Okay, this is the first time I see this pattern inverted - usually we know the function and apply its args later. functools.partial is supported via a plugin and doesn't handle all corner cases.

In 1.11.0, if I'm not mistaken, we started handling partial more strictly. Before that you were facing essentially a Callable[..., RetType], any arguments would've been accepted in this scenario.

In 1.14.0 we started tracking paramspec binding in partial, but it only works one way - given a callable, we record whether it's paramspec args and/or kwargs are bound in the partial signature. This should be fixable, but fairly non-trivial, we don't have any precedent of backtracking from arguments to callable AFAIC. That explains "too few arguments".

This should be fixable, but may require completely different approach. Perhaps it's possible to reconstruct the arguments from partial and the call together, then check a call as usual? We'll save a bunch of callable transformations, and that should be more reliable.