Proposal: don't simplify unions in expand_type() #14178
Merged
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Fixes #6730
Currently
expand_type()
is inherently recursive, going throughexpand_type
->make_simplified_union
->is_proper_subtype
->map_instance_to_supertype
->expand_type
. TBH I never liked this, so I propose that we don't do this. One one hand, this is a significant change in semantics, but on the other hand:To make transition smoother, I propose to make trivial simplifications, like removing
<nothing>
(andNone
without strict optional), removing everything else if there is anobject
type, and remove strict duplicates. Notably, with these few things all existing tests pass (and even without it, only half a dozen tests fail onreveal_type()
).