Adds ES5 to ES3 transformer for reserved words

src/compiler/transformer.ts

@@ -4,6 +4,7 @@
 /// <reference path="transformers/es2017.ts" />
 /// <reference path="transformers/es2016.ts" />
 /// <reference path="transformers/es2015.ts" />
+/// <reference path="transformers/es5.ts" />
 /// <reference path="transformers/generators.ts" />
 /// <reference path="transformers/module/module.ts" />
 /// <reference path="transformers/module/system.ts" />
@@ -129,6 +130,10 @@ namespace ts {
             transformers.push(transformGenerators);
         }
 
+        if (languageVersion < ScriptTarget.ES5) {
+            transformers.push(transformES5);
+        }
+
         return transformers;
     }
 

src/compiler/transformers/es5.ts

@@ -0,0 +1,83 @@
+/// <reference path="../factory.ts" />
+/// <reference path="../visitor.ts" />
+
+/*@internal*/
+namespace ts {
+    /**
+     * Transforms ES5 syntax into ES3 syntax.
+     *
+     * @param context Context and state information for the transformation.
+     */
+    export function transformES5(context: TransformationContext) {
+        const previousOnSubstituteNode = context.onSubstituteNode;
+        context.onSubstituteNode = onSubstituteNode;
+        context.enableSubstitution(SyntaxKind.PropertyAccessExpression);
+        context.enableSubstitution(SyntaxKind.PropertyAssignment);
+        return transformSourceFile;
+
+        /**
+         * Transforms an ES5 source file to ES3.
+         *
+         * @param node A SourceFile
+         */
+        function transformSourceFile(node: SourceFile) {
+            return node;
+        }
+
+        /**
+         * Hooks node substitutions.
+         *
+         * @param emitContext The context for the emitter.
+         * @param node The node to substitute.
+         */
+        function onSubstituteNode(emitContext: EmitContext, node: Node) {
+            node = previousOnSubstituteNode(emitContext, node);
+            if (isPropertyAccessExpression(node)) {
+                return substitutePropertyAccessExpression(node);
+            }
+            else if (isPropertyAssignment(node)) {
+                return substitutePropertyAssignment(node);
+            }
+            return node;
+        }
+
+        /**
+         * Substitutes a PropertyAccessExpression whose name is a reserved word.
+         *
+         * @param node A PropertyAccessExpression
+         */
+        function substitutePropertyAccessExpression(node: PropertyAccessExpression): Expression {
+            const literalName = trySubstituteReservedName(node.name);
+            if (literalName) {
+                return createElementAccess(node.expression, literalName, /*location*/ node);
+            }
+            return node;
+        }
+
+        /**
+         * Substitutes a PropertyAssignment whose name is a reserved word.
+         *
+         * @param node A PropertyAssignment
+         */
+        function substitutePropertyAssignment(node: PropertyAssignment): PropertyAssignment {
+            const literalName = isIdentifier(node.name) && trySubstituteReservedName(node.name);
+            if (literalName) {
+                return updatePropertyAssignment(node, literalName, node.initializer);
+            }
+            return node;
+        }
+
+        /**
+         * If an identifier name is a reserved word, returns a string literal for the name.
+         *
+         * @param name An Identifier
+         */
+        function trySubstituteReservedName(name: Identifier) {
+            const token = name.originalKeywordKind || (nodeIsSynthesized(name) ? stringToToken(name.text) : undefined);
+            if (token >= SyntaxKind.FirstReservedWord && token <= SyntaxKind.LastReservedWord) {
+                return createLiteral(name, /*location*/ name);
+            }
+            return undefined;
+        }
+    }
+}

src/compiler/transformers/module/module.ts

@@ -958,39 +958,19 @@ namespace ts {
                 const declaration = resolver.getReferencedImportDeclaration(node);
                 if (declaration) {
                     if (isImportClause(declaration)) {
-                        if (languageVersion >= ScriptTarget.ES5) {
-                            return createPropertyAccess(
-                                getGeneratedNameForNode(declaration.parent),
-                                createIdentifier("default"),
-                                /*location*/ node
-                            );
-                        }
-                        else {
-                            // TODO: ES3 transform to handle x.default -> x["default"]
-                            return createElementAccess(
-                                getGeneratedNameForNode(declaration.parent),
-                                createLiteral("default"),
-                                /*location*/ node
-                            );
-                        }
+                        return createPropertyAccess(
+                            getGeneratedNameForNode(declaration.parent),
+                            createIdentifier("default"),
+                            /*location*/ node
+                        );
                     }
                     else if (isImportSpecifier(declaration)) {
                         const name = declaration.propertyName || declaration.name;
-                        if (name.originalKeywordKind === SyntaxKind.DefaultKeyword && languageVersion <= ScriptTarget.ES3) {
-                            // TODO: ES3 transform to handle x.default -> x["default"]
-                            return createElementAccess(
-                                getGeneratedNameForNode(declaration.parent.parent.parent),
-                                createLiteral(name.text),
-                                /*location*/ node
-                            );
-                        }
-                        else {
-                            return createPropertyAccess(
-                                getGeneratedNameForNode(declaration.parent.parent.parent),
-                                getSynthesizedClone(name),
-                                /*location*/ node
-                            );
-                        }
+                        return createPropertyAccess(
+                            getGeneratedNameForNode(declaration.parent.parent.parent),
+                            getSynthesizedClone(name),
+                            /*location*/ node
+                        );
                     }
                 }
             }
@@ -1027,15 +1007,10 @@ namespace ts {
 
         function createExportAssignment(name: Identifier, value: Expression) {
             return createAssignment(
-                name.originalKeywordKind === SyntaxKind.DefaultKeyword && languageVersion === ScriptTarget.ES3
-                    ? createElementAccess(
-                        createIdentifier("exports"),
-                        createLiteral(name.text)
-                    )
-                    : createPropertyAccess(
-                        createIdentifier("exports"),
-                        getSynthesizedClone(name)
-                    ),
+                createPropertyAccess(
+                    createIdentifier("exports"),
+                    getSynthesizedClone(name)
+                ),
                 value
             );
         }

src/compiler/transformers/module/system.ts

@@ -19,7 +19,6 @@ namespace ts {
         const compilerOptions = context.getCompilerOptions();
         const resolver = context.getEmitResolver();
         const host = context.getEmitHost();
-        const languageVersion = getEmitScriptTarget(compilerOptions);
         const previousOnSubstituteNode = context.onSubstituteNode;
         const previousOnEmitNode = context.onEmitNode;
         context.onSubstituteNode = onSubstituteNode;
@@ -1317,12 +1316,7 @@ namespace ts {
                 return undefined;
             }
 
-            if (name.originalKeywordKind && languageVersion === ScriptTarget.ES3) {
-                return createElementAccess(importAlias, createLiteral(name.text));
-            }
-            else {
-                return createPropertyAccess(importAlias, getSynthesizedClone(name));
-            }
+            return createPropertyAccess(importAlias, getSynthesizedClone(name));
         }
 
         function collectDependencyGroups(externalImports: (ImportDeclaration | ImportEqualsDeclaration | ExportDeclaration)[]) {

src/compiler/tsconfig.json

@@ -27,6 +27,7 @@
         "transformers/es2017.ts",
         "transformers/es2016.ts",
         "transformers/es2015.ts",
+        "transformers/es5.ts",
         "transformers/generators.ts",
         "transformers/destructuring.ts",
         "transformers/module/module.ts",

src/harness/tsconfig.json

@@ -29,6 +29,7 @@
         "../compiler/transformers/es2017.ts",
         "../compiler/transformers/es2016.ts",
         "../compiler/transformers/es2015.ts",
+        "../compiler/transformers/es5.ts",
         "../compiler/transformers/generators.ts",
         "../compiler/transformers/destructuring.ts",
         "../compiler/transformers/module/module.ts",

src/services/tsconfig.json

@@ -28,6 +28,7 @@
         "../compiler/transformers/es2017.ts",
         "../compiler/transformers/es2016.ts",
         "../compiler/transformers/es2015.ts",
+        "../compiler/transformers/es5.ts",
         "../compiler/transformers/generators.ts",
         "../compiler/transformers/destructuring.ts",
         "../compiler/transformers/module/module.ts",