dmypy suggest generates syntax error in annotation in some cases

[asottile-sentry]

Bug Report

sometimes dmypy puts a : for some annotations instead of a . and is inconsistent with some types from typing

To Reproduce

class C: pass

def f1():
    return [C()]

def f2():
    return [1]

def f3():
    return (C(),)

def f4():
    return (1,)

[mypy]
check_untyped_defs = true

Expected Behavior

$ dmypy run .
...
$ dmypy suggest t.f1
() -> List[t.C]
$ dmypy suggest t.f2
() -> List[int]
$ dmypy suggest t.f3
() -> Tuple[t.C]
$ dmypy suggest t.f4
() -> Tuple[int]

Actual Behavior

$ dmypy run .
...
$ dmypy suggest t.f1
() -> typing:List[t.C]
$ dmypy suggest t.f2
() -> typing.List[int]
$ dmypy suggest t.f3
() -> Tuple[t.C]
$ dmypy suggest t.f4
() -> Tuple[int]

two separate oddities here:

• the first produces typing:List (with a colon) instead of typing.List (the colon appears to come from here --

  mypy/mypy/suggestions.py

  Line 853 in 454989f

  delim = "." if "." not in obj else ":"

  )
  • I guess the colon is supposed to help with differentiating mod.Class.NestedClass vs mod.submod.Class ? though it seems to make no sense for List here
• typing.List and Tuple should either both be fully qualified or neither

Your Environment

• Mypy version used: 1.15.0
• Mypy command-line flags: see above
• Mypy configuration options from mypy.ini (and other config files): see above
• Python version used: 3.13.1