`unannotated-parameter` if first classmethod parameter not named `cls`

[jorenham]

Describe the Bug

When I enable the unannotated-parameter error in scipy-stubs (scipy/scipy-stubs#1262), 17 errors are reported (gh action log) for the first parameter of classmethods or __new__ methods if its name isn't cls

Repro

class A:
    def __new__(cls, a: int) -> A: ...  # ✔️ 

class B:
    def __new__(_cls, a: int) -> B: ...  # ❌ `__new__` is missing an annotation for parameter `_cls`

(sandbox)

I'd rather just name them cls, but I'm not able to, because then it wouldn't match the runtime name (i.e., stubtest will complain).

And although it's not an issue for scipy-stubs, I also noticed that this is also the case for self parameters of instance methods (sandbox).

---

The opposite also seems to be the case, i.e. non-instance method parameters called self or cls without annotation, regardless of position, will not be reported as unannotated. For example the following will be accepted:

def f(a: str, self, cls, b: int) -> None: ...  # ✔️ 

(sandbox)

Sandbox Link

https://pyrefly.org/sandbox/?project=N4IgZglgNgpgziAXKOBDAdgEwEYHsAeAdAA4CeSIAxlKnHAAQCCiAOuvR-ZjGPQPp90MAO4CAFNTgAaeqkT0I6AC4BKegFoAfE3mE9bNtVoMAQq3aduvAUNF8xfSTLkLlarfTP09hNiCkgAK5K0HAk5IggAMT0AKohUBBKpPRggeiUIbjocAZYPKm4AE4AtqhKgoEl2DBFYvjyiqoa2nBKReac9EUwSoFF7GAsIAByVTUd9MD4AL7DfgFkPWBQpIRKuCVQFDEACqTLq-RoWHj49JTZkADm-eUQ2b7oMQDKMDD0ABZKSsRwiAB6AFLHirQjFa4AmDoAGYXCUOAAy7oG53LIwwpFWQAN1Q0FQ2FgFyuEFuRXu2XouGI6LCbDISk%2B2XU2NqcAe7AAvPRhgBmQgARgALPN0GwANq1IrFOAAXTYEBKxESlCS6gwKW5wylxVF6Qw6FwSnKMEw6mIqHJJV6tXoWpAOqKevQBqNJrNPT6AztPIdRWlTpAfhmAVQmQgrIAYtAYBQQSs1hstiAZkA

(Only applicable for extension issues) IDE Information

No response

[jackulau]

Hi! I'd like to work on this issue, could you please assign this to me?