Reduce some match type in inlining to avoid opaque type headaches #20457
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The inliner tries to handle opaque types by replacing prefixes containing them by proxy objects with type aliases. When the type we're mapping is a match type application, this can end up breaking its reduction. Reducing match type applications instead of performing this mapping seems to avoid the issue in practice, but I don't know if it completely solves the problem. Fixes scala#20427.
EugeneFlesselle
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Jul 1, 2024
Change the rhs of the added refinements from `TypeAlias`es to `RealTypeBounds`s. This allows the opaque types to remain abstract type constructors, which is necessary for the `MatchTypeCasePattern.AbstractTypeConstructor` logic. In particular, an AppliedType where the tycon was a reference to the refinement, used to dealias before proceeding with the comparison of the tycons, which is a requirement of the aforementioned `AbstractTypeConstructor` case of the MatchReducer. Fixes scala#20427 Alternative to scala#20457
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The inliner tries to handle opaque types by replacing prefixes containing them by proxy objects with type aliases. When the type we're mapping is a match type application, this can end up breaking its reduction.
Reducing match type applications instead of performing this mapping seems to avoid the issue in practice, but I don't know if it completely solves the problem.
Fixes #20427.