Fix narrowing information not propagated in assignment and boolean expressions #11207
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…pressions Fixes python#8925. Consider the following narrowing (more realistically with TypedDicts), and the current outcome: ```py class A: tag: Literal["A"] class B: tag: Literal["B"] abo: A | B | None if abo is not None and abo.tag == "A": reveal_type(abo.tag) # Type is Literal["A"] reveal_type(abo) # Type is A | B ``` The RHS of the comparison correctly takes into account the LHS, and the `abo.tag` expression is correctly narrowed based on it, but this does not propagate upward to then narrow `abo` to `A`. The problem is that `and`/`or/`not`/assignment expressions recurse using the `find_isinstance_check_helper` function, which omits the `propagate_up_typemap_info` calls that its parent function `find_isinstance_check` performs. Fix this by replacing these recursive `find_isinstance_check_helper` calls with `find_isinstance_check`. This might not always be necessary, but I do not think that always propagating upwards should do any harm, anyways.
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JukkaL
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Oct 1, 2021
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Description
Fixes #8925.
Consider the following narrowing (more realistically with TypedDicts),
and the current outcome:
The RHS of the comparison correctly takes into account the LHS, and the
abo.tagexpression is correctly narrowed based on it, but this doesnot propagate upward to then narrow
abotoA.The problem is that
and/or/not/assignment expressions recurse usingthe
find_isinstance_check_helperfunction, which omits thepropagate_up_typemap_infocalls that its parent functionfind_isinstance_checkperforms.Fix this by replacing these recursive
find_isinstance_check_helpercalls with
find_isinstance_check. This might not always be necessary,but I do not think that always propagating upwards should do any harm,
anyways.
Test Plan
Added a test case, fails before and passes after.