Add named property symbol for known Symbol properties

Author: JsonFreeman

src/compiler/binder.ts

@@ -87,13 +87,18 @@ module ts {
             if (symbolKind & SymbolFlags.Value && !symbol.valueDeclaration) symbol.valueDeclaration = node;
         }
 
-        // Should not be called on a declaration with a computed property name.
+        // Should not be called on a declaration with a computed property name,
+        // unless it is a well known Symbol.
         function getDeclarationName(node: Declaration): string {
             if (node.name) {
                 if (node.kind === SyntaxKind.ModuleDeclaration && node.name.kind === SyntaxKind.StringLiteral) {
                     return '"' + (<LiteralExpression>node.name).text + '"';
                 }
-                Debug.assert(!hasDynamicName(node));
+                if (node.name.kind === SyntaxKind.ComputedPropertyName) {
+                    var nameExpression = (<ComputedPropertyName>node.name).expression;
+                    Debug.assert(isWellKnownSymbolSyntactically(nameExpression));
+                    return "__@" + (<PropertyAccessExpression>nameExpression).name.text;
+                }
                 return (<Identifier | LiteralExpression>node.name).text;
             }
             switch (node.kind) {

src/compiler/checker.ts

@@ -706,9 +706,15 @@ module ts {
             return type;
         }
 
-        // A reserved member name starts with two underscores followed by a non-underscore
+        // A reserved member name starts with two underscores, but the third character cannot be an underscore
+        // or the @ symbol. A third underscore indicates an escaped form of an identifer that started
+        // with at least two underscores. The @ character indicates that the name is denoted by a well known ES
+        // Symbol instance.
         function isReservedMemberName(name: string) {
-            return name.charCodeAt(0) === CharacterCodes._ && name.charCodeAt(1) === CharacterCodes._ && name.charCodeAt(2) !== CharacterCodes._;
+            return name.charCodeAt(0) === CharacterCodes._ &&
+                name.charCodeAt(1) === CharacterCodes._ &&
+                name.charCodeAt(2) !== CharacterCodes._ &&
+                name.charCodeAt(2) !== CharacterCodes.at;
         }
 
         function getNamedMembers(members: SymbolTable): Symbol[] {

src/compiler/utilities.ts

@@ -848,7 +848,7 @@ module ts {
             !isWellKnownSymbolSyntactically((<ComputedPropertyName>declaration.name).expression);
     }
 
-    export function isWellKnownSymbolSyntactically(node: Node): boolean {
+    export function isWellKnownSymbolSyntactically(node: Expression): boolean {
         return node.kind === SyntaxKind.PropertyAccessExpression && isESSymbolIdentifier((<PropertyAccessExpression>node).expression);
     }
 

tests/baselines/reference/parserSymbolProperty8.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolProperty8.ts ===
 var x: {
->x : {}
+>x : { [Symbol.toPrimitive](): string; }
 
     [Symbol.toPrimitive](): string
 >Symbol.toPrimitive : Symbol

tests/baselines/reference/parserSymbolProperty9.types

@@ -1,6 +1,6 @@
 === tests/cases/conformance/parser/ecmascript6/Symbols/parserSymbolProperty9.ts ===
 var x: {
->x : {}
+>x : { [Symbol.toPrimitive]: string; }
 
     [Symbol.toPrimitive]: string
 >Symbol.toPrimitive : Symbol