Well, mypy never infers return types from the code. So we do recommend the trick with the typevar. It's not particularly often that you need this though, so I'm not keen on adding magic to the type system just to make that less verbose.
If a return type annotation is omitted, static type checkers will typically infer the return type from the implementation, by evaluating the types of all returned expressions and unioning them together.
I need to amend my previous statement though. It appears that mypy doesn't implement this capability currently. I would think that it would be straightforward to implement in mypy.
```python
from typing import Any
class Foo:
def parse(self, data: bytes):
return self
@classmethod
def bar(cls, *args: Any, **kwargs: Any):
return cls()
class Bar(Foo):
pass
x = Bar.bar()
reveal_type(x) # Pyright says "Bar", mypy says "Any"
y = Bar().parse(b"")
reveal_type(y) # Pyright says "Bar", mypy says "Any"
```
--
Eric Traut
Contributor to Pyright & Pylance
Microsoft Corp
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