Fix class name emit in ES5

src/compiler/factory.ts

@@ -2937,6 +2937,28 @@ namespace ts {
         );
     }
 
+    /**
+     * Gets the internal name of a declaration. This is primarily used for declarations that can be
+     * referred to by name in the body of an ES5 class function body. An internal name will *never*
+     * be prefixed with an module or namespace export modifier like "exports." when emitted as an
+     * expression. An internal name will also *never* be renamed due to a collision with a block
+     * scoped variable.
+     *
+     * @param node The declaration.
+     * @param allowComments A value indicating whether comments may be emitted for the name.
+     * @param allowSourceMaps A value indicating whether source maps may be emitted for the name.
+     */
+    export function getInternalName(node: Declaration, allowComments?: boolean, allowSourceMaps?: boolean) {
+        return getName(node, allowComments, allowSourceMaps, EmitFlags.LocalName | EmitFlags.InternalName);
+    }
+
+    /**
+     * Gets whether an identifier should only be referred to by its internal name.
+     */
+    export function isInternalName(node: Identifier) {
+        return (getEmitFlags(node) & EmitFlags.InternalName) !== 0;
+    }
+
     /**
      * Gets the local name of a declaration. This is primarily used for declarations that can be
      * referred to by name in the declaration's immediate scope (classes, enums, namespaces). A

src/compiler/transformers/es2015.ts

@@ -813,7 +813,7 @@ namespace ts {
 
             // Create a synthetic text range for the return statement.
             const closingBraceLocation = createTokenRange(skipTrivia(currentText, node.members.end), SyntaxKind.CloseBraceToken);
-            const localName = getLocalName(node);
+            const localName = getInternalName(node);
 
             // The following partially-emitted expression exists purely to align our sourcemap
             // emit with the original emitter.
@@ -870,7 +870,7 @@ namespace ts {
                 /*decorators*/ undefined,
                 /*modifiers*/ undefined,
                 /*asteriskToken*/ undefined,
-                getDeclarationName(node),
+                getInternalName(node),
                 /*typeParameters*/ undefined,
                 transformConstructorParameters(constructor, hasSynthesizedSuper),
                 /*type*/ undefined,
@@ -3725,7 +3725,7 @@ namespace ts {
         function substituteIdentifier(node: Identifier) {
             // Only substitute the identifier if we have enabled substitutions for block-scoped
             // bindings.
-            if (enabledSubstitutions & ES2015SubstitutionFlags.BlockScopedBindings) {
+            if (enabledSubstitutions & ES2015SubstitutionFlags.BlockScopedBindings && !isInternalName(node)) {
                 const original = getParseTreeNode(node, isIdentifier);
                 if (original && isNameOfDeclarationWithCollidingName(original)) {
                     return setTextRange(getGeneratedNameForNode(original), node);
@@ -3778,7 +3778,7 @@ namespace ts {
          * @param node An Identifier node.
          */
         function substituteExpressionIdentifier(node: Identifier): Identifier {
-            if (enabledSubstitutions & ES2015SubstitutionFlags.BlockScopedBindings) {
+            if (enabledSubstitutions & ES2015SubstitutionFlags.BlockScopedBindings && !isInternalName(node)) {
                 const declaration = resolver.getReferencedDeclarationWithCollidingName(node);
                 if (declaration) {
                     return setTextRange(getGeneratedNameForNode(declaration.name), node);
@@ -3802,8 +3802,9 @@ namespace ts {
         }
 
         function getClassMemberPrefix(node: ClassExpression | ClassDeclaration, member: ClassElement) {
-            const expression = getLocalName(node);
-            return hasModifier(member, ModifierFlags.Static) ? expression : createPropertyAccess(expression, "prototype");
+            return hasModifier(member, ModifierFlags.Static)
+                ? getLocalName(node)
+                : createPropertyAccess(getInternalName(node), "prototype");
         }
 
         function hasSynthesizedDefaultSuperCall(constructor: ConstructorDeclaration, hasExtendsClause: boolean) {

src/compiler/types.ts

@@ -3940,14 +3940,15 @@ namespace ts {
         HelperName = 1 << 12,
         ExportName = 1 << 13,                    // Ensure an export prefix is added for an identifier that points to an exported declaration with a local name (see SymbolFlags.ExportHasLocal).
         LocalName = 1 << 14,                     // Ensure an export prefix is not added for an identifier that points to an exported declaration.
-        Indented = 1 << 15,                      // Adds an explicit extra indentation level for class and function bodies when printing (used to match old emitter).
-        NoIndentation = 1 << 16,                 // Do not indent the node.
-        AsyncFunctionBody = 1 << 17,
-        ReuseTempVariableScope = 1 << 18,        // Reuse the existing temp variable scope during emit.
-        CustomPrologue = 1 << 19,                // Treat the statement as if it were a prologue directive (NOTE: Prologue directives are *not* transformed).
-        NoHoisting = 1 << 20,                    // Do not hoist this declaration in --module system
-        HasEndOfDeclarationMarker = 1 << 21,     // Declaration has an associated NotEmittedStatement to mark the end of the declaration
-        Iterator = 1 << 22,                      // The expression to a `yield*` should be treated as an Iterator when down-leveling, not an Iterable.
+        InternalName = 1 << 15,                  // The name is internal to an ES5 class body function.
+        Indented = 1 << 16,                      // Adds an explicit extra indentation level for class and function bodies when printing (used to match old emitter).
+        NoIndentation = 1 << 17,                 // Do not indent the node.
+        AsyncFunctionBody = 1 << 18,
+        ReuseTempVariableScope = 1 << 19,        // Reuse the existing temp variable scope during emit.
+        CustomPrologue = 1 << 20,                // Treat the statement as if it were a prologue directive (NOTE: Prologue directives are *not* transformed).
+        NoHoisting = 1 << 21,                    // Do not hoist this declaration in --module system
+        HasEndOfDeclarationMarker = 1 << 22,     // Declaration has an associated NotEmittedStatement to mark the end of the declaration
+        Iterator = 1 << 23,                      // The expression to a `yield*` should be treated as an Iterator when down-leveling, not an Iterable.
     }
 
     export interface EmitHelper {