Disallow underspecified types (#21485)

eslint.config.js

@@ -132,7 +132,16 @@ export default tseslint.config(
       'no-cond-assign': 'error',
       'no-debugger': 'error',
       'no-duplicate-case': 'error',
-      'no-restricted-syntax': ['error', ...commonRestrictedSyntaxRules],
+      'no-restricted-syntax': [
+        'error',
+        ...commonRestrictedSyntaxRules,
+        {
+          selector:
+            'UnaryExpression[operator="typeof"] > MemberExpression[computed=true][property.type="Literal"]',
+          message:
+            'Do not use typeof to check object properties. Define a TypeScript interface and a type guard function instead.',
+        },
+      ],
       'no-unsafe-finally': 'error',
       'no-unused-expressions': 'off', // Disable base rule
       '@typescript-eslint/no-unused-expressions': [
@@ -263,6 +272,7 @@ export default tseslint.config(
       ...vitest.configs.recommended.rules,
       'vitest/expect-expect': 'off',
       'vitest/no-commented-out-tests': 'off',
+      'no-restricted-syntax': ['error', ...commonRestrictedSyntaxRules],
     },
   },
   {