

src/compiler/core.ts

@@ -11,20 +11,6 @@ namespace ts {
 
 /* @internal */
 namespace ts {
-    /**
-     * Ternary values are defined such that
-     * x & y is False if either x or y is False.
-     * x & y is Maybe if either x or y is Maybe, but neither x or y is False.
-     * x & y is True if both x and y are True.
-     * x | y is False if both x and y are False.
-     * x | y is Maybe if either x or y is Maybe, but neither x or y is True.
-     * x | y is True if either x or y is True.
-     */
-    export const enum Ternary {
-        False = 0,
-        Maybe = 1,
-        True = -1
-    }
 
     // More efficient to create a collator once and use its `compare` than to call `a.localeCompare(b)` many times.
     export const collator: { compare(a: string, b: string): number } = typeof Intl === "object" && typeof Intl.Collator === "function" ? new Intl.Collator(/*locales*/ undefined, { usage: "sort", sensitivity: "accent" }) : undefined;

src/compiler/emitter.ts

@@ -1346,7 +1346,9 @@ namespace ts {
 
             emitExpression(node.left);
             increaseIndentIf(indentBeforeOperator, isCommaOperator ? " " : undefined);
+            emitLeadingCommentsOfPosition(node.operatorToken.pos);
             writeTokenNode(node.operatorToken);
+            emitTrailingCommentsOfPosition(node.operatorToken.end);
             increaseIndentIf(indentAfterOperator, " ");
             emitExpression(node.right);
             decreaseIndentIf(indentBeforeOperator, indentAfterOperator);

src/compiler/parser.ts

@@ -2061,7 +2061,7 @@ namespace ts {
             return <TemplateMiddle | TemplateTail>fragment;
         }
 
-        function parseLiteralLikeNode(kind: SyntaxKind): LiteralLikeNode {
+        function parseLiteralLikeNode(kind: SyntaxKind): LiteralExpression | LiteralLikeNode {
             const node = <LiteralExpression>createNode(kind);
             const text = scanner.getTokenValue();
             node.text = text;
@@ -2611,11 +2611,31 @@ namespace ts {
             return token() === SyntaxKind.DotToken ? undefined : node;
         }
 
-        function parseLiteralTypeNode(): LiteralTypeNode {
-            const node = <LiteralTypeNode>createNode(SyntaxKind.LiteralType);
-            node.literal = parseSimpleUnaryExpression();
-            finishNode(node);
-            return node;
+        function parseLiteralTypeNode(negative?: boolean): LiteralTypeNode {
+            const node = createNode(SyntaxKind.LiteralType) as LiteralTypeNode;
+            let unaryMinusExpression: PrefixUnaryExpression;
+            if (negative) {
+                unaryMinusExpression = createNode(SyntaxKind.PrefixUnaryExpression) as PrefixUnaryExpression;
+                unaryMinusExpression.operator = SyntaxKind.MinusToken;
+                nextToken();
+            }
+            let expression: UnaryExpression;
+            switch (token()) {
+                case SyntaxKind.StringLiteral:
+                case SyntaxKind.NumericLiteral:
+                    expression = parseLiteralLikeNode(token()) as LiteralExpression;
+                    break;
+                case SyntaxKind.TrueKeyword:
+                case SyntaxKind.FalseKeyword:
+                    expression = parseTokenNode();
+            }
+            if (negative) {
+                unaryMinusExpression.operand = expression;
+                finishNode(unaryMinusExpression);
+                expression = unaryMinusExpression;
+            }
+            node.literal = expression;
+            return finishNode(node);
         }
 
         function nextTokenIsNumericLiteral() {
@@ -2650,7 +2670,7 @@ namespace ts {
                 case SyntaxKind.FalseKeyword:
                     return parseLiteralTypeNode();
                 case SyntaxKind.MinusToken:
-                    return lookAhead(nextTokenIsNumericLiteral) ? parseLiteralTypeNode() : parseTypeReference();
+                    return lookAhead(nextTokenIsNumericLiteral) ? parseLiteralTypeNode(/*negative*/ true) : parseTypeReference();
                 case SyntaxKind.VoidKeyword:
                 case SyntaxKind.NullKeyword:
                     return parseTokenNode<TypeNode>();