Merge branch 'main' into fix/62487

Author: a-tarasyuk

.github/workflows/ci.yml

@@ -164,12 +164,12 @@ jobs:
         run: npm test -- --no-lint --coverage
 
       - name: Upload coverage artifact
-        uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5.0.0
+        uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
         with:
           name: coverage
           path: coverage
 
-      - uses: codecov/codecov-action@5a1091511ad55cbe89839c7260b706298ca349f7 # v5.5.1
+      - uses: codecov/codecov-action@671740ac38dd9b0130fbe1cec585b89eea48d3de # v5.5.2
         with:
           use_oidc: ${{ !(github.event_name == 'pull_request' && github.event.pull_request.head.repo.fork) }}
           disable_search: true
@@ -211,7 +211,7 @@ jobs:
           node-version: 'lts/*'
       - run: npm ci
 
-      - uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
+      - uses: actions/cache@9255dc7a253b0ccc959486e2bca901246202afeb # v5.0.1
         with:
           path: ~/.cache/dprint
           key: ${{ runner.os }}-dprint-${{ hashFiles('package-lock.json', '.dprint.jsonc') }}
@@ -418,7 +418,7 @@ jobs:
 
       - name: Upload baseline diff artifact
         if: ${{ failure() && steps.check-baselines.conclusion == 'failure' }}
-        uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5.0.0
+        uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
         with:
           name: fix_baselines.patch
           path: fix_baselines.patch

.github/workflows/codeql.yml

@@ -46,7 +46,7 @@ jobs:
 
       # Initializes the CodeQL tools for scanning.
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@cf1bb45a277cb3c205638b2cd5c984db1c46a412 # v4.31.7
+        uses: github/codeql-action/init@1b168cd39490f61582a9beae412bb7057a6b2c4e # v4.31.8
         with:
           config-file: ./.github/codeql/codeql-configuration.yml
         # Override language selection by uncommenting this and choosing your languages
@@ -56,7 +56,7 @@ jobs:
       # Autobuild attempts to build any compiled languages (C/C++, C#, or Java).
       # If this step fails, then you should remove it and run the build manually (see below).
       - name: Autobuild
-        uses: github/codeql-action/autobuild@cf1bb45a277cb3c205638b2cd5c984db1c46a412 # v4.31.7
+        uses: github/codeql-action/autobuild@1b168cd39490f61582a9beae412bb7057a6b2c4e # v4.31.8
 
       # ℹ️ Command-line programs to run using the OS shell.
       # 📚 See https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstepsrun
@@ -70,4 +70,4 @@ jobs:
       #     make release
 
       - name: Perform CodeQL Analysis
-        uses: github/codeql-action/analyze@cf1bb45a277cb3c205638b2cd5c984db1c46a412 # v4.31.7
+        uses: github/codeql-action/analyze@1b168cd39490f61582a9beae412bb7057a6b2c4e # v4.31.8

.github/workflows/release-branch-artifact.yaml

@@ -44,7 +44,7 @@ jobs:
           npm pack ./
           mv typescript-*.tgz typescript.tgz
       - name: Upload built tarfile
-        uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5.0.0
+        uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
         with:
           name: tgz
           path: typescript.tgz

.github/workflows/scorecard.yml

@@ -47,14 +47,14 @@ jobs:
       # Upload the results as artifacts (optional). Commenting out will disable uploads of run results in SARIF
       # format to the repository Actions tab.
       - name: 'Upload artifact'
-        uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5.0.0
+        uses: actions/upload-artifact@b7c566a772e6b6bfb58ed0dc250532a479d7789f # v6.0.0
         with:
           name: SARIF file
           path: results.sarif
           retention-days: 5
 
       # Upload the results to GitHub's code scanning dashboard.
       - name: 'Upload to code-scanning'
-        uses: github/codeql-action/upload-sarif@cf1bb45a277cb3c205638b2cd5c984db1c46a412 # v4.31.7
+        uses: github/codeql-action/upload-sarif@1b168cd39490f61582a9beae412bb7057a6b2c4e # v4.31.8
         with:
           sarif_file: results.sarif

CONTRIBUTING.md

@@ -1,3 +1,7 @@
+# Note
+
+🚨 **Important** 🚨: All code changes should be submitted to the https://github.com/microsoft/typescript-go repo. Development in this codebase [is winding down](https://devblogs.microsoft.com/typescript/progress-on-typescript-7-december-2025/#typescript-6.0-is-the-last-javascript-based-release) and PRs will only be merged if they fix **critical** 6.0 issues (at minimum, any bug that existed in 5.9 is not critical unless it's a security issue).
+
 # Instructions for Logging Issues
 
 ## 1. Read the FAQ
@@ -45,7 +49,7 @@ In general, things we find useful when reviewing suggestions are:
   * Code examples showing the generated JavaScript (if applicable)
 * If relevant, precedent in other languages can be useful for establishing context and expected behavior
 
-# Instructions for Contributing Code
+# Instructions for Contributing Code (Legacy)
 
 ## What You'll Need
 

scripts/CopyrightNotice.txt

@@ -7,7 +7,7 @@ License at http://www.apache.org/licenses/LICENSE-2.0
 THIS CODE IS PROVIDED ON AN *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
 WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
-MERCHANTABLITY OR NON-INFRINGEMENT.
+MERCHANTABILITY OR NON-INFRINGEMENT.
 
 See the Apache Version 2.0 License for specific language governing permissions
 and limitations under the License.

src/compiler/binder.ts

@@ -1000,6 +1000,7 @@ function createBinder(): (file: SourceFile, options: CompilerOptions) => void {
             const saveExceptionTarget = currentExceptionTarget;
             const saveActiveLabelList = activeLabelList;
             const saveHasExplicitReturn = hasExplicitReturn;
+            const saveSeenThisKeyword = seenThisKeyword;
             const isImmediatelyInvoked = (
                 containerFlags & ContainerFlags.IsFunctionExpression &&
                 !hasSyntacticModifier(node, ModifierFlags.Async) &&
@@ -1022,19 +1023,22 @@ function createBinder(): (file: SourceFile, options: CompilerOptions) => void {
             currentContinueTarget = undefined;
             activeLabelList = undefined;
             hasExplicitReturn = false;
+            seenThisKeyword = false;
             bindChildren(node);
-            // Reset all reachability check related flags on node (for incremental scenarios)
-            node.flags &= ~NodeFlags.ReachabilityAndEmitFlags;
+            // Reset flags (for incremental scenarios)
+            node.flags &= ~(NodeFlags.ReachabilityAndEmitFlags | NodeFlags.ContainsThis);
             if (!(currentFlow.flags & FlowFlags.Unreachable) && containerFlags & ContainerFlags.IsFunctionLike && nodeIsPresent((node as FunctionLikeDeclaration | ClassStaticBlockDeclaration).body)) {
                 node.flags |= NodeFlags.HasImplicitReturn;
                 if (hasExplicitReturn) node.flags |= NodeFlags.HasExplicitReturn;
                 (node as FunctionLikeDeclaration | ClassStaticBlockDeclaration).endFlowNode = currentFlow;
             }
+            if (seenThisKeyword) {
+                node.flags |= NodeFlags.ContainsThis;
+            }
             if (node.kind === SyntaxKind.SourceFile) {
                 node.flags |= emitFlags;
                 (node as SourceFile).endFlowNode = currentFlow;
             }
-
             if (currentReturnTarget) {
                 addAntecedent(currentReturnTarget, currentFlow);
                 currentFlow = finishFlowLabel(currentReturnTarget);
@@ -1051,12 +1055,15 @@ function createBinder(): (file: SourceFile, options: CompilerOptions) => void {
             currentExceptionTarget = saveExceptionTarget;
             activeLabelList = saveActiveLabelList;
             hasExplicitReturn = saveHasExplicitReturn;
+            seenThisKeyword = node.kind === SyntaxKind.ArrowFunction ? saveSeenThisKeyword || seenThisKeyword : saveSeenThisKeyword;
         }
         else if (containerFlags & ContainerFlags.IsInterface) {
+            const saveSeenThisKeyword = seenThisKeyword;
             seenThisKeyword = false;
             bindChildren(node);
             Debug.assertNotNode(node, isIdentifier); // ContainsThis cannot overlap with HasExtendedUnicodeEscape on Identifier
             node.flags = seenThisKeyword ? node.flags | NodeFlags.ContainsThis : node.flags & ~NodeFlags.ContainsThis;
+            seenThisKeyword = saveSeenThisKeyword;
         }
         else {
             bindChildren(node);
@@ -2852,6 +2859,9 @@ function createBinder(): (file: SourceFile, options: CompilerOptions) => void {
                 }
                 // falls through
             case SyntaxKind.ThisKeyword:
+                if (node.kind === SyntaxKind.ThisKeyword) {
+                    seenThisKeyword = true;
+                }
                 // TODO: Why use `isExpression` here? both Identifier and ThisKeyword are expressions.
                 if (currentFlow && (isExpression(node) || parent.kind === SyntaxKind.ShorthandPropertyAssignment)) {
                     (node as Identifier | ThisExpression).flowNode = currentFlow;
@@ -3833,28 +3843,27 @@ export function getContainerFlags(node: Node): ContainerFlags {
             // falls through
         case SyntaxKind.Constructor:
         case SyntaxKind.FunctionDeclaration:
+        case SyntaxKind.ClassStaticBlockDeclaration:
+            return ContainerFlags.IsContainer | ContainerFlags.IsControlFlowContainer | ContainerFlags.HasLocals | ContainerFlags.IsFunctionLike;
         case SyntaxKind.MethodSignature:
         case SyntaxKind.CallSignature:
         case SyntaxKind.JSDocSignature:
         case SyntaxKind.JSDocFunctionType:
         case SyntaxKind.FunctionType:
         case SyntaxKind.ConstructSignature:
         case SyntaxKind.ConstructorType:
-        case SyntaxKind.ClassStaticBlockDeclaration:
-            return ContainerFlags.IsContainer | ContainerFlags.IsControlFlowContainer | ContainerFlags.HasLocals | ContainerFlags.IsFunctionLike;
+            return ContainerFlags.IsContainer | ContainerFlags.HasLocals | ContainerFlags.IsFunctionLike;
 
         case SyntaxKind.JSDocImportTag:
             // treat as a container to prevent using an enclosing effective host, ensuring import bindings are scoped correctly
-            return ContainerFlags.IsContainer | ContainerFlags.IsControlFlowContainer | ContainerFlags.HasLocals;
+            return ContainerFlags.IsContainer | ContainerFlags.HasLocals;
 
         case SyntaxKind.FunctionExpression:
         case SyntaxKind.ArrowFunction:
             return ContainerFlags.IsContainer | ContainerFlags.IsControlFlowContainer | ContainerFlags.HasLocals | ContainerFlags.IsFunctionLike | ContainerFlags.IsFunctionExpression;
 
         case SyntaxKind.ModuleBlock:
             return ContainerFlags.IsControlFlowContainer;
-        case SyntaxKind.PropertyDeclaration:
-            return (node as PropertyDeclaration).initializer ? ContainerFlags.IsControlFlowContainer : 0;
 
         case SyntaxKind.CatchClause:
         case SyntaxKind.ForStatement:

src/compiler/checker.ts

@@ -347,7 +347,6 @@ import {
     getNamespaceDeclarationNode,
     getNewTargetContainer,
     getNonAugmentationDeclaration,
-    getNonModifierTokenPosOfNode,
     getNormalizedAbsolutePath,
     getObjectFlags,
     getOriginalNode,
@@ -21143,9 +21142,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 const { initializer } = node as JsxAttribute;
                 return !!initializer && isContextSensitive(initializer);
             }
-            case SyntaxKind.JsxExpression: {
+            case SyntaxKind.JsxExpression:
+            case SyntaxKind.YieldExpression: {
                 // It is possible to that node.expression is undefined (e.g <div x={} />)
-                const { expression } = node as JsxExpression;
+                const { expression } = node as JsxExpression | YieldExpression;
                 return !!expression && isContextSensitive(expression);
             }
         }
@@ -21154,7 +21154,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     }
 
     function isContextSensitiveFunctionLikeDeclaration(node: FunctionLikeDeclaration): boolean {
-        return hasContextSensitiveParameters(node) || hasContextSensitiveReturnExpression(node);
+        return hasContextSensitiveParameters(node) || hasContextSensitiveReturnExpression(node) || hasContextSensitiveYieldExpression(node);
     }
 
     function hasContextSensitiveReturnExpression(node: FunctionLikeDeclaration) {
@@ -21167,6 +21167,17 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return !!forEachReturnStatement(node.body as Block, statement => !!statement.expression && isContextSensitive(statement.expression));
     }
 
+    function hasContextSensitiveYieldExpression(node: FunctionLikeDeclaration): boolean {
+        // yield expressions can be context sensitive in situations like:
+        //
+        // declare function test(gen: () => Generator<(arg: number) => string, void, void>): void;
+        //
+        // test(function* () {
+        //   yield (arg) => String(arg);
+        // });
+        return !!(getFunctionFlags(node) & FunctionFlags.Generator && node.body && forEachYieldExpression(node.body as Block, isContextSensitive));
+    }
+
     function isContextSensitiveFunctionOrObjectLiteralMethod(func: Node): func is FunctionExpression | ArrowFunction | MethodDeclaration {
         return (isFunctionExpressionOrArrowFunction(func) || isObjectLiteralMethod(func)) &&
             isContextSensitiveFunctionLikeDeclaration(func);
@@ -32629,17 +32640,22 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             if (inferenceContext && contextFlags! & ContextFlags.Signature && some(inferenceContext.inferences, hasInferenceCandidatesOrDefault)) {
                 // For contextual signatures we incorporate all inferences made so far, e.g. from return
                 // types as well as arguments to the left in a function call.
-                return instantiateInstantiableTypes(contextualType, inferenceContext.nonFixingMapper);
+                const type = instantiateInstantiableTypes(contextualType, inferenceContext.nonFixingMapper);
+                if (!(type.flags & TypeFlags.AnyOrUnknown)) {
+                    return type;
+                }
             }
             if (inferenceContext?.returnMapper) {
                 // For other purposes (e.g. determining whether to produce literal types) we only
                 // incorporate inferences made from the return type in a function call. We remove
                 // the 'boolean' type from the contextual type such that contextually typed boolean
                 // literals actually end up widening to 'boolean' (see #48363).
                 const type = instantiateInstantiableTypes(contextualType, inferenceContext.returnMapper);
-                return type.flags & TypeFlags.Union && containsType((type as UnionType).types, regularFalseType) && containsType((type as UnionType).types, regularTrueType) ?
-                    filterType(type, t => t !== regularFalseType && t !== regularTrueType) :
-                    type;
+                if (!(type.flags & TypeFlags.AnyOrUnknown)) {
+                    return type.flags & TypeFlags.Union && containsType((type as UnionType).types, regularFalseType) && containsType((type as UnionType).types, regularTrueType) ?
+                        filterType(type, t => t !== regularFalseType && t !== regularTrueType) :
+                        type;
+                }
             }
         }
         return contextualType;
@@ -48104,12 +48120,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             if (isIdentifier(node.name)) {
                 checkCollisionsForDeclarationName(node, node.name);
                 if (!(node.flags & (NodeFlags.Namespace | NodeFlags.GlobalAugmentation))) {
-                    const sourceFile = getSourceFileOfNode(node);
-                    const pos = getNonModifierTokenPosOfNode(node);
-                    const span = getSpanOfTokenAtPosition(sourceFile, pos);
-                    suggestionDiagnostics.add(
-                        createFileDiagnostic(sourceFile, span.start, span.length, Diagnostics.A_namespace_declaration_should_not_be_declared_using_the_module_keyword_Please_use_the_namespace_keyword_instead),
-                    );
+                    error(node.name, Diagnostics.A_namespace_declaration_should_not_be_declared_using_the_module_keyword_Please_use_the_namespace_keyword_instead);
                 }
             }
 

src/compiler/diagnosticMessages.json

@@ -1821,9 +1821,8 @@
         "code": 1539
     },
     "A 'namespace' declaration should not be declared using the 'module' keyword. Please use the 'namespace' keyword instead.": {
-        "category": "Suggestion",
-        "code": 1540,
-        "reportsDeprecated": true
+        "category": "Error",
+        "code": 1540
     },
     "Type-only import of an ECMAScript module from a CommonJS module must have a 'resolution-mode' attribute.": {
         "category": "Error",

src/compiler/types.ts

@@ -6526,7 +6526,7 @@ export const enum ObjectFlags {
     /** @internal */
     ContainsObjectOrArrayLiteral = 1 << 17, // Type is or contains object literal type
     /** @internal */
-    NonInferrableType = 1 << 18, // Type is or contains anyFunctionType or silentNeverType
+    NonInferrableType = 1 << 18, // Type is or contains anyFunctionType or silentNeverType, or it's a context free `returnTypeOnly`
     /** @internal */
     CouldContainTypeVariablesComputed = 1 << 19, // CouldContainTypeVariables flag has been computed
     /** @internal */