Only set `supertype` if nominal typing is enabled (#3958)

The code for printing and emitting the experimental nominal type constructors
added in #3933 assumes that supertypes were only returned from `getSuperType`
when nominal typing was enabled. `getSuperType` in turn was assuming that the
supertype field would only be set if nominal typing was enabled, but this was
not the case. This bug caused use-after-free errors because equirecursive
canonicalization left the supertype field pointing to a temporary HeapTypeInfo
that would be freed at the end of parsing but then accessed during module
writing.

To fix the issue, only set `supertype` if nominal typing is enabled, as
originally intended.

0 files changed, 0 insertions, 0 deletions