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[1.16 regression] narrowing a typevar via comparison to None #19166

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@Redoubts

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@Redoubts

Bug Report

Consider the following: https://mypy-play.net/?mypy=master&python=3.12&gist=dbad46bbd0f39d316a2e82262ceeb4fa

In 1.16, this code raises an error at the first return after the None check, Incompatible return value type (got "None", expected "T"), though it was fine in 1.15

Your Environment

  • Mypy version used: 1.16
  • Mypy command-line flags: stock
  • Mypy configuration options from mypy.ini (and other config files): n/a
  • Python version used: 3.11, 3.12

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    bugmypy got something wrongtopic-type-narrowingConditional type narrowing / binder

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