Commits on Jun 20, 2023

1. Run all MatchType reduction under Mode.Type …

   There are a number of calls to ".simplified", which changes behaviour
   based on Mode.Type.  It does _less_ under Mode.Type, so we
   conservatively call it all under Mode.Type.
   
   Transcribing and paraphrasing from smarter's comment in
   scala#16408 (comment) :
   
   Type erasure assumes method signatures aren't simplified, since
   simplification logic is implementation-defined.  For instance, some
   intersection types can be simplified down, but intersection types and
   their simplification can erase to different types - prefering classes
   over traits, for instance (for Java interop, as it matches Java's
   erasure).
   
   Also note, simplify doesn't simplify intersections and unions in Type
   mode.  But Match Types will cache their reduction without considering
   the type mode as a cache input, thus the simplified reduction leaks even
   when called in Type mode.
   
   So we call simplified in Mode.Type, in both cases (another desire), so
   only that result is cached instead.
   
   Using normalise doesn't work because, for example, that doesn't
   normalise match types that are applied type args (e.g. args of Pair).
   And not caching the result of those reductions means that they'll get
   repeat over and over.

   

   dwijnand committed Jun 20, 2023
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