Add support for 'new.target' meta-property

src/compiler/binder.ts

@@ -3133,6 +3133,7 @@ namespace ts {
             case SyntaxKind.TaggedTemplateExpression:
             case SyntaxKind.ShorthandPropertyAssignment:
             case SyntaxKind.StaticKeyword:
+            case SyntaxKind.MetaProperty:
                 // These nodes are ES6 syntax.
                 transformFlags |= TransformFlags.AssertES2015;
                 break;

src/compiler/checker.ts

@@ -241,6 +241,7 @@ namespace ts {
         const visitedFlowNodes: FlowNode[] = [];
         const visitedFlowTypes: FlowType[] = [];
         const potentialThisCollisions: Node[] = [];
+        const potentialNewTargetCollisions: Node[] = [];
         const awaitedTypeStack: number[] = [];
 
         const diagnostics = createDiagnosticCollection();
@@ -10196,6 +10197,7 @@ namespace ts {
 
             checkCollisionWithCapturedSuperVariable(node, node);
             checkCollisionWithCapturedThisVariable(node, node);
+            checkCollisionWithCapturedNewTargetVariable(node, node);
             checkNestedBlockScopedBinding(node, symbol);
 
             const type = getTypeOfSymbol(localOrExportSymbol);
@@ -13720,6 +13722,24 @@ namespace ts {
             return getNonNullableType(checkExpression(node.expression));
         }
 
+        function checkMetaProperty(node: MetaProperty) {
+            checkGrammarMetaProperty(node);
+            Debug.assert(node.keywordToken === SyntaxKind.NewKeyword && node.name.text === "target", "Unrecognized meta-property.");
+            const container = getNewTargetContainer(node);
+            if (!container) {
+                error(node, Diagnostics.Meta_property_0_is_only_allowed_in_the_body_of_a_function_declaration_function_expression_or_constructor, "new.target");
+                return unknownType;
+            }
+            else if (container.kind === SyntaxKind.Constructor) {
+                const symbol = getSymbolOfNode(container.parent);
+                return getTypeOfSymbol(symbol);
+            }
+            else {
+                const symbol = getSymbolOfNode(container);
+                return getTypeOfSymbol(symbol);
+            }
+        }
+
         function getTypeOfParameter(symbol: Symbol) {
             const type = getTypeOfSymbol(symbol);
             if (strictNullChecks) {
@@ -14128,6 +14148,7 @@ namespace ts {
             if (produceDiagnostics && node.kind !== SyntaxKind.MethodDeclaration) {
                 checkCollisionWithCapturedSuperVariable(node, (<FunctionExpression>node).name);
                 checkCollisionWithCapturedThisVariable(node, (<FunctionExpression>node).name);
+                checkCollisionWithCapturedNewTargetVariable(node, (<FunctionExpression>node).name);
             }
 
             return type;
@@ -15152,6 +15173,8 @@ namespace ts {
                     return checkAssertion(<AssertionExpression>node);
                 case SyntaxKind.NonNullExpression:
                     return checkNonNullAssertion(<NonNullExpression>node);
+                case SyntaxKind.MetaProperty:
+                    return checkMetaProperty(<MetaProperty>node);
                 case SyntaxKind.DeleteExpression:
                     return checkDeleteExpression(<DeleteExpression>node);
                 case SyntaxKind.VoidExpression:
@@ -16552,6 +16575,7 @@ namespace ts {
 
                 checkCollisionWithCapturedSuperVariable(node, node.name);
                 checkCollisionWithCapturedThisVariable(node, node.name);
+                checkCollisionWithCapturedNewTargetVariable(node, node.name);
                 checkCollisionWithRequireExportsInGeneratedCode(node, node.name);
                 checkCollisionWithGlobalPromiseInGeneratedCode(node, node.name);
             }
@@ -16835,6 +16859,12 @@ namespace ts {
             }
         }
 
+        function checkCollisionWithCapturedNewTargetVariable(node: Node, name: Identifier): void {
+            if (needCollisionCheckForIdentifier(node, name, "_newTarget")) {
+                potentialNewTargetCollisions.push(node);
+            }
+        }
+
         // this function will run after checking the source file so 'CaptureThis' is correct for all nodes
         function checkIfThisIsCapturedInEnclosingScope(node: Node): void {
             let current = node;
@@ -16853,6 +16883,23 @@ namespace ts {
             }
         }
 
+        function checkIfNewTargetIsCapturedInEnclosingScope(node: Node): void {
+            let current = node;
+            while (current) {
+                if (getNodeCheckFlags(current) & NodeCheckFlags.CaptureNewTarget) {
+                    const isDeclaration = node.kind !== SyntaxKind.Identifier;
+                    if (isDeclaration) {
+                        error((<Declaration>node).name, Diagnostics.Duplicate_identifier_newTarget_Compiler_uses_variable_declaration_newTarget_to_capture_new_target_meta_property_reference);
+                    }
+                    else {
+                        error(node, Diagnostics.Expression_resolves_to_variable_declaration_newTarget_that_compiler_uses_to_capture_new_target_meta_property_reference);
+                    }
+                    return;
+                }
+                current = current.parent;
+            }
+        }
+
         function checkCollisionWithCapturedSuperVariable(node: Node, name: Identifier) {
             if (!needCollisionCheckForIdentifier(node, name, "_super")) {
                 return;
@@ -17148,6 +17195,7 @@ namespace ts {
                 }
                 checkCollisionWithCapturedSuperVariable(node, <Identifier>node.name);
                 checkCollisionWithCapturedThisVariable(node, <Identifier>node.name);
+                checkCollisionWithCapturedNewTargetVariable(node, <Identifier>node.name);
                 checkCollisionWithRequireExportsInGeneratedCode(node, <Identifier>node.name);
                 checkCollisionWithGlobalPromiseInGeneratedCode(node, <Identifier>node.name);
             }
@@ -17984,6 +18032,7 @@ namespace ts {
             if (node.name) {
                 checkTypeNameIsReserved(node.name, Diagnostics.Class_name_cannot_be_0);
                 checkCollisionWithCapturedThisVariable(node, node.name);
+                checkCollisionWithCapturedNewTargetVariable(node, node.name);
                 checkCollisionWithRequireExportsInGeneratedCode(node, node.name);
                 checkCollisionWithGlobalPromiseInGeneratedCode(node, node.name);
             }
@@ -18518,6 +18567,7 @@ namespace ts {
 
             checkTypeNameIsReserved(node.name, Diagnostics.Enum_name_cannot_be_0);
             checkCollisionWithCapturedThisVariable(node, node.name);
+            checkCollisionWithCapturedNewTargetVariable(node, node.name);
             checkCollisionWithRequireExportsInGeneratedCode(node, node.name);
             checkCollisionWithGlobalPromiseInGeneratedCode(node, node.name);
             checkExportsOnMergedDeclarations(node);
@@ -19223,6 +19273,7 @@ namespace ts {
                 checkGrammarSourceFile(node);
 
                 potentialThisCollisions.length = 0;
+                potentialNewTargetCollisions.length = 0;
 
                 deferredNodes = [];
                 deferredUnusedIdentifierNodes = produceDiagnostics && noUnusedIdentifiers ? [] : undefined;
@@ -19251,6 +19302,11 @@ namespace ts {
                     potentialThisCollisions.length = 0;
                 }
 
+                if (potentialNewTargetCollisions.length) {
+                    forEach(potentialNewTargetCollisions, checkIfNewTargetIsCapturedInEnclosingScope)
+                    potentialNewTargetCollisions.length = 0;
+                }
+
                 links.flags |= NodeCheckFlags.TypeChecked;
             }
         }
@@ -21581,6 +21637,14 @@ namespace ts {
             }
         }
 
+        function checkGrammarMetaProperty(node: MetaProperty) {
+            if (node.keywordToken === SyntaxKind.NewKeyword) {
+                if (node.name.text !== "target") {
+                    return grammarErrorOnNode(node.name, Diagnostics._0_is_not_a_valid_meta_property_for_keyword_1_Did_you_mean_0, node.name.text, tokenToString(node.keywordToken), "target");
+                }
+            }
+        }
+
         function hasParseDiagnostics(sourceFile: SourceFile): boolean {
             return sourceFile.parseDiagnostics.length > 0;
         }

src/compiler/core.ts

@@ -568,6 +568,8 @@ namespace ts {
      * is created if `value` was appended.
      * @param value The value to append to the array. If `value` is `undefined`, nothing is
      * appended.
+     * @param copyOnWrite Indicates whether to return a fresh array rather than modify the
+     * existing array.
      */
     export function append<T>(to: T[] | undefined, value: T | undefined): T[] | undefined {
         if (value === undefined) return to;

src/compiler/diagnosticMessages.json

@@ -1771,6 +1771,14 @@
         "category": "Error",
         "code": 2542
     },
+    "Duplicate identifier '_newTarget'. Compiler uses variable declaration '_newTarget' to capture 'new.target' meta-property reference.": {
+        "category": "Error",
+        "code": 2543
+    },
+    "Expression resolves to variable declaration '_newTarget' that compiler uses to capture 'new.target' meta-property reference.": {
+        "category": "Error",
+        "code": 2544
+    },
     "JSX element attributes type '{0}' may not be a union type.": {
         "category": "Error",
         "code": 2600
@@ -3169,6 +3177,14 @@
         "category": "Error",
         "code": 17011
     },
+    "'{0}' is not a valid meta-property for keyword '{1}'. Did you mean '{0}'?": {
+        "category": "Error",
+        "code": 17012
+    },
+    "Meta-property '{0}' is only allowed in the body of a function declaration, function expression, or constructor.": {
+        "category": "Error",
+        "code": 17013
+    },
 
     "Circularity detected while resolving configuration: {0}": {
         "category": "Error",

src/compiler/emitter.ts

@@ -660,6 +660,8 @@ namespace ts {
                     return emitAsExpression(<AsExpression>node);
                 case SyntaxKind.NonNullExpression:
                     return emitNonNullExpression(<NonNullExpression>node);
+                case SyntaxKind.MetaProperty:
+                    return emitMetaProperty(<MetaProperty>node);
 
                 // JSX
                 case SyntaxKind.JsxElement:
@@ -1249,6 +1251,12 @@ namespace ts {
             write("!");
         }
 
+        function emitMetaProperty(node: MetaProperty) {
+            writeToken(node.keywordToken, node.pos);
+            write(".");
+            emit(node.name);
+        }
+
         //
         // Misc
         //
@@ -2571,6 +2579,13 @@ namespace ts {
             return makeUniqueName("class");
         }
 
+        function generateNameForMethodOrAccessor(node: MethodDeclaration | AccessorDeclaration) {
+            if (isIdentifier(node.name)) {
+                return generateNameForNodeCached(node.name);
+            }
+            return makeTempVariableName(TempFlags.Auto);
+        }
+
         /**
          * Generates a unique name from a node.
          *
@@ -2592,6 +2607,10 @@ namespace ts {
                     return generateNameForExportDefault();
                 case SyntaxKind.ClassExpression:
                     return generateNameForClassExpression();
+                case SyntaxKind.MethodDeclaration:
+                case SyntaxKind.GetAccessor:
+                case SyntaxKind.SetAccessor:
+                    return generateNameForMethodOrAccessor(<MethodDeclaration | AccessorDeclaration>node);
                 default:
                     return makeTempVariableName(TempFlags.Auto);
             }
@@ -2642,6 +2661,11 @@ namespace ts {
             return node;
         }
 
+        function generateNameForNodeCached(node: Node) {
+            const nodeId = getNodeId(node);
+            return nodeIdToGeneratedName[nodeId] || (nodeIdToGeneratedName[nodeId] = unescapeIdentifier(generateNameForNode(node)));
+        }
+
         /**
          * Gets the generated identifier text from a generated identifier.
          *
@@ -2652,8 +2676,7 @@ namespace ts {
                 // Generated names generate unique names based on their original node
                 // and are cached based on that node's id
                 const node = getNodeForGeneratedName(name);
-                const nodeId = getNodeId(node);
-                return nodeIdToGeneratedName[nodeId] || (nodeIdToGeneratedName[nodeId] = unescapeIdentifier(generateNameForNode(node)));
+                return generateNameForNodeCached(node);
             }
             else {
                 // Auto, Loop, and Unique names are cached based on their unique

src/compiler/parser.ts

@@ -198,6 +198,8 @@ namespace ts {
                     visitNode(cbNode, (<AsExpression>node).type);
             case SyntaxKind.NonNullExpression:
                 return visitNode(cbNode, (<NonNullExpression>node).expression);
+            case SyntaxKind.MetaProperty:
+                return visitNode(cbNode, (<MetaProperty>node).name);
             case SyntaxKind.ConditionalExpression:
                 return visitNode(cbNode, (<ConditionalExpression>node).condition) ||
                     visitNode(cbNode, (<ConditionalExpression>node).questionToken) ||
@@ -4329,15 +4331,22 @@ namespace ts {
             return isIdentifier() ? parseIdentifier() : undefined;
         }
 
-        function parseNewExpression(): NewExpression {
-            const node = <NewExpression>createNode(SyntaxKind.NewExpression);
+        function parseNewExpression(): NewExpression | MetaProperty {
+            const fullStart = scanner.getStartPos();
             parseExpected(SyntaxKind.NewKeyword);
+            if (parseOptional(SyntaxKind.DotToken)) {
+                const node = <MetaProperty>createNode(SyntaxKind.MetaProperty, fullStart);
+                node.keywordToken = SyntaxKind.NewKeyword;
+                node.name = parseIdentifierName();
+                return finishNode(node);
+            }
+
+            const node = <NewExpression>createNode(SyntaxKind.NewExpression, fullStart);
             node.expression = parseMemberExpressionOrHigher();
             node.typeArguments = tryParse(parseTypeArgumentsInExpression);
             if (node.typeArguments || token() === SyntaxKind.OpenParenToken) {
                 node.arguments = parseArgumentList();
             }
-
             return finishNode(node);
         }