Use union of current context and left side for right side narrowing of binary ops #19249
+34
−1
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Fixes #12001. Fixes #6898. Fixes #15368. Improves #17790 and #11508.
When encountering
a {and,or} b
, we used to usea
as primary context forb
inference. This results in weird errors whena
andb
are completely unrelated, and in many cases return type/assignment type context can do much better. Inferring to union should be harmless in most cases, so use union ofa
and current context instead.