TypedDict does not treat union of string literals as a string literal
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bug
topic-literal-types
topic-typed-dict
- Dominant language
- Python
- Stars
- 20.6k
- Forks
- 3.3k
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Description
Bug Report
To Reproduce
https://mypy-play.net/?mypy=latest&python=3.14&gist=a2d228294e0a7a613472376043c62642
from typing import NotRequired, TypedDict
class Foo(TypedDict):
key1: NotRequired[str]
key2: NotRequired[int]
foo = Foo()
for key in "key1", "key2":
reveal_type(key)
del foo[key]
Expected Behavior
This should type check with no errors.
Actual Behavior
main.py:11: note: Revealed type is "Literal['key1']? | Literal['key2']?"
main.py:12: error: Expected TypedDict key to be string literal [misc]
Found 1 error in 1 file (checked 1 source file)
Your Environment
- Mypy version used: 1.18.2
- Python version used: 3.14
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reproducing the example from the mypy-play link in main.py with mypy 1.18.2 and Python 3.14. Trace how the TypedDict deletion check handles the revealed union of string literals, then add coverage for this example and verify that it type checks without errors.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 48/100