diff --git a/src/compiler/binder.ts b/src/compiler/binder.ts
index 3387c4860c7..2e141e720df 100644
--- a/src/compiler/binder.ts
+++ b/src/compiler/binder.ts
@@ -778,7 +778,7 @@ namespace ts {
         function isNarrowableReference(expr: Expression): boolean {
             return expr.kind === SyntaxKind.Identifier || expr.kind === SyntaxKind.ThisKeyword || expr.kind === SyntaxKind.SuperKeyword ||
                 (isPropertyAccessExpression(expr) || isNonNullExpression(expr) || isParenthesizedExpression(expr)) && isNarrowableReference(expr.expression) ||
-                isElementAccessExpression(expr) && expr.argumentExpression &&
+                isElementAccessExpression(expr) &&
                 (isStringLiteral(expr.argumentExpression) || isNumericLiteral(expr.argumentExpression)) &&
                 isNarrowableReference(expr.expression);
         }
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 5d52dd9b69b..8d166c39888 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -384,11 +384,11 @@ namespace ts {
             typeToTypeNode: nodeBuilder.typeToTypeNode,
             indexInfoToIndexSignatureDeclaration: nodeBuilder.indexInfoToIndexSignatureDeclaration,
             signatureToSignatureDeclaration: nodeBuilder.signatureToSignatureDeclaration,
-            symbolToEntityName: nodeBuilder.symbolToEntityName as (symbol: Symbol, meaning: SymbolFlags, enclosingDeclaration?: Node, flags?: NodeBuilderFlags) => EntityName, // TODO: GH#18217
-            symbolToExpression: nodeBuilder.symbolToExpression as (symbol: Symbol, meaning: SymbolFlags, enclosingDeclaration?: Node, flags?: NodeBuilderFlags) => Expression, // TODO: GH#18217
+            symbolToEntityName: nodeBuilder.symbolToEntityName,
+            symbolToExpression: nodeBuilder.symbolToExpression,
             symbolToTypeParameterDeclarations: nodeBuilder.symbolToTypeParameterDeclarations,
-            symbolToParameterDeclaration: nodeBuilder.symbolToParameterDeclaration as (symbol: Symbol, enclosingDeclaration?: Node, flags?: NodeBuilderFlags) => ParameterDeclaration, // TODO: GH#18217
-            typeParameterToDeclaration: nodeBuilder.typeParameterToDeclaration as (parameter: TypeParameter, enclosingDeclaration?: Node, flags?: NodeBuilderFlags) => TypeParameterDeclaration, // TODO: GH#18217
+            symbolToParameterDeclaration: nodeBuilder.symbolToParameterDeclaration,
+            typeParameterToDeclaration: nodeBuilder.typeParameterToDeclaration,
             getSymbolsInScope: (location, meaning) => {
                 location = getParseTreeNode(location);
                 return location ? getSymbolsInScope(location, meaning) : [];
@@ -557,7 +557,7 @@ namespace ts {
             },
             getJsxNamespace: n => unescapeLeadingUnderscores(getJsxNamespace(n)),
             getAccessibleSymbolChain,
-            getTypePredicateOfSignature: getTypePredicateOfSignature as (signature: Signature) => TypePredicate, // TODO: GH#18217
+            getTypePredicateOfSignature,
             resolveExternalModuleSymbol,
             tryGetThisTypeAt: (node, includeGlobalThis) => {
                 node = getParseTreeNode(node);
@@ -884,7 +884,7 @@ namespace ts {
                     }
                     const jsxPragma = file.pragmas.get("jsx");
                     if (jsxPragma) {
-                        const chosenpragma: any = isArray(jsxPragma) ? jsxPragma[0] : jsxPragma; // TODO: GH#18217
+                        const chosenpragma = isArray(jsxPragma) ? jsxPragma[0] : jsxPragma;
                         file.localJsxFactory = parseIsolatedEntityName(chosenpragma.arguments.factory, languageVersion);
                         if (file.localJsxFactory) {
                             return file.localJsxNamespace = getFirstIdentifier(file.localJsxFactory).escapedText;
@@ -2564,10 +2564,6 @@ namespace ts {
         }
 
         function resolveExternalModule(location: Node, moduleReference: string, moduleNotFoundError: DiagnosticMessage | undefined, errorNode: Node, isForAugmentation = false): Symbol | undefined {
-            if (moduleReference === undefined) {
-                return;
-            }
-
             if (startsWith(moduleReference, "@types/")) {
                 const diag = Diagnostics.Cannot_import_type_declaration_files_Consider_importing_0_instead_of_1;
                 const withoutAtTypePrefix = removePrefix(moduleReference, "@types/");
@@ -3265,12 +3261,12 @@ namespace ts {
             return access.accessibility === SymbolAccessibility.Accessible;
         }
 
-        function isValueSymbolAccessible(typeSymbol: Symbol, enclosingDeclaration: Node): boolean {
+        function isValueSymbolAccessible(typeSymbol: Symbol, enclosingDeclaration: Node | undefined): boolean {
             const access = isSymbolAccessible(typeSymbol, enclosingDeclaration, SymbolFlags.Value, /*shouldComputeAliasesToMakeVisible*/ false);
             return access.accessibility === SymbolAccessibility.Accessible;
         }
 
-        function isAnySymbolAccessible(symbols: Symbol[] | undefined, enclosingDeclaration: Node, initialSymbol: Symbol, meaning: SymbolFlags, shouldComputeAliasesToMakeVisible: boolean): SymbolAccessibilityResult | undefined {
+        function isAnySymbolAccessible(symbols: Symbol[] | undefined, enclosingDeclaration: Node | undefined, initialSymbol: Symbol, meaning: SymbolFlags, shouldComputeAliasesToMakeVisible: boolean): SymbolAccessibilityResult | undefined {
             if (!length(symbols)) return;
 
             let hadAccessibleChain: Symbol | undefined;
@@ -3544,7 +3540,7 @@ namespace ts {
                 typeToTypeNode: (type: Type, enclosingDeclaration?: Node, flags?: NodeBuilderFlags, tracker?: SymbolTracker) =>
                     withContext(enclosingDeclaration, flags, tracker, context => typeToTypeNodeHelper(type, context)),
                 indexInfoToIndexSignatureDeclaration: (indexInfo: IndexInfo, kind: IndexKind, enclosingDeclaration?: Node, flags?: NodeBuilderFlags, tracker?: SymbolTracker) =>
-                    withContext(enclosingDeclaration, flags, tracker, context => indexInfoToIndexSignatureDeclarationHelper(indexInfo, kind, context))!, // TODO: GH#18217
+                    withContext(enclosingDeclaration, flags, tracker, context => indexInfoToIndexSignatureDeclarationHelper(indexInfo, kind, context)),
                 signatureToSignatureDeclaration: (signature: Signature, kind: SyntaxKind, enclosingDeclaration?: Node, flags?: NodeBuilderFlags, tracker?: SymbolTracker) =>
                     withContext(enclosingDeclaration, flags, tracker, context => signatureToSignatureDeclarationHelper(signature, kind, context)),
                 symbolToEntityName: (symbol: Symbol, meaning: SymbolFlags, enclosingDeclaration?: Node, flags?: NodeBuilderFlags, tracker?: SymbolTracker) =>
@@ -3653,7 +3649,7 @@ namespace ts {
                 }
                 if (type.flags & TypeFlags.UniqueESSymbol) {
                     if (!(context.flags & NodeBuilderFlags.AllowUniqueESSymbolType)) {
-                        if (isValueSymbolAccessible(type.symbol, context.enclosingDeclaration!)) {
+                        if (isValueSymbolAccessible(type.symbol, context.enclosingDeclaration)) {
                             context.approximateLength += 6;
                             return symbolToTypeNode(type.symbol, context, SymbolFlags.Value);
                         }
@@ -3864,7 +3860,7 @@ namespace ts {
                         if (isStaticMethodSymbol || isNonLocalFunctionSymbol) {
                             // typeof is allowed only for static/non local functions
                             return (!!(context.flags & NodeBuilderFlags.UseTypeOfFunction) || (context.visitedTypes && context.visitedTypes.has(typeId))) && // it is type of the symbol uses itself recursively
-                                (!(context.flags & NodeBuilderFlags.UseStructuralFallback) || isValueSymbolAccessible(symbol, context.enclosingDeclaration!)); // TODO: GH#18217 // And the build is going to succeed without visibility error or there is no structural fallback allowed
+                                (!(context.flags & NodeBuilderFlags.UseStructuralFallback) || isValueSymbolAccessible(symbol, context.enclosingDeclaration)); // And the build is going to succeed without visibility error or there is no structural fallback allowed
                         }
                     }
                 }
@@ -3941,7 +3937,7 @@ namespace ts {
                     else if (context.flags & NodeBuilderFlags.WriteClassExpressionAsTypeLiteral &&
                         type.symbol.valueDeclaration &&
                         isClassLike(type.symbol.valueDeclaration) &&
-                        !isValueSymbolAccessible(type.symbol, context.enclosingDeclaration!)
+                        !isValueSymbolAccessible(type.symbol, context.enclosingDeclaration)
                     ) {
                         return createAnonymousTypeNode(type);
                     }
@@ -7159,7 +7155,7 @@ namespace ts {
             const baseConstructorType = getBaseConstructorTypeOfClass(classType);
             const baseSignatures = getSignaturesOfType(baseConstructorType, SignatureKind.Construct);
             if (baseSignatures.length === 0) {
-                return [createSignature(undefined, classType.localTypeParameters, undefined, emptyArray, classType, /*resolvedTypePredicate*/ undefined, 0, /*hasRestParameter*/ false, /*hasLiteralTypes*/ false)]; // TODO: GH#18217
+                return [createSignature(undefined, classType.localTypeParameters, undefined, emptyArray, classType, /*resolvedTypePredicate*/ undefined, 0, /*hasRestParameter*/ false, /*hasLiteralTypes*/ false)];
             }
             const baseTypeNode = getBaseTypeNodeOfClass(classType)!;
             const isJavaScript = isInJSFile(baseTypeNode);
@@ -10229,9 +10225,11 @@ namespace ts {
                     case SyntaxKind.ReadonlyKeyword:
                         links.resolvedType = getTypeFromTypeNode(node.type);
                         break;
+                    default:
+                        throw Debug.assertNever(node.operator);
                 }
             }
-            return links.resolvedType!; // TODO: GH#18217
+            return links.resolvedType;
         }
 
         function createIndexedAccessType(objectType: Type, indexType: Type) {
@@ -10813,11 +10811,11 @@ namespace ts {
                         getNodeLinks(current.parent).resolvedSymbol = next;
                         currentNamespace = next;
                     }
-                    resolveImportSymbolType(node, links, currentNamespace, targetMeaning);
+                    links.resolvedType = resolveImportSymbolType(node, links, currentNamespace, targetMeaning);
                 }
                 else {
                     if (moduleSymbol.flags & targetMeaning) {
-                        resolveImportSymbolType(node, links, moduleSymbol, targetMeaning);
+                        links.resolvedType = resolveImportSymbolType(node, links, moduleSymbol, targetMeaning);
                     }
                     else {
                         const errorMessage = targetMeaning === SymbolFlags.Value
@@ -10831,17 +10829,17 @@ namespace ts {
                     }
                 }
             }
-            return links.resolvedType!; // TODO: GH#18217
+            return links.resolvedType;
         }
 
         function resolveImportSymbolType(node: ImportTypeNode, links: NodeLinks, symbol: Symbol, meaning: SymbolFlags) {
             const resolvedSymbol = resolveSymbol(symbol);
             links.resolvedSymbol = resolvedSymbol;
             if (meaning === SymbolFlags.Value) {
-                return links.resolvedType = getTypeOfSymbol(symbol); // intentionally doesn't use resolved symbol so type is cached as expected on the alias
+                return getTypeOfSymbol(symbol); // intentionally doesn't use resolved symbol so type is cached as expected on the alias
             }
             else {
-                return links.resolvedType = getTypeReferenceType(node, resolvedSymbol); // getTypeReferenceType doesn't handle aliases - it must get the resolved symbol
+                return getTypeReferenceType(node, resolvedSymbol); // getTypeReferenceType doesn't handle aliases - it must get the resolved symbol
             }
         }
 
@@ -14204,7 +14202,7 @@ namespace ts {
                 if (isGenericMappedType(source)) {
                     // A generic mapped type { [P in K]: T } is related to an index signature { [x: string]: U }
                     // if T is related to U.
-                    return (kind === IndexKind.String && isRelatedTo(getTemplateTypeFromMappedType(source), targetInfo.type, reportErrors)) as any as Ternary; // TODO: GH#18217
+                    return kind === IndexKind.String ? isRelatedTo(getTemplateTypeFromMappedType(source), targetInfo.type, reportErrors) : Ternary.False;
                 }
                 if (isObjectTypeWithInferableIndex(source)) {
                     let related = Ternary.True;
@@ -17414,7 +17412,7 @@ namespace ts {
             }
 
             function narrowTypeByTypeof(type: Type, typeOfExpr: TypeOfExpression, operator: SyntaxKind, literal: LiteralExpression, assumeTrue: boolean): Type {
-                // We have '==', '!=', '====', or !==' operator with 'typeof xxx' and string literal operands
+                // We have '==', '!=', '===', or !==' operator with 'typeof xxx' and string literal operands
                 const target = getReferenceCandidate(typeOfExpr.expression);
                 if (!isMatchingReference(reference, target)) {
                     // For a reference of the form 'x.y', a 'typeof x === ...' type guard resets the
@@ -19874,6 +19872,12 @@ namespace ts {
         }
 
         function isValidSpreadType(type: Type): boolean {
+            if (type.flags & TypeFlags.Instantiable) {
+                const constraint = getBaseConstraintOfType(type);
+                if (constraint !== undefined) {
+                    return isValidSpreadType(constraint);
+                }
+            }
             return !!(type.flags & (TypeFlags.AnyOrUnknown | TypeFlags.NonPrimitive | TypeFlags.Object | TypeFlags.InstantiableNonPrimitive) ||
                 getFalsyFlags(type) & TypeFlags.DefinitelyFalsy && isValidSpreadType(removeDefinitelyFalsyTypes(type)) ||
                 type.flags & TypeFlags.UnionOrIntersection && every((<UnionOrIntersectionType>type).types, isValidSpreadType));
@@ -20822,7 +20826,7 @@ namespace ts {
             let relatedInfo: Diagnostic | undefined;
             if (containingType.flags & TypeFlags.Union && !(containingType.flags & TypeFlags.Primitive)) {
                 for (const subtype of (containingType as UnionType).types) {
-                    if (!getPropertyOfType(subtype, propNode.escapedText)) {
+                    if (!getPropertyOfType(subtype, propNode.escapedText) && !getIndexInfoOfType(subtype, IndexKind.String)) {
                         errorInfo = chainDiagnosticMessages(errorInfo, Diagnostics.Property_0_does_not_exist_on_type_1, declarationNameToString(propNode), typeToString(subtype));
                         break;
                     }
@@ -21054,21 +21058,6 @@ namespace ts {
             const objectType = getAssignmentTargetKind(node) !== AssignmentKind.None || isMethodAccessForCall(node) ? getWidenedType(exprType) : exprType;
 
             const indexExpression = node.argumentExpression;
-            if (!indexExpression) {
-                const sourceFile = getSourceFileOfNode(node);
-                if (node.parent.kind === SyntaxKind.NewExpression && (<NewExpression>node.parent).expression === node) {
-                    const start = skipTrivia(sourceFile.text, node.expression.end);
-                    const end = node.end;
-                    grammarErrorAtPos(sourceFile, start, end - start, Diagnostics.new_T_cannot_be_used_to_create_an_array_Use_new_Array_T_instead);
-                }
-                else {
-                    const start = node.end - "]".length;
-                    const end = node.end;
-                    grammarErrorAtPos(sourceFile, start, end - start, Diagnostics.Expression_expected);
-                }
-                return errorType;
-            }
-
             const indexType = checkExpression(indexExpression);
 
             if (objectType === errorType || objectType === silentNeverType) {
@@ -29737,9 +29726,7 @@ namespace ts {
                                     name = ex.name.escapedText;
                                 }
                                 else {
-                                    const argument = ex.argumentExpression;
-                                    Debug.assert(isLiteralExpression(argument));
-                                    name = escapeLeadingUnderscores((argument as LiteralExpression).text);
+                                    name = escapeLeadingUnderscores(cast(ex.argumentExpression, isLiteralExpression).text);
                                 }
                                 return evaluateEnumMember(expr, type.symbol, name);
                             }
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 3c282ca092f..492f853c347 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -459,10 +459,6 @@
         "category": "Error",
         "code": 1149
     },
-    "'new T[]' cannot be used to create an array. Use 'new Array<T>()' instead.": {
-        "category": "Error",
-        "code": 1150
-    },
     "'const' declarations must be initialized.": {
         "category": "Error",
         "code": 1155
diff --git a/src/compiler/parser.ts b/src/compiler/parser.ts
index ee5193975df..292c72fd160 100644
--- a/src/compiler/parser.ts
+++ b/src/compiler/parser.ts
@@ -5490,10 +5490,22 @@ namespace ts {
         }
 
         function parseDeclaration(): Statement {
+            const modifiers = lookAhead(() => (parseDecorators(), parseModifiers()));
+            // `parseListElement` attempted to get the reused node at this position,
+            // but the ambient context flag was not yet set, so the node appeared
+            // not reusable in that context.
+            const isAmbient = some(modifiers, isDeclareModifier);
+            if (isAmbient) {
+                const node = tryReuseAmbientDeclaration();
+                if (node) {
+                    return node;
+                }
+            }
+
             const node = <Statement>createNodeWithJSDoc(SyntaxKind.Unknown);
             node.decorators = parseDecorators();
             node.modifiers = parseModifiers();
-            if (some(node.modifiers, isDeclareModifier)) {
+            if (isAmbient) {
                 for (const m of node.modifiers!) {
                     m.flags |= NodeFlags.Ambient;
                 }
@@ -5504,6 +5516,15 @@ namespace ts {
             }
         }
 
+        function tryReuseAmbientDeclaration(): Statement | undefined {
+            return doInsideOfContext(NodeFlags.Ambient, () => {
+                const node = currentNode(parsingContext);
+                if (node) {
+                    return consumeNode(node) as Statement;
+                }
+            });
+        }
+
         function parseDeclarationWorker(node: Statement): Statement {
             switch (token()) {
                 case SyntaxKind.VarKeyword:
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index b08c09225ed..8bb018f53cb 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -1142,7 +1142,7 @@ namespace ts {
             // If we change our policy of rechecking failed lookups on each program create,
             // we should adjust the value returned here.
             function moduleNameResolvesToAmbientModuleInNonModifiedFile(moduleName: string): boolean {
-                const resolutionToFile = getResolvedModule(oldSourceFile!, moduleName);
+                const resolutionToFile = getResolvedModule(oldSourceFile, moduleName);
                 const resolvedFile = resolutionToFile && oldProgram!.getSourceFile(resolutionToFile.resolvedFileName);
                 if (resolutionToFile && resolvedFile) {
                     // In the old program, we resolved to an ambient module that was in the same
@@ -1831,6 +1831,7 @@ namespace ts {
 
                     switch (parent.kind) {
                         case SyntaxKind.ClassDeclaration:
+                        case SyntaxKind.ClassExpression:
                         case SyntaxKind.MethodDeclaration:
                         case SyntaxKind.MethodSignature:
                         case SyntaxKind.Constructor:
@@ -1840,7 +1841,7 @@ namespace ts {
                         case SyntaxKind.FunctionDeclaration:
                         case SyntaxKind.ArrowFunction:
                             // Check type parameters
-                            if (nodes === (<ClassDeclaration | FunctionLikeDeclaration>parent).typeParameters) {
+                            if (nodes === (<ClassLikeDeclaration | FunctionLikeDeclaration>parent).typeParameters) {
                                 diagnostics.push(createDiagnosticForNodeArray(nodes, Diagnostics.type_parameter_declarations_can_only_be_used_in_a_ts_file));
                                 return;
                             }
diff --git a/src/compiler/scanner.ts b/src/compiler/scanner.ts
index ac6be3ba555..05e41cf6bc7 100644
--- a/src/compiler/scanner.ts
+++ b/src/compiler/scanner.ts
@@ -879,7 +879,7 @@ namespace ts {
 
         setText(text, start, length);
 
-        return {
+        const scanner: Scanner = {
             getStartPos: () => startPos,
             getTextPos: () => pos,
             getToken: () => token,
@@ -915,6 +915,17 @@ namespace ts {
             scanRange,
         };
 
+        if (Debug.isDebugging) {
+            Object.defineProperty(scanner, "__debugShowCurrentPositionInText", {
+                get: () => {
+                    const text = scanner.getText();
+                    return text.slice(0, scanner.getStartPos()) + "║" + text.slice(scanner.getStartPos());
+                },
+            });
+        }
+
+        return scanner;
+
         function error(message: DiagnosticMessage): void;
         function error(message: DiagnosticMessage, errPos: number, length: number): void;
         function error(message: DiagnosticMessage, errPos: number = pos, length?: number): void {
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 2eb3eb78066..647d26b4e40 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -3346,7 +3346,7 @@ namespace ts {
          * This should be called in a loop climbing parents of the symbol, so we'll get `N`.
          */
         /* @internal */ getAccessibleSymbolChain(symbol: Symbol, enclosingDeclaration: Node | undefined, meaning: SymbolFlags, useOnlyExternalAliasing: boolean): Symbol[] | undefined;
-        /* @internal */ getTypePredicateOfSignature(signature: Signature): TypePredicate;
+        /* @internal */ getTypePredicateOfSignature(signature: Signature): TypePredicate | undefined;
         /**
          * An external module with an 'export =' declaration resolves to the target of the 'export =' declaration,
          * and an external module with no 'export =' declaration resolves to the module itself.
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index fbe4210cc3a..b123c2f48f5 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -220,7 +220,7 @@ namespace ts {
         return node.end - node.pos;
     }
 
-    export function getResolvedModule(sourceFile: SourceFile, moduleNameText: string): ResolvedModuleFull | undefined {
+    export function getResolvedModule(sourceFile: SourceFile | undefined, moduleNameText: string): ResolvedModuleFull | undefined {
         return sourceFile && sourceFile.resolvedModules && sourceFile.resolvedModules.get(moduleNameText);
     }
 
diff --git a/src/lib/es2019.array.d.ts b/src/lib/es2019.array.d.ts
index 07fc76a9c77..9e3e04e5815 100644
--- a/src/lib/es2019.array.d.ts
+++ b/src/lib/es2019.array.d.ts
@@ -110,7 +110,7 @@ interface ReadonlyArray<T> {
      * @param depth The maximum recursion depth
      */
     flat<U>(depth?: number): any[];
-  }
+}
 
 interface Array<T> {
 
diff --git a/src/lib/es5.d.ts b/src/lib/es5.d.ts
index 07048926b35..097830ee032 100644
--- a/src/lib/es5.d.ts
+++ b/src/lib/es5.d.ts
@@ -1094,7 +1094,7 @@ interface ReadonlyArray<T> {
     /**
      * Returns a section of an array.
      * @param start The beginning of the specified portion of the array.
-     * @param end The end of the specified portion of the array.
+     * @param end The end of the specified portion of the array. This is exclusive of the element at the index 'end'.
      */
     slice(start?: number, end?: number): T[];
     /**
@@ -1230,7 +1230,7 @@ interface Array<T> {
     /**
      * Returns a section of an array.
      * @param start The beginning of the specified portion of the array.
-     * @param end The end of the specified portion of the array.
+     * @param end The end of the specified portion of the array. This is exclusive of the element at the index 'end'.
      */
     slice(start?: number, end?: number): T[];
     /**
@@ -1860,7 +1860,7 @@ interface Int8Array {
     /**
      * Returns a section of an array.
      * @param start The beginning of the specified portion of the array.
-     * @param end The end of the specified portion of the array.
+     * @param end The end of the specified portion of the array. This is exclusive of the element at the index 'end'.
      */
     slice(start?: number, end?: number): Int8Array;
 
@@ -1887,7 +1887,7 @@ interface Int8Array {
      * @param begin The index of the beginning of the array.
      * @param end The index of the end of the array.
      */
-    subarray(begin: number, end?: number): Int8Array;
+    subarray(begin?: number, end?: number): Int8Array;
 
     /**
      * Converts a number to a string by using the current locale.
@@ -2135,7 +2135,7 @@ interface Uint8Array {
     /**
      * Returns a section of an array.
      * @param start The beginning of the specified portion of the array.
-     * @param end The end of the specified portion of the array.
+     * @param end The end of the specified portion of the array. This is exclusive of the element at the index 'end'.
      */
     slice(start?: number, end?: number): Uint8Array;
 
@@ -2162,7 +2162,7 @@ interface Uint8Array {
      * @param begin The index of the beginning of the array.
      * @param end The index of the end of the array.
      */
-    subarray(begin: number, end?: number): Uint8Array;
+    subarray(begin?: number, end?: number): Uint8Array;
 
     /**
      * Converts a number to a string by using the current locale.
@@ -2410,7 +2410,7 @@ interface Uint8ClampedArray {
     /**
      * Returns a section of an array.
      * @param start The beginning of the specified portion of the array.
-     * @param end The end of the specified portion of the array.
+     * @param end The end of the specified portion of the array. This is exclusive of the element at the index 'end'.
      */
     slice(start?: number, end?: number): Uint8ClampedArray;
 
@@ -2437,7 +2437,7 @@ interface Uint8ClampedArray {
      * @param begin The index of the beginning of the array.
      * @param end The index of the end of the array.
      */
-    subarray(begin: number, end?: number): Uint8ClampedArray;
+    subarray(begin?: number, end?: number): Uint8ClampedArray;
 
     /**
      * Converts a number to a string by using the current locale.
@@ -2683,7 +2683,7 @@ interface Int16Array {
     /**
      * Returns a section of an array.
      * @param start The beginning of the specified portion of the array.
-     * @param end The end of the specified portion of the array.
+     * @param end The end of the specified portion of the array. This is exclusive of the element at the index 'end'.
      */
     slice(start?: number, end?: number): Int16Array;
 
@@ -2710,7 +2710,7 @@ interface Int16Array {
      * @param begin The index of the beginning of the array.
      * @param end The index of the end of the array.
      */
-    subarray(begin: number, end?: number): Int16Array;
+    subarray(begin?: number, end?: number): Int16Array;
 
     /**
      * Converts a number to a string by using the current locale.
@@ -2959,7 +2959,7 @@ interface Uint16Array {
     /**
      * Returns a section of an array.
      * @param start The beginning of the specified portion of the array.
-     * @param end The end of the specified portion of the array.
+     * @param end The end of the specified portion of the array. This is exclusive of the element at the index 'end'.
      */
     slice(start?: number, end?: number): Uint16Array;
 
@@ -2986,7 +2986,7 @@ interface Uint16Array {
      * @param begin The index of the beginning of the array.
      * @param end The index of the end of the array.
      */
-    subarray(begin: number, end?: number): Uint16Array;
+    subarray(begin?: number, end?: number): Uint16Array;
 
     /**
      * Converts a number to a string by using the current locale.
@@ -3234,7 +3234,7 @@ interface Int32Array {
     /**
      * Returns a section of an array.
      * @param start The beginning of the specified portion of the array.
-     * @param end The end of the specified portion of the array.
+     * @param end The end of the specified portion of the array. This is exclusive of the element at the index 'end'.
      */
     slice(start?: number, end?: number): Int32Array;
 
@@ -3261,7 +3261,7 @@ interface Int32Array {
      * @param begin The index of the beginning of the array.
      * @param end The index of the end of the array.
      */
-    subarray(begin: number, end?: number): Int32Array;
+    subarray(begin?: number, end?: number): Int32Array;
 
     /**
      * Converts a number to a string by using the current locale.
@@ -3508,7 +3508,7 @@ interface Uint32Array {
     /**
      * Returns a section of an array.
      * @param start The beginning of the specified portion of the array.
-     * @param end The end of the specified portion of the array.
+     * @param end The end of the specified portion of the array. This is exclusive of the element at the index 'end'.
      */
     slice(start?: number, end?: number): Uint32Array;
 
@@ -3535,7 +3535,7 @@ interface Uint32Array {
      * @param begin The index of the beginning of the array.
      * @param end The index of the end of the array.
      */
-    subarray(begin: number, end?: number): Uint32Array;
+    subarray(begin?: number, end?: number): Uint32Array;
 
     /**
      * Converts a number to a string by using the current locale.
@@ -3783,7 +3783,7 @@ interface Float32Array {
     /**
      * Returns a section of an array.
      * @param start The beginning of the specified portion of the array.
-     * @param end The end of the specified portion of the array.
+     * @param end The end of the specified portion of the array. This is exclusive of the element at the index 'end'.
      */
     slice(start?: number, end?: number): Float32Array;
 
@@ -3810,7 +3810,7 @@ interface Float32Array {
      * @param begin The index of the beginning of the array.
      * @param end The index of the end of the array.
      */
-    subarray(begin: number, end?: number): Float32Array;
+    subarray(begin?: number, end?: number): Float32Array;
 
     /**
      * Converts a number to a string by using the current locale.
@@ -4059,7 +4059,7 @@ interface Float64Array {
     /**
      * Returns a section of an array.
      * @param start The beginning of the specified portion of the array.
-     * @param end The end of the specified portion of the array.
+     * @param end The end of the specified portion of the array. This is exclusive of the element at the index 'end'.
      */
     slice(start?: number, end?: number): Float64Array;
 
@@ -4081,21 +4081,12 @@ interface Float64Array {
     sort(compareFn?: (a: number, b: number) => number): this;
 
     /**
-     * Gets a new Float64Array view of the ArrayBuffer store for this array, referencing the elements
      * at begin, inclusive, up to end, exclusive.
      * @param begin The index of the beginning of the array.
      * @param end The index of the end of the array.
      */
-    subarray(begin: number, end?: number): Float64Array;
+    subarray(begin?: number, end?: number): Float64Array;
 
-    /**
-     * Converts a number to a string by using the current locale.
-     */
-    toLocaleString(): string;
-
-    /**
-     * Returns a string representation of an array.
-     */
     toString(): string;
 
     [index: number]: number;
diff --git a/src/lib/esnext.bigint.d.ts b/src/lib/esnext.bigint.d.ts
index b017ebd3799..332b654fc97 100644
--- a/src/lib/esnext.bigint.d.ts
+++ b/src/lib/esnext.bigint.d.ts
@@ -260,7 +260,7 @@ interface BigInt64Array {
      * @param begin The index of the beginning of the array.
      * @param end The index of the end of the array.
      */
-    subarray(begin: number, end?: number): BigInt64Array;
+    subarray(begin?: number, end?: number): BigInt64Array;
 
     /** Converts the array to a string by using the current locale. */
     toLocaleString(): string;
@@ -529,7 +529,7 @@ interface BigUint64Array {
      * @param begin The index of the beginning of the array.
      * @param end The index of the end of the array.
      */
-    subarray(begin: number, end?: number): BigUint64Array;
+    subarray(begin?: number, end?: number): BigUint64Array;
 
     /** Converts the array to a string by using the current locale. */
     toLocaleString(): string;
diff --git a/src/lib/esnext.d.ts b/src/lib/esnext.d.ts
index b46f8df7620..9ea131785ba 100644
--- a/src/lib/esnext.d.ts
+++ b/src/lib/esnext.d.ts
@@ -1,3 +1,3 @@
-/// <reference lib="es2019" />
+/// <reference lib="es2020" />
 /// <reference lib="esnext.bigint" />
 /// <reference lib="esnext.intl" />
diff --git a/src/testRunner/unittests/incrementalParser.ts b/src/testRunner/unittests/incrementalParser.ts
index 503462ceb39..5884067d9aa 100644
--- a/src/testRunner/unittests/incrementalParser.ts
+++ b/src/testRunner/unittests/incrementalParser.ts
@@ -673,7 +673,7 @@ module m3 { }\
             const oldText = ScriptSnapshot.fromString(source);
             const newTextAndChange = withInsert(oldText, 0, "{");
 
-            compareTrees(oldText, newTextAndChange.text, newTextAndChange.textChangeRange, 4);
+            compareTrees(oldText, newTextAndChange.text, newTextAndChange.textChangeRange, 9);
         });
 
         it("Removing block around function declarations", () => {
@@ -682,7 +682,7 @@ module m3 { }\
             const oldText = ScriptSnapshot.fromString(source);
             const newTextAndChange = withDelete(oldText, 0, "{".length);
 
-            compareTrees(oldText, newTextAndChange.text, newTextAndChange.textChangeRange, 4);
+            compareTrees(oldText, newTextAndChange.text, newTextAndChange.textChangeRange, 9);
         });
 
         it("Moving methods from class to object literal", () => {
diff --git a/tests/baselines/reference/bigint64ArraySubarray.js b/tests/baselines/reference/bigint64ArraySubarray.js
new file mode 100644
index 00000000000..c68297b17bb
--- /dev/null
+++ b/tests/baselines/reference/bigint64ArraySubarray.js
@@ -0,0 +1,16 @@
+//// [bigint64ArraySubarray.ts]
+function bigInt64ArraySubarray() {
+    var arr = new BigInt64Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+
+//// [bigint64ArraySubarray.js]
+function bigInt64ArraySubarray() {
+    var arr = new BigInt64Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
diff --git a/tests/baselines/reference/bigint64ArraySubarray.symbols b/tests/baselines/reference/bigint64ArraySubarray.symbols
new file mode 100644
index 00000000000..b6eb3e1ec75
--- /dev/null
+++ b/tests/baselines/reference/bigint64ArraySubarray.symbols
@@ -0,0 +1,24 @@
+=== tests/cases/compiler/bigint64ArraySubarray.ts ===
+function bigInt64ArraySubarray() {
+>bigInt64ArraySubarray : Symbol(bigInt64ArraySubarray, Decl(bigint64ArraySubarray.ts, 0, 0))
+
+    var arr = new BigInt64Array(10);
+>arr : Symbol(arr, Decl(bigint64ArraySubarray.ts, 1, 7))
+>BigInt64Array : Symbol(BigInt64Array, Decl(lib.esnext.bigint.d.ts, --, --), Decl(lib.esnext.bigint.d.ts, --, --))
+
+    arr.subarray();
+>arr.subarray : Symbol(BigInt64Array.subarray, Decl(lib.esnext.bigint.d.ts, --, --))
+>arr : Symbol(arr, Decl(bigint64ArraySubarray.ts, 1, 7))
+>subarray : Symbol(BigInt64Array.subarray, Decl(lib.esnext.bigint.d.ts, --, --))
+
+    arr.subarray(0);
+>arr.subarray : Symbol(BigInt64Array.subarray, Decl(lib.esnext.bigint.d.ts, --, --))
+>arr : Symbol(arr, Decl(bigint64ArraySubarray.ts, 1, 7))
+>subarray : Symbol(BigInt64Array.subarray, Decl(lib.esnext.bigint.d.ts, --, --))
+
+    arr.subarray(0, 10);
+>arr.subarray : Symbol(BigInt64Array.subarray, Decl(lib.esnext.bigint.d.ts, --, --))
+>arr : Symbol(arr, Decl(bigint64ArraySubarray.ts, 1, 7))
+>subarray : Symbol(BigInt64Array.subarray, Decl(lib.esnext.bigint.d.ts, --, --))
+}
+
diff --git a/tests/baselines/reference/bigint64ArraySubarray.types b/tests/baselines/reference/bigint64ArraySubarray.types
new file mode 100644
index 00000000000..12c92f2dd14
--- /dev/null
+++ b/tests/baselines/reference/bigint64ArraySubarray.types
@@ -0,0 +1,32 @@
+=== tests/cases/compiler/bigint64ArraySubarray.ts ===
+function bigInt64ArraySubarray() {
+>bigInt64ArraySubarray : () => void
+
+    var arr = new BigInt64Array(10);
+>arr : BigInt64Array
+>new BigInt64Array(10) : BigInt64Array
+>BigInt64Array : BigInt64ArrayConstructor
+>10 : 10
+
+    arr.subarray();
+>arr.subarray() : BigInt64Array
+>arr.subarray : (begin?: number, end?: number) => BigInt64Array
+>arr : BigInt64Array
+>subarray : (begin?: number, end?: number) => BigInt64Array
+
+    arr.subarray(0);
+>arr.subarray(0) : BigInt64Array
+>arr.subarray : (begin?: number, end?: number) => BigInt64Array
+>arr : BigInt64Array
+>subarray : (begin?: number, end?: number) => BigInt64Array
+>0 : 0
+
+    arr.subarray(0, 10);
+>arr.subarray(0, 10) : BigInt64Array
+>arr.subarray : (begin?: number, end?: number) => BigInt64Array
+>arr : BigInt64Array
+>subarray : (begin?: number, end?: number) => BigInt64Array
+>0 : 0
+>10 : 10
+}
+
diff --git a/tests/baselines/reference/bigintIndex.symbols b/tests/baselines/reference/bigintIndex.symbols
index dff23a016ee..4a72dcc42c9 100644
--- a/tests/baselines/reference/bigintIndex.symbols
+++ b/tests/baselines/reference/bigintIndex.symbols
@@ -53,7 +53,7 @@ typedArray[bigNum] = 0xAA; // should error
 
 typedArray[String(bigNum)] = 0xAA;
 >typedArray : Symbol(typedArray, Decl(a.ts, 17, 5))
->String : Symbol(String, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --) ... and 3 more)
+>String : Symbol(String, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --) ... and 4 more)
 >bigNum : Symbol(bigNum, Decl(a.ts, 16, 5))
 
 typedArray["1"] = 0xBB;
diff --git a/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClassExpression.errors.txt b/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClassExpression.errors.txt
new file mode 100644
index 00000000000..61bf225dddc
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClassExpression.errors.txt
@@ -0,0 +1,8 @@
+tests/cases/compiler/a.js(1,19): error TS8004: 'type parameter declarations' can only be used in a .ts file.
+
+
+==== tests/cases/compiler/a.js (1 errors) ====
+    const Bar = class<T> {};
+                      ~
+!!! error TS8004: 'type parameter declarations' can only be used in a .ts file.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClassExpression.symbols b/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClassExpression.symbols
new file mode 100644
index 00000000000..f3aa9cd5926
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClassExpression.symbols
@@ -0,0 +1,5 @@
+=== tests/cases/compiler/a.js ===
+const Bar = class<T> {};
+>Bar : Symbol(Bar, Decl(a.js, 0, 5))
+>T : Symbol(T, Decl(a.js, 0, 18))
+
diff --git a/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClassExpression.types b/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClassExpression.types
new file mode 100644
index 00000000000..5538564ec86
--- /dev/null
+++ b/tests/baselines/reference/jsFileCompilationTypeParameterSyntaxOfClassExpression.types
@@ -0,0 +1,5 @@
+=== tests/cases/compiler/a.js ===
+const Bar = class<T> {};
+>Bar : typeof Bar
+>class<T> {} : typeof Bar
+
diff --git a/tests/baselines/reference/regexMatchAll-esnext.js b/tests/baselines/reference/regexMatchAll-esnext.js
new file mode 100644
index 00000000000..545a78fcbec
--- /dev/null
+++ b/tests/baselines/reference/regexMatchAll-esnext.js
@@ -0,0 +1,10 @@
+//// [regexMatchAll-esnext.ts]
+const matches = /\w/g[Symbol.matchAll]("matchAll");
+const array = [...matches];
+const { index, input } = array[0];
+
+
+//// [regexMatchAll-esnext.js]
+const matches = /\w/g[Symbol.matchAll]("matchAll");
+const array = [...matches];
+const { index, input } = array[0];
diff --git a/tests/baselines/reference/regexMatchAll-esnext.symbols b/tests/baselines/reference/regexMatchAll-esnext.symbols
new file mode 100644
index 00000000000..374d076c4d0
--- /dev/null
+++ b/tests/baselines/reference/regexMatchAll-esnext.symbols
@@ -0,0 +1,16 @@
+=== tests/cases/compiler/regexMatchAll-esnext.ts ===
+const matches = /\w/g[Symbol.matchAll]("matchAll");
+>matches : Symbol(matches, Decl(regexMatchAll-esnext.ts, 0, 5))
+>Symbol.matchAll : Symbol(SymbolConstructor.matchAll, Decl(lib.es2020.symbol.wellknown.d.ts, --, --))
+>Symbol : Symbol(Symbol, Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.symbol.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2019.symbol.d.ts, --, --))
+>matchAll : Symbol(SymbolConstructor.matchAll, Decl(lib.es2020.symbol.wellknown.d.ts, --, --))
+
+const array = [...matches];
+>array : Symbol(array, Decl(regexMatchAll-esnext.ts, 1, 5))
+>matches : Symbol(matches, Decl(regexMatchAll-esnext.ts, 0, 5))
+
+const { index, input } = array[0];
+>index : Symbol(index, Decl(regexMatchAll-esnext.ts, 2, 7))
+>input : Symbol(input, Decl(regexMatchAll-esnext.ts, 2, 14))
+>array : Symbol(array, Decl(regexMatchAll-esnext.ts, 1, 5))
+
diff --git a/tests/baselines/reference/regexMatchAll-esnext.types b/tests/baselines/reference/regexMatchAll-esnext.types
new file mode 100644
index 00000000000..9a902b60000
--- /dev/null
+++ b/tests/baselines/reference/regexMatchAll-esnext.types
@@ -0,0 +1,24 @@
+=== tests/cases/compiler/regexMatchAll-esnext.ts ===
+const matches = /\w/g[Symbol.matchAll]("matchAll");
+>matches : IterableIterator<RegExpMatchArray>
+>/\w/g[Symbol.matchAll]("matchAll") : IterableIterator<RegExpMatchArray>
+>/\w/g[Symbol.matchAll] : (str: string) => IterableIterator<RegExpMatchArray>
+>/\w/g : RegExp
+>Symbol.matchAll : symbol
+>Symbol : SymbolConstructor
+>matchAll : symbol
+>"matchAll" : "matchAll"
+
+const array = [...matches];
+>array : RegExpMatchArray[]
+>[...matches] : RegExpMatchArray[]
+>...matches : RegExpMatchArray
+>matches : IterableIterator<RegExpMatchArray>
+
+const { index, input } = array[0];
+>index : number
+>input : string
+>array[0] : RegExpMatchArray
+>array : RegExpMatchArray[]
+>0 : 0
+
diff --git a/tests/baselines/reference/restInvalidArgumentType.errors.txt b/tests/baselines/reference/restInvalidArgumentType.errors.txt
index 7e0c852316a..22d2528fbb3 100644
--- a/tests/baselines/reference/restInvalidArgumentType.errors.txt
+++ b/tests/baselines/reference/restInvalidArgumentType.errors.txt
@@ -1,3 +1,4 @@
+tests/cases/compiler/restInvalidArgumentType.ts(30,13): error TS2700: Rest types may only be created from object types.
 tests/cases/compiler/restInvalidArgumentType.ts(31,13): error TS2700: Rest types may only be created from object types.
 tests/cases/compiler/restInvalidArgumentType.ts(37,13): error TS2700: Rest types may only be created from object types.
 tests/cases/compiler/restInvalidArgumentType.ts(40,13): error TS2700: Rest types may only be created from object types.
@@ -10,7 +11,7 @@ tests/cases/compiler/restInvalidArgumentType.ts(51,13): error TS2700: Rest types
 tests/cases/compiler/restInvalidArgumentType.ts(53,13): error TS2700: Rest types may only be created from object types.
 
 
-==== tests/cases/compiler/restInvalidArgumentType.ts (10 errors) ====
+==== tests/cases/compiler/restInvalidArgumentType.ts (11 errors) ====
     enum E { v1, v2 };
     
     function f<T extends { b: string }>(p1: T, p2: T[]) {
@@ -41,6 +42,8 @@ tests/cases/compiler/restInvalidArgumentType.ts(53,13): error TS2700: Rest types
         var {...r2} = p2;   // OK
         var {...r3} = t;   // Error, generic type paramter
         var {...r4} = i;   // Error, index access
+                ~~
+!!! error TS2700: Rest types may only be created from object types.
         var {...r5} = k;   // Error, index
                 ~~
 !!! error TS2700: Rest types may only be created from object types.
diff --git a/tests/baselines/reference/restInvalidArgumentType.types b/tests/baselines/reference/restInvalidArgumentType.types
index d88ee53796a..638634e8bea 100644
--- a/tests/baselines/reference/restInvalidArgumentType.types
+++ b/tests/baselines/reference/restInvalidArgumentType.types
@@ -79,7 +79,7 @@ function f<T extends { b: string }>(p1: T, p2: T[]) {
 >t : T
 
     var {...r4} = i;   // Error, index access
->r4 : T["b"]
+>r4 : any
 >i : T["b"]
 
     var {...r5} = k;   // Error, index
diff --git a/tests/baselines/reference/spreadInvalidArgumentType.errors.txt b/tests/baselines/reference/spreadInvalidArgumentType.errors.txt
index cb2b74b7b19..36bc2b36fe3 100644
--- a/tests/baselines/reference/spreadInvalidArgumentType.errors.txt
+++ b/tests/baselines/reference/spreadInvalidArgumentType.errors.txt
@@ -1,3 +1,4 @@
+tests/cases/compiler/spreadInvalidArgumentType.ts(33,16): error TS2698: Spread types may only be created from object types.
 tests/cases/compiler/spreadInvalidArgumentType.ts(34,16): error TS2698: Spread types may only be created from object types.
 tests/cases/compiler/spreadInvalidArgumentType.ts(39,16): error TS2698: Spread types may only be created from object types.
 tests/cases/compiler/spreadInvalidArgumentType.ts(42,17): error TS2698: Spread types may only be created from object types.
@@ -10,7 +11,7 @@ tests/cases/compiler/spreadInvalidArgumentType.ts(53,17): error TS2698: Spread t
 tests/cases/compiler/spreadInvalidArgumentType.ts(55,17): error TS2698: Spread types may only be created from object types.
 
 
-==== tests/cases/compiler/spreadInvalidArgumentType.ts (10 errors) ====
+==== tests/cases/compiler/spreadInvalidArgumentType.ts (11 errors) ====
     enum E { v1, v2 };
     
     function f<T extends { b: string }>(p1: T, p2: T[]) {
@@ -43,7 +44,9 @@ tests/cases/compiler/spreadInvalidArgumentType.ts(55,17): error TS2698: Spread t
         var o1 = { ...p1 };  // OK, generic type paramterre
         var o2 = { ...p2 };  // OK
         var o3 = { ...t };   // OK, generic type paramter
-        var o4 = { ...i };   // OK, index access
+        var o4 = { ...i };   // Error, index access
+                   ~~~~
+!!! error TS2698: Spread types may only be created from object types.
         var o5 = { ...k };   // Error, index
                    ~~~~
 !!! error TS2698: Spread types may only be created from object types.
diff --git a/tests/baselines/reference/spreadInvalidArgumentType.js b/tests/baselines/reference/spreadInvalidArgumentType.js
index b1cb2561eca..fc96c5971fb 100644
--- a/tests/baselines/reference/spreadInvalidArgumentType.js
+++ b/tests/baselines/reference/spreadInvalidArgumentType.js
@@ -31,7 +31,7 @@ function f<T extends { b: string }>(p1: T, p2: T[]) {
     var o1 = { ...p1 };  // OK, generic type paramterre
     var o2 = { ...p2 };  // OK
     var o3 = { ...t };   // OK, generic type paramter
-    var o4 = { ...i };   // OK, index access
+    var o4 = { ...i };   // Error, index access
     var o5 = { ...k };   // Error, index
     var o6 = { ...mapped_generic }; // OK, generic mapped object type
     var o7 = { ...mapped };  // OK, non-generic mapped type
@@ -96,7 +96,7 @@ function f(p1, p2) {
     var o1 = __assign({}, p1); // OK, generic type paramterre
     var o2 = __assign({}, p2); // OK
     var o3 = __assign({}, t); // OK, generic type paramter
-    var o4 = __assign({}, i); // OK, index access
+    var o4 = __assign({}, i); // Error, index access
     var o5 = __assign({}, k); // Error, index
     var o6 = __assign({}, mapped_generic); // OK, generic mapped object type
     var o7 = __assign({}, mapped); // OK, non-generic mapped type
diff --git a/tests/baselines/reference/spreadInvalidArgumentType.symbols b/tests/baselines/reference/spreadInvalidArgumentType.symbols
index 8c29a923d37..f4d7af9cca8 100644
--- a/tests/baselines/reference/spreadInvalidArgumentType.symbols
+++ b/tests/baselines/reference/spreadInvalidArgumentType.symbols
@@ -94,7 +94,7 @@ function f<T extends { b: string }>(p1: T, p2: T[]) {
 >o3 : Symbol(o3, Decl(spreadInvalidArgumentType.ts, 31, 7))
 >t : Symbol(t, Decl(spreadInvalidArgumentType.ts, 3, 7))
 
-    var o4 = { ...i };   // OK, index access
+    var o4 = { ...i };   // Error, index access
 >o4 : Symbol(o4, Decl(spreadInvalidArgumentType.ts, 32, 7))
 >i : Symbol(i, Decl(spreadInvalidArgumentType.ts, 5, 7))
 
diff --git a/tests/baselines/reference/spreadInvalidArgumentType.types b/tests/baselines/reference/spreadInvalidArgumentType.types
index 8a833c966ff..ec1b7faa9ec 100644
--- a/tests/baselines/reference/spreadInvalidArgumentType.types
+++ b/tests/baselines/reference/spreadInvalidArgumentType.types
@@ -82,9 +82,9 @@ function f<T extends { b: string }>(p1: T, p2: T[]) {
 >{ ...t } : T
 >t : T
 
-    var o4 = { ...i };   // OK, index access
->o4 : T["b"]
->{ ...i } : T["b"]
+    var o4 = { ...i };   // Error, index access
+>o4 : any
+>{ ...i } : any
 >i : T["b"]
 
     var o5 = { ...k };   // Error, index
diff --git a/tests/baselines/reference/spreadTypeVariable.errors.txt b/tests/baselines/reference/spreadTypeVariable.errors.txt
new file mode 100644
index 00000000000..b3ac4188670
--- /dev/null
+++ b/tests/baselines/reference/spreadTypeVariable.errors.txt
@@ -0,0 +1,37 @@
+tests/cases/conformance/types/spread/spreadTypeVariable.ts(2,12): error TS2698: Spread types may only be created from object types.
+tests/cases/conformance/types/spread/spreadTypeVariable.ts(10,12): error TS2698: Spread types may only be created from object types.
+tests/cases/conformance/types/spread/spreadTypeVariable.ts(14,12): error TS2698: Spread types may only be created from object types.
+
+
+==== tests/cases/conformance/types/spread/spreadTypeVariable.ts (3 errors) ====
+    function f1<T extends number>(arg: T) {
+      return { ...arg };
+               ~~~~~~
+!!! error TS2698: Spread types may only be created from object types.
+    }
+    
+    function f2<T extends string[]>(arg: T) {
+      return { ...arg }
+    }
+    
+    function f3<T extends number | string[]>(arg: T) {
+      return { ...arg }
+               ~~~~~~
+!!! error TS2698: Spread types may only be created from object types.
+    }
+    
+    function f4<T extends number | { [key: string]: any }>(arg: T) {
+      return { ...arg }
+               ~~~~~~
+!!! error TS2698: Spread types may only be created from object types.
+    }
+    
+    function f5<T extends string[] | { [key: string]: any }>(arg: T) {
+      return { ...arg }
+    }
+    
+    function f6<T>(arg: T) {
+      return { ...arg }
+    }
+    
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/spreadTypeVariable.js b/tests/baselines/reference/spreadTypeVariable.js
new file mode 100644
index 00000000000..7574faab99e
--- /dev/null
+++ b/tests/baselines/reference/spreadTypeVariable.js
@@ -0,0 +1,57 @@
+//// [spreadTypeVariable.ts]
+function f1<T extends number>(arg: T) {
+  return { ...arg };
+}
+
+function f2<T extends string[]>(arg: T) {
+  return { ...arg }
+}
+
+function f3<T extends number | string[]>(arg: T) {
+  return { ...arg }
+}
+
+function f4<T extends number | { [key: string]: any }>(arg: T) {
+  return { ...arg }
+}
+
+function f5<T extends string[] | { [key: string]: any }>(arg: T) {
+  return { ...arg }
+}
+
+function f6<T>(arg: T) {
+  return { ...arg }
+}
+
+
+
+//// [spreadTypeVariable.js]
+var __assign = (this && this.__assign) || function () {
+    __assign = Object.assign || function(t) {
+        for (var s, i = 1, n = arguments.length; i < n; i++) {
+            s = arguments[i];
+            for (var p in s) if (Object.prototype.hasOwnProperty.call(s, p))
+                t[p] = s[p];
+        }
+        return t;
+    };
+    return __assign.apply(this, arguments);
+};
+function f1(arg) {
+    return __assign({}, arg);
+}
+function f2(arg) {
+    return __assign({}, arg);
+}
+function f3(arg) {
+    return __assign({}, arg);
+}
+function f4(arg) {
+    return __assign({}, arg);
+}
+function f5(arg) {
+    return __assign({}, arg);
+}
+function f6(arg) {
+    return __assign({}, arg);
+}
diff --git a/tests/baselines/reference/spreadTypeVariable.symbols b/tests/baselines/reference/spreadTypeVariable.symbols
new file mode 100644
index 00000000000..dee763309a0
--- /dev/null
+++ b/tests/baselines/reference/spreadTypeVariable.symbols
@@ -0,0 +1,64 @@
+=== tests/cases/conformance/types/spread/spreadTypeVariable.ts ===
+function f1<T extends number>(arg: T) {
+>f1 : Symbol(f1, Decl(spreadTypeVariable.ts, 0, 0))
+>T : Symbol(T, Decl(spreadTypeVariable.ts, 0, 12))
+>arg : Symbol(arg, Decl(spreadTypeVariable.ts, 0, 30))
+>T : Symbol(T, Decl(spreadTypeVariable.ts, 0, 12))
+
+  return { ...arg };
+>arg : Symbol(arg, Decl(spreadTypeVariable.ts, 0, 30))
+}
+
+function f2<T extends string[]>(arg: T) {
+>f2 : Symbol(f2, Decl(spreadTypeVariable.ts, 2, 1))
+>T : Symbol(T, Decl(spreadTypeVariable.ts, 4, 12))
+>arg : Symbol(arg, Decl(spreadTypeVariable.ts, 4, 32))
+>T : Symbol(T, Decl(spreadTypeVariable.ts, 4, 12))
+
+  return { ...arg }
+>arg : Symbol(arg, Decl(spreadTypeVariable.ts, 4, 32))
+}
+
+function f3<T extends number | string[]>(arg: T) {
+>f3 : Symbol(f3, Decl(spreadTypeVariable.ts, 6, 1))
+>T : Symbol(T, Decl(spreadTypeVariable.ts, 8, 12))
+>arg : Symbol(arg, Decl(spreadTypeVariable.ts, 8, 41))
+>T : Symbol(T, Decl(spreadTypeVariable.ts, 8, 12))
+
+  return { ...arg }
+>arg : Symbol(arg, Decl(spreadTypeVariable.ts, 8, 41))
+}
+
+function f4<T extends number | { [key: string]: any }>(arg: T) {
+>f4 : Symbol(f4, Decl(spreadTypeVariable.ts, 10, 1))
+>T : Symbol(T, Decl(spreadTypeVariable.ts, 12, 12))
+>key : Symbol(key, Decl(spreadTypeVariable.ts, 12, 34))
+>arg : Symbol(arg, Decl(spreadTypeVariable.ts, 12, 55))
+>T : Symbol(T, Decl(spreadTypeVariable.ts, 12, 12))
+
+  return { ...arg }
+>arg : Symbol(arg, Decl(spreadTypeVariable.ts, 12, 55))
+}
+
+function f5<T extends string[] | { [key: string]: any }>(arg: T) {
+>f5 : Symbol(f5, Decl(spreadTypeVariable.ts, 14, 1))
+>T : Symbol(T, Decl(spreadTypeVariable.ts, 16, 12))
+>key : Symbol(key, Decl(spreadTypeVariable.ts, 16, 36))
+>arg : Symbol(arg, Decl(spreadTypeVariable.ts, 16, 57))
+>T : Symbol(T, Decl(spreadTypeVariable.ts, 16, 12))
+
+  return { ...arg }
+>arg : Symbol(arg, Decl(spreadTypeVariable.ts, 16, 57))
+}
+
+function f6<T>(arg: T) {
+>f6 : Symbol(f6, Decl(spreadTypeVariable.ts, 18, 1))
+>T : Symbol(T, Decl(spreadTypeVariable.ts, 20, 12))
+>arg : Symbol(arg, Decl(spreadTypeVariable.ts, 20, 15))
+>T : Symbol(T, Decl(spreadTypeVariable.ts, 20, 12))
+
+  return { ...arg }
+>arg : Symbol(arg, Decl(spreadTypeVariable.ts, 20, 15))
+}
+
+
diff --git a/tests/baselines/reference/spreadTypeVariable.types b/tests/baselines/reference/spreadTypeVariable.types
new file mode 100644
index 00000000000..c5de712fb19
--- /dev/null
+++ b/tests/baselines/reference/spreadTypeVariable.types
@@ -0,0 +1,58 @@
+=== tests/cases/conformance/types/spread/spreadTypeVariable.ts ===
+function f1<T extends number>(arg: T) {
+>f1 : <T extends number>(arg: T) => any
+>arg : T
+
+  return { ...arg };
+>{ ...arg } : any
+>arg : T
+}
+
+function f2<T extends string[]>(arg: T) {
+>f2 : <T extends string[]>(arg: T) => T
+>arg : T
+
+  return { ...arg }
+>{ ...arg } : T
+>arg : T
+}
+
+function f3<T extends number | string[]>(arg: T) {
+>f3 : <T extends number | string[]>(arg: T) => any
+>arg : T
+
+  return { ...arg }
+>{ ...arg } : any
+>arg : T
+}
+
+function f4<T extends number | { [key: string]: any }>(arg: T) {
+>f4 : <T extends number | { [key: string]: any; }>(arg: T) => any
+>key : string
+>arg : T
+
+  return { ...arg }
+>{ ...arg } : any
+>arg : T
+}
+
+function f5<T extends string[] | { [key: string]: any }>(arg: T) {
+>f5 : <T extends string[] | { [key: string]: any; }>(arg: T) => T
+>key : string
+>arg : T
+
+  return { ...arg }
+>{ ...arg } : T
+>arg : T
+}
+
+function f6<T>(arg: T) {
+>f6 : <T>(arg: T) => T
+>arg : T
+
+  return { ...arg }
+>{ ...arg } : T
+>arg : T
+}
+
+
diff --git a/tests/baselines/reference/typedArraysSubarray.js b/tests/baselines/reference/typedArraysSubarray.js
new file mode 100644
index 00000000000..c20bfab2edc
--- /dev/null
+++ b/tests/baselines/reference/typedArraysSubarray.js
@@ -0,0 +1,120 @@
+//// [typedArraysSubarray.ts]
+function int8ArraySubarray() {
+    var arr = new Int8Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function uint8ArraySubarray() {
+    var arr = new Uint8Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function uint8ClampedArraySubarray() {
+    var arr = new Uint8ClampedArray(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function int16ArraySubarray() {
+    var arr = new Int16Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function uint16ArraySubarray() {
+    var arr = new Uint16Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function int32ArraySubarray() {
+    var arr = new Int32Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function uint32ArraySubarray() {
+    var arr = new Uint32Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function float32ArraySubarray() {
+    var arr = new Float32Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function float64ArraySubarray() {
+    var arr = new Float64Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+
+//// [typedArraysSubarray.js]
+function int8ArraySubarray() {
+    var arr = new Int8Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+function uint8ArraySubarray() {
+    var arr = new Uint8Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+function uint8ClampedArraySubarray() {
+    var arr = new Uint8ClampedArray(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+function int16ArraySubarray() {
+    var arr = new Int16Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+function uint16ArraySubarray() {
+    var arr = new Uint16Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+function int32ArraySubarray() {
+    var arr = new Int32Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+function uint32ArraySubarray() {
+    var arr = new Uint32Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+function float32ArraySubarray() {
+    var arr = new Float32Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+function float64ArraySubarray() {
+    var arr = new Float64Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
diff --git a/tests/baselines/reference/typedArraysSubarray.symbols b/tests/baselines/reference/typedArraysSubarray.symbols
new file mode 100644
index 00000000000..7beebb9d585
--- /dev/null
+++ b/tests/baselines/reference/typedArraysSubarray.symbols
@@ -0,0 +1,208 @@
+=== tests/cases/compiler/typedArraysSubarray.ts ===
+function int8ArraySubarray() {
+>int8ArraySubarray : Symbol(int8ArraySubarray, Decl(typedArraysSubarray.ts, 0, 0))
+
+    var arr = new Int8Array(10);
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 1, 7))
+>Int8Array : Symbol(Int8Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray();
+>arr.subarray : Symbol(Int8Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 1, 7))
+>subarray : Symbol(Int8Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0);
+>arr.subarray : Symbol(Int8Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 1, 7))
+>subarray : Symbol(Int8Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0, 10);
+>arr.subarray : Symbol(Int8Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 1, 7))
+>subarray : Symbol(Int8Array.subarray, Decl(lib.es5.d.ts, --, --))
+}
+
+function uint8ArraySubarray() {
+>uint8ArraySubarray : Symbol(uint8ArraySubarray, Decl(typedArraysSubarray.ts, 5, 1))
+
+    var arr = new Uint8Array(10);
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 8, 7))
+>Uint8Array : Symbol(Uint8Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray();
+>arr.subarray : Symbol(Uint8Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 8, 7))
+>subarray : Symbol(Uint8Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0);
+>arr.subarray : Symbol(Uint8Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 8, 7))
+>subarray : Symbol(Uint8Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0, 10);
+>arr.subarray : Symbol(Uint8Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 8, 7))
+>subarray : Symbol(Uint8Array.subarray, Decl(lib.es5.d.ts, --, --))
+}
+
+function uint8ClampedArraySubarray() {
+>uint8ClampedArraySubarray : Symbol(uint8ClampedArraySubarray, Decl(typedArraysSubarray.ts, 12, 1))
+
+    var arr = new Uint8ClampedArray(10);
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 15, 7))
+>Uint8ClampedArray : Symbol(Uint8ClampedArray, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray();
+>arr.subarray : Symbol(Uint8ClampedArray.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 15, 7))
+>subarray : Symbol(Uint8ClampedArray.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0);
+>arr.subarray : Symbol(Uint8ClampedArray.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 15, 7))
+>subarray : Symbol(Uint8ClampedArray.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0, 10);
+>arr.subarray : Symbol(Uint8ClampedArray.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 15, 7))
+>subarray : Symbol(Uint8ClampedArray.subarray, Decl(lib.es5.d.ts, --, --))
+}
+
+function int16ArraySubarray() {
+>int16ArraySubarray : Symbol(int16ArraySubarray, Decl(typedArraysSubarray.ts, 19, 1))
+
+    var arr = new Int16Array(10);
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 22, 7))
+>Int16Array : Symbol(Int16Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray();
+>arr.subarray : Symbol(Int16Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 22, 7))
+>subarray : Symbol(Int16Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0);
+>arr.subarray : Symbol(Int16Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 22, 7))
+>subarray : Symbol(Int16Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0, 10);
+>arr.subarray : Symbol(Int16Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 22, 7))
+>subarray : Symbol(Int16Array.subarray, Decl(lib.es5.d.ts, --, --))
+}
+
+function uint16ArraySubarray() {
+>uint16ArraySubarray : Symbol(uint16ArraySubarray, Decl(typedArraysSubarray.ts, 26, 1))
+
+    var arr = new Uint16Array(10);
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 29, 7))
+>Uint16Array : Symbol(Uint16Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray();
+>arr.subarray : Symbol(Uint16Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 29, 7))
+>subarray : Symbol(Uint16Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0);
+>arr.subarray : Symbol(Uint16Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 29, 7))
+>subarray : Symbol(Uint16Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0, 10);
+>arr.subarray : Symbol(Uint16Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 29, 7))
+>subarray : Symbol(Uint16Array.subarray, Decl(lib.es5.d.ts, --, --))
+}
+
+function int32ArraySubarray() {
+>int32ArraySubarray : Symbol(int32ArraySubarray, Decl(typedArraysSubarray.ts, 33, 1))
+
+    var arr = new Int32Array(10);
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 36, 7))
+>Int32Array : Symbol(Int32Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray();
+>arr.subarray : Symbol(Int32Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 36, 7))
+>subarray : Symbol(Int32Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0);
+>arr.subarray : Symbol(Int32Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 36, 7))
+>subarray : Symbol(Int32Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0, 10);
+>arr.subarray : Symbol(Int32Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 36, 7))
+>subarray : Symbol(Int32Array.subarray, Decl(lib.es5.d.ts, --, --))
+}
+
+function uint32ArraySubarray() {
+>uint32ArraySubarray : Symbol(uint32ArraySubarray, Decl(typedArraysSubarray.ts, 40, 1))
+
+    var arr = new Uint32Array(10);
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 43, 7))
+>Uint32Array : Symbol(Uint32Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray();
+>arr.subarray : Symbol(Uint32Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 43, 7))
+>subarray : Symbol(Uint32Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0);
+>arr.subarray : Symbol(Uint32Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 43, 7))
+>subarray : Symbol(Uint32Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0, 10);
+>arr.subarray : Symbol(Uint32Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 43, 7))
+>subarray : Symbol(Uint32Array.subarray, Decl(lib.es5.d.ts, --, --))
+}
+
+function float32ArraySubarray() {
+>float32ArraySubarray : Symbol(float32ArraySubarray, Decl(typedArraysSubarray.ts, 47, 1))
+
+    var arr = new Float32Array(10);
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 50, 7))
+>Float32Array : Symbol(Float32Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray();
+>arr.subarray : Symbol(Float32Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 50, 7))
+>subarray : Symbol(Float32Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0);
+>arr.subarray : Symbol(Float32Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 50, 7))
+>subarray : Symbol(Float32Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0, 10);
+>arr.subarray : Symbol(Float32Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 50, 7))
+>subarray : Symbol(Float32Array.subarray, Decl(lib.es5.d.ts, --, --))
+}
+
+function float64ArraySubarray() {
+>float64ArraySubarray : Symbol(float64ArraySubarray, Decl(typedArraysSubarray.ts, 54, 1))
+
+    var arr = new Float64Array(10);
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 57, 7))
+>Float64Array : Symbol(Float64Array, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray();
+>arr.subarray : Symbol(Float64Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 57, 7))
+>subarray : Symbol(Float64Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0);
+>arr.subarray : Symbol(Float64Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 57, 7))
+>subarray : Symbol(Float64Array.subarray, Decl(lib.es5.d.ts, --, --))
+
+    arr.subarray(0, 10);
+>arr.subarray : Symbol(Float64Array.subarray, Decl(lib.es5.d.ts, --, --))
+>arr : Symbol(arr, Decl(typedArraysSubarray.ts, 57, 7))
+>subarray : Symbol(Float64Array.subarray, Decl(lib.es5.d.ts, --, --))
+}
+
diff --git a/tests/baselines/reference/typedArraysSubarray.types b/tests/baselines/reference/typedArraysSubarray.types
new file mode 100644
index 00000000000..5e31d7992a5
--- /dev/null
+++ b/tests/baselines/reference/typedArraysSubarray.types
@@ -0,0 +1,280 @@
+=== tests/cases/compiler/typedArraysSubarray.ts ===
+function int8ArraySubarray() {
+>int8ArraySubarray : () => void
+
+    var arr = new Int8Array(10);
+>arr : Int8Array
+>new Int8Array(10) : Int8Array
+>Int8Array : Int8ArrayConstructor
+>10 : 10
+
+    arr.subarray();
+>arr.subarray() : Int8Array
+>arr.subarray : (begin?: number, end?: number) => Int8Array
+>arr : Int8Array
+>subarray : (begin?: number, end?: number) => Int8Array
+
+    arr.subarray(0);
+>arr.subarray(0) : Int8Array
+>arr.subarray : (begin?: number, end?: number) => Int8Array
+>arr : Int8Array
+>subarray : (begin?: number, end?: number) => Int8Array
+>0 : 0
+
+    arr.subarray(0, 10);
+>arr.subarray(0, 10) : Int8Array
+>arr.subarray : (begin?: number, end?: number) => Int8Array
+>arr : Int8Array
+>subarray : (begin?: number, end?: number) => Int8Array
+>0 : 0
+>10 : 10
+}
+
+function uint8ArraySubarray() {
+>uint8ArraySubarray : () => void
+
+    var arr = new Uint8Array(10);
+>arr : Uint8Array
+>new Uint8Array(10) : Uint8Array
+>Uint8Array : Uint8ArrayConstructor
+>10 : 10
+
+    arr.subarray();
+>arr.subarray() : Uint8Array
+>arr.subarray : (begin?: number, end?: number) => Uint8Array
+>arr : Uint8Array
+>subarray : (begin?: number, end?: number) => Uint8Array
+
+    arr.subarray(0);
+>arr.subarray(0) : Uint8Array
+>arr.subarray : (begin?: number, end?: number) => Uint8Array
+>arr : Uint8Array
+>subarray : (begin?: number, end?: number) => Uint8Array
+>0 : 0
+
+    arr.subarray(0, 10);
+>arr.subarray(0, 10) : Uint8Array
+>arr.subarray : (begin?: number, end?: number) => Uint8Array
+>arr : Uint8Array
+>subarray : (begin?: number, end?: number) => Uint8Array
+>0 : 0
+>10 : 10
+}
+
+function uint8ClampedArraySubarray() {
+>uint8ClampedArraySubarray : () => void
+
+    var arr = new Uint8ClampedArray(10);
+>arr : Uint8ClampedArray
+>new Uint8ClampedArray(10) : Uint8ClampedArray
+>Uint8ClampedArray : Uint8ClampedArrayConstructor
+>10 : 10
+
+    arr.subarray();
+>arr.subarray() : Uint8ClampedArray
+>arr.subarray : (begin?: number, end?: number) => Uint8ClampedArray
+>arr : Uint8ClampedArray
+>subarray : (begin?: number, end?: number) => Uint8ClampedArray
+
+    arr.subarray(0);
+>arr.subarray(0) : Uint8ClampedArray
+>arr.subarray : (begin?: number, end?: number) => Uint8ClampedArray
+>arr : Uint8ClampedArray
+>subarray : (begin?: number, end?: number) => Uint8ClampedArray
+>0 : 0
+
+    arr.subarray(0, 10);
+>arr.subarray(0, 10) : Uint8ClampedArray
+>arr.subarray : (begin?: number, end?: number) => Uint8ClampedArray
+>arr : Uint8ClampedArray
+>subarray : (begin?: number, end?: number) => Uint8ClampedArray
+>0 : 0
+>10 : 10
+}
+
+function int16ArraySubarray() {
+>int16ArraySubarray : () => void
+
+    var arr = new Int16Array(10);
+>arr : Int16Array
+>new Int16Array(10) : Int16Array
+>Int16Array : Int16ArrayConstructor
+>10 : 10
+
+    arr.subarray();
+>arr.subarray() : Int16Array
+>arr.subarray : (begin?: number, end?: number) => Int16Array
+>arr : Int16Array
+>subarray : (begin?: number, end?: number) => Int16Array
+
+    arr.subarray(0);
+>arr.subarray(0) : Int16Array
+>arr.subarray : (begin?: number, end?: number) => Int16Array
+>arr : Int16Array
+>subarray : (begin?: number, end?: number) => Int16Array
+>0 : 0
+
+    arr.subarray(0, 10);
+>arr.subarray(0, 10) : Int16Array
+>arr.subarray : (begin?: number, end?: number) => Int16Array
+>arr : Int16Array
+>subarray : (begin?: number, end?: number) => Int16Array
+>0 : 0
+>10 : 10
+}
+
+function uint16ArraySubarray() {
+>uint16ArraySubarray : () => void
+
+    var arr = new Uint16Array(10);
+>arr : Uint16Array
+>new Uint16Array(10) : Uint16Array
+>Uint16Array : Uint16ArrayConstructor
+>10 : 10
+
+    arr.subarray();
+>arr.subarray() : Uint16Array
+>arr.subarray : (begin?: number, end?: number) => Uint16Array
+>arr : Uint16Array
+>subarray : (begin?: number, end?: number) => Uint16Array
+
+    arr.subarray(0);
+>arr.subarray(0) : Uint16Array
+>arr.subarray : (begin?: number, end?: number) => Uint16Array
+>arr : Uint16Array
+>subarray : (begin?: number, end?: number) => Uint16Array
+>0 : 0
+
+    arr.subarray(0, 10);
+>arr.subarray(0, 10) : Uint16Array
+>arr.subarray : (begin?: number, end?: number) => Uint16Array
+>arr : Uint16Array
+>subarray : (begin?: number, end?: number) => Uint16Array
+>0 : 0
+>10 : 10
+}
+
+function int32ArraySubarray() {
+>int32ArraySubarray : () => void
+
+    var arr = new Int32Array(10);
+>arr : Int32Array
+>new Int32Array(10) : Int32Array
+>Int32Array : Int32ArrayConstructor
+>10 : 10
+
+    arr.subarray();
+>arr.subarray() : Int32Array
+>arr.subarray : (begin?: number, end?: number) => Int32Array
+>arr : Int32Array
+>subarray : (begin?: number, end?: number) => Int32Array
+
+    arr.subarray(0);
+>arr.subarray(0) : Int32Array
+>arr.subarray : (begin?: number, end?: number) => Int32Array
+>arr : Int32Array
+>subarray : (begin?: number, end?: number) => Int32Array
+>0 : 0
+
+    arr.subarray(0, 10);
+>arr.subarray(0, 10) : Int32Array
+>arr.subarray : (begin?: number, end?: number) => Int32Array
+>arr : Int32Array
+>subarray : (begin?: number, end?: number) => Int32Array
+>0 : 0
+>10 : 10
+}
+
+function uint32ArraySubarray() {
+>uint32ArraySubarray : () => void
+
+    var arr = new Uint32Array(10);
+>arr : Uint32Array
+>new Uint32Array(10) : Uint32Array
+>Uint32Array : Uint32ArrayConstructor
+>10 : 10
+
+    arr.subarray();
+>arr.subarray() : Uint32Array
+>arr.subarray : (begin?: number, end?: number) => Uint32Array
+>arr : Uint32Array
+>subarray : (begin?: number, end?: number) => Uint32Array
+
+    arr.subarray(0);
+>arr.subarray(0) : Uint32Array
+>arr.subarray : (begin?: number, end?: number) => Uint32Array
+>arr : Uint32Array
+>subarray : (begin?: number, end?: number) => Uint32Array
+>0 : 0
+
+    arr.subarray(0, 10);
+>arr.subarray(0, 10) : Uint32Array
+>arr.subarray : (begin?: number, end?: number) => Uint32Array
+>arr : Uint32Array
+>subarray : (begin?: number, end?: number) => Uint32Array
+>0 : 0
+>10 : 10
+}
+
+function float32ArraySubarray() {
+>float32ArraySubarray : () => void
+
+    var arr = new Float32Array(10);
+>arr : Float32Array
+>new Float32Array(10) : Float32Array
+>Float32Array : Float32ArrayConstructor
+>10 : 10
+
+    arr.subarray();
+>arr.subarray() : Float32Array
+>arr.subarray : (begin?: number, end?: number) => Float32Array
+>arr : Float32Array
+>subarray : (begin?: number, end?: number) => Float32Array
+
+    arr.subarray(0);
+>arr.subarray(0) : Float32Array
+>arr.subarray : (begin?: number, end?: number) => Float32Array
+>arr : Float32Array
+>subarray : (begin?: number, end?: number) => Float32Array
+>0 : 0
+
+    arr.subarray(0, 10);
+>arr.subarray(0, 10) : Float32Array
+>arr.subarray : (begin?: number, end?: number) => Float32Array
+>arr : Float32Array
+>subarray : (begin?: number, end?: number) => Float32Array
+>0 : 0
+>10 : 10
+}
+
+function float64ArraySubarray() {
+>float64ArraySubarray : () => void
+
+    var arr = new Float64Array(10);
+>arr : Float64Array
+>new Float64Array(10) : Float64Array
+>Float64Array : Float64ArrayConstructor
+>10 : 10
+
+    arr.subarray();
+>arr.subarray() : Float64Array
+>arr.subarray : (begin?: number, end?: number) => Float64Array
+>arr : Float64Array
+>subarray : (begin?: number, end?: number) => Float64Array
+
+    arr.subarray(0);
+>arr.subarray(0) : Float64Array
+>arr.subarray : (begin?: number, end?: number) => Float64Array
+>arr : Float64Array
+>subarray : (begin?: number, end?: number) => Float64Array
+>0 : 0
+
+    arr.subarray(0, 10);
+>arr.subarray(0, 10) : Float64Array
+>arr.subarray : (begin?: number, end?: number) => Float64Array
+>arr : Float64Array
+>subarray : (begin?: number, end?: number) => Float64Array
+>0 : 0
+>10 : 10
+}
+
diff --git a/tests/baselines/reference/unionTypeWithIndexSignature.errors.txt b/tests/baselines/reference/unionTypeWithIndexSignature.errors.txt
index 14a3ffc58a6..8ad20f21060 100644
--- a/tests/baselines/reference/unionTypeWithIndexSignature.errors.txt
+++ b/tests/baselines/reference/unionTypeWithIndexSignature.errors.txt
@@ -1,5 +1,5 @@
 tests/cases/conformance/types/union/unionTypeWithIndexSignature.ts(11,3): error TS2339: Property 'bar' does not exist on type 'Missing'.
-  Property 'bar' does not exist on type '{ [s: string]: string; }'.
+  Property 'bar' does not exist on type '{ foo: boolean; }'.
 tests/cases/conformance/types/union/unionTypeWithIndexSignature.ts(14,4): error TS2540: Cannot assign to 'foo' because it is a read-only property.
 tests/cases/conformance/types/union/unionTypeWithIndexSignature.ts(24,1): error TS7053: Element implicitly has an 'any' type because expression of type '1' can't be used to index type 'Both'.
   Property '1' does not exist on type 'Both'.
@@ -22,7 +22,7 @@ tests/cases/conformance/types/union/unionTypeWithIndexSignature.ts(26,1): error
     m.bar
       ~~~
 !!! error TS2339: Property 'bar' does not exist on type 'Missing'.
-!!! error TS2339:   Property 'bar' does not exist on type '{ [s: string]: string; }'.
+!!! error TS2339:   Property 'bar' does not exist on type '{ foo: boolean; }'.
     type RO = { foo: number } | { readonly [s: string]: string }
     declare var ro: RO
     ro.foo = 'not allowed'
diff --git a/tests/cases/compiler/bigint64ArraySubarray.ts b/tests/cases/compiler/bigint64ArraySubarray.ts
new file mode 100644
index 00000000000..1f8e3da9d18
--- /dev/null
+++ b/tests/cases/compiler/bigint64ArraySubarray.ts
@@ -0,0 +1,8 @@
+// @target: esnext
+
+function bigInt64ArraySubarray() {
+    var arr = new BigInt64Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
diff --git a/tests/cases/compiler/jsFileCompilationTypeParameterSyntaxOfClassExpression.ts b/tests/cases/compiler/jsFileCompilationTypeParameterSyntaxOfClassExpression.ts
new file mode 100644
index 00000000000..81b07637422
--- /dev/null
+++ b/tests/cases/compiler/jsFileCompilationTypeParameterSyntaxOfClassExpression.ts
@@ -0,0 +1,4 @@
+// @allowJs: true
+// @noEmit: true
+// @filename: a.js
+const Bar = class<T> {};
diff --git a/tests/cases/compiler/regexMatchAll-esnext.ts b/tests/cases/compiler/regexMatchAll-esnext.ts
new file mode 100644
index 00000000000..7c72b652540
--- /dev/null
+++ b/tests/cases/compiler/regexMatchAll-esnext.ts
@@ -0,0 +1,5 @@
+// @target: esnext
+
+const matches = /\w/g[Symbol.matchAll]("matchAll");
+const array = [...matches];
+const { index, input } = array[0];
diff --git a/tests/cases/compiler/spreadInvalidArgumentType.ts b/tests/cases/compiler/spreadInvalidArgumentType.ts
index d75d606cc73..82e59fbac59 100644
--- a/tests/cases/compiler/spreadInvalidArgumentType.ts
+++ b/tests/cases/compiler/spreadInvalidArgumentType.ts
@@ -30,7 +30,7 @@ function f<T extends { b: string }>(p1: T, p2: T[]) {
     var o1 = { ...p1 };  // OK, generic type paramterre
     var o2 = { ...p2 };  // OK
     var o3 = { ...t };   // OK, generic type paramter
-    var o4 = { ...i };   // OK, index access
+    var o4 = { ...i };   // Error, index access
     var o5 = { ...k };   // Error, index
     var o6 = { ...mapped_generic }; // OK, generic mapped object type
     var o7 = { ...mapped };  // OK, non-generic mapped type
diff --git a/tests/cases/compiler/typedArraysSubarray.ts b/tests/cases/compiler/typedArraysSubarray.ts
new file mode 100644
index 00000000000..f85b953b839
--- /dev/null
+++ b/tests/cases/compiler/typedArraysSubarray.ts
@@ -0,0 +1,62 @@
+function int8ArraySubarray() {
+    var arr = new Int8Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function uint8ArraySubarray() {
+    var arr = new Uint8Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function uint8ClampedArraySubarray() {
+    var arr = new Uint8ClampedArray(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function int16ArraySubarray() {
+    var arr = new Int16Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function uint16ArraySubarray() {
+    var arr = new Uint16Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function int32ArraySubarray() {
+    var arr = new Int32Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function uint32ArraySubarray() {
+    var arr = new Uint32Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function float32ArraySubarray() {
+    var arr = new Float32Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
+
+function float64ArraySubarray() {
+    var arr = new Float64Array(10);
+    arr.subarray();
+    arr.subarray(0);
+    arr.subarray(0, 10);
+}
diff --git a/tests/cases/conformance/types/spread/spreadTypeVariable.ts b/tests/cases/conformance/types/spread/spreadTypeVariable.ts
new file mode 100644
index 00000000000..7a0054cfc86
--- /dev/null
+++ b/tests/cases/conformance/types/spread/spreadTypeVariable.ts
@@ -0,0 +1,24 @@
+function f1<T extends number>(arg: T) {
+  return { ...arg };
+}
+
+function f2<T extends string[]>(arg: T) {
+  return { ...arg }
+}
+
+function f3<T extends number | string[]>(arg: T) {
+  return { ...arg }
+}
+
+function f4<T extends number | { [key: string]: any }>(arg: T) {
+  return { ...arg }
+}
+
+function f5<T extends string[] | { [key: string]: any }>(arg: T) {
+  return { ...arg }
+}
+
+function f6<T>(arg: T) {
+  return { ...arg }
+}
+
diff --git a/tests/lib/lib.d.ts b/tests/lib/lib.d.ts
index 5f089bb3c82..9edbdec2b1b 100644
--- a/tests/lib/lib.d.ts
+++ b/tests/lib/lib.d.ts
@@ -1622,7 +1622,7 @@ interface Int8Array {
       * @param begin The index of the beginning of the array.
       * @param end The index of the end of the array.
       */
-    subarray(begin: number, end?: number): Int8Array;
+    subarray(begin?: number, end?: number): Int8Array;
 
     /**
       * Converts a number to a string by using the current locale.
@@ -1895,7 +1895,7 @@ interface Uint8Array {
       * @param begin The index of the beginning of the array.
       * @param end The index of the end of the array.
       */
-    subarray(begin: number, end?: number): Uint8Array;
+    subarray(begin?: number, end?: number): Uint8Array;
 
     /**
       * Converts a number to a string by using the current locale.
@@ -2169,7 +2169,7 @@ interface Uint8ClampedArray {
       * @param begin The index of the beginning of the array.
       * @param end The index of the end of the array.
       */
-    subarray(begin: number, end?: number): Uint8ClampedArray;
+    subarray(begin?: number, end?: number): Uint8ClampedArray;
 
     /**
       * Converts a number to a string by using the current locale.
@@ -2442,7 +2442,7 @@ interface Int16Array {
       * @param begin The index of the beginning of the array.
       * @param end The index of the end of the array.
       */
-    subarray(begin: number, end?: number): Int16Array;
+    subarray(begin?: number, end?: number): Int16Array;
 
     /**
       * Converts a number to a string by using the current locale.
@@ -2716,7 +2716,7 @@ interface Uint16Array {
       * @param begin The index of the beginning of the array.
       * @param end The index of the end of the array.
       */
-    subarray(begin: number, end?: number): Uint16Array;
+    subarray(begin?: number, end?: number): Uint16Array;
 
     /**
       * Converts a number to a string by using the current locale.
@@ -2989,7 +2989,7 @@ interface Int32Array {
       * @param begin The index of the beginning of the array.
       * @param end The index of the end of the array.
       */
-    subarray(begin: number, end?: number): Int32Array;
+    subarray(begin?: number, end?: number): Int32Array;
 
     /**
       * Converts a number to a string by using the current locale.
@@ -3262,7 +3262,7 @@ interface Uint32Array {
       * @param begin The index of the beginning of the array.
       * @param end The index of the end of the array.
       */
-    subarray(begin: number, end?: number): Uint32Array;
+    subarray(begin?: number, end?: number): Uint32Array;
 
     /**
       * Converts a number to a string by using the current locale.
@@ -3535,7 +3535,7 @@ interface Float32Array {
       * @param begin The index of the beginning of the array.
       * @param end The index of the end of the array.
       */
-    subarray(begin: number, end?: number): Float32Array;
+    subarray(begin?: number, end?: number): Float32Array;
 
     /**
       * Converts a number to a string by using the current locale.
@@ -3809,7 +3809,7 @@ interface Float64Array {
       * @param begin The index of the beginning of the array.
       * @param end The index of the end of the array.
       */
-    subarray(begin: number, end?: number): Float64Array;
+    subarray(begin?: number, end?: number): Float64Array;
 
     /**
       * Converts a number to a string by using the current locale.