[1.14 regression] Unpacking an iterator converts the inner type to `Any`
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Description
Bug Report
Unpacking an iterator into a list produces a list[Any] instead of the more specific type. This worked correctly in mypy 1.13.0 but no longer works in 1.14.0.
To Reproduce
from typing import reveal_type
x = [1, 2]
reveal_type([*reversed(x)])
y = [3, 4]
reveal_type([*map(str, y)])
Expected Behavior
In mypy 1.13.0:
x.py:3: note: Revealed type is "builtins.list[builtins.int]"
x.py:5: note: Revealed type is "builtins.list[builtins.str]"
Actual Behavior
In mypy 1.14.0:
x.py:3: note: Revealed type is "builtins.list[Any]"
x.py:5: note: Revealed type is "builtins.list[Any]"
Your Environment
- Mypy version used: 1.14.0
- Mypy command-line flags: none
- Mypy configuration options from
mypy.ini(and other config files): none - Python version used: 3.13.0
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 with the supplied Python reproducer and compare the reveal_type output between mypy 1.13.0 and 1.14.0, focusing on list unpacking from reversed and map. Done means mypy reports list[int] and list[str] rather than list[Any] for those two expressions without special flags.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100