From 426f294ec8ffc3fb42fe3eb55b3fa1280cf73cbe Mon Sep 17 00:00:00 2001
From: Eric Traut <eric@traut.com>
Date: Thu, 23 Jan 2025 09:30:21 -0800
Subject: [PATCH] Added `@override` enforcement for an overloaded method that
 has no implementation. This addresses #9746.

---
 .../pyright-internal/src/analyzer/checker.ts  |  8 +++
 .../src/tests/samples/override1.py            | 52 +++++++++++--------
 .../src/tests/typeEvaluator5.test.ts          |  2 +-
 3 files changed, 40 insertions(+), 22 deletions(-)

diff --git a/packages/pyright-internal/src/analyzer/checker.ts b/packages/pyright-internal/src/analyzer/checker.ts
index ef625e775f17..103ea3b86971 100644
--- a/packages/pyright-internal/src/analyzer/checker.ts
+++ b/packages/pyright-internal/src/analyzer/checker.ts
@@ -6562,6 +6562,14 @@ export class Checker extends ParseTreeWalker {
             if (impl && isFunction(impl)) {
                 overrideFunction = impl;
             }
+
+            // If there is no implementation present, use the first overload.
+            if (!impl) {
+                const overloads = OverloadedType.getOverloads(overrideType);
+                if (overloads.length > 0) {
+                    overrideFunction = overloads[0];
+                }
+            }
         } else if (isClassInstance(overrideType) && ClassType.isPropertyClass(overrideType)) {
             if (overrideType.priv.fgetInfo) {
                 overrideFunction = overrideType.priv.fgetInfo.methodType;
diff --git a/packages/pyright-internal/src/tests/samples/override1.py b/packages/pyright-internal/src/tests/samples/override1.py
index e9366e97ffd0..99ab73d11a1f 100644
--- a/packages/pyright-internal/src/tests/samples/override1.py
+++ b/packages/pyright-internal/src/tests/samples/override1.py
@@ -1,7 +1,7 @@
 # This sample tests the handling of the @override decorator as described
 # in PEP 698.
 
-from typing import Callable
+from typing import Callable, Protocol
 from typing_extensions import (  # pyright: ignore[reportMissingModuleSource]
     Any,
     overload,
@@ -19,15 +19,12 @@ def method3(self) -> None:
         pass
 
     @overload
-    def method5(self, x: int) -> int:
-        ...
+    def method5(self, x: int) -> int: ...
 
     @overload
-    def method5(self, x: str) -> str:
-        ...
+    def method5(self, x: str) -> str: ...
 
-    def method5(self, x: int | str) -> int | str:
-        ...
+    def method5(self, x: int | str) -> int | str: ...
 
 
 class ClassC(ClassA, ClassB):
@@ -56,34 +53,27 @@ def method4(self) -> None:
         pass
 
     @overload
-    def method5(self, x: int) -> int:
-        ...
+    def method5(self, x: int) -> int: ...
 
     @overload
-    def method5(self, x: str) -> str:
-        ...
+    def method5(self, x: str) -> str: ...
 
     @override
-    def method5(self, x: int | str) -> int | str:
-        ...
+    def method5(self, x: int | str) -> int | str: ...
 
     @overload
-    def method6(self, x: int) -> int:
-        ...
+    def method6(self, x: int) -> int: ...
 
     @overload
-    def method6(self, x: str) -> str:
-        ...
+    def method6(self, x: str) -> str: ...
 
     @override
     # This should generate an error because method6 does not
     # override anything in a base class.
-    def method6(self, x: int | str) -> int | str:
-        ...
+    def method6(self, x: int | str) -> int | str: ...
 
 
-class ClassD(Any):
-    ...
+class ClassD(Any): ...
 
 
 class ClassE(ClassD):
@@ -109,3 +99,23 @@ class G(F):
     @evil_wrapper
     def method1(self):
         pass
+
+
+class H(Protocol):
+    pass
+
+
+class I(H, Protocol):
+    @override
+    # This should generate an error because method1 isn't present
+    # in the base.
+    def method1(self):
+        pass
+
+    @overload
+    @override
+    # This should generate an error because method2 isn't present
+    # in the base.
+    def method2(self, x: int) -> int: ...
+    @overload
+    def method2(self, x: str) -> str: ...
diff --git a/packages/pyright-internal/src/tests/typeEvaluator5.test.ts b/packages/pyright-internal/src/tests/typeEvaluator5.test.ts
index 246a9e75fa36..ca8dce83fc8e 100644
--- a/packages/pyright-internal/src/tests/typeEvaluator5.test.ts
+++ b/packages/pyright-internal/src/tests/typeEvaluator5.test.ts
@@ -179,7 +179,7 @@ test('Hashability3', () => {
 
 test('Override1', () => {
     const analysisResults = TestUtils.typeAnalyzeSampleFiles(['override1.py']);
-    TestUtils.validateResults(analysisResults, 3);
+    TestUtils.validateResults(analysisResults, 5);
 });
 
 test('Override2', () => {