Multiple dispatch not recognized

[oskarpfeffer]

Ruff does not recognize multiple dispatch methods.

Example:

from plum import dispatch

@dispatch
def f(x: str):
    return "This is a string!"

@dispatch
def f(x: int):
    return "This is an integer!"

$ ruff check test.py
test.py:10:5: F811 Redefinition of unused `f` from line 5
Found 1 error.

$ ruff --version           
ruff 0.4.9

Is there a way to include it as a rule to ignore the redefinition when there is @dispatch before the function?

[MichaReiser]

Hi

This is an interesting use of type annotations. I don't think it's feasible for us to add an exception for plum. Plum bends python semantics in a way that are difficult to understand for static analysis tools and we rather avoid coding framework specific behavior into ruff, unless it is a very popular framework.

I just tried your example with Pyright and it also reports error when type checking the code

  /home/micha/astral/test/dispatch.py:4:5 - error: Function declaration "f" is obscured by a declaration of the same name (reportRedeclaration)
  /home/micha/astral/test/dispatch.py:12:3 - error: Argument of type "Literal['test']" cannot be assigned to parameter "x" of type "int" in function "f"
    "Literal['test']" is incompatible with "int" (reportArgumentType)
2 errors, 0 warnings, 0 information