diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index d1716a5d14b..307680d941e 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -13647,9 +13647,6 @@ namespace ts {
                 }
             }
 
-            checkCollisionWithCapturedSuperVariable(node, node);
-            checkCollisionWithCapturedThisVariable(node, node);
-            checkCollisionWithCapturedNewTargetVariable(node, node);
             checkNestedBlockScopedBinding(node, symbol);
 
             const type = getConstraintForLocation(getTypeOfSymbol(localOrExportSymbol), node);
@@ -18852,12 +18849,6 @@ namespace ts {
                 }
             }
 
-            if (produceDiagnostics && node.kind !== SyntaxKind.MethodDeclaration) {
-                checkCollisionWithCapturedSuperVariable(node, node.name);
-                checkCollisionWithCapturedThisVariable(node, node.name);
-                checkCollisionWithCapturedNewTargetVariable(node, node.name);
-            }
-
             return type;
         }
 
@@ -21585,9 +21576,6 @@ namespace ts {
             if (produceDiagnostics) {
                 checkFunctionOrMethodDeclaration(node);
                 checkGrammarForGenerator(node);
-                checkCollisionWithCapturedSuperVariable(node, node.name);
-                checkCollisionWithCapturedThisVariable(node, node.name);
-                checkCollisionWithCapturedNewTargetVariable(node, node.name);
                 checkCollisionWithRequireExportsInGeneratedCode(node, node.name);
                 checkCollisionWithGlobalPromiseInGeneratedCode(node, node.name);
             }
@@ -22012,18 +22000,6 @@ namespace ts {
             return true;
         }
 
-        function checkCollisionWithCapturedThisVariable(node: Node, name: Identifier): void {
-            if (languageVersion <= ScriptTarget.ES5 && !compilerOptions.noEmit && needCollisionCheckForIdentifier(node, name, "_this")) {
-                potentialThisCollisions.push(node);
-            }
-        }
-
-        function checkCollisionWithCapturedNewTargetVariable(node: Node, name: Identifier): void {
-            if (languageVersion <= ScriptTarget.ES5 && !compilerOptions.noEmit && needCollisionCheckForIdentifier(node, name, "_newTarget")) {
-                potentialNewTargetCollisions.push(node);
-            }
-        }
-
         // this function will run after checking the source file so 'CaptureThis' is correct for all nodes
         function checkIfThisIsCapturedInEnclosingScope(node: Node): void {
             findAncestor(node, current => {
@@ -22055,33 +22031,6 @@ namespace ts {
             });
         }
 
-        function checkCollisionWithCapturedSuperVariable(node: Node, name: Identifier) {
-            if (languageVersion >= ScriptTarget.ES2015 || compilerOptions.noEmit) {
-                return;
-            }
-
-            if (!needCollisionCheckForIdentifier(node, name, "_super")) {
-                return;
-            }
-
-            // bubble up and find containing type
-            const enclosingClass = getContainingClass(node);
-            // if containing type was not found or it is ambient - exit (no codegen)
-            if (!enclosingClass || enclosingClass.flags & NodeFlags.Ambient) {
-                return;
-            }
-
-            if (getClassExtendsHeritageClauseElement(enclosingClass)) {
-                const isDeclaration = node.kind !== SyntaxKind.Identifier;
-                if (isDeclaration) {
-                    error(node, Diagnostics.Duplicate_identifier_super_Compiler_uses_super_to_capture_base_class_reference);
-                }
-                else {
-                    error(node, Diagnostics.Expression_resolves_to_super_that_compiler_uses_to_capture_base_class_reference);
-                }
-            }
-        }
-
         function checkCollisionWithRequireExportsInGeneratedCode(node: Node, name: Identifier) {
             // No need to check for require or exports for ES6 modules and later
             if (modulekind >= ModuleKind.ES2015 || compilerOptions.noEmit) {
@@ -22378,9 +22327,6 @@ namespace ts {
                 if (node.kind === SyntaxKind.VariableDeclaration || node.kind === SyntaxKind.BindingElement) {
                     checkVarDeclaredNamesNotShadowed(node);
                 }
-                checkCollisionWithCapturedSuperVariable(node, <Identifier>node.name);
-                checkCollisionWithCapturedThisVariable(node, <Identifier>node.name);
-                checkCollisionWithCapturedNewTargetVariable(node, <Identifier>node.name);
                 checkCollisionWithRequireExportsInGeneratedCode(node, <Identifier>node.name);
                 checkCollisionWithGlobalPromiseInGeneratedCode(node, <Identifier>node.name);
             }
@@ -23377,8 +23323,6 @@ namespace ts {
             checkDecorators(node);
             if (node.name) {
                 checkTypeNameIsReserved(node.name, Diagnostics.Class_name_cannot_be_0);
-                checkCollisionWithCapturedThisVariable(node, node.name);
-                checkCollisionWithCapturedNewTargetVariable(node, node.name);
                 checkCollisionWithRequireExportsInGeneratedCode(node, node.name);
                 checkCollisionWithGlobalPromiseInGeneratedCode(node, node.name);
             }
@@ -23907,8 +23851,6 @@ namespace ts {
             checkGrammarDecoratorsAndModifiers(node);
 
             checkTypeNameIsReserved(node.name, Diagnostics.Enum_name_cannot_be_0);
-            checkCollisionWithCapturedThisVariable(node, node.name);
-            checkCollisionWithCapturedNewTargetVariable(node, node.name);
             checkCollisionWithRequireExportsInGeneratedCode(node, node.name);
             checkCollisionWithGlobalPromiseInGeneratedCode(node, node.name);
             checkExportsOnMergedDeclarations(node);
@@ -24014,7 +23956,6 @@ namespace ts {
                 }
 
                 if (isIdentifier(node.name)) {
-                    checkCollisionWithCapturedThisVariable(node, node.name);
                     checkCollisionWithRequireExportsInGeneratedCode(node, node.name);
                     checkCollisionWithGlobalPromiseInGeneratedCode(node, node.name);
                 }
@@ -24222,7 +24163,6 @@ namespace ts {
         }
 
         function checkImportBinding(node: ImportEqualsDeclaration | ImportClause | NamespaceImport | ImportSpecifier) {
-            checkCollisionWithCapturedThisVariable(node, node.name);
             checkCollisionWithRequireExportsInGeneratedCode(node, node.name);
             checkCollisionWithGlobalPromiseInGeneratedCode(node, node.name);
             checkAliasSymbol(node);
diff --git a/src/compiler/core.ts b/src/compiler/core.ts
index 017d3545206..ae7e8de2ae1 100644
--- a/src/compiler/core.ts
+++ b/src/compiler/core.ts
@@ -2034,7 +2034,7 @@ namespace ts {
         return compilerOptions.target || ScriptTarget.ES3;
     }
 
-    export function getEmitModuleKind(compilerOptions: CompilerOptions) {
+    export function getEmitModuleKind(compilerOptions: {module?: CompilerOptions["module"], target?: CompilerOptions["target"]}) {
         return typeof compilerOptions.module === "number" ?
             compilerOptions.module :
             getEmitScriptTarget(compilerOptions) >= ScriptTarget.ES2015 ? ModuleKind.ES2015 : ModuleKind.CommonJS;
diff --git a/src/compiler/emitter.ts b/src/compiler/emitter.ts
index 34fef4e431f..072b5f9608a 100644
--- a/src/compiler/emitter.ts
+++ b/src/compiler/emitter.ts
@@ -89,7 +89,6 @@ namespace ts {
     // targetSourceFile is when users only want one file in entire project to be emitted. This is used in compileOnSave feature
     export function emitFiles(resolver: EmitResolver, host: EmitHost, targetSourceFile: SourceFile, emitOnlyDtsFiles?: boolean, transformers?: TransformerFactory<SourceFile>[]): EmitResult {
         const compilerOptions = host.getCompilerOptions();
-        const moduleKind = getEmitModuleKind(compilerOptions);
         const sourceMapDataList: SourceMapData[] = (compilerOptions.sourceMap || compilerOptions.inlineSourceMap || getAreDeclarationMapsEnabled(compilerOptions)) ? [] : undefined;
         const emittedFilesList: string[] = compilerOptions.listEmittedFiles ? [] : undefined;
         const emitterDiagnostics = createDiagnosticCollection();
@@ -104,9 +103,6 @@ namespace ts {
             // Explicitly do not passthru either `inline` option
         });
 
-        let currentSourceFile: SourceFile;
-        let bundledHelpers: Map<boolean>;
-        let isOwnFileEmit: boolean;
         let emitSkipped = false;
 
         // Emit each output file
@@ -153,7 +149,7 @@ namespace ts {
             const transform = transformNodes(resolver, host, compilerOptions, sourceFiles, transformers, /*allowDtsFiles*/ false);
 
             // Create a printer to print the nodes
-            const printer = createPrinter(compilerOptions, {
+            const printer = createPrinter({ ...compilerOptions, noEmitHelpers: compilerOptions.noEmitHelpers } as PrinterOptions, {
                 // resolver hooks
                 hasGlobalName: resolver.hasGlobalName,
 
@@ -167,7 +163,6 @@ namespace ts {
                 onEmitSourceMapOfPosition: sourceMap.emitPos,
 
                 // emitter hooks
-                onEmitHelpers: emitHelpers,
                 onSetSourceFile: setSourceFile,
             });
 
@@ -191,7 +186,7 @@ namespace ts {
                     emitterDiagnostics.add(diagnostic);
                 }
             }
-            const declarationPrinter = createPrinter({ ...compilerOptions, onlyPrintJsDocStyle: true } as PrinterOptions, {
+            const declarationPrinter = createPrinter({ ...compilerOptions, onlyPrintJsDocStyle: true, noEmitHelpers: true } as PrinterOptions, {
                 // resolver hooks
                 hasGlobalName: resolver.hasGlobalName,
 
@@ -220,12 +215,9 @@ namespace ts {
             mapRecorder.initialize(jsFilePath, sourceMapFilePath || "", sourceFileOrBundle, sourceMapDataList);
 
             if (bundle) {
-                bundledHelpers = createMap<boolean>();
-                isOwnFileEmit = false;
                 printer.writeBundle(bundle, writer);
             }
             else {
-                isOwnFileEmit = true;
                 printer.writeFile(sourceFile, writer);
             }
 
@@ -247,67 +239,15 @@ namespace ts {
             // Reset state
             mapRecorder.reset();
             writer.clear();
-
-            currentSourceFile = undefined;
-            bundledHelpers = undefined;
-            isOwnFileEmit = false;
         }
 
         function setSourceFile(node: SourceFile) {
-            currentSourceFile = node;
             sourceMap.setSourceFile(node);
         }
 
         function setSourceFileForDeclarationSourceMaps(node: SourceFile) {
-            currentSourceFile = node;
             declarationSourceMap.setSourceFile(node);
         }
-
-        function emitHelpers(node: Node, writeLines: (text: string) => void) {
-            let helpersEmitted = false;
-            const bundle = node.kind === SyntaxKind.Bundle ? <Bundle>node : undefined;
-            if (bundle && moduleKind === ModuleKind.None) {
-                return;
-            }
-
-            const numNodes = bundle ? bundle.sourceFiles.length : 1;
-            for (let i = 0; i < numNodes; i++) {
-                const currentNode = bundle ? bundle.sourceFiles[i] : node;
-                const sourceFile = isSourceFile(currentNode) ? currentNode : currentSourceFile;
-                const shouldSkip = compilerOptions.noEmitHelpers || getExternalHelpersModuleName(sourceFile) !== undefined;
-                const shouldBundle = isSourceFile(currentNode) && !isOwnFileEmit;
-                const helpers = getEmitHelpers(currentNode);
-                if (helpers) {
-                    for (const helper of stableSort(helpers, compareEmitHelpers)) {
-                        if (!helper.scoped) {
-                            // Skip the helper if it can be skipped and the noEmitHelpers compiler
-                            // option is set, or if it can be imported and the importHelpers compiler
-                            // option is set.
-                            if (shouldSkip) continue;
-
-                            // Skip the helper if it can be bundled but hasn't already been emitted and we
-                            // are emitting a bundled module.
-                            if (shouldBundle) {
-                                if (bundledHelpers.get(helper.name)) {
-                                    continue;
-                                }
-
-                                bundledHelpers.set(helper.name, true);
-                            }
-                        }
-                        else if (bundle) {
-                            // Skip the helper if it is scoped and we are emitting bundled helpers
-                            continue;
-                        }
-
-                        writeLines(helper.text);
-                        helpersEmitted = true;
-                    }
-                }
-            }
-
-            return helpersEmitted;
-        }
     }
 
     export function createPrinter(printerOptions: PrinterOptions = {}, handlers: PrintHandlers = {}): Printer {
@@ -317,7 +257,6 @@ namespace ts {
             onEmitSourceMapOfToken,
             onEmitSourceMapOfPosition,
             onEmitNode,
-            onEmitHelpers,
             onSetSourceFile,
             substituteNode,
             onBeforeEmitNodeArray,
@@ -355,6 +294,9 @@ namespace ts {
             writeSemicolon = deferWriteSemicolon;
         }
         const syntheticParent: TextRange = { pos: -1, end: -1 };
+        const moduleKind = getEmitModuleKind(printerOptions);
+        const bundledHelpers = createMap<boolean>();
+        let isOwnFileEmit: boolean;
 
         reset();
         return {
@@ -431,11 +373,12 @@ namespace ts {
         }
 
         function writeBundle(bundle: Bundle, output: EmitTextWriter) {
+            isOwnFileEmit = false;
             const previousWriter = writer;
             setWriter(output);
             emitShebangIfNeeded(bundle);
             emitPrologueDirectivesIfNeeded(bundle);
-            emitHelpersIndirect(bundle);
+            emitHelpers(bundle);
             emitSyntheticTripleSlashReferencesIfNeeded(bundle);
             for (const sourceFile of bundle.sourceFiles) {
                 print(EmitHint.SourceFile, sourceFile, sourceFile);
@@ -445,6 +388,7 @@ namespace ts {
         }
 
         function writeFile(sourceFile: SourceFile, output: EmitTextWriter) {
+            isOwnFileEmit = true;
             const previousWriter = writer;
             setWriter(output);
             emitShebangIfNeeded(sourceFile);
@@ -949,10 +893,55 @@ namespace ts {
             return node && substituteNode && substituteNode(hint, node) || node;
         }
 
-        function emitHelpersIndirect(node: Node) {
-            if (onEmitHelpers) {
-                onEmitHelpers(node, writeLines);
+        function emitHelpers(node: Node) {
+            let helpersEmitted = false;
+            const bundle = node.kind === SyntaxKind.Bundle ? <Bundle>node : undefined;
+            if (bundle && moduleKind === ModuleKind.None) {
+                return;
             }
+
+            const numNodes = bundle ? bundle.sourceFiles.length : 1;
+            for (let i = 0; i < numNodes; i++) {
+                const currentNode = bundle ? bundle.sourceFiles[i] : node;
+                const sourceFile = isSourceFile(currentNode) ? currentNode : currentSourceFile;
+                const shouldSkip = printerOptions.noEmitHelpers || getExternalHelpersModuleName(sourceFile) !== undefined;
+                const shouldBundle = isSourceFile(currentNode) && !isOwnFileEmit;
+                const helpers = getEmitHelpers(currentNode);
+                if (helpers) {
+                    for (const helper of stableSort(helpers, compareEmitHelpers)) {
+                        if (!helper.scoped) {
+                            // Skip the helper if it can be skipped and the noEmitHelpers compiler
+                            // option is set, or if it can be imported and the importHelpers compiler
+                            // option is set.
+                            if (shouldSkip) continue;
+
+                            // Skip the helper if it can be bundled but hasn't already been emitted and we
+                            // are emitting a bundled module.
+                            if (shouldBundle) {
+                                if (bundledHelpers.get(helper.name)) {
+                                    continue;
+                                }
+
+                                bundledHelpers.set(helper.name, true);
+                            }
+                        }
+                        else if (bundle) {
+                            // Skip the helper if it is scoped and we are emitting bundled helpers
+                            continue;
+                        }
+
+                        if (typeof helper.text === "string") {
+                            writeLines(helper.text);
+                        }
+                        else {
+                            writeLines(helper.text(makeFileLevelOptmiisticUniqueName));
+                        }
+                        helpersEmitted = true;
+                    }
+                }
+            }
+
+            return helpersEmitted;
         }
 
         //
@@ -2006,7 +1995,7 @@ namespace ts {
             // Emit all the prologue directives (like "use strict").
             const statementOffset = emitPrologueDirectives(body.statements, /*startWithNewLine*/ true);
             const pos = writer.getTextPos();
-            emitHelpersIndirect(body);
+            emitHelpers(body);
             if (statementOffset === 0 && pos === writer.getTextPos() && emitBlockFunctionBodyOnSingleLine) {
                 decreaseIndent();
                 emitList(body, body.statements, ListFormat.SingleLineFunctionBodyStatements);
@@ -2513,7 +2502,7 @@ namespace ts {
         function emitSourceFileWorker(node: SourceFile) {
             const statements = node.statements;
             pushNameGenerationScope(node);
-            emitHelpersIndirect(node);
+            emitHelpers(node);
             const index = findIndex(statements, statement => !isPrologueDirective(statement));
             emitTripleSlashDirectivesIfNeeded(node);
             emitList(node, statements, ListFormat.MultiLine, index === -1 ? statements.length : index);
@@ -3256,12 +3245,18 @@ namespace ts {
          * or within the NameGenerator.
          */
         function isUniqueName(name: string): boolean {
-            return !(hasGlobalName && hasGlobalName(name))
-                && !currentSourceFile.identifiers.has(name)
+            return isFileLevelUniqueName(name)
                 && !generatedNames.has(name)
                 && !(reservedNames && reservedNames.has(name));
         }
 
+        /**
+         * Returns a value indicating whether a name is unique globally or within the current file.
+         */
+        function isFileLevelUniqueName(name: string) {
+            return ts.isFileLevelUniqueName(currentSourceFile, name, hasGlobalName);
+        }
+
         /**
          * Returns a value indicating whether a name is unique within a container.
          */
@@ -3319,9 +3314,9 @@ namespace ts {
          * makeUniqueName are guaranteed to never conflict.
          * If `optimistic` is set, the first instance will use 'baseName' verbatim instead of 'baseName_1'
          */
-        function makeUniqueName(baseName: string, optimistic?: boolean): string {
+        function makeUniqueName(baseName: string, checkFn: (name: string) => boolean = isUniqueName, optimistic?: boolean): string {
             if (optimistic) {
-                if (isUniqueName(baseName)) {
+                if (checkFn(baseName)) {
                     generatedNames.set(baseName, true);
                     return baseName;
                 }
@@ -3333,7 +3328,7 @@ namespace ts {
             let i = 1;
             while (true) {
                 const generatedName = baseName + i;
-                if (isUniqueName(generatedName)) {
+                if (checkFn(generatedName)) {
                     generatedNames.set(generatedName, true);
                     return generatedName;
                 }
@@ -3341,6 +3336,10 @@ namespace ts {
             }
         }
 
+        function makeFileLevelOptmiisticUniqueName(name: string) {
+            return makeUniqueName(name, isFileLevelUniqueName, /*optimistic*/ true);
+        }
+
         /**
          * Generates a unique name for a ModuleDeclaration or EnumDeclaration.
          */
@@ -3419,9 +3418,11 @@ namespace ts {
                 case GeneratedIdentifierFlags.Loop:
                     return makeTempVariableName(TempFlags._i, !!(name.autoGenerateFlags & GeneratedIdentifierFlags.ReservedInNestedScopes));
                 case GeneratedIdentifierFlags.Unique:
-                    return makeUniqueName(idText(name));
-                case GeneratedIdentifierFlags.OptimisticUnique:
-                    return makeUniqueName(idText(name), /*optimistic*/ true);
+                    return makeUniqueName(
+                        idText(name),
+                        (name.autoGenerateFlags & GeneratedIdentifierFlags.FileLevel) ? isFileLevelUniqueName : isUniqueName,
+                        !!(name.autoGenerateFlags & GeneratedIdentifierFlags.Optimistic)
+                    );
             }
 
             Debug.fail("Unsupported GeneratedIdentifierKind.");
diff --git a/src/compiler/factory.ts b/src/compiler/factory.ts
index 1b951c5b0b7..c83ffd056af 100644
--- a/src/compiler/factory.ts
+++ b/src/compiler/factory.ts
@@ -177,12 +177,19 @@ namespace ts {
     /** Create a unique name based on the supplied text. */
     export function createOptimisticUniqueName(text: string): Identifier {
         const name = createIdentifier(text);
-        name.autoGenerateFlags = GeneratedIdentifierFlags.OptimisticUnique;
+        name.autoGenerateFlags = GeneratedIdentifierFlags.Unique | GeneratedIdentifierFlags.Optimistic;
         name.autoGenerateId = nextAutoGenerateId;
         nextAutoGenerateId++;
         return name;
     }
 
+    /** Create a unique name based on the supplied text. This does not consider names injected by the transformer. */
+    export function createFileLevelUniqueName(text: string): Identifier {
+        const name = createOptimisticUniqueName(text);
+        name.autoGenerateFlags |= GeneratedIdentifierFlags.FileLevel;
+        return name;
+    }
+
     /** Create a unique name generated for a node. */
     export function getGeneratedNameForNode(node: Node): Identifier;
     /* @internal */ export function getGeneratedNameForNode(node: Node, shouldSkipNameGenerationScope?: boolean): Identifier; // tslint:disable-line unified-signatures
diff --git a/src/compiler/transformers/es2015.ts b/src/compiler/transformers/es2015.ts
index 17c02052e60..72068688f9d 100644
--- a/src/compiler/transformers/es2015.ts
+++ b/src/compiler/transformers/es2015.ts
@@ -561,7 +561,7 @@ namespace ts {
         }
 
         function returnCapturedThis(node: Node): ReturnStatement {
-            return setOriginalNode(createReturn(createIdentifier("_this")), node);
+            return setOriginalNode(createReturn(createFileLevelUniqueName("_this")), node);
         }
 
         function visitReturnStatement(node: ReturnStatement): Statement {
@@ -779,7 +779,7 @@ namespace ts {
                 /*asteriskToken*/ undefined,
                 /*name*/ undefined,
                 /*typeParameters*/ undefined,
-                extendsClauseElement ? [createParameter(/*decorators*/ undefined, /*modifiers*/ undefined, /*dotDotDotToken*/ undefined, "_super")] : [],
+                extendsClauseElement ? [createParameter(/*decorators*/ undefined, /*modifiers*/ undefined, /*dotDotDotToken*/ undefined, createFileLevelUniqueName("_super"))] : [],
                 /*type*/ undefined,
                 transformClassBody(node, extendsClauseElement)
             );
@@ -978,7 +978,7 @@ namespace ts {
                 && !(constructor && isSufficientlyCoveredByReturnStatements(constructor.body))) {
                 statements.push(
                     createReturn(
-                        createIdentifier("_this")
+                        createFileLevelUniqueName("_this")
                     )
                 );
             }
@@ -1142,11 +1142,11 @@ namespace ts {
             return createLogicalOr(
                 createLogicalAnd(
                     createStrictInequality(
-                        createIdentifier("_super"),
+                        createFileLevelUniqueName("_super"),
                         createNull()
                     ),
                     createFunctionApply(
-                        createIdentifier("_super"),
+                        createFileLevelUniqueName("_super"),
                         createActualThis(),
                         createIdentifier("arguments"),
                     )
@@ -1452,7 +1452,7 @@ namespace ts {
                 /*modifiers*/ undefined,
                 createVariableDeclarationList([
                     createVariableDeclaration(
-                        "_this",
+                        createFileLevelUniqueName("_this"),
                         /*type*/ undefined,
                         initializer
                     )
@@ -1517,7 +1517,7 @@ namespace ts {
                     /*modifiers*/ undefined,
                     createVariableDeclarationList([
                         createVariableDeclaration(
-                            "_newTarget",
+                            createFileLevelUniqueName("_newTarget"),
                             /*type*/ undefined,
                             newTarget
                         )
@@ -3490,7 +3490,7 @@ namespace ts {
                             actualThis
                         );
                     resultingCall = assignToCapturedThis
-                        ? createAssignment(createIdentifier("_this"), initializer)
+                        ? createAssignment(createFileLevelUniqueName("_this"), initializer)
                         : initializer;
                 }
                 return setOriginalNode(resultingCall, node);
@@ -3811,8 +3811,8 @@ namespace ts {
         function visitSuperKeyword(isExpressionOfCall: boolean): LeftHandSideExpression {
             return hierarchyFacts & HierarchyFacts.NonStaticClassElement
                 && !isExpressionOfCall
-                    ? createPropertyAccess(createIdentifier("_super"), "prototype")
-                    : createIdentifier("_super");
+                    ? createPropertyAccess(createFileLevelUniqueName("_super"), "prototype")
+                    : createFileLevelUniqueName("_super");
         }
 
         function visitMetaProperty(node: MetaProperty) {
@@ -3823,7 +3823,7 @@ namespace ts {
                 else {
                     hierarchyFacts |= HierarchyFacts.NewTarget;
                 }
-                return createIdentifier("_newTarget");
+                return createFileLevelUniqueName("_newTarget");
             }
             return node;
         }
@@ -4000,7 +4000,7 @@ namespace ts {
         function substituteThisKeyword(node: PrimaryExpression): PrimaryExpression {
             if (enabledSubstitutions & ES2015SubstitutionFlags.CapturedThis
                 && hierarchyFacts & HierarchyFacts.CapturesThis) {
-                return setTextRange(createIdentifier("_this"), node);
+                return setTextRange(createFileLevelUniqueName("_this"), node);
             }
             return node;
         }
@@ -4052,7 +4052,7 @@ namespace ts {
             /*typeArguments*/ undefined,
             [
                 name,
-                createIdentifier("_super")
+                createFileLevelUniqueName("_super")
             ]
         );
     }
diff --git a/src/compiler/transformers/es2017.ts b/src/compiler/transformers/es2017.ts
index bee99cdf533..f2a5aeb35d2 100644
--- a/src/compiler/transformers/es2017.ts
+++ b/src/compiler/transformers/es2017.ts
@@ -600,7 +600,7 @@ namespace ts {
                 return setTextRange(
                     createPropertyAccess(
                         createCall(
-                            createIdentifier("_super"),
+                            createFileLevelUniqueName("_super"),
                             /*typeArguments*/ undefined,
                             [argumentExpression]
                         ),
@@ -612,7 +612,7 @@ namespace ts {
             else {
                 return setTextRange(
                     createCall(
-                        createIdentifier("_super"),
+                        createFileLevelUniqueName("_super"),
                         /*typeArguments*/ undefined,
                         [argumentExpression]
                     ),
@@ -668,15 +668,15 @@ namespace ts {
     export const asyncSuperHelper: EmitHelper = {
         name: "typescript:async-super",
         scoped: true,
-        text: `
-            const _super = name => super[name];`
+        text: helperString`
+            const ${"_super"} = name => super[name];`
     };
 
     export const advancedAsyncSuperHelper: EmitHelper = {
         name: "typescript:advanced-async-super",
         scoped: true,
-        text: `
-            const _super = (function (geti, seti) {
+        text: helperString`
+            const ${"_super"} = (function (geti, seti) {
                 const cache = Object.create(null);
                 return name => cache[name] || (cache[name] = { get value() { return geti(name); }, set value(v) { seti(name, v); } });
             })(name => super[name], (name, value) => super[name] = value);`
diff --git a/src/compiler/transformers/utilities.ts b/src/compiler/transformers/utilities.ts
index 55adeba0b76..935f5b0ffd4 100644
--- a/src/compiler/transformers/utilities.ts
+++ b/src/compiler/transformers/utilities.ts
@@ -219,4 +219,20 @@ namespace ts {
             isKeyword(expression.kind) ||
             isIdentifier(expression);
     }
+
+    /**
+     * @param input Template string input strings
+     * @param args Names which need to be made file-level unique
+     */
+    export function helperString(input: TemplateStringsArray, ...args: string[]) {
+        return (uniqueName: EmitHelperUniqueNameCallback) => {
+            let result = "";
+            for (let i = 0; i < args.length; i++) {
+                result += input[i];
+                result += uniqueName(args[i]);
+            }
+            result += input[input.length - 1];
+            return result;
+        };
+    }
 }
\ No newline at end of file
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 6f4d556107d..b92e371febe 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -699,12 +699,13 @@ namespace ts {
         Loop = 2,                           // Automatically generated identifier with a preference for '_i'.
         Unique = 3,                         // Unique name based on the 'text' property.
         Node = 4,                           // Unique name based on the node in the 'original' property.
-        OptimisticUnique = 5,               // Unique name based on the 'text' property, first instance won't use '_#' if there's no conflict
         KindMask = 7,                       // Mask to extract the kind of identifier from its flags.
 
         // Flags
         SkipNameGenerationScope = 1 << 3,   // Should skip a name generation scope when generating the name for this identifier
         ReservedInNestedScopes = 1 << 4,    // Reserve the generated name in nested scopes
+        Optimistic = 1 << 5,                // First instance won't use '_#' if there's no conflict
+        FileLevel = 1 << 6,                 // Use only the file identifiers list and not generated names to search for conflicts
     }
 
     export interface Identifier extends PrimaryExpression, Declaration {
@@ -4755,12 +4756,17 @@ namespace ts {
     }
 
     export interface EmitHelper {
-        readonly name: string;      // A unique name for this helper.
-        readonly scoped: boolean;   // Indicates whether the helper MUST be emitted in the current scope.
-        readonly text: string;      // ES3-compatible raw script text.
-        readonly priority?: number; // Helpers with a higher priority are emitted earlier than other helpers on the node.
+        readonly name: string;                                          // A unique name for this helper.
+        readonly scoped: boolean;                                       // Indicates whether the helper MUST be emitted in the current scope.
+        readonly text: string | ((node: EmitHelperUniqueNameCallback) => string);  // ES3-compatible raw script text, or a function yielding such a string
+        readonly priority?: number;                                     // Helpers with a higher priority are emitted earlier than other helpers on the node.
     }
 
+    /* @internal */
+    export type UniqueNameHandler = (baseName: string, checkFn?: (name: string) => boolean, optimistic?: boolean) => string;
+
+    export type EmitHelperUniqueNameCallback = (name: string) => string;
+
     /**
      * Used by the checker, this enum keeps track of external emit helpers that should be type
      * checked.
@@ -5024,7 +5030,6 @@ namespace ts {
         /*@internal*/ onEmitSourceMapOfNode?: (hint: EmitHint, node: Node, emitCallback: (hint: EmitHint, node: Node) => void) => void;
         /*@internal*/ onEmitSourceMapOfToken?: (node: Node, token: SyntaxKind, writer: (s: string) => void, pos: number, emitCallback: (token: SyntaxKind, writer: (s: string) => void, pos: number) => number) => number;
         /*@internal*/ onEmitSourceMapOfPosition?: (pos: number) => void;
-        /*@internal*/ onEmitHelpers?: (node: Node, writeLines: (text: string) => void) => void;
         /*@internal*/ onSetSourceFile?: (node: SourceFile) => void;
         /*@internal*/ onBeforeEmitNodeArray?: (nodes: NodeArray<any>) => void;
         /*@internal*/ onAfterEmitNodeArray?: (nodes: NodeArray<any>) => void;
@@ -5036,6 +5041,9 @@ namespace ts {
         removeComments?: boolean;
         newLine?: NewLineKind;
         omitTrailingSemicolon?: boolean;
+        noEmitHelpers?: boolean;
+        /*@internal*/ module?: CompilerOptions["module"];
+        /*@internal*/ target?: CompilerOptions["target"];
         /*@internal*/ sourceMap?: boolean;
         /*@internal*/ inlineSourceMap?: boolean;
         /*@internal*/ extendedDiagnostics?: boolean;
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 9a6fbcc8c21..b85c7dfe3cf 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -229,6 +229,14 @@ namespace ts {
         }
     }
 
+    /**
+     * Returns a value indicating whether a name is unique globally or within the current file
+     */
+    export function isFileLevelUniqueName(currentSourceFile: SourceFile, name: string, hasGlobalName?: PrintHandlers["hasGlobalName"]): boolean {
+        return !(hasGlobalName && hasGlobalName(name))
+            && !currentSourceFile.identifiers.has(name);
+    }
+
     // Returns true if this node is missing from the actual source code. A 'missing' node is different
     // from 'undefined/defined'. When a node is undefined (which can happen for optional nodes
     // in the tree), it is definitely missing. However, a node may be defined, but still be
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index 1d499a9e5e4..a8d31ef8fe9 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -2585,9 +2585,10 @@ declare namespace ts {
     interface EmitHelper {
         readonly name: string;
         readonly scoped: boolean;
-        readonly text: string;
+        readonly text: string | ((node: EmitHelperUniqueNameCallback) => string);
         readonly priority?: number;
     }
+    type EmitHelperUniqueNameCallback = (name: string) => string;
     enum EmitHint {
         SourceFile = 0,
         Expression = 1,
@@ -2759,6 +2760,7 @@ declare namespace ts {
         removeComments?: boolean;
         newLine?: NewLineKind;
         omitTrailingSemicolon?: boolean;
+        noEmitHelpers?: boolean;
     }
     /** @deprecated See comment on SymbolWriter */
     interface SymbolTracker {
@@ -3451,6 +3453,8 @@ declare namespace ts {
     function createUniqueName(text: string): Identifier;
     /** Create a unique name based on the supplied text. */
     function createOptimisticUniqueName(text: string): Identifier;
+    /** Create a unique name based on the supplied text. This does not consider names injected by the transformer. */
+    function createFileLevelUniqueName(text: string): Identifier;
     /** Create a unique name generated for a node. */
     function getGeneratedNameForNode(node: Node): Identifier;
     function createToken<TKind extends SyntaxKind>(token: TKind): Token<TKind>;
diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
index 5a8196f9bdf..76dbc06058b 100644
--- a/tests/baselines/reference/api/typescript.d.ts
+++ b/tests/baselines/reference/api/typescript.d.ts
@@ -2585,9 +2585,10 @@ declare namespace ts {
     interface EmitHelper {
         readonly name: string;
         readonly scoped: boolean;
-        readonly text: string;
+        readonly text: string | ((node: EmitHelperUniqueNameCallback) => string);
         readonly priority?: number;
     }
+    type EmitHelperUniqueNameCallback = (name: string) => string;
     enum EmitHint {
         SourceFile = 0,
         Expression = 1,
@@ -2759,6 +2760,7 @@ declare namespace ts {
         removeComments?: boolean;
         newLine?: NewLineKind;
         omitTrailingSemicolon?: boolean;
+        noEmitHelpers?: boolean;
     }
     /** @deprecated See comment on SymbolWriter */
     interface SymbolTracker {
@@ -3398,6 +3400,8 @@ declare namespace ts {
     function createUniqueName(text: string): Identifier;
     /** Create a unique name based on the supplied text. */
     function createOptimisticUniqueName(text: string): Identifier;
+    /** Create a unique name based on the supplied text. This does not consider names injected by the transformer. */
+    function createFileLevelUniqueName(text: string): Identifier;
     /** Create a unique name generated for a node. */
     function getGeneratedNameForNode(node: Node): Identifier;
     function createToken<TKind extends SyntaxKind>(token: TKind): Token<TKind>;
diff --git a/tests/baselines/reference/asyncMethodWithSuperConflict_es6.js b/tests/baselines/reference/asyncMethodWithSuperConflict_es6.js
new file mode 100644
index 00000000000..4b33d8492e9
--- /dev/null
+++ b/tests/baselines/reference/asyncMethodWithSuperConflict_es6.js
@@ -0,0 +1,111 @@
+//// [asyncMethodWithSuperConflict_es6.ts]
+class A {
+    x() {
+    }
+}
+
+class B extends A {
+    // async method with only call/get on 'super' does not require a binding
+    async simple() {
+        const _super = null;
+        // call with property access
+        super.x();
+
+        // call with element access
+        super["x"]();
+
+        // property access (read)
+        const a = super.x;
+
+        // element access (read)
+        const b = super["x"];
+    }
+
+    // async method with assignment/destructuring on 'super' requires a binding
+    async advanced() {
+        const _super = null;
+        const f = () => {};
+
+        // call with property access
+        super.x();
+
+        // call with element access
+        super["x"]();
+
+        // property access (read)
+        const a = super.x;
+
+        // element access (read)
+        const b = super["x"];
+
+        // property access (assign)
+        super.x = f;
+
+        // element access (assign)
+        super["x"] = f;
+
+        // destructuring assign with property access
+        ({ f: super.x } = { f });
+
+        // destructuring assign with element access
+        ({ f: super["x"] } = { f });
+    }
+}
+
+//// [asyncMethodWithSuperConflict_es6.js]
+var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
+    return new (P || (P = Promise))(function (resolve, reject) {
+        function fulfilled(value) { try { step(generator.next(value)); } catch (e) { reject(e); } }
+        function rejected(value) { try { step(generator["throw"](value)); } catch (e) { reject(e); } }
+        function step(result) { result.done ? resolve(result.value) : new P(function (resolve) { resolve(result.value); }).then(fulfilled, rejected); }
+        step((generator = generator.apply(thisArg, _arguments || [])).next());
+    });
+};
+class A {
+    x() {
+    }
+}
+class B extends A {
+    // async method with only call/get on 'super' does not require a binding
+    simple() {
+        const _super_1 = name => super[name];
+        return __awaiter(this, void 0, void 0, function* () {
+            const _super = null;
+            // call with property access
+            _super_1("x").call(this);
+            // call with element access
+            _super_1("x").call(this);
+            // property access (read)
+            const a = _super_1("x");
+            // element access (read)
+            const b = _super_1("x");
+        });
+    }
+    // async method with assignment/destructuring on 'super' requires a binding
+    advanced() {
+        const _super_1 = (function (geti, seti) {
+            const cache = Object.create(null);
+            return name => cache[name] || (cache[name] = { get value() { return geti(name); }, set value(v) { seti(name, v); } });
+        })(name => super[name], (name, value) => super[name] = value);
+        return __awaiter(this, void 0, void 0, function* () {
+            const _super = null;
+            const f = () => { };
+            // call with property access
+            _super_1("x").value.call(this);
+            // call with element access
+            _super_1("x").value.call(this);
+            // property access (read)
+            const a = _super_1("x").value;
+            // element access (read)
+            const b = _super_1("x").value;
+            // property access (assign)
+            _super_1("x").value = f;
+            // element access (assign)
+            _super_1("x").value = f;
+            // destructuring assign with property access
+            ({ f: _super_1("x").value } = { f });
+            // destructuring assign with element access
+            ({ f: _super_1("x").value } = { f });
+        });
+    }
+}
diff --git a/tests/baselines/reference/asyncMethodWithSuperConflict_es6.symbols b/tests/baselines/reference/asyncMethodWithSuperConflict_es6.symbols
new file mode 100644
index 00000000000..ddc8fdf013c
--- /dev/null
+++ b/tests/baselines/reference/asyncMethodWithSuperConflict_es6.symbols
@@ -0,0 +1,108 @@
+=== tests/cases/conformance/async/es2017/asyncMethodWithSuperConflict_es6.ts ===
+class A {
+>A : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+
+    x() {
+>x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+    }
+}
+
+class B extends A {
+>B : Symbol(B, Decl(asyncMethodWithSuperConflict_es6.ts, 3, 1))
+>A : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+
+    // async method with only call/get on 'super' does not require a binding
+    async simple() {
+>simple : Symbol(B.simple, Decl(asyncMethodWithSuperConflict_es6.ts, 5, 19))
+
+        const _super = null;
+>_super : Symbol(_super, Decl(asyncMethodWithSuperConflict_es6.ts, 8, 13))
+
+        // call with property access
+        super.x();
+>super.x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+>super : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+>x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+
+        // call with element access
+        super["x"]();
+>super : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+>"x" : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+
+        // property access (read)
+        const a = super.x;
+>a : Symbol(a, Decl(asyncMethodWithSuperConflict_es6.ts, 16, 13))
+>super.x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+>super : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+>x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+
+        // element access (read)
+        const b = super["x"];
+>b : Symbol(b, Decl(asyncMethodWithSuperConflict_es6.ts, 19, 13))
+>super : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+>"x" : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+    }
+
+    // async method with assignment/destructuring on 'super' requires a binding
+    async advanced() {
+>advanced : Symbol(B.advanced, Decl(asyncMethodWithSuperConflict_es6.ts, 20, 5))
+
+        const _super = null;
+>_super : Symbol(_super, Decl(asyncMethodWithSuperConflict_es6.ts, 24, 13))
+
+        const f = () => {};
+>f : Symbol(f, Decl(asyncMethodWithSuperConflict_es6.ts, 25, 13))
+
+        // call with property access
+        super.x();
+>super.x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+>super : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+>x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+
+        // call with element access
+        super["x"]();
+>super : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+>"x" : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+
+        // property access (read)
+        const a = super.x;
+>a : Symbol(a, Decl(asyncMethodWithSuperConflict_es6.ts, 34, 13))
+>super.x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+>super : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+>x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+
+        // element access (read)
+        const b = super["x"];
+>b : Symbol(b, Decl(asyncMethodWithSuperConflict_es6.ts, 37, 13))
+>super : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+>"x" : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+
+        // property access (assign)
+        super.x = f;
+>super.x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+>super : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+>x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+>f : Symbol(f, Decl(asyncMethodWithSuperConflict_es6.ts, 25, 13))
+
+        // element access (assign)
+        super["x"] = f;
+>super : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+>"x" : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+>f : Symbol(f, Decl(asyncMethodWithSuperConflict_es6.ts, 25, 13))
+
+        // destructuring assign with property access
+        ({ f: super.x } = { f });
+>f : Symbol(f, Decl(asyncMethodWithSuperConflict_es6.ts, 46, 10))
+>super.x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+>super : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+>x : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+>f : Symbol(f, Decl(asyncMethodWithSuperConflict_es6.ts, 46, 27))
+
+        // destructuring assign with element access
+        ({ f: super["x"] } = { f });
+>f : Symbol(f, Decl(asyncMethodWithSuperConflict_es6.ts, 49, 10))
+>super : Symbol(A, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 0))
+>"x" : Symbol(A.x, Decl(asyncMethodWithSuperConflict_es6.ts, 0, 9))
+>f : Symbol(f, Decl(asyncMethodWithSuperConflict_es6.ts, 49, 30))
+    }
+}
diff --git a/tests/baselines/reference/asyncMethodWithSuperConflict_es6.types b/tests/baselines/reference/asyncMethodWithSuperConflict_es6.types
new file mode 100644
index 00000000000..ac82440a3d8
--- /dev/null
+++ b/tests/baselines/reference/asyncMethodWithSuperConflict_es6.types
@@ -0,0 +1,131 @@
+=== tests/cases/conformance/async/es2017/asyncMethodWithSuperConflict_es6.ts ===
+class A {
+>A : A
+
+    x() {
+>x : () => void
+    }
+}
+
+class B extends A {
+>B : B
+>A : A
+
+    // async method with only call/get on 'super' does not require a binding
+    async simple() {
+>simple : () => Promise<void>
+
+        const _super = null;
+>_super : any
+>null : null
+
+        // call with property access
+        super.x();
+>super.x() : void
+>super.x : () => void
+>super : A
+>x : () => void
+
+        // call with element access
+        super["x"]();
+>super["x"]() : void
+>super["x"] : () => void
+>super : A
+>"x" : "x"
+
+        // property access (read)
+        const a = super.x;
+>a : () => void
+>super.x : () => void
+>super : A
+>x : () => void
+
+        // element access (read)
+        const b = super["x"];
+>b : () => void
+>super["x"] : () => void
+>super : A
+>"x" : "x"
+    }
+
+    // async method with assignment/destructuring on 'super' requires a binding
+    async advanced() {
+>advanced : () => Promise<void>
+
+        const _super = null;
+>_super : any
+>null : null
+
+        const f = () => {};
+>f : () => void
+>() => {} : () => void
+
+        // call with property access
+        super.x();
+>super.x() : void
+>super.x : () => void
+>super : A
+>x : () => void
+
+        // call with element access
+        super["x"]();
+>super["x"]() : void
+>super["x"] : () => void
+>super : A
+>"x" : "x"
+
+        // property access (read)
+        const a = super.x;
+>a : () => void
+>super.x : () => void
+>super : A
+>x : () => void
+
+        // element access (read)
+        const b = super["x"];
+>b : () => void
+>super["x"] : () => void
+>super : A
+>"x" : "x"
+
+        // property access (assign)
+        super.x = f;
+>super.x = f : () => void
+>super.x : () => void
+>super : A
+>x : () => void
+>f : () => void
+
+        // element access (assign)
+        super["x"] = f;
+>super["x"] = f : () => void
+>super["x"] : () => void
+>super : A
+>"x" : "x"
+>f : () => void
+
+        // destructuring assign with property access
+        ({ f: super.x } = { f });
+>({ f: super.x } = { f }) : { f: () => void; }
+>{ f: super.x } = { f } : { f: () => void; }
+>{ f: super.x } : { f: () => void; }
+>f : () => void
+>super.x : () => void
+>super : A
+>x : () => void
+>{ f } : { f: () => void; }
+>f : () => void
+
+        // destructuring assign with element access
+        ({ f: super["x"] } = { f });
+>({ f: super["x"] } = { f }) : { f: () => void; }
+>{ f: super["x"] } = { f } : { f: () => void; }
+>{ f: super["x"] } : { f: () => void; }
+>f : () => void
+>super["x"] : () => void
+>super : A
+>"x" : "x"
+>{ f } : { f: () => void; }
+>f : () => void
+    }
+}
diff --git a/tests/baselines/reference/collisionSuperAndLocalFunctionInAccessors.errors.txt b/tests/baselines/reference/collisionSuperAndLocalFunctionInAccessors.errors.txt
deleted file mode 100644
index 16b4edced7b..00000000000
--- a/tests/baselines/reference/collisionSuperAndLocalFunctionInAccessors.errors.txt
+++ /dev/null
@@ -1,72 +0,0 @@
-tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts(4,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts(9,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts(15,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts(16,18): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts(20,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts(21,18): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts(26,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts(28,22): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts(33,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts(35,22): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-
-
-==== tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts (10 errors) ====
-    function _super() { // No error
-    }
-    class Foo {
-        get prop1(): number {
-            ~~~~~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            function _super() { // No error
-            }
-            return 10;
-        }
-        set prop1(val: number) {
-            ~~~~~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            function _super() { // No error
-            }
-        }
-    }
-    class b extends Foo {
-        get prop2(): number {
-            ~~~~~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            function _super() { // Should be error
-                     ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            }
-            return 10;
-        }
-        set prop2(val: number) {
-            ~~~~~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            function _super() { // Should be error
-                     ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            }
-        }
-    }
-    class c extends Foo {
-        get prop2(): number {
-            ~~~~~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            var x = () => {
-                function _super() { // Should be error
-                         ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-                }
-            }
-            return 10;
-        }
-        set prop2(val: number) {
-            ~~~~~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            var x = () => {
-                function _super() { // Should be error
-                         ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-                }
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionSuperAndLocalFunctionInAccessors.js b/tests/baselines/reference/collisionSuperAndLocalFunctionInAccessors.js
index 000c3cfe35e..9c9dfa787ea 100644
--- a/tests/baselines/reference/collisionSuperAndLocalFunctionInAccessors.js
+++ b/tests/baselines/reference/collisionSuperAndLocalFunctionInAccessors.js
@@ -70,10 +70,10 @@ var Foo = /** @class */ (function () {
     });
     return Foo;
 }());
-var b = /** @class */ (function (_super) {
-    __extends(b, _super);
+var b = /** @class */ (function (_super_1) {
+    __extends(b, _super_1);
     function b() {
-        return _super !== null && _super.apply(this, arguments) || this;
+        return _super_1 !== null && _super_1.apply(this, arguments) || this;
     }
     Object.defineProperty(b.prototype, "prop2", {
         get: function () {
@@ -90,10 +90,10 @@ var b = /** @class */ (function (_super) {
     });
     return b;
 }(Foo));
-var c = /** @class */ (function (_super) {
-    __extends(c, _super);
+var c = /** @class */ (function (_super_1) {
+    __extends(c, _super_1);
     function c() {
-        return _super !== null && _super.apply(this, arguments) || this;
+        return _super_1 !== null && _super_1.apply(this, arguments) || this;
     }
     Object.defineProperty(c.prototype, "prop2", {
         get: function () {
diff --git a/tests/baselines/reference/collisionSuperAndLocalFunctionInConstructor.errors.txt b/tests/baselines/reference/collisionSuperAndLocalFunctionInConstructor.errors.txt
deleted file mode 100644
index 5e1ec686bfd..00000000000
--- a/tests/baselines/reference/collisionSuperAndLocalFunctionInConstructor.errors.txt
+++ /dev/null
@@ -1,33 +0,0 @@
-tests/cases/compiler/collisionSuperAndLocalFunctionInConstructor.ts(12,18): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndLocalFunctionInConstructor.ts(20,22): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-
-
-==== tests/cases/compiler/collisionSuperAndLocalFunctionInConstructor.ts (2 errors) ====
-    function _super() { // No error
-    }
-    class Foo {
-        constructor() {
-            function _super() { // No error
-            }
-        }
-    }
-    class b extends Foo {
-        constructor() {
-            super();
-            function _super() { // Should be error
-                     ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            }
-        }
-    }
-    class c extends Foo {
-        constructor() {
-            super();
-            var x = () => {
-                function _super() { // Should be error
-                         ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-                }
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionSuperAndLocalFunctionInConstructor.js b/tests/baselines/reference/collisionSuperAndLocalFunctionInConstructor.js
index 4c2d6fce349..368a05ed9a9 100644
--- a/tests/baselines/reference/collisionSuperAndLocalFunctionInConstructor.js
+++ b/tests/baselines/reference/collisionSuperAndLocalFunctionInConstructor.js
@@ -44,20 +44,20 @@ var Foo = /** @class */ (function () {
     }
     return Foo;
 }());
-var b = /** @class */ (function (_super) {
-    __extends(b, _super);
+var b = /** @class */ (function (_super_1) {
+    __extends(b, _super_1);
     function b() {
-        var _this = _super.call(this) || this;
+        var _this = _super_1.call(this) || this;
         function _super() {
         }
         return _this;
     }
     return b;
 }(Foo));
-var c = /** @class */ (function (_super) {
-    __extends(c, _super);
+var c = /** @class */ (function (_super_1) {
+    __extends(c, _super_1);
     function c() {
-        var _this = _super.call(this) || this;
+        var _this = _super_1.call(this) || this;
         var x = function () {
             function _super() {
             }
diff --git a/tests/baselines/reference/collisionSuperAndLocalFunctionInMethod.errors.txt b/tests/baselines/reference/collisionSuperAndLocalFunctionInMethod.errors.txt
deleted file mode 100644
index e899858fcc9..00000000000
--- a/tests/baselines/reference/collisionSuperAndLocalFunctionInMethod.errors.txt
+++ /dev/null
@@ -1,37 +0,0 @@
-tests/cases/compiler/collisionSuperAndLocalFunctionInMethod.ts(13,18): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndLocalFunctionInMethod.ts(22,22): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-
-
-==== tests/cases/compiler/collisionSuperAndLocalFunctionInMethod.ts (2 errors) ====
-    function _super() { // No error
-    } 
-    class Foo {
-        x() {
-            function _super() { // No error
-            } 
-        }
-        _super() { // No error
-        }
-    }
-    class b extends Foo {
-        public foo() {
-            function _super() { // should be error
-                     ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            } 
-        }
-        _super() { // No Error
-        }
-    }
-    class c extends Foo {
-        public foo() {
-            var x = () => {
-                function _super() { // should be error
-                         ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-                } 
-            }
-        }
-        _super() { // No error
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionSuperAndLocalFunctionInMethod.js b/tests/baselines/reference/collisionSuperAndLocalFunctionInMethod.js
index 74ca7f80ce4..ec36afb9c7e 100644
--- a/tests/baselines/reference/collisionSuperAndLocalFunctionInMethod.js
+++ b/tests/baselines/reference/collisionSuperAndLocalFunctionInMethod.js
@@ -52,10 +52,10 @@ var Foo = /** @class */ (function () {
     };
     return Foo;
 }());
-var b = /** @class */ (function (_super) {
-    __extends(b, _super);
+var b = /** @class */ (function (_super_1) {
+    __extends(b, _super_1);
     function b() {
-        return _super !== null && _super.apply(this, arguments) || this;
+        return _super_1 !== null && _super_1.apply(this, arguments) || this;
     }
     b.prototype.foo = function () {
         function _super() {
@@ -65,10 +65,10 @@ var b = /** @class */ (function (_super) {
     };
     return b;
 }(Foo));
-var c = /** @class */ (function (_super) {
-    __extends(c, _super);
+var c = /** @class */ (function (_super_1) {
+    __extends(c, _super_1);
     function c() {
-        return _super !== null && _super.apply(this, arguments) || this;
+        return _super_1 !== null && _super_1.apply(this, arguments) || this;
     }
     c.prototype.foo = function () {
         var x = function () {
diff --git a/tests/baselines/reference/collisionSuperAndLocalFunctionInProperty.errors.txt b/tests/baselines/reference/collisionSuperAndLocalFunctionInProperty.errors.txt
deleted file mode 100644
index f5c585525e0..00000000000
--- a/tests/baselines/reference/collisionSuperAndLocalFunctionInProperty.errors.txt
+++ /dev/null
@@ -1,24 +0,0 @@
-tests/cases/compiler/collisionSuperAndLocalFunctionInProperty.ts(14,22): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-
-
-==== tests/cases/compiler/collisionSuperAndLocalFunctionInProperty.ts (1 errors) ====
-    function _super() { // No error
-    } 
-    class Foo {
-       public prop1 = {
-            doStuff: () => {
-                function _super() { // No error
-                } 
-            }
-       }
-    }
-    class b extends Foo {
-        public prop2 = {
-            doStuff: () => {
-                function _super() { // error
-                         ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-                } 
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionSuperAndLocalFunctionInProperty.js b/tests/baselines/reference/collisionSuperAndLocalFunctionInProperty.js
index 586315b1607..dcff481846f 100644
--- a/tests/baselines/reference/collisionSuperAndLocalFunctionInProperty.js
+++ b/tests/baselines/reference/collisionSuperAndLocalFunctionInProperty.js
@@ -42,10 +42,10 @@ var Foo = /** @class */ (function () {
     }
     return Foo;
 }());
-var b = /** @class */ (function (_super) {
-    __extends(b, _super);
+var b = /** @class */ (function (_super_1) {
+    __extends(b, _super_1);
     function b() {
-        var _this = _super !== null && _super.apply(this, arguments) || this;
+        var _this = _super_1 !== null && _super_1.apply(this, arguments) || this;
         _this.prop2 = {
             doStuff: function () {
                 function _super() {
diff --git a/tests/baselines/reference/collisionSuperAndLocalVarInAccessors.errors.txt b/tests/baselines/reference/collisionSuperAndLocalVarInAccessors.errors.txt
deleted file mode 100644
index 7e0f80f0658..00000000000
--- a/tests/baselines/reference/collisionSuperAndLocalVarInAccessors.errors.txt
+++ /dev/null
@@ -1,65 +0,0 @@
-tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts(3,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts(7,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts(12,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts(13,13): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts(16,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts(17,13): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts(21,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts(23,17): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts(27,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts(29,17): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-
-
-==== tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts (10 errors) ====
-    var _super = 10; // No Error
-    class Foo {
-        get prop1(): number {
-            ~~~~~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            var _super = 10; // No error
-            return 10;
-        }
-        set prop1(val: number) {
-            ~~~~~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            var _super = 10; // No error
-        }
-    }
-    class b extends Foo {
-        get prop2(): number {
-            ~~~~~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            var _super = 10; // Should be error
-                ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            return 10;
-        }
-        set prop2(val: number) {
-            ~~~~~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            var _super = 10; // Should be error
-                ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-        }
-    }
-    class c extends Foo {
-        get prop2(): number {
-            ~~~~~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            var x = () => {
-                var _super = 10; // Should be error
-                    ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            }
-            return 10;
-        }
-        set prop2(val: number) {
-            ~~~~~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            var x = () => {
-                var _super = 10; // Should be error
-                    ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionSuperAndLocalVarInAccessors.js b/tests/baselines/reference/collisionSuperAndLocalVarInAccessors.js
index d5541889a81..7339e62c6ac 100644
--- a/tests/baselines/reference/collisionSuperAndLocalVarInAccessors.js
+++ b/tests/baselines/reference/collisionSuperAndLocalVarInAccessors.js
@@ -60,10 +60,10 @@ var Foo = /** @class */ (function () {
     });
     return Foo;
 }());
-var b = /** @class */ (function (_super) {
-    __extends(b, _super);
+var b = /** @class */ (function (_super_1) {
+    __extends(b, _super_1);
     function b() {
-        return _super !== null && _super.apply(this, arguments) || this;
+        return _super_1 !== null && _super_1.apply(this, arguments) || this;
     }
     Object.defineProperty(b.prototype, "prop2", {
         get: function () {
@@ -78,10 +78,10 @@ var b = /** @class */ (function (_super) {
     });
     return b;
 }(Foo));
-var c = /** @class */ (function (_super) {
-    __extends(c, _super);
+var c = /** @class */ (function (_super_1) {
+    __extends(c, _super_1);
     function c() {
-        return _super !== null && _super.apply(this, arguments) || this;
+        return _super_1 !== null && _super_1.apply(this, arguments) || this;
     }
     Object.defineProperty(c.prototype, "prop2", {
         get: function () {
diff --git a/tests/baselines/reference/collisionSuperAndLocalVarInConstructor.errors.txt b/tests/baselines/reference/collisionSuperAndLocalVarInConstructor.errors.txt
deleted file mode 100644
index 4097187c3bf..00000000000
--- a/tests/baselines/reference/collisionSuperAndLocalVarInConstructor.errors.txt
+++ /dev/null
@@ -1,29 +0,0 @@
-tests/cases/compiler/collisionSuperAndLocalVarInConstructor.ts(10,13): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndLocalVarInConstructor.ts(17,17): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-
-
-==== tests/cases/compiler/collisionSuperAndLocalVarInConstructor.ts (2 errors) ====
-    var _super = 10; // No Error
-    class Foo {
-        constructor() {
-            var _super = 10; // No error
-        }
-    }
-    class b extends Foo {
-        constructor() {
-            super();
-            var _super = 10; // Should be error 
-                ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-        }
-    }
-    class c extends Foo {
-        constructor() {
-            super();
-            var x = () => {
-                var _super = 10; // Should be error
-                    ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionSuperAndLocalVarInConstructor.js b/tests/baselines/reference/collisionSuperAndLocalVarInConstructor.js
index e586b4dc55e..c5725e59906 100644
--- a/tests/baselines/reference/collisionSuperAndLocalVarInConstructor.js
+++ b/tests/baselines/reference/collisionSuperAndLocalVarInConstructor.js
@@ -38,19 +38,19 @@ var Foo = /** @class */ (function () {
     }
     return Foo;
 }());
-var b = /** @class */ (function (_super) {
-    __extends(b, _super);
+var b = /** @class */ (function (_super_1) {
+    __extends(b, _super_1);
     function b() {
-        var _this = _super.call(this) || this;
+        var _this = _super_1.call(this) || this;
         var _super = 10; // Should be error 
         return _this;
     }
     return b;
 }(Foo));
-var c = /** @class */ (function (_super) {
-    __extends(c, _super);
+var c = /** @class */ (function (_super_1) {
+    __extends(c, _super_1);
     function c() {
-        var _this = _super.call(this) || this;
+        var _this = _super_1.call(this) || this;
         var x = function () {
             var _super = 10; // Should be error
         };
diff --git a/tests/baselines/reference/collisionSuperAndLocalVarInMethod.errors.txt b/tests/baselines/reference/collisionSuperAndLocalVarInMethod.errors.txt
deleted file mode 100644
index 72e19e20094..00000000000
--- a/tests/baselines/reference/collisionSuperAndLocalVarInMethod.errors.txt
+++ /dev/null
@@ -1,27 +0,0 @@
-tests/cases/compiler/collisionSuperAndLocalVarInMethod.ts(9,13): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndLocalVarInMethod.ts(15,17): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-
-
-==== tests/cases/compiler/collisionSuperAndLocalVarInMethod.ts (2 errors) ====
-    var _super = 10; // No Error
-    class Foo {
-        x() {
-            var _super = 10; // No error
-        }
-    }
-    class b extends Foo {
-        public foo() {
-            var _super = 10; // Should be error 
-                ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-        }
-    }
-    class c extends Foo {
-        public foo() {
-            var x = () => {
-                var _super = 10; // Should be error
-                    ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionSuperAndLocalVarInMethod.js b/tests/baselines/reference/collisionSuperAndLocalVarInMethod.js
index 54ed127b6c1..883219d0a5a 100644
--- a/tests/baselines/reference/collisionSuperAndLocalVarInMethod.js
+++ b/tests/baselines/reference/collisionSuperAndLocalVarInMethod.js
@@ -38,20 +38,20 @@ var Foo = /** @class */ (function () {
     };
     return Foo;
 }());
-var b = /** @class */ (function (_super) {
-    __extends(b, _super);
+var b = /** @class */ (function (_super_1) {
+    __extends(b, _super_1);
     function b() {
-        return _super !== null && _super.apply(this, arguments) || this;
+        return _super_1 !== null && _super_1.apply(this, arguments) || this;
     }
     b.prototype.foo = function () {
         var _super = 10; // Should be error 
     };
     return b;
 }(Foo));
-var c = /** @class */ (function (_super) {
-    __extends(c, _super);
+var c = /** @class */ (function (_super_1) {
+    __extends(c, _super_1);
     function c() {
-        return _super !== null && _super.apply(this, arguments) || this;
+        return _super_1 !== null && _super_1.apply(this, arguments) || this;
     }
     c.prototype.foo = function () {
         var x = function () {
diff --git a/tests/baselines/reference/collisionSuperAndLocalVarInProperty.errors.txt b/tests/baselines/reference/collisionSuperAndLocalVarInProperty.errors.txt
deleted file mode 100644
index 6c786c83d8a..00000000000
--- a/tests/baselines/reference/collisionSuperAndLocalVarInProperty.errors.txt
+++ /dev/null
@@ -1,23 +0,0 @@
-tests/cases/compiler/collisionSuperAndLocalVarInProperty.ts(13,17): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-
-
-==== tests/cases/compiler/collisionSuperAndLocalVarInProperty.ts (1 errors) ====
-    var _super = 10; // No Error
-    class Foo {
-       public prop1 = {
-            doStuff: () => {
-                var _super = 10; // No error
-            }
-        }
-        public _super = 10; // No error
-    }
-    class b extends Foo {
-        public prop2 = {
-            doStuff: () => {
-                var _super = 10; // Should be error 
-                    ~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            }
-        }
-        public _super = 10; // No error
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionSuperAndLocalVarInProperty.js b/tests/baselines/reference/collisionSuperAndLocalVarInProperty.js
index b7b9490a115..9dfc8cb86bf 100644
--- a/tests/baselines/reference/collisionSuperAndLocalVarInProperty.js
+++ b/tests/baselines/reference/collisionSuperAndLocalVarInProperty.js
@@ -40,10 +40,10 @@ var Foo = /** @class */ (function () {
     }
     return Foo;
 }());
-var b = /** @class */ (function (_super) {
-    __extends(b, _super);
+var b = /** @class */ (function (_super_1) {
+    __extends(b, _super_1);
     function b() {
-        var _this = _super !== null && _super.apply(this, arguments) || this;
+        var _this = _super_1 !== null && _super_1.apply(this, arguments) || this;
         _this.prop2 = {
             doStuff: function () {
                 var _super = 10; // Should be error 
diff --git a/tests/baselines/reference/collisionSuperAndNameResolution.errors.txt b/tests/baselines/reference/collisionSuperAndNameResolution.errors.txt
deleted file mode 100644
index ea874952320..00000000000
--- a/tests/baselines/reference/collisionSuperAndNameResolution.errors.txt
+++ /dev/null
@@ -1,17 +0,0 @@
-tests/cases/compiler/collisionSuperAndNameResolution.ts(9,21): error TS2402: Expression resolves to '_super' that compiler uses to capture base class reference.
-
-
-==== tests/cases/compiler/collisionSuperAndNameResolution.ts (1 errors) ====
-    var console: {
-        log(message: any);
-    }
-    var _super = 10; // No error
-    class base {
-    }
-    class Foo extends base {
-        x() {
-            console.log(_super); // Error as this doesnt not resolve to user defined _super
-                        ~~~~~~
-!!! error TS2402: Expression resolves to '_super' that compiler uses to capture base class reference.
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionSuperAndNameResolution.js b/tests/baselines/reference/collisionSuperAndNameResolution.js
index c8489e006a8..933e3f5f204 100644
--- a/tests/baselines/reference/collisionSuperAndNameResolution.js
+++ b/tests/baselines/reference/collisionSuperAndNameResolution.js
@@ -29,10 +29,10 @@ var base = /** @class */ (function () {
     }
     return base;
 }());
-var Foo = /** @class */ (function (_super) {
-    __extends(Foo, _super);
+var Foo = /** @class */ (function (_super_1) {
+    __extends(Foo, _super_1);
     function Foo() {
-        return _super !== null && _super.apply(this, arguments) || this;
+        return _super_1 !== null && _super_1.apply(this, arguments) || this;
     }
     Foo.prototype.x = function () {
         console.log(_super); // Error as this doesnt not resolve to user defined _super
diff --git a/tests/baselines/reference/collisionSuperAndParameter.errors.txt b/tests/baselines/reference/collisionSuperAndParameter.errors.txt
deleted file mode 100644
index 65dddd95d48..00000000000
--- a/tests/baselines/reference/collisionSuperAndParameter.errors.txt
+++ /dev/null
@@ -1,92 +0,0 @@
-tests/cases/compiler/collisionSuperAndParameter.ts(12,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndParameter.ts(17,22): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndParameter.ts(21,7): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndParameter.ts(26,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionSuperAndParameter.ts(26,11): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndParameter.ts(32,19): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndParameter.ts(35,17): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndParameter.ts(52,17): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndParameter.ts(57,7): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-
-
-==== tests/cases/compiler/collisionSuperAndParameter.ts (9 errors) ====
-    class Foo {
-        a() {
-            var lamda = (_super: number) => { // No Error 
-                return x => this;   // New scope.  So should inject new _this capture
-            }
-        }
-        b(_super: number) { // No Error 
-            var lambda = () => {
-                return x => this;   // New scope.  So should inject new _this capture
-            }
-        }
-        set c(_super: number) { // No error
-            ~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-        }
-    }
-    class Foo2 extends Foo {
-        x() {
-            var lamda = (_super: number) => { // Error 
-                         ~~~~~~~~~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-                return x => this;   // New scope.  So should inject new _this capture
-            }
-        }
-        y(_super: number) { // Error 
-          ~~~~~~~~~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            var lambda = () => {
-                return x => this;   // New scope.  So should inject new _this capture
-            }
-        }
-        set z(_super: number) { // Error
-            ~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-              ~~~~~~~~~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-        }
-        public prop3: {
-            doStuff: (_super: number) => void; // no error - no code gen
-        }
-        public prop4 = {
-            doStuff: (_super: number) => { // should be error
-                      ~~~~~~~~~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            }
-        }
-        constructor(_super: number) { // should be error
-                    ~~~~~~~~~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            super();
-        }
-    }
-    declare class Foo3 extends Foo {
-        x();
-        y(_super: number); // No error - no code gen
-        constructor(_super: number); // No error - no code gen
-        public prop2: {
-            doStuff: (_super: number) => void; // no error - no code gen
-        };
-        public _super: number; // No error
-    }
-    
-    class Foo4 extends Foo {
-        constructor(_super: number); // no code gen - no error
-        constructor(_super: string);// no code gen - no error
-        constructor(_super: any) { // should be error
-                    ~~~~~~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            super();
-        }
-        y(_super: number); // no code gen - no error
-        y(_super: string); // no code gen - no error
-        y(_super: any) { // Error 
-          ~~~~~~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            var lambda = () => {
-                return x => this;   // New scope.  So should inject new _this capture
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionSuperAndParameter.js b/tests/baselines/reference/collisionSuperAndParameter.js
index 9ee69713883..cde7eef54e1 100644
--- a/tests/baselines/reference/collisionSuperAndParameter.js
+++ b/tests/baselines/reference/collisionSuperAndParameter.js
@@ -96,10 +96,10 @@ var Foo = /** @class */ (function () {
     });
     return Foo;
 }());
-var Foo2 = /** @class */ (function (_super) {
-    __extends(Foo2, _super);
+var Foo2 = /** @class */ (function (_super_1) {
+    __extends(Foo2, _super_1);
     function Foo2(_super) {
-        var _this = _super.call(this) || this;
+        var _this = _super_1.call(this) || this;
         _this.prop4 = {
             doStuff: function (_super) {
             }
@@ -126,10 +126,10 @@ var Foo2 = /** @class */ (function (_super) {
     });
     return Foo2;
 }(Foo));
-var Foo4 = /** @class */ (function (_super) {
-    __extends(Foo4, _super);
+var Foo4 = /** @class */ (function (_super_1) {
+    __extends(Foo4, _super_1);
     function Foo4(_super) {
-        return _super.call(this) || this;
+        return _super_1.call(this) || this;
     }
     Foo4.prototype.y = function (_super) {
         var _this = this;
diff --git a/tests/baselines/reference/collisionSuperAndParameter1.errors.txt b/tests/baselines/reference/collisionSuperAndParameter1.errors.txt
deleted file mode 100644
index 361ecc1668e..00000000000
--- a/tests/baselines/reference/collisionSuperAndParameter1.errors.txt
+++ /dev/null
@@ -1,15 +0,0 @@
-tests/cases/compiler/collisionSuperAndParameter1.ts(6,23): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-
-
-==== tests/cases/compiler/collisionSuperAndParameter1.ts (1 errors) ====
-    class Foo {
-    }
-    
-    class Foo2 extends Foo {
-        x() {
-            var lambda = (_super: number) => { // Error 
-                          ~~~~~~~~~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionSuperAndParameter1.js b/tests/baselines/reference/collisionSuperAndParameter1.js
index f665a5d03df..65f4ca4d10c 100644
--- a/tests/baselines/reference/collisionSuperAndParameter1.js
+++ b/tests/baselines/reference/collisionSuperAndParameter1.js
@@ -25,10 +25,10 @@ var Foo = /** @class */ (function () {
     }
     return Foo;
 }());
-var Foo2 = /** @class */ (function (_super) {
-    __extends(Foo2, _super);
+var Foo2 = /** @class */ (function (_super_1) {
+    __extends(Foo2, _super_1);
     function Foo2() {
-        return _super !== null && _super.apply(this, arguments) || this;
+        return _super_1 !== null && _super_1.apply(this, arguments) || this;
     }
     Foo2.prototype.x = function () {
         var lambda = function (_super) {
diff --git a/tests/baselines/reference/collisionSuperAndPropertyNameAsConstuctorParameter.errors.txt b/tests/baselines/reference/collisionSuperAndPropertyNameAsConstuctorParameter.errors.txt
deleted file mode 100644
index 20e71ee1b7a..00000000000
--- a/tests/baselines/reference/collisionSuperAndPropertyNameAsConstuctorParameter.errors.txt
+++ /dev/null
@@ -1,45 +0,0 @@
-tests/cases/compiler/collisionSuperAndPropertyNameAsConstuctorParameter.ts(5,17): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndPropertyNameAsConstuctorParameter.ts(11,17): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndPropertyNameAsConstuctorParameter.ts(19,17): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-tests/cases/compiler/collisionSuperAndPropertyNameAsConstuctorParameter.ts(27,17): error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-
-
-==== tests/cases/compiler/collisionSuperAndPropertyNameAsConstuctorParameter.ts (4 errors) ====
-    class a {
-    }
-    
-    class b1 extends a {
-        constructor(_super: number) { // should be error
-                    ~~~~~~~~~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            super();
-        }
-    }
-    
-    class b2 extends a {
-        constructor(private _super: number) { // should be error
-                    ~~~~~~~~~~~~~~~~~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            super();
-        }
-    }
-    
-    class b3 extends a {
-        constructor(_super: number); // no code gen - no error
-        constructor(_super: string);// no code gen - no error
-        constructor(_super: any) { // should be error
-                    ~~~~~~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            super();
-        }
-    }
-    
-    class b4 extends a {
-        constructor(_super: number); // no code gen - no error
-        constructor(_super: string);// no code gen - no error
-        constructor(private _super: any) { // should be error
-                    ~~~~~~~~~~~~~~~~~~~
-!!! error TS2401: Duplicate identifier '_super'. Compiler uses '_super' to capture base class reference.
-            super();
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionSuperAndPropertyNameAsConstuctorParameter.js b/tests/baselines/reference/collisionSuperAndPropertyNameAsConstuctorParameter.js
index a98bb021c55..9bc347b4361 100644
--- a/tests/baselines/reference/collisionSuperAndPropertyNameAsConstuctorParameter.js
+++ b/tests/baselines/reference/collisionSuperAndPropertyNameAsConstuctorParameter.js
@@ -46,33 +46,33 @@ var a = /** @class */ (function () {
     }
     return a;
 }());
-var b1 = /** @class */ (function (_super) {
-    __extends(b1, _super);
+var b1 = /** @class */ (function (_super_1) {
+    __extends(b1, _super_1);
     function b1(_super) {
-        return _super.call(this) || this;
+        return _super_1.call(this) || this;
     }
     return b1;
 }(a));
-var b2 = /** @class */ (function (_super) {
-    __extends(b2, _super);
+var b2 = /** @class */ (function (_super_1) {
+    __extends(b2, _super_1);
     function b2(_super) {
-        var _this = _super.call(this) || this;
+        var _this = _super_1.call(this) || this;
         _this._super = _super;
         return _this;
     }
     return b2;
 }(a));
-var b3 = /** @class */ (function (_super) {
-    __extends(b3, _super);
+var b3 = /** @class */ (function (_super_1) {
+    __extends(b3, _super_1);
     function b3(_super) {
-        return _super.call(this) || this;
+        return _super_1.call(this) || this;
     }
     return b3;
 }(a));
-var b4 = /** @class */ (function (_super) {
-    __extends(b4, _super);
+var b4 = /** @class */ (function (_super_1) {
+    __extends(b4, _super_1);
     function b4(_super) {
-        var _this = _super.call(this) || this;
+        var _this = _super_1.call(this) || this;
         _this._super = _super;
         return _this;
     }
diff --git a/tests/baselines/reference/collisionThisExpressionAndAliasInGlobal.errors.txt b/tests/baselines/reference/collisionThisExpressionAndAliasInGlobal.errors.txt
deleted file mode 100644
index 96f05d6bfcc..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndAliasInGlobal.errors.txt
+++ /dev/null
@@ -1,11 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndAliasInGlobal.ts(5,8): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndAliasInGlobal.ts (1 errors) ====
-    module a {
-        export var b = 10;
-    }
-    var f = () => this;
-    import _this = a; // Error
-           ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndAliasInGlobal.js b/tests/baselines/reference/collisionThisExpressionAndAliasInGlobal.js
index 1f613798642..423b685c8d6 100644
--- a/tests/baselines/reference/collisionThisExpressionAndAliasInGlobal.js
+++ b/tests/baselines/reference/collisionThisExpressionAndAliasInGlobal.js
@@ -6,10 +6,10 @@ var f = () => this;
 import _this = a; // Error
 
 //// [collisionThisExpressionAndAliasInGlobal.js]
-var _this = this;
+var _this_1 = this;
 var a;
 (function (a) {
     a.b = 10;
 })(a || (a = {}));
-var f = function () { return _this; };
+var f = function () { return _this_1; };
 var _this = a; // Error
diff --git a/tests/baselines/reference/collisionThisExpressionAndAmbientClassInGlobal.errors.txt b/tests/baselines/reference/collisionThisExpressionAndAmbientClassInGlobal.errors.txt
deleted file mode 100644
index 562f0d2a94a..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndAmbientClassInGlobal.errors.txt
+++ /dev/null
@@ -1,10 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndAmbientClassInGlobal.ts(4,13): error TS2400: Expression resolves to variable declaration '_this' that compiler uses to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndAmbientClassInGlobal.ts (1 errors) ====
-    declare class _this { // no error - as no code generation
-    }
-    var f = () => this;
-    var a = new _this(); // Error
-                ~~~~~
-!!! error TS2400: Expression resolves to variable declaration '_this' that compiler uses to capture 'this' reference.
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndAmbientClassInGlobal.js b/tests/baselines/reference/collisionThisExpressionAndAmbientClassInGlobal.js
index b99311b0c3e..8e9cb96df1a 100644
--- a/tests/baselines/reference/collisionThisExpressionAndAmbientClassInGlobal.js
+++ b/tests/baselines/reference/collisionThisExpressionAndAmbientClassInGlobal.js
@@ -5,6 +5,6 @@ var f = () => this;
 var a = new _this(); // Error
 
 //// [collisionThisExpressionAndAmbientClassInGlobal.js]
-var _this = this;
-var f = function () { return _this; };
+var _this_1 = this;
+var f = function () { return _this_1; };
 var a = new _this(); // Error
diff --git a/tests/baselines/reference/collisionThisExpressionAndAmbientVarInGlobal.errors.txt b/tests/baselines/reference/collisionThisExpressionAndAmbientVarInGlobal.errors.txt
deleted file mode 100644
index 412b2c8e18d..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndAmbientVarInGlobal.errors.txt
+++ /dev/null
@@ -1,9 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndAmbientVarInGlobal.ts(3,1): error TS2400: Expression resolves to variable declaration '_this' that compiler uses to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndAmbientVarInGlobal.ts (1 errors) ====
-    declare var _this: number; // no error as no code gen
-    var f = () => this;
-    _this = 10; // Error
-    ~~~~~
-!!! error TS2400: Expression resolves to variable declaration '_this' that compiler uses to capture 'this' reference.
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndAmbientVarInGlobal.js b/tests/baselines/reference/collisionThisExpressionAndAmbientVarInGlobal.js
index c6c54869056..3f7e2c80d49 100644
--- a/tests/baselines/reference/collisionThisExpressionAndAmbientVarInGlobal.js
+++ b/tests/baselines/reference/collisionThisExpressionAndAmbientVarInGlobal.js
@@ -4,6 +4,6 @@ var f = () => this;
 _this = 10; // Error
 
 //// [collisionThisExpressionAndAmbientVarInGlobal.js]
-var _this = this;
-var f = function () { return _this; };
+var _this_1 = this;
+var f = function () { return _this_1; };
 _this = 10; // Error
diff --git a/tests/baselines/reference/collisionThisExpressionAndClassInGlobal.errors.txt b/tests/baselines/reference/collisionThisExpressionAndClassInGlobal.errors.txt
deleted file mode 100644
index 26e37d4b327..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndClassInGlobal.errors.txt
+++ /dev/null
@@ -1,9 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndClassInGlobal.ts(1,7): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndClassInGlobal.ts (1 errors) ====
-    class _this {
-          ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-    }
-    var f = () => this;
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndClassInGlobal.js b/tests/baselines/reference/collisionThisExpressionAndClassInGlobal.js
index f3158047a54..2b1ffbe1182 100644
--- a/tests/baselines/reference/collisionThisExpressionAndClassInGlobal.js
+++ b/tests/baselines/reference/collisionThisExpressionAndClassInGlobal.js
@@ -4,10 +4,10 @@ class _this {
 var f = () => this;
 
 //// [collisionThisExpressionAndClassInGlobal.js]
-var _this = this;
+var _this_1 = this;
 var _this = /** @class */ (function () {
     function _this() {
     }
     return _this;
 }());
-var f = function () { return _this; };
+var f = function () { return _this_1; };
diff --git a/tests/baselines/reference/collisionThisExpressionAndEnumInGlobal.errors.txt b/tests/baselines/reference/collisionThisExpressionAndEnumInGlobal.errors.txt
deleted file mode 100644
index e6c7b70216c..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndEnumInGlobal.errors.txt
+++ /dev/null
@@ -1,11 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndEnumInGlobal.ts(1,6): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndEnumInGlobal.ts (1 errors) ====
-    enum _this { // Error
-         ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-        _thisVal1,
-        _thisVal2,
-    }
-    var f = () => this;
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndEnumInGlobal.js b/tests/baselines/reference/collisionThisExpressionAndEnumInGlobal.js
index 4ab929a3877..c2dc1db265b 100644
--- a/tests/baselines/reference/collisionThisExpressionAndEnumInGlobal.js
+++ b/tests/baselines/reference/collisionThisExpressionAndEnumInGlobal.js
@@ -6,10 +6,10 @@ enum _this { // Error
 var f = () => this;
 
 //// [collisionThisExpressionAndEnumInGlobal.js]
-var _this = this;
+var _this_1 = this;
 var _this;
 (function (_this) {
     _this[_this["_thisVal1"] = 0] = "_thisVal1";
     _this[_this["_thisVal2"] = 1] = "_thisVal2";
 })(_this || (_this = {}));
-var f = function () { return _this; };
+var f = function () { return _this_1; };
diff --git a/tests/baselines/reference/collisionThisExpressionAndFunctionInGlobal.errors.txt b/tests/baselines/reference/collisionThisExpressionAndFunctionInGlobal.errors.txt
deleted file mode 100644
index 30fa4a444e2..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndFunctionInGlobal.errors.txt
+++ /dev/null
@@ -1,10 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndFunctionInGlobal.ts(1,10): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndFunctionInGlobal.ts (1 errors) ====
-    function _this() { //Error
-             ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-        return 10;
-    }
-    var f = () => this;
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndFunctionInGlobal.js b/tests/baselines/reference/collisionThisExpressionAndFunctionInGlobal.js
index 3c6232ba0ba..eabf46e9ae6 100644
--- a/tests/baselines/reference/collisionThisExpressionAndFunctionInGlobal.js
+++ b/tests/baselines/reference/collisionThisExpressionAndFunctionInGlobal.js
@@ -5,8 +5,8 @@ function _this() { //Error
 var f = () => this;
 
 //// [collisionThisExpressionAndFunctionInGlobal.js]
-var _this = this;
+var _this_1 = this;
 function _this() {
     return 10;
 }
-var f = function () { return _this; };
+var f = function () { return _this_1; };
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarInAccessors.errors.txt b/tests/baselines/reference/collisionThisExpressionAndLocalVarInAccessors.errors.txt
deleted file mode 100644
index cbe371c5934..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarInAccessors.errors.txt
+++ /dev/null
@@ -1,70 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts(2,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts(5,21): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts(12,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts(15,21): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts(24,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts(25,13): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts(34,9): error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts(35,13): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts (8 errors) ====
-    class class1 {
-        get a(): number {
-            ~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            var x2 = {
-                doStuff: (callback) => () => {
-                    var _this = 2;
-                        ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-                    return callback(this);
-                }
-            }
-    
-            return 10;
-        }
-        set a(val: number) {
-            ~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            var x2 = {
-                doStuff: (callback) => () => {
-                    var _this = 2;
-                        ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-                    return callback(this);
-                }
-            }
-    
-        }
-    }
-    
-    class class2 {
-        get a(): number {
-            ~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            var _this = 2;
-                ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            var x2 = {
-                doStuff: (callback) => () => {
-                    return callback(this);
-                }
-            }
-    
-            return 10;
-        }
-        set a(val: number) {
-            ~
-!!! error TS1056: Accessors are only available when targeting ECMAScript 5 and higher.
-            var _this = 2;
-                ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            var x2 = {
-                doStuff: (callback) => () => {
-                    return callback(this);
-                }
-            }
-    
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarInAccessors.js b/tests/baselines/reference/collisionThisExpressionAndLocalVarInAccessors.js
index 4a7875bfe40..ffa350a04ef 100644
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarInAccessors.js
+++ b/tests/baselines/reference/collisionThisExpressionAndLocalVarInAccessors.js
@@ -49,21 +49,21 @@ var class1 = /** @class */ (function () {
     }
     Object.defineProperty(class1.prototype, "a", {
         get: function () {
-            var _this = this;
+            var _this_1 = this;
             var x2 = {
                 doStuff: function (callback) { return function () {
                     var _this = 2;
-                    return callback(_this);
+                    return callback(_this_1);
                 }; }
             };
             return 10;
         },
         set: function (val) {
-            var _this = this;
+            var _this_1 = this;
             var x2 = {
                 doStuff: function (callback) { return function () {
                     var _this = 2;
-                    return callback(_this);
+                    return callback(_this_1);
                 }; }
             };
         },
@@ -77,21 +77,21 @@ var class2 = /** @class */ (function () {
     }
     Object.defineProperty(class2.prototype, "a", {
         get: function () {
-            var _this = this;
+            var _this_1 = this;
             var _this = 2;
             var x2 = {
                 doStuff: function (callback) { return function () {
-                    return callback(_this);
+                    return callback(_this_1);
                 }; }
             };
             return 10;
         },
         set: function (val) {
-            var _this = this;
+            var _this_1 = this;
             var _this = 2;
             var x2 = {
                 doStuff: function (callback) { return function () {
-                    return callback(_this);
+                    return callback(_this_1);
                 }; }
             };
         },
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarInConstructor.errors.txt b/tests/baselines/reference/collisionThisExpressionAndLocalVarInConstructor.errors.txt
deleted file mode 100644
index af1b43786a4..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarInConstructor.errors.txt
+++ /dev/null
@@ -1,30 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndLocalVarInConstructor.ts(5,21): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndLocalVarInConstructor.ts(14,13): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndLocalVarInConstructor.ts (2 errors) ====
-    class class1 {
-        constructor() {
-            var x2 = {
-                doStuff: (callback) => () => {
-                    var _this = 2;
-                        ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-                    return callback(this);
-                }
-            }
-        }
-    }
-    
-    class class2 {
-        constructor() {
-            var _this = 2;
-                ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            var x2 = {
-                doStuff: (callback) => () => {
-                    return callback(this);
-                }
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarInConstructor.js b/tests/baselines/reference/collisionThisExpressionAndLocalVarInConstructor.js
index ab60d6244a1..e5e2a92d9d1 100644
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarInConstructor.js
+++ b/tests/baselines/reference/collisionThisExpressionAndLocalVarInConstructor.js
@@ -24,11 +24,11 @@ class class2 {
 //// [collisionThisExpressionAndLocalVarInConstructor.js]
 var class1 = /** @class */ (function () {
     function class1() {
-        var _this = this;
+        var _this_1 = this;
         var x2 = {
             doStuff: function (callback) { return function () {
                 var _this = 2;
-                return callback(_this);
+                return callback(_this_1);
             }; }
         };
     }
@@ -36,11 +36,11 @@ var class1 = /** @class */ (function () {
 }());
 var class2 = /** @class */ (function () {
     function class2() {
-        var _this = this;
+        var _this_1 = this;
         var _this = 2;
         var x2 = {
             doStuff: function (callback) { return function () {
-                return callback(_this);
+                return callback(_this_1);
             }; }
         };
     }
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarInFunction.errors.txt b/tests/baselines/reference/collisionThisExpressionAndLocalVarInFunction.errors.txt
deleted file mode 100644
index 3dd4f6e31a3..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarInFunction.errors.txt
+++ /dev/null
@@ -1,13 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndLocalVarInFunction.ts(5,9): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndLocalVarInFunction.ts (1 errors) ====
-    var console: {
-        log(val: any);
-    }
-    function x() {
-        var _this = 5;
-            ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-        x => { console.log(this.x); };
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarInFunction.js b/tests/baselines/reference/collisionThisExpressionAndLocalVarInFunction.js
index 879dd83d778..27de7125b8e 100644
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarInFunction.js
+++ b/tests/baselines/reference/collisionThisExpressionAndLocalVarInFunction.js
@@ -10,7 +10,7 @@ function x() {
 //// [collisionThisExpressionAndLocalVarInFunction.js]
 var console;
 function x() {
-    var _this = this;
+    var _this_1 = this;
     var _this = 5;
-    (function (x) { console.log(_this.x); });
+    (function (x) { console.log(_this_1.x); });
 }
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarInLambda.errors.txt b/tests/baselines/reference/collisionThisExpressionAndLocalVarInLambda.errors.txt
deleted file mode 100644
index 3b6e8cb4cca..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarInLambda.errors.txt
+++ /dev/null
@@ -1,15 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndLocalVarInLambda.ts(5,13): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndLocalVarInLambda.ts (1 errors) ====
-    declare function alert(message?: any): void;
-    
-    var x = {
-        doStuff: (callback) => () => {
-            var _this = 2;
-                ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            return callback(this);
-        }
-    }
-    alert(x.doStuff(x => alert(x)));
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarInLambda.js b/tests/baselines/reference/collisionThisExpressionAndLocalVarInLambda.js
index e8b7a0db7f3..be2785ddfba 100644
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarInLambda.js
+++ b/tests/baselines/reference/collisionThisExpressionAndLocalVarInLambda.js
@@ -10,11 +10,11 @@ var x = {
 alert(x.doStuff(x => alert(x)));
 
 //// [collisionThisExpressionAndLocalVarInLambda.js]
-var _this = this;
+var _this_1 = this;
 var x = {
     doStuff: function (callback) { return function () {
         var _this = 2;
-        return callback(_this);
+        return callback(_this_1);
     }; }
 };
 alert(x.doStuff(function (x) { return alert(x); }));
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarInMethod.errors.txt b/tests/baselines/reference/collisionThisExpressionAndLocalVarInMethod.errors.txt
deleted file mode 100644
index 018f3bb49d2..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarInMethod.errors.txt
+++ /dev/null
@@ -1,27 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndLocalVarInMethod.ts(5,21): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndLocalVarInMethod.ts(11,13): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndLocalVarInMethod.ts (2 errors) ====
-    class a {
-        method1() {
-            return {
-                doStuff: (callback) => () => {
-                    var _this = 2;
-                        ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-                    return callback(this);
-                }
-            }
-        }
-        method2() {
-            var _this = 2;
-                ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            return {
-                doStuff: (callback) => () => {
-                    return callback(this);
-                }
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarInMethod.js b/tests/baselines/reference/collisionThisExpressionAndLocalVarInMethod.js
index 2d5de593909..16f288174a5 100644
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarInMethod.js
+++ b/tests/baselines/reference/collisionThisExpressionAndLocalVarInMethod.js
@@ -23,20 +23,20 @@ var a = /** @class */ (function () {
     function a() {
     }
     a.prototype.method1 = function () {
-        var _this = this;
+        var _this_1 = this;
         return {
             doStuff: function (callback) { return function () {
                 var _this = 2;
-                return callback(_this);
+                return callback(_this_1);
             }; }
         };
     };
     a.prototype.method2 = function () {
-        var _this = this;
+        var _this_1 = this;
         var _this = 2;
         return {
             doStuff: function (callback) { return function () {
-                return callback(_this);
+                return callback(_this_1);
             }; }
         };
     };
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarInProperty.errors.txt b/tests/baselines/reference/collisionThisExpressionAndLocalVarInProperty.errors.txt
deleted file mode 100644
index 4c166ac13ac..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarInProperty.errors.txt
+++ /dev/null
@@ -1,28 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndLocalVarInProperty.ts(4,17): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndLocalVarInProperty.ts(12,13): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndLocalVarInProperty.ts (2 errors) ====
-    class class1 {
-        public prop1 = {
-            doStuff: (callback) => () => {
-                var _this = 2;
-                    ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-                return callback(this);
-            }
-        }
-    }
-    
-    class class2 {
-        constructor() {
-            var _this = 2;
-                ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-        }
-        public prop1 = {
-            doStuff: (callback) => () => {
-                return callback(this);
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarInProperty.js b/tests/baselines/reference/collisionThisExpressionAndLocalVarInProperty.js
index 4ce4f08a778..70760396df6 100644
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarInProperty.js
+++ b/tests/baselines/reference/collisionThisExpressionAndLocalVarInProperty.js
@@ -22,11 +22,11 @@ class class2 {
 //// [collisionThisExpressionAndLocalVarInProperty.js]
 var class1 = /** @class */ (function () {
     function class1() {
-        var _this = this;
+        var _this_1 = this;
         this.prop1 = {
             doStuff: function (callback) { return function () {
                 var _this = 2;
-                return callback(_this);
+                return callback(_this_1);
             }; }
         };
     }
@@ -34,10 +34,10 @@ var class1 = /** @class */ (function () {
 }());
 var class2 = /** @class */ (function () {
     function class2() {
-        var _this = this;
+        var _this_1 = this;
         this.prop1 = {
             doStuff: function (callback) { return function () {
-                return callback(_this);
+                return callback(_this_1);
             }; }
         };
         var _this = 2;
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarWithSuperExperssion.errors.txt b/tests/baselines/reference/collisionThisExpressionAndLocalVarWithSuperExperssion.errors.txt
deleted file mode 100644
index df308b894f1..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarWithSuperExperssion.errors.txt
+++ /dev/null
@@ -1,27 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndLocalVarWithSuperExperssion.ts(7,13): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndLocalVarWithSuperExperssion.ts(14,17): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndLocalVarWithSuperExperssion.ts (2 errors) ====
-    class a {
-        public foo() {
-        }
-    }
-    class b extends a {
-        public foo() {
-            var _this = 10;
-                ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            var f = () => super.foo();
-        }
-    }
-    class b2 extends a {
-        public foo() {
-            var f = () => {
-                var _this = 10;
-                    ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-                return super.foo()
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndLocalVarWithSuperExperssion.js b/tests/baselines/reference/collisionThisExpressionAndLocalVarWithSuperExperssion.js
index a1bc5d36965..6e99ba3ba0c 100644
--- a/tests/baselines/reference/collisionThisExpressionAndLocalVarWithSuperExperssion.js
+++ b/tests/baselines/reference/collisionThisExpressionAndLocalVarWithSuperExperssion.js
@@ -42,9 +42,9 @@ var b = /** @class */ (function (_super) {
         return _super !== null && _super.apply(this, arguments) || this;
     }
     b.prototype.foo = function () {
-        var _this = this;
+        var _this_1 = this;
         var _this = 10;
-        var f = function () { return _super.prototype.foo.call(_this); };
+        var f = function () { return _super.prototype.foo.call(_this_1); };
     };
     return b;
 }(a));
@@ -54,10 +54,10 @@ var b2 = /** @class */ (function (_super) {
         return _super !== null && _super.apply(this, arguments) || this;
     }
     b2.prototype.foo = function () {
-        var _this = this;
+        var _this_1 = this;
         var f = function () {
             var _this = 10;
-            return _super.prototype.foo.call(_this);
+            return _super.prototype.foo.call(_this_1);
         };
     };
     return b2;
diff --git a/tests/baselines/reference/collisionThisExpressionAndModuleInGlobal.errors.txt b/tests/baselines/reference/collisionThisExpressionAndModuleInGlobal.errors.txt
deleted file mode 100644
index bcc719972dc..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndModuleInGlobal.errors.txt
+++ /dev/null
@@ -1,11 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndModuleInGlobal.ts(1,8): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndModuleInGlobal.ts (1 errors) ====
-    module _this { //Error
-           ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-        class c {
-        }
-    }
-    var f = () => this;
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndModuleInGlobal.js b/tests/baselines/reference/collisionThisExpressionAndModuleInGlobal.js
index 36dca587068..14627f19959 100644
--- a/tests/baselines/reference/collisionThisExpressionAndModuleInGlobal.js
+++ b/tests/baselines/reference/collisionThisExpressionAndModuleInGlobal.js
@@ -6,7 +6,7 @@ module _this { //Error
 var f = () => this;
 
 //// [collisionThisExpressionAndModuleInGlobal.js]
-var _this = this;
+var _this_1 = this;
 var _this;
 (function (_this) {
     var c = /** @class */ (function () {
@@ -15,4 +15,4 @@ var _this;
         return c;
     }());
 })(_this || (_this = {}));
-var f = function () { return _this; };
+var f = function () { return _this_1; };
diff --git a/tests/baselines/reference/collisionThisExpressionAndNameResolution.errors.txt b/tests/baselines/reference/collisionThisExpressionAndNameResolution.errors.txt
deleted file mode 100644
index 76875f46e46..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndNameResolution.errors.txt
+++ /dev/null
@@ -1,18 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndNameResolution.ts(8,25): error TS2400: Expression resolves to variable declaration '_this' that compiler uses to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndNameResolution.ts (1 errors) ====
-    var console : {
-        log(message: any);
-    }
-    class Foo {
-        x() {
-            var _this = 10; // Local var. No this capture in x(), so no conflict.
-            function inner() {
-                console.log(_this); // Error as this doesnt not resolve to user defined _this
-                            ~~~~~
-!!! error TS2400: Expression resolves to variable declaration '_this' that compiler uses to capture 'this' reference.
-                return x => this;   // New scope.  So should inject new _this capture into function inner
-            }
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndNameResolution.js b/tests/baselines/reference/collisionThisExpressionAndNameResolution.js
index 2e981ad33d9..380449edc21 100644
--- a/tests/baselines/reference/collisionThisExpressionAndNameResolution.js
+++ b/tests/baselines/reference/collisionThisExpressionAndNameResolution.js
@@ -20,9 +20,9 @@ var Foo = /** @class */ (function () {
     Foo.prototype.x = function () {
         var _this = 10; // Local var. No this capture in x(), so no conflict.
         function inner() {
-            var _this = this;
+            var _this_1 = this;
             console.log(_this); // Error as this doesnt not resolve to user defined _this
-            return function (x) { return _this; }; // New scope.  So should inject new _this capture into function inner
+            return function (x) { return _this_1; }; // New scope.  So should inject new _this capture into function inner
         }
     };
     return Foo;
diff --git a/tests/baselines/reference/collisionThisExpressionAndParameter.errors.txt b/tests/baselines/reference/collisionThisExpressionAndParameter.errors.txt
deleted file mode 100644
index d2bf00483e4..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndParameter.errors.txt
+++ /dev/null
@@ -1,120 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndParameter.ts(4,24): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndParameter.ts(9,22): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndParameter.ts(13,7): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndParameter.ts(34,17): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndParameter.ts(46,13): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndParameter.ts(59,17): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndParameter.ts(69,7): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndParameter.ts(81,13): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndParameter.ts (8 errors) ====
-    class Foo {
-        x() {
-            var _this = 10; // Local var. No this capture in x(), so no conflict.
-            function inner(_this: number) { // Error 
-                           ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-                return x => this;   // New scope.  So should inject new _this capture into function inner
-            }
-        }
-        y() {
-            var lamda = (_this: number) => { // Error 
-                         ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-                return x => this;   // New scope.  So should inject new _this capture
-            }
-        }
-        z(_this: number) { // Error 
-          ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            var lambda = () => {
-                return x => this;   // New scope.  So should inject new _this capture
-            }
-        }
-    
-        x1() {
-            var _this = 10; // Local var. No this capture in x(), so no conflict.
-            function inner(_this: number) { // No Error 
-            }
-        }
-        y1() {
-            var lamda = (_this: number) => { // No Error 
-            }
-        }
-        z1(_this: number) { // No Error 
-            var lambda = () => {
-            }
-        }
-    }
-    class Foo1 {
-        constructor(_this: number) { // Error
-                    ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            var x2 = {
-                doStuff: (callback) => () => {
-                    return callback(this);
-                }
-            }
-        }
-    }
-    declare var console: {
-        log(msg: any);
-    }
-    
-    function f1(_this: number) {
-                ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-        x => { console.log(this.x); };
-    }
-    
-    declare class Foo2 {
-        constructor(_this: number); // no error - no code gen
-        z(_this: number); // no error - no code gen
-    }
-    declare function f2(_this: number); // no error
-    
-    class Foo3 {
-        constructor(_this: string); // no code gen - no error
-        constructor(_this: number); // no code gen - no error
-        constructor(_this: any) { // Error
-                    ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            var x2 = {
-                doStuff: (callback) => () => {
-                    return callback(this);
-                }
-            }
-        }
-    
-        z(_this: string); // no code gen - no error
-        z(_this: number); // no code gen - no error
-        z(_this: any) { // Error 
-          ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            var lambda = () => {
-                return x => this;   // New scope.  So should inject new _this capture
-            }
-        }
-    }
-    declare var console: {
-        log(msg: any);
-    }
-    
-    function f3(_this: number); // no code gen - no error
-    function f3(_this: string); // no code gen - no error
-    function f3(_this: any) {
-                ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-        x => { console.log(this.x); };
-    }
-    
-    declare class Foo4 {
-        constructor(_this: string); // no code gen - no error
-        constructor(_this: number); // no code gen - no error
-        z(_this: string); // no code gen - no error
-        z(_this: number); // no code gen - no error
-    }
-    
-    declare function f4(_this: number); // no code gen - no error
-    declare function f4(_this: string); // no code gen - no error
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndParameter.js b/tests/baselines/reference/collisionThisExpressionAndParameter.js
index acaceb9170b..b6367480e02 100644
--- a/tests/baselines/reference/collisionThisExpressionAndParameter.js
+++ b/tests/baselines/reference/collisionThisExpressionAndParameter.js
@@ -100,20 +100,20 @@ var Foo = /** @class */ (function () {
     Foo.prototype.x = function () {
         var _this = 10; // Local var. No this capture in x(), so no conflict.
         function inner(_this) {
-            var _this = this;
-            return function (x) { return _this; }; // New scope.  So should inject new _this capture into function inner
+            var _this_1 = this;
+            return function (x) { return _this_1; }; // New scope.  So should inject new _this capture into function inner
         }
     };
     Foo.prototype.y = function () {
-        var _this = this;
+        var _this_1 = this;
         var lamda = function (_this) {
-            return function (x) { return _this; }; // New scope.  So should inject new _this capture
+            return function (x) { return _this_1; }; // New scope.  So should inject new _this capture
         };
     };
     Foo.prototype.z = function (_this) {
-        var _this = this;
+        var _this_1 = this;
         var lambda = function () {
-            return function (x) { return _this; }; // New scope.  So should inject new _this capture
+            return function (x) { return _this_1; }; // New scope.  So should inject new _this capture
         };
     };
     Foo.prototype.x1 = function () {
@@ -133,37 +133,37 @@ var Foo = /** @class */ (function () {
 }());
 var Foo1 = /** @class */ (function () {
     function Foo1(_this) {
-        var _this = this;
+        var _this_1 = this;
         var x2 = {
             doStuff: function (callback) { return function () {
-                return callback(_this);
+                return callback(_this_1);
             }; }
         };
     }
     return Foo1;
 }());
 function f1(_this) {
-    var _this = this;
-    (function (x) { console.log(_this.x); });
+    var _this_1 = this;
+    (function (x) { console.log(_this_1.x); });
 }
 var Foo3 = /** @class */ (function () {
     function Foo3(_this) {
-        var _this = this;
+        var _this_1 = this;
         var x2 = {
             doStuff: function (callback) { return function () {
-                return callback(_this);
+                return callback(_this_1);
             }; }
         };
     }
     Foo3.prototype.z = function (_this) {
-        var _this = this;
+        var _this_1 = this;
         var lambda = function () {
-            return function (x) { return _this; }; // New scope.  So should inject new _this capture
+            return function (x) { return _this_1; }; // New scope.  So should inject new _this capture
         };
     };
     return Foo3;
 }());
 function f3(_this) {
-    var _this = this;
-    (function (x) { console.log(_this.x); });
+    var _this_1 = this;
+    (function (x) { console.log(_this_1.x); });
 }
diff --git a/tests/baselines/reference/collisionThisExpressionAndPropertyNameAsConstuctorParameter.errors.txt b/tests/baselines/reference/collisionThisExpressionAndPropertyNameAsConstuctorParameter.errors.txt
deleted file mode 100644
index fda0ebc930d..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndPropertyNameAsConstuctorParameter.errors.txt
+++ /dev/null
@@ -1,50 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndPropertyNameAsConstuctorParameter.ts(2,17): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndPropertyNameAsConstuctorParameter.ts(10,25): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndPropertyNameAsConstuctorParameter.ts(20,17): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-tests/cases/compiler/collisionThisExpressionAndPropertyNameAsConstuctorParameter.ts(30,25): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndPropertyNameAsConstuctorParameter.ts (4 errors) ====
-    class Foo2 {
-        constructor(_this: number) { //Error
-                    ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            var lambda = () => {
-                return x => this;   // New scope.  So should inject new _this capture
-            }
-        }
-    }
-    
-    class Foo3 {
-        constructor(private _this: number) { // Error
-                            ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            var lambda = () => {
-                return x => this;   // New scope.  So should inject new _this capture
-            }
-        }
-    }   
-    
-    class Foo4 {
-        constructor(_this: number); // No code gen - no error
-        constructor(_this: string); // No code gen - no error
-        constructor(_this: any) { // Error
-                    ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            var lambda = () => {
-                return x => this;   // New scope.  So should inject new _this capture
-            }
-        }
-    }  
-    
-    class Foo5 {
-        constructor(_this: number); // No code gen - no error
-        constructor(_this: string); // No code gen - no error
-        constructor(private _this: any) { // Error
-                            ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            var lambda = () => {
-                return x => this;   // New scope.  So should inject new _this capture
-            }
-        }
-    }  
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndPropertyNameAsConstuctorParameter.js b/tests/baselines/reference/collisionThisExpressionAndPropertyNameAsConstuctorParameter.js
index 3758cfdecda..360b147ad24 100644
--- a/tests/baselines/reference/collisionThisExpressionAndPropertyNameAsConstuctorParameter.js
+++ b/tests/baselines/reference/collisionThisExpressionAndPropertyNameAsConstuctorParameter.js
@@ -38,38 +38,38 @@ class Foo5 {
 //// [collisionThisExpressionAndPropertyNameAsConstuctorParameter.js]
 var Foo2 = /** @class */ (function () {
     function Foo2(_this) {
-        var _this = this;
+        var _this_1 = this;
         var lambda = function () {
-            return function (x) { return _this; }; // New scope.  So should inject new _this capture
+            return function (x) { return _this_1; }; // New scope.  So should inject new _this capture
         };
     }
     return Foo2;
 }());
 var Foo3 = /** @class */ (function () {
     function Foo3(_this) {
-        var _this = this;
+        var _this_1 = this;
         this._this = _this;
         var lambda = function () {
-            return function (x) { return _this; }; // New scope.  So should inject new _this capture
+            return function (x) { return _this_1; }; // New scope.  So should inject new _this capture
         };
     }
     return Foo3;
 }());
 var Foo4 = /** @class */ (function () {
     function Foo4(_this) {
-        var _this = this;
+        var _this_1 = this;
         var lambda = function () {
-            return function (x) { return _this; }; // New scope.  So should inject new _this capture
+            return function (x) { return _this_1; }; // New scope.  So should inject new _this capture
         };
     }
     return Foo4;
 }());
 var Foo5 = /** @class */ (function () {
     function Foo5(_this) {
-        var _this = this;
+        var _this_1 = this;
         this._this = _this;
         var lambda = function () {
-            return function (x) { return _this; }; // New scope.  So should inject new _this capture
+            return function (x) { return _this_1; }; // New scope.  So should inject new _this capture
         };
     }
     return Foo5;
diff --git a/tests/baselines/reference/collisionThisExpressionAndVarInGlobal.errors.txt b/tests/baselines/reference/collisionThisExpressionAndVarInGlobal.errors.txt
deleted file mode 100644
index 31e37f9c255..00000000000
--- a/tests/baselines/reference/collisionThisExpressionAndVarInGlobal.errors.txt
+++ /dev/null
@@ -1,8 +0,0 @@
-tests/cases/compiler/collisionThisExpressionAndVarInGlobal.ts(1,5): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/collisionThisExpressionAndVarInGlobal.ts (1 errors) ====
-    var _this = 1;
-        ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-    var f = () => this;
\ No newline at end of file
diff --git a/tests/baselines/reference/collisionThisExpressionAndVarInGlobal.js b/tests/baselines/reference/collisionThisExpressionAndVarInGlobal.js
index 7057ad7ac55..954b9c47d24 100644
--- a/tests/baselines/reference/collisionThisExpressionAndVarInGlobal.js
+++ b/tests/baselines/reference/collisionThisExpressionAndVarInGlobal.js
@@ -3,6 +3,6 @@ var _this = 1;
 var f = () => this;
 
 //// [collisionThisExpressionAndVarInGlobal.js]
-var _this = this;
+var _this_1 = this;
 var _this = 1;
-var f = function () { return _this; };
+var f = function () { return _this_1; };
diff --git a/tests/baselines/reference/moduleNoneOutFile.js b/tests/baselines/reference/moduleNoneOutFile.js
new file mode 100644
index 00000000000..865e9fbae91
--- /dev/null
+++ b/tests/baselines/reference/moduleNoneOutFile.js
@@ -0,0 +1,30 @@
+//// [tests/cases/compiler/moduleNoneOutFile.ts] ////
+
+//// [first.ts]
+class Foo {}
+//// [second.ts]
+class Bar extends Foo {}
+
+//// [bundle.js]
+var Foo = /** @class */ (function () {
+    function Foo() {
+    }
+    return Foo;
+}());
+var __extends = (this && this.__extends) || (function () {
+    var extendStatics = Object.setPrototypeOf ||
+        ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
+        function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
+    return function (d, b) {
+        extendStatics(d, b);
+        function __() { this.constructor = d; }
+        d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
+    };
+})();
+var Bar = /** @class */ (function (_super) {
+    __extends(Bar, _super);
+    function Bar() {
+        return _super !== null && _super.apply(this, arguments) || this;
+    }
+    return Bar;
+}(Foo));
diff --git a/tests/baselines/reference/moduleNoneOutFile.symbols b/tests/baselines/reference/moduleNoneOutFile.symbols
new file mode 100644
index 00000000000..e6b770085da
--- /dev/null
+++ b/tests/baselines/reference/moduleNoneOutFile.symbols
@@ -0,0 +1,9 @@
+=== tests/cases/compiler/first.ts ===
+class Foo {}
+>Foo : Symbol(Foo, Decl(first.ts, 0, 0))
+
+=== tests/cases/compiler/second.ts ===
+class Bar extends Foo {}
+>Bar : Symbol(Bar, Decl(second.ts, 0, 0))
+>Foo : Symbol(Foo, Decl(first.ts, 0, 0))
+
diff --git a/tests/baselines/reference/moduleNoneOutFile.types b/tests/baselines/reference/moduleNoneOutFile.types
new file mode 100644
index 00000000000..0748898110c
--- /dev/null
+++ b/tests/baselines/reference/moduleNoneOutFile.types
@@ -0,0 +1,9 @@
+=== tests/cases/compiler/first.ts ===
+class Foo {}
+>Foo : Foo
+
+=== tests/cases/compiler/second.ts ===
+class Bar extends Foo {}
+>Bar : Bar
+>Foo : Foo
+
diff --git a/tests/baselines/reference/noCollisionThisExpressionInFunctionAndVarInGlobal.js b/tests/baselines/reference/noCollisionThisExpressionInFunctionAndVarInGlobal.js
index b3677681822..a1e76c48212 100644
--- a/tests/baselines/reference/noCollisionThisExpressionInFunctionAndVarInGlobal.js
+++ b/tests/baselines/reference/noCollisionThisExpressionInFunctionAndVarInGlobal.js
@@ -11,6 +11,6 @@ function x() {
 var console;
 var _this = 5;
 function x() {
-    var _this = this;
-    (function (x) { console.log(_this); });
+    var _this_1 = this;
+    (function (x) { console.log(_this_1); });
 }
diff --git a/tests/baselines/reference/underscoreThisInDerivedClass01.errors.txt b/tests/baselines/reference/underscoreThisInDerivedClass01.errors.txt
deleted file mode 100644
index 3828825cb6b..00000000000
--- a/tests/baselines/reference/underscoreThisInDerivedClass01.errors.txt
+++ /dev/null
@@ -1,29 +0,0 @@
-tests/cases/compiler/underscoreThisInDerivedClass01.ts(20,13): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/underscoreThisInDerivedClass01.ts (1 errors) ====
-    // @target es5
-    
-    // Original test intent:
-    // When arrow functions capture 'this', the lexical 'this' owner
-    // currently captures 'this' using a variable named '_this'.
-    // That means that '_this' becomes a reserved identifier in certain places.
-    //
-    // Constructors have adopted the same identifier name ('_this')
-    // for capturing any potential return values from super calls,
-    // so we expect the same behavior.
-    
-    class C {
-        constructor() {
-            return {};
-        }
-    }
-    
-    class D extends C {
-        constructor() {
-            var _this = "uh-oh?";
-                ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-            super();
-        }
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/underscoreThisInDerivedClass01.js b/tests/baselines/reference/underscoreThisInDerivedClass01.js
index 4663b4f75ec..f544fa7cb7d 100644
--- a/tests/baselines/reference/underscoreThisInDerivedClass01.js
+++ b/tests/baselines/reference/underscoreThisInDerivedClass01.js
@@ -52,10 +52,10 @@ var C = /** @class */ (function () {
 var D = /** @class */ (function (_super) {
     __extends(D, _super);
     function D() {
-        var _this = this;
+        var _this_1 = this;
         var _this = "uh-oh?";
-        _this = _super.call(this) || this;
-        return _this;
+        _this_1 = _super.call(this) || this;
+        return _this_1;
     }
     return D;
 }(C));
diff --git a/tests/baselines/reference/underscoreThisInDerivedClass02.errors.txt b/tests/baselines/reference/underscoreThisInDerivedClass02.errors.txt
deleted file mode 100644
index 5569ebf1af6..00000000000
--- a/tests/baselines/reference/underscoreThisInDerivedClass02.errors.txt
+++ /dev/null
@@ -1,28 +0,0 @@
-tests/cases/compiler/underscoreThisInDerivedClass02.ts(14,5): error TS2377: Constructors for derived classes must contain a 'super' call.
-tests/cases/compiler/underscoreThisInDerivedClass02.ts(15,13): error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-
-
-==== tests/cases/compiler/underscoreThisInDerivedClass02.ts (2 errors) ====
-    // @target es5
-    
-    // Original test intent:
-    // Errors on '_this' should be reported in derived constructors,
-    // even if 'super()' is not called.
-    
-    class C {
-        constructor() {
-            return {};
-        }
-    }
-    
-    class D extends C {
-        constructor() {
-        ~~~~~~~~~~~~~~~
-            var _this = "uh-oh?";
-    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-                ~~~~~
-!!! error TS2399: Duplicate identifier '_this'. Compiler uses variable declaration '_this' to capture 'this' reference.
-        }
-    ~~~~~
-!!! error TS2377: Constructors for derived classes must contain a 'super' call.
-    }
\ No newline at end of file
diff --git a/tests/baselines/reference/underscoreThisInDerivedClass02.js b/tests/baselines/reference/underscoreThisInDerivedClass02.js
index d88f8eba101..4b0ef6e1e73 100644
--- a/tests/baselines/reference/underscoreThisInDerivedClass02.js
+++ b/tests/baselines/reference/underscoreThisInDerivedClass02.js
@@ -13,6 +13,7 @@ class C {
 
 class D extends C {
     constructor() {
+        super();
         var _this = "uh-oh?";
     }
 }
@@ -41,9 +42,9 @@ var C = /** @class */ (function () {
 var D = /** @class */ (function (_super) {
     __extends(D, _super);
     function D() {
-        var _this = this;
+        var _this_1 = _super.call(this) || this;
         var _this = "uh-oh?";
-        return _this;
+        return _this_1;
     }
     return D;
 }(C));
diff --git a/tests/baselines/reference/underscoreThisInDerivedClass02.symbols b/tests/baselines/reference/underscoreThisInDerivedClass02.symbols
index dd2a2df81b7..5ccf39a1375 100644
--- a/tests/baselines/reference/underscoreThisInDerivedClass02.symbols
+++ b/tests/baselines/reference/underscoreThisInDerivedClass02.symbols
@@ -18,7 +18,10 @@ class D extends C {
 >C : Symbol(C, Decl(underscoreThisInDerivedClass02.ts, 0, 0))
 
     constructor() {
+        super();
+>super : Symbol(C, Decl(underscoreThisInDerivedClass02.ts, 0, 0))
+
         var _this = "uh-oh?";
->_this : Symbol(_this, Decl(underscoreThisInDerivedClass02.ts, 14, 11))
+>_this : Symbol(_this, Decl(underscoreThisInDerivedClass02.ts, 15, 11))
     }
 }
diff --git a/tests/baselines/reference/underscoreThisInDerivedClass02.types b/tests/baselines/reference/underscoreThisInDerivedClass02.types
index 3b12cdc0b05..0c206e0887c 100644
--- a/tests/baselines/reference/underscoreThisInDerivedClass02.types
+++ b/tests/baselines/reference/underscoreThisInDerivedClass02.types
@@ -19,6 +19,10 @@ class D extends C {
 >C : C
 
     constructor() {
+        super();
+>super() : void
+>super : typeof C
+
         var _this = "uh-oh?";
 >_this : string
 >"uh-oh?" : "uh-oh?"
diff --git a/tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts b/tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts
index aa635990b94..14252622a4a 100644
--- a/tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts
+++ b/tests/cases/compiler/collisionSuperAndLocalFunctionInAccessors.ts
@@ -1,3 +1,4 @@
+// @target: es5
 function _super() { // No error
 }
 class Foo {
diff --git a/tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts b/tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts
index e8a1e1e417b..0f45a469abd 100644
--- a/tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts
+++ b/tests/cases/compiler/collisionSuperAndLocalVarInAccessors.ts
@@ -1,3 +1,4 @@
+// @target: es5
 var _super = 10; // No Error
 class Foo {
     get prop1(): number {
diff --git a/tests/cases/compiler/collisionSuperAndParameter.ts b/tests/cases/compiler/collisionSuperAndParameter.ts
index 4e3c0c5832d..88c0235a5b5 100644
--- a/tests/cases/compiler/collisionSuperAndParameter.ts
+++ b/tests/cases/compiler/collisionSuperAndParameter.ts
@@ -1,3 +1,4 @@
+// @target: es5
 class Foo {
     a() {
         var lamda = (_super: number) => { // No Error 
diff --git a/tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts b/tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts
index 23df5b01b94..d3546733e10 100644
--- a/tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts
+++ b/tests/cases/compiler/collisionThisExpressionAndLocalVarInAccessors.ts
@@ -1,3 +1,4 @@
+// @target: es5
 class class1 {
     get a(): number {
         var x2 = {
diff --git a/tests/cases/compiler/moduleNoneOutFile.ts b/tests/cases/compiler/moduleNoneOutFile.ts
new file mode 100644
index 00000000000..f3213619fcf
--- /dev/null
+++ b/tests/cases/compiler/moduleNoneOutFile.ts
@@ -0,0 +1,6 @@
+// @module: none
+// @outFile: bundle.js
+// @filename: first.ts
+class Foo {}
+// @filename: second.ts
+class Bar extends Foo {}
\ No newline at end of file
diff --git a/tests/cases/compiler/underscoreThisInDerivedClass02.ts b/tests/cases/compiler/underscoreThisInDerivedClass02.ts
index da197258a73..66fe1389392 100644
--- a/tests/cases/compiler/underscoreThisInDerivedClass02.ts
+++ b/tests/cases/compiler/underscoreThisInDerivedClass02.ts
@@ -12,6 +12,7 @@ class C {
 
 class D extends C {
     constructor() {
+        super();
         var _this = "uh-oh?";
     }
 }
\ No newline at end of file
diff --git a/tests/cases/conformance/async/es2017/asyncMethodWithSuperConflict_es6.ts b/tests/cases/conformance/async/es2017/asyncMethodWithSuperConflict_es6.ts
new file mode 100644
index 00000000000..364f0264b23
--- /dev/null
+++ b/tests/cases/conformance/async/es2017/asyncMethodWithSuperConflict_es6.ts
@@ -0,0 +1,53 @@
+// @target: es6
+class A {
+    x() {
+    }
+}
+
+class B extends A {
+    // async method with only call/get on 'super' does not require a binding
+    async simple() {
+        const _super = null;
+        // call with property access
+        super.x();
+
+        // call with element access
+        super["x"]();
+
+        // property access (read)
+        const a = super.x;
+
+        // element access (read)
+        const b = super["x"];
+    }
+
+    // async method with assignment/destructuring on 'super' requires a binding
+    async advanced() {
+        const _super = null;
+        const f = () => {};
+
+        // call with property access
+        super.x();
+
+        // call with element access
+        super["x"]();
+
+        // property access (read)
+        const a = super.x;
+
+        // element access (read)
+        const b = super["x"];
+
+        // property access (assign)
+        super.x = f;
+
+        // element access (assign)
+        super["x"] = f;
+
+        // destructuring assign with property access
+        ({ f: super.x } = { f });
+
+        // destructuring assign with element access
+        ({ f: super["x"] } = { f });
+    }
+}
\ No newline at end of file