typescript-eslint · kirkwaiblinger · Sep 1, 2025 · Aug 29, 2025 · Sep 1, 2025 · Sep 1, 2025
diff --git a/eslint.config.mjs b/eslint.config.mjs
@@ -236,7 +236,9 @@ export default defineConfig(
       'no-lonely-if': 'error',
       'no-mixed-operators': 'error',
       'no-process-exit': 'error',
+      'no-unassigned-vars': 'error',
       'no-unreachable-loop': 'error',
+      'no-useless-assignment': 'error',
       'no-useless-call': 'error',
       'no-useless-computed-key': 'error',
       'no-useless-concat': 'error',

diff --git a/packages/eslint-plugin/src/util/getFunctionHeadLoc.ts b/packages/eslint-plugin/src/util/getFunctionHeadLoc.ts
@@ -154,8 +154,8 @@ export function getFunctionHeadLoc(
   sourceCode: TSESLint.SourceCode,
 ): TSESTree.SourceLocation {
   const parent = node.parent;
-  let start: TSESTree.Position | null = null;
-  let end: TSESTree.Position | null = null;
+  let start: TSESTree.Position;
+  let end: TSESTree.Position;
 
   if (
     parent.type === AST_NODE_TYPES.MethodDefinition ||

diff --git a/packages/eslint-plugin/tools/generate-breaking-changes.mts b/packages/eslint-plugin/tools/generate-breaking-changes.mts
@@ -22,6 +22,7 @@ async function getNewRulesAsOfMajorVersion(
   // Normally we wouldn't condone using the 'eval' API...
   // But this is an internal-only script and it's the easiest way to convert
   // the JS raw text into a runtime object. 🤷
+  // eslint-disable-next-line no-unassigned-vars -- assigned by eval
   let oldRulesObject!: { rules: TypeScriptESLintRules };
   eval(`oldRulesObject = ${oldObjectText}`);
   const oldRuleNames = new Set(Object.keys(oldRulesObject.rules));

diff --git a/packages/rule-tester/src/RuleTester.ts b/packages/rule-tester/src/RuleTester.ts
@@ -761,8 +761,8 @@ export class RuleTester extends TestFramework {
 
     // Verify the code.
     let initialMessages: Linter.LintMessage[] | null = null;
-    let messages: Linter.LintMessage[] | null = null;
-    let fixedResult: SourceCodeFixer.AppliedFixes | null = null;
+    let messages: Linter.LintMessage[];
+    let fixedResult: SourceCodeFixer.AppliedFixes;
     let passNumber = 0;
     const outputs: string[] = [];
     const configWithoutCustomKeys = omitCustomConfigProperties(config);

diff --git a/packages/scope-manager/src/referencer/ClassVisitor.ts b/packages/scope-manager/src/referencer/ClassVisitor.ts
@@ -9,23 +9,18 @@ import { TypeVisitor } from './TypeVisitor';
 import { Visitor } from './Visitor';
 
 export class ClassVisitor extends Visitor {
-  readonly #classNode: TSESTree.ClassDeclaration | TSESTree.ClassExpression;
   readonly #referencer: Referencer;
 
-  constructor(
-    referencer: Referencer,
-    node: TSESTree.ClassDeclaration | TSESTree.ClassExpression,
-  ) {
+  constructor(referencer: Referencer) {
     super(referencer);
     this.#referencer = referencer;
-    this.#classNode = node;
   }
 
   static visit(
     referencer: Referencer,
     node: TSESTree.ClassDeclaration | TSESTree.ClassExpression,
   ): void {
-    const classVisitor = new ClassVisitor(referencer, node);
+    const classVisitor = new ClassVisitor(referencer);
     classVisitor.visitClass(node);
   }
 
@@ -97,18 +92,15 @@ export class ClassVisitor extends Visitor {
     }
 
     if (node.value.type === AST_NODE_TYPES.FunctionExpression) {
-      this.visitMethodFunction(node.value, node);
+      this.visitMethodFunction(node.value);
     } else {
       this.#referencer.visit(node.value);
     }
 
     node.decorators.forEach(d => this.#referencer.visit(d));
   }
 
-  protected visitMethodFunction(
-    node: TSESTree.FunctionExpression,
-    methodNode: TSESTree.MethodDefinition,
-  ): void {
+  protected visitMethodFunction(node: TSESTree.FunctionExpression): void {
     if (node.id) {
       // FunctionExpression with name creates its special scope;
       // FunctionExpressionNameScope.
@@ -122,71 +114,6 @@ export class ClassVisitor extends Visitor {
     // Consider this function is in the MethodDefinition.
     this.#referencer.scopeManager.nestFunctionScope(node, true);
 
-    /**
-     * class A {
-     *   @meta     // <--- check this
-     *   foo(a: Type) {}
-     *
-     *   @meta     // <--- check this
-     *   foo(): Type {}
-     * }
-     */
-    let withMethodDecorators = !!methodNode.decorators.length;
-    /**
-     * class A {
-     *   foo(
-     *     @meta    // <--- check this
-     *     a: Type
-     *   ) {}
-     *
-     *   set foo(
-     *     @meta    // <--- EXCEPT this. TS do nothing for this
-     *     a: Type
-     *   ) {}
-     * }
-     */
-    withMethodDecorators ||=
-      methodNode.kind !== 'set' &&
-      node.params.some(param => param.decorators.length);
-    if (!withMethodDecorators && methodNode.kind === 'set') {
-      const keyName = getLiteralMethodKeyName(methodNode);
-
-      /**
-       * class A {
-       *   @meta      // <--- check this
-       *   get a() {}
-       *   set ['a'](v: Type) {}
-       * }
-       */
-      if (
-        keyName != null &&
-        this.#classNode.body.body.find(
-          (node): node is TSESTree.MethodDefinition =>
-            node !== methodNode &&
-            node.type === AST_NODE_TYPES.MethodDefinition &&
-            // Node must both be static or not
-            node.static === methodNode.static &&
-            getLiteralMethodKeyName(node) === keyName,
-        )?.decorators.length
-      ) {
-        withMethodDecorators = true;
-      }
-    }
-
-    /**
-     * @meta      // <--- check this
-     * class A {
-     *   constructor(a: Type) {}
-     * }
-     */
-    if (
-      !withMethodDecorators &&
-      methodNode.kind === 'constructor' &&
-      this.#classNode.decorators.length
-    ) {
-      withMethodDecorators = true;
-    }
-
     // Process parameter declarations.
     for (const param of node.params) {
       this.visitPattern(
@@ -337,39 +264,3 @@ export class ClassVisitor extends Visitor {
     this.visitType(node);
   }
 }
-
-/**
- * Only if key is one of [identifier, string, number], ts will combine metadata of accessors .
- * class A {
- *   get a() {}
- *   set ['a'](v: Type) {}
- *
- *   get [1]() {}
- *   set [1](v: Type) {}
- *
- *   // Following won't be combined
- *   get [key]() {}
- *   set [key](v: Type) {}
- *
- *   get [true]() {}
- *   set [true](v: Type) {}
- *
- *   get ['a'+'b']() {}
- *   set ['a'+'b']() {}
- * }
- */
-function getLiteralMethodKeyName(
-  node: TSESTree.MethodDefinition,
-): number | string | null {
-  if (node.computed && node.key.type === AST_NODE_TYPES.Literal) {
-    if (
-      typeof node.key.value === 'string' ||
-      typeof node.key.value === 'number'
-    ) {
-      return node.key.value;
-    }
-  } else if (!node.computed && node.key.type === AST_NODE_TYPES.Identifier) {
-    return node.key.name;
-  }
-  return null;
-}
diff --git a/packages/scope-manager/tests/eslint-scope/es6-class.test.ts b/packages/scope-manager/tests/eslint-scope/es6-class.test.ts
@@ -140,6 +140,7 @@ describe('ES6 class', () => {
     assert.isScopeOfType(scope, ScopeType.global);
     expect(scope.block.type).toBe(AST_NODE_TYPES.Program);
     expect(scope.isStrict).toBe(false);
+    expect(variables).toHaveLength(0);
 
     scope = scopeManager.scopes[1];
     variables = getRealVariables(scope.variables);

diff --git a/packages/scope-manager/tests/eslint-scope/es6-object.test.ts b/packages/scope-manager/tests/eslint-scope/es6-object.test.ts
@@ -19,6 +19,7 @@ describe('ES6 object', () => {
     assert.isScopeOfType(scope, ScopeType.global);
     expect(scope.block.type).toBe(AST_NODE_TYPES.Program);
     expect(scope.isStrict).toBe(false);
+    expect(variables).toHaveLength(0);
 
     scope = scopeManager.scopes[1];
     variables = getRealVariables(scope.variables);
@@ -51,6 +52,7 @@ describe('ES6 object', () => {
     assert.isScopeOfType(scope, ScopeType.global);
     expect(scope.block.type).toBe(AST_NODE_TYPES.Program);
     expect(scope.isStrict).toBe(false);
+    expect(variables).toHaveLength(0);
 
     scope = scopeManager.scopes[1];
     variables = getRealVariables(scope.variables);

diff --git a/packages/website/src/components/editor/createProvideTwoslashInlay.ts b/packages/website/src/components/editor/createProvideTwoslashInlay.ts
@@ -8,14 +8,9 @@ import type * as ts from 'typescript';
 import type { SandboxInstance } from './useSandboxServices';
 
 function findTwoshashQueries(code: string): RegExpExecArray[] {
-  let match: RegExpExecArray | null = null;
-  const matches: RegExpExecArray[] = [];
   // RegExp that matches '^<spaces>//?<spaces>$'
-  const twoslashQueryRegex = /^(\s*\/\/\s*\^\?)\s*$/gm;
-  while ((match = twoslashQueryRegex.exec(code))) {
-    matches.push(match);
-  }
-  return matches;
+  const twoslashQueryRegex = /^(\s*\/\/\s*\^\?)\s*$/m;
+  return [...code.matchAll(twoslashQueryRegex)];
 }
 
 export function createTwoslashInlayProvider(