diff --git a/eslint.config.mjs b/eslint.config.mjs
index bf79a45f39b6..a7dac74adc10 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -208,6 +208,7 @@ export default tseslint.config(
         { commentPattern: '.*intentional fallthrough.*' },
       ],
       'no-lonely-if': 'error',
+      'no-unreachable-loop': 'error',
       'no-useless-call': 'error',
       'no-useless-computed-key': 'error',
       'no-useless-concat': 'error',
diff --git a/packages/eslint-plugin/src/rules/no-mixed-enums.ts b/packages/eslint-plugin/src/rules/no-mixed-enums.ts
index e8a06d9861e0..a3eddf6f2a0f 100644
--- a/packages/eslint-plugin/src/rules/no-mixed-enums.ts
+++ b/packages/eslint-plugin/src/rules/no-mixed-enums.ts
@@ -170,18 +170,15 @@ export default createRule({
           .getSymbolAtLocation(tsNode)!
           .getDeclarations()!;
 
-        for (const declaration of declarations) {
-          for (const member of (declaration as ts.EnumDeclaration).members) {
-            return member.initializer
-              ? tsutils.isTypeFlagSet(
-                  typeChecker.getTypeAtLocation(member.initializer),
-                  ts.TypeFlags.StringLike,
-                )
-                ? AllowedType.String
-                : AllowedType.Number
-              : AllowedType.Number;
-          }
-        }
+        const [{ initializer }] = (declarations[0] as ts.EnumDeclaration)
+          .members;
+        return initializer &&
+          tsutils.isTypeFlagSet(
+            typeChecker.getTypeAtLocation(initializer),
+            ts.TypeFlags.StringLike,
+          )
+          ? AllowedType.String
+          : AllowedType.Number;
       }
 
       // Finally, we default to the type of the first enum member
diff --git a/packages/eslint-plugin/src/rules/no-unsafe-return.ts b/packages/eslint-plugin/src/rules/no-unsafe-return.ts
index ae959627c09d..d9c7cd60cc0f 100644
--- a/packages/eslint-plugin/src/rules/no-unsafe-return.ts
+++ b/packages/eslint-plugin/src/rules/no-unsafe-return.ts
@@ -166,7 +166,8 @@ export default createRule({
         });
       }
 
-      for (const signature of functionType.getCallSignatures()) {
+      const signature = functionType.getCallSignatures().at(0);
+      if (signature) {
         const functionReturnType = signature.getReturnType();
         const result = isUnsafeAssignment(
           returnNodeType,
diff --git a/packages/eslint-plugin/tests/rules/no-unsafe-return.test.ts b/packages/eslint-plugin/tests/rules/no-unsafe-return.test.ts
index dc5e1df369d6..c30c6a2b0bf1 100644
--- a/packages/eslint-plugin/tests/rules/no-unsafe-return.test.ts
+++ b/packages/eslint-plugin/tests/rules/no-unsafe-return.test.ts
@@ -127,6 +127,7 @@ function foo(): Set<number> {
         return [] as any[];
       }
     `,
+    'const foo: (() => void) | undefined = () => 1;',
   ],
   invalid: [
     {