Be more lenient with computed property names.

src/services/syntax/parser.ts

@@ -3753,9 +3753,11 @@ module TypeScript.Parser {
             // ComputedPropertyName[Yield] :
             //      [AssignmentExpression[In, ?Yield]]
 
+            // Note: we allow any expression inside the computed property name.  We'll report any 
+            // issues later in the grammar checker if an invalid expression is provided.
             return new ComputedPropertyNameSyntax(contextFlags,
                 eatToken(SyntaxKind.OpenBracketToken),
-                allowInAnd(parseAssignmentExpressionOrHigher),
+                allowInAnd(parseExpression),
                 eatToken(SyntaxKind.CloseBracketToken));
         }
 

src/services/syntax/syntaxTree.ts

@@ -1040,6 +1040,15 @@ module TypeScript {
             super.visitBreakStatement(node);
         }
 
+        public visitComputedPropertyName(node: ComputedPropertyNameSyntax): void {
+            if (node.expression.kind === SyntaxKind.BinaryExpression && (<BinaryExpressionSyntax>node.expression).operatorToken.kind === SyntaxKind.CommaToken) {
+                this.pushDiagnostic((<BinaryExpressionSyntax>node.expression).operatorToken, DiagnosticCode.comma_expression_cannot_appear_in_a_computed_property_name);
+                return;
+            }
+
+            super.visitComputedPropertyName(node);
+        }
+
         public visitContinueStatement(node: ContinueStatementSyntax): void {
             if (this.checkForStatementInAmbientContxt(node) ||
                 this.checkContinueStatementTarget(node)) {