"Statement is unreachable" when doing `match` on `type` objects

[woodruffw]

Hello mypy maintainers! I attempted to search for a dupe for this but couldn't find one, apologies if I missed it.

Bug Report

When running mypy with warn_unreachable = true (set in pyproject, but also on CLI), I get what appears to be a false positive for unreachable code on match statements where the matched object is a type and some of the arms are types.

For example (minimized/abstracted from my actual code):

import builtins
import typing
import types

def frobulate(field_type: type) -> str:
 match field_type:
 case builtins.int:
 ret = "foo"
 case builtins.str:
 ret = "foo"
 case builtins.bytes:
 ret = "foo"
 case builtins.bool:
 ret = "foo"
 case types.NoneType:
 ret = "foo"
 case _:
 return "bar"
 
 
 return ret

Produces:

main.py:10: error: Statement is unreachable [unreachable]
main.py:12: error: Statement is unreachable [unreachable]
main.py:16: error: Statement is unreachable [unreachable]
Found 3 errors in 1 file (checked 1 source file)

However, at runtime, I can confirm that these case arms are matched correctly.

To Reproduce

Playground reproducer: https://mypy-play.net/?mypy=latest&python=3.13&flags=warn-unreachable&gist=416b0d53cd61032acee0341e9b24de11

(Note that --warn-unreachable needs to be enabled for reproduction. I think the Playground link should preserve this, but just in case!)

Expected Behavior

I expected mypy to match on type objects correctly, as Python itself appears to do correctly at runtime.

Actual Behavior

From above:

main.py:10: error: Statement is unreachable [unreachable]
main.py:12: error: Statement is unreachable [unreachable]
main.py:16: error: Statement is unreachable [unreachable]
Found 3 errors in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 1.14.1
• Mypy command-line flags: --warn-unreachable
• Mypy configuration options from mypy.ini (and other config files): N/A
• Python version used: 3.13

[sterliakov]

That's also type vs type[Any] issue. With type[Any] unreachable warnings are mostly gone, but the output is no better:

import builtins
import typing
import types

def frobulate(field_type: type[typing.Any]) -> str:
 match field_type:
 case builtins.int:
 reveal_type(field_type)
 ret = "foo"
 case builtins.str:
 reveal_type(field_type)
 ret = "foo"
 case builtins.bytes:
 reveal_type(field_type)
 ret = "foo"
 case builtins.bool:
 reveal_type(field_type)
 ret = "foo"
 case types.NoneType:
 reveal_type(field_type)
 ret = "foo"
 case _:
 reveal_type(field_type)
 return "bar"
 
 return ret

main.py:8: note: Revealed type is "type[Any]"
main.py:11: note: Revealed type is "Never"
main.py:14: note: Revealed type is "Never"
main.py:17: note: Revealed type is "type[builtins.bool]"
main.py:20: error: Statement is unreachable [unreachable]
main.py:23: note: Revealed type is "type[builtins.bool]"

[woodruffw]

Thanks @hauntsaninja!

[hauntsaninja]

Technically the OP got fixed by #19338 . The thing I just fixed is sterliakov's case