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Invalid return type with sentinel and dict.get #21866

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#21888
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Invalid return type with sentinel and dict.get#21866
#21888
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bugmypy got something wrong

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@cdce8p
cdce8p
opened on Aug 18, 2026
from typing import assert_type
from typing_extensions import sentinel

Unknown = sentinel("Unknown")

def func(d: dict[str, str]) -> None:
    var = d.get("key", Unknown)
    assert_type(var, str | Unknown)  # <- Error
test.py:8: error: Expression is of type "str | sentinel", not "str | Unknown"  [assert-type]

/CC @JelleZijlstra @edgarrmondragon

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  1. cdce8p
    added
    bugmypy got something wrong
    on Aug 18, 2026

  2. edgarrmondragon commented on Aug 24, 2026

    @edgarrmondragon
    edgarrmondragon
    on Aug 24, 2026
    Contributor

    Thanks for the ping and sorry for the delay (I was on holiday last week). Here's a PR: #21888.

  3. sobolevn
    added a commit that references this issue on Aug 27, 2026

    Fix sentinel identity loss through generic substitution and inference (…

    44c0d9f
  4. sobolevn
    closed this as completedin #21888on Aug 27, 2026
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