reveal_type() may affect inferred type / overload resolution
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Description
The first filter call below generates an error when using --py2, but the same call without reveal_type(...) is fine:
from typing import Any, List
a = 0 # type: Any
x = filter(None, reveal_type(a)) # type: List[str] # Error
x2 = filter(None, a) # type: List[str] # No error
The error message is Incompatible types in assignment (expression has type "Tuple[<nothing>, ...]", variable has type "List[str]").
reveal_type should have no effect on inferred types, since it's often used to diagnose issues with type inference.
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Research direction
Start with the provided Python reproducer using --py2, comparing filter(None, reveal_type(a)) with filter(None, a) and the reported assignment error. Trace how reveal_type affects inferred types and overload resolution; done means both calls produce the same inferred result and reveal_type remains diagnostic only.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- compilers, devtools
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 42/100