John McCall 7a8d8b4997 Fix the mapping of pack types into opened element environments. ...

First, we need this to work on both lowered and unlowered types,
so Type::subst is problematic: it'll assert if it sees a type
like SILFunctionType.  In this case, the substitution is simple
enough that that's never a problem, but Type::subst doesn't know
that, and the assertion is generally a good one.

Second, we need this to not recurse into nested pack expansions.

Third, we need this to not mess around with any existing element
archetypes we might see in the type, so mapping in and out of
context is not really okay.

Fortunately, because we're mapping between structures (pack and
element archetypes) that are guaranteed to have the same
constraints, this transformation is really easy and we can just
do it with transformRec.

2023-03-15 17:45:55 -04:00

14 KiB

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