function typing info is lost after applying functools.lru_cache

[raceychan]

Note: if you are reporting a wrong signature of a function or a class in the standard library, then the typeshed tracker is better suited for this report: https://github.com/python/typeshed/issues.

If you have a question about typing or a behavior that you’re seeing in Pyright (as opposed to a bug report or enhancement request), consider posting to the Pyright discussion forum.

Describe the bug
I read that [a wrong signature of a function or a class in the standard library] should be reported to typeshed
but the signature of functools.lru_cache seems to be doing fine, however,
when a function is decorated by functools.lru_cache, its typing info would be lost

Code or Screenshots

@lru_cache
def test(a: int) -> int:
    return a


test() # this woud not show any error

If your code relies on symbols that are imported from a third-party library, include the associated import statements and specify which versions of those libraries you have installed.

VS Code extension or command-line
Are you running pyright as a VS Code extension, a language server in another editor, integrated into Pylance, or the command-line tool? Which version?
vscode latest version

[erictraut]

Pyright is working as designed here. It's applying the type information supplied in the functools.pyi type stub.

If you would like to report a problem with the way lru_cache is defined in typeshed, please file a bug in the typeshed project. The current definition does not use a ParamSpec to retain the signature of the decorated function.