Consolidating strict mode reserved identifier checking in single method in binder

Author: ahejlsberg

src/compiler/binder.ts

@@ -560,6 +560,23 @@ namespace ts {
             bindBlockScopedDeclaration(node, SymbolFlags.BlockScopedVariable, SymbolFlags.BlockScopedVariableExcludes);
         }
 
+        // The binder visits every node in the syntax tree so it is a convenient place to perform a single localized
+        // check for reserved words used as identifiers in strict mode code.
+        function checkStrictModeIdentifier(node: Identifier) {
+            if (node.parserContextFlags & ParserContextFlags.StrictMode &&
+                node.originalKeywordKind >= SyntaxKind.FirstFutureReservedWord &&
+                node.originalKeywordKind <= SyntaxKind.LastFutureReservedWord &&
+                !isIdentifierName(node)) {
+                // Report error only if there are no parse errors in file
+                if (!file.parseDiagnostics.length) {
+                    let message = getAncestor(node, SyntaxKind.ClassDeclaration) || getAncestor(node, SyntaxKind.ClassExpression) ?
+                        Diagnostics.Identifier_expected_0_is_a_reserved_word_in_strict_mode_Class_definitions_are_automatically_in_strict_mode :
+                        Diagnostics.Identifier_expected_0_is_a_reserved_word_in_strict_mode;
+                    file.bindDiagnostics.push(createDiagnosticForNode(node, message, declarationNameToString(node)));
+                }
+            }
+        }
+
         function getDestructuringParameterName(node: Declaration) {
             return "__" + indexOf((<SignatureDeclaration>node.parent).parameters, node);
         }
@@ -588,6 +605,8 @@ namespace ts {
 
         function bindWorker(node: Node) {
             switch (node.kind) {
+                case SyntaxKind.Identifier:
+                    return checkStrictModeIdentifier(<Identifier>node);
                 case SyntaxKind.TypeParameter:
                     return declareSymbolAndAddToSymbolTable(<Declaration>node, SymbolFlags.TypeParameter, SymbolFlags.TypeParameterExcludes);
                 case SyntaxKind.Parameter: