Inferring an optional type when first initializer uses non-optional type

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
compilers

Research direction

Reproduce the two examples from the issue with --strict-optional and inspect the type-inference path for conditional assignments. Confirm that both reveal_type calls report Optional[int] rather than producing None compatibility errors; the issue does not name specific files or tests.

Written by the indexing model from the issue text.

Description

false-positive feature needs discussion priority-0-high topic-inference

In these cases mypy can't infer an optional type when using --strict-optional, even though it likely should:

def f(): pass

y = 1
if f():
    y = None  # None not compatible with int
reveal_type(y)

if f():
    z = 1
else:
    z = None  # None not compatible with int
reveal_type(z)

The desired behavior would be to infer Optional[int] as the type of both y and z.

Dominant language
Python
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