typescript-eslint · Higangssh · Nov 16, 2025 · Nov 16, 2025 · Nov 17, 2025 · Nov 17, 2025
diff --git a/packages/eslint-plugin/src/rules/restrict-template-expressions.ts b/packages/eslint-plugin/src/rules/restrict-template-expressions.ts
@@ -1,12 +1,13 @@
 import type { TSESTree } from '@typescript-eslint/utils';
-import type { Type, TypeChecker } from 'typescript';
+import type { InterfaceType, Type, TypeChecker } from 'typescript';
 
 import {
   typeMatchesSomeSpecifier,
   typeOrValueSpecifiersSchema,
 } from '@typescript-eslint/type-utils';
 import { AST_NODE_TYPES } from '@typescript-eslint/utils';
-import { TypeFlags } from 'typescript';
+import { isObjectFlagSet, isObjectType } from 'ts-api-utils';
+import { ObjectFlags, TypeFlags } from 'typescript';
 
 import type { TypeOrValueSpecifier } from '../util';
 
@@ -130,6 +131,33 @@ export default createRule<Options, MessageId>({
       ({ option }) => options[option],
     );
 
+    function hasBaseTypes(type: Type): type is InterfaceType {
+      return (
+        isObjectType(type) &&
+        isObjectFlagSet(type, ObjectFlags.Interface | ObjectFlags.Class)
+      );
+    }
+
+    function isAllowedTypeOrBase(type: Type, seen = new Set<Type>()): boolean {
+      if (seen.has(type)) {
+        return false;
+      }
+
+      seen.add(type);
+
+      if (typeMatchesSomeSpecifier(type, allow, program)) {
+        return true;
+      }
+
+      if (hasBaseTypes(type)) {
+        return checker
+          .getBaseTypes(type)
+          .some(base => isAllowedTypeOrBase(base, seen));
+      }
+
+      return false;
+    }
+
     return {
       TemplateLiteral(node: TSESTree.TemplateLiteral): void {
         // don't check tagged template literals
@@ -165,7 +193,7 @@ export default createRule<Options, MessageId>({
 
       return (
         isTypeFlagSet(innerType, TypeFlags.StringLike) ||
-        typeMatchesSomeSpecifier(innerType, allow, program) ||
+        isAllowedTypeOrBase(innerType) ||
         enabledOptionTesters.some(({ tester }) =>
           tester(innerType, checker, recursivelyCheckType),
         )

diff --git a/packages/eslint-plugin/tests/rules/restrict-template-expressions.test.ts b/packages/eslint-plugin/tests/rules/restrict-template-expressions.test.ts
@@ -344,6 +344,52 @@ ruleTester.run('restrict-template-expressions', rule, {
     'const msg = `arg = ${undefined}`;',
     'const msg = `arg = ${123}`;',
     "const msg = `arg = ${'abc'}`;",
+    // https://github.com/typescript-eslint/typescript-eslint/issues/11759
+    // allow should check base types
+    {
+      code: `
+        class Base {}
+        class Derived extends Base {}
+        const foo = new Base();
+        const bar = new Derived();
+        \`\${foo}\${bar}\`;
+      `,
+      options: [{ allow: [{ from: 'file', name: 'Base' }] }],
+    },
+    // allow should check base types - multi-level inheritance
+    {
+      code: `
+        class Base {}
+        class Derived extends Base {}
+        class DerivedTwice extends Derived {}
+        const value = new DerivedTwice();
+        \`\${value}\`;
+      `,
+      options: [{ allow: [{ from: 'file', name: 'Base' }] }],
+    },
+    // allow should check base types - interface inheritance
+    {
+      code: `
+        interface Base {
+          value: string;
+        }
+        interface Derived extends Base {
+          extra: number;
+        }
+        declare const obj: Derived;
+        \`\${obj}\`;
+      `,
+      options: [{ allow: [{ from: 'file', name: 'Base' }] }],
+    },
+    // allow list with type alias without base types
+    {
+      code: `
+        type Custom = { value: string };
+        declare const obj: Custom;
+        \`\${obj}\`;
+      `,
+      options: [{ allow: [{ from: 'file', name: 'Custom' }] }],
+    },
   ],
 
   invalid: [
@@ -614,5 +660,42 @@ ruleTester.run('restrict-template-expressions', rule, {
       ],
       options: [{ allowAny: true }],
     },
+    // https://github.com/typescript-eslint/typescript-eslint/issues/11759
+    // derived type should error when base type is not in allow list
+    {
+      code: `
+        class Base {}
+        class Derived extends Base {}
+        const bar = new Derived();
+        \`\${bar}\`;
+      `,
+      errors: [
+        {
+          data: { type: 'Derived' },
+          messageId: 'invalidType',
+        },
+      ],
+      options: [{ allow: [] }],
+    },
+    // derived interface should error when base type is not in allow list
+    {
+      code: `
+        interface Base {
+          value: string;
+        }
+        interface Derived extends Base {
+          extra: number;
+        }
+        declare const obj: Derived;
+        \`\${obj}\`;
+      `,
+      errors: [
+        {
+          data: { type: 'Derived' },
+          messageId: 'invalidType',
+        },
+      ],
+      options: [{ allow: [] }],
+    },
   ],
 });