[mypyc] Fix crash when exception variable is captured by nested function (#22249)

Fixes mypyc/mypyc#1184.

This crashed with "unexpected type DeletedType":

```python
def f() -> None:
    try:
        raise RuntimeError()
    except RuntimeError as exc:
        fn = lambda: print(exc)
```

Mypy gives the variable of an except clause the type `DeletedType` after
the except block, and this type is used when adding a captured variable
to the environment class of the function. Now we map `DeletedType` to
`object`.

Author: JukkaL

mypyc/irbuild/mapper.py

@@ -6,6 +6,7 @@
 from mypy.types import (
     AnyType,
     CallableType,
+    DeletedType,
     Instance,
     LiteralType,
     NoneTyp,
@@ -166,6 +167,9 @@ def type_to_rtype(self, typ: Type | None) -> RType:
         elif isinstance(typ, (UninhabitedType, UnboundType)):
             # Sure, whatever!
             return object_rprimitive
+        elif isinstance(typ, DeletedType):
+            # The type of an exception variable after the except block, for example
+            return object_rprimitive
 
         # I think we've covered everything that is supposed to
         # actually show up, so anything else is a bug somewhere.

mypyc/test-data/run-exceptions.test

@@ -665,3 +665,32 @@ from typing import Any
 class OtherException(Exception):
     def __new__(cls) -> Any:
         return ValueError("other")
+
+[case testExceptionVariableCapturedByNestedFunction]
+from typing import Callable, Iterator
+
+def call(f: Callable[[], str]) -> str:
+    return f()
+
+def test_lambda() -> None:
+    try:
+        raise RuntimeError("x")
+    except RuntimeError as exc:
+        assert call(lambda: str(exc)) == "x"
+
+def test_nested_function() -> None:
+    try:
+        raise ValueError("y")
+    except Exception as exc:
+        def f() -> str:
+            return type(exc).__name__ + str(exc)
+        assert call(f) == "ValueErrory"
+
+def gen() -> Iterator[str]:
+    try:
+        raise KeyError("z")
+    except KeyError as exc:
+        yield call(lambda: repr(exc))
+
+def test_generator() -> None:
+    assert list(gen()) == ["KeyError('z')"]