Fix typechecking for async generators

mypy/checkexpr.py

@@ -5585,8 +5585,13 @@ def visit_set_comprehension(self, e: SetComprehension) -> Type:
 
  def visit_generator_expr(self, e: GeneratorExpr) -> Type:
  # If any of the comprehensions use async for, the expression will return an async generator
- # object, or if the left-side expression uses await.
- if any(e.is_async) or has_await_expression(e.left_expr):
+ # object, or await is used anywhere but in the leftmost sequence.
+ if (
+ any(e.is_async)
+ or has_await_expression(e.left_expr)
+ or any(has_await_expression(sequence) for sequence in e.sequences[1:])
+ or any(has_await_expression(cond) for condlist in e.condlists for cond in condlist)
+ ):
  typ = "typing.AsyncGenerator"
  # received type is always None in async generator expressions
  additional_args: list[Type] = [NoneType()]

test-data/unit/check-async-await.test

@@ -573,6 +573,25 @@ async def return_f() -> AsyncGenerator[int, None]:
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-async.pyi]
 
+[case testImplicitAsyncGenerator]
+from typing import List
+
+async def get_list() -> List[int]:
+ return [1]
+
+async def predicate() -> bool:
+ return True
+
+async def test_implicit_generators() -> None:
+ reveal_type(await predicate() for _ in [1]) # N: Revealed type is "typing.AsyncGenerator[builtins.bool, None]"
+ reveal_type(x for x in [1] if await predicate()) # N: Revealed type is "typing.AsyncGenerator[builtins.int, None]"
+ reveal_type(x for x in await get_list()) # N: Revealed type is "typing.Generator[builtins.int, None, None]"
+ reveal_type(x for _ in [1] for x in await get_list()) # N: Revealed type is "typing.AsyncGenerator[builtins.int, None]"
+
+[builtins fixtures/dict.pyi]
+[typing fixtures/typing-async.pyi]
+
+
 -- The full matrix of coroutine compatibility
 -- ------------------------------------------