Old TypeVar and new [T:] annotations are not equivalent

[jolaf]

Bug Report

If the same function is defined with old TypeVar syntax in one place and with new [T:] syntax in other place, mypy doesn't consider them equivalent.

To Reproduce

https://mypy-play.net/?mypy=1.11.2&python=3.12&enable-incomplete-feature=NewGenericSyntax&gist=78806d2f754ba0e5ce9bdcb61909fbc6

[erictraut]

Your two examples are different. In one case, you're defining a type variable with an upper bound (Callable[..., Any]) and in the other case, you're omitting the upper bound. Changing your sample to the following eliminates the type error:

    F = TypeVar("F", bound=Callable[..., Any])

[jolaf]

Your two examples are different

Oh, I see now. Thanks!

But if that is so, it should probably be reflected in the output?

For now, the 'Redefinition' output is just missing, which is definitely wrong (bug number 1).
It becomes visible though if in the newer format type variable name is changed: https://mypy-play.net/?mypy=1.11.2&python=3.12&enable-incomplete-feature=NewGenericSyntax&gist=06224b5d473a6be86cae73f00e4643f1
And it looks like the types being compared are essentially identical, so it's difficult for a user to understand what's wrong and the situation looks like a mypy bug to a user.

For this not to be the case, bound= should be visible in the printout (bug number 2).

Should I file separate issues for these?

[jolaf]

Or should we reopen this one?

[jolaf]

I've filed #17791 and #17792 to note the respective two bugs.