[mypyc] Fix crash when '__enter__'/'__exit__' inherited from Python class

mypyc/irbuild/statement.py

@@ -1137,7 +1137,13 @@ def transform_with(
     if not is_async and mgr_v.type == lock_rprimitive:
         transform_with_lock(builder, mgr_v, target, body, line)
         return
-    is_native = isinstance(mgr_v.type, RInstance)
+    # The methods may be inherited from a non-native class, and then they can't be
+    # called natively.
+    is_native = (
+        isinstance(mgr_v.type, RInstance)
+        and mgr_v.type.class_ir.has_method(f"__{al}enter__")
+        and mgr_v.type.class_ir.has_method(f"__{al}exit__")
+    )
     if is_native:
         value = builder.add(MethodCall(mgr_v, f"__{al}enter__", args=[], line=line))
         exit_ = None

mypyc/test-data/run-misc.test

@@ -1148,6 +1148,8 @@ def test_redefinition() -> None:
     assert i == b"foo"
 
 [case testWithNative]
+from base import Base, EnterBase
+
 class DummyContext:
     def __init__(self):
         self.c = 0
@@ -1162,6 +1164,50 @@ def test_dummy_context() -> None:
         assert c.c == 1
     assert c.c == 0
 
+class InheritsEnter(EnterBase):
+    def __init__(self) -> None:
+        self.log: list[str] = []
+
+    def __exit__(self, exc_type: object, exc_value: object, traceback: object) -> None:
+        self.log.append("exit")
+
+class InheritsExit(Base):
+    def __enter__(self) -> str:
+        return "enter"
+
+class InheritsBoth(Base):
+    pass
+
+def test_inherited_enter() -> None:
+    c = InheritsEnter()
+    with c as x:
+        assert x is c
+        c.log.append("body")
+    assert c.log == ["body", "exit"]
+
+def test_inherited_exit() -> None:
+    with InheritsExit() as x:
+        assert x == "enter"
+    with InheritsExit():
+        # Base.__exit__ suppresses the exception
+        raise ValueError()
+
+def test_inherited_both() -> None:
+    with InheritsBoth() as x:
+        assert x == "base"
+
+[file base.py]
+class EnterBase:
+    def __enter__(self) -> "EnterBase":
+        return self
+
+class Base:
+    def __enter__(self) -> str:
+        return "base"
+
+    def __exit__(self, exc_type: object, exc_value: object, traceback: object) -> bool:
+        return True
+
 [case testWithNativeVarArgs]
 class DummyContext:
     def __init__(self):