Do match type reduction atPhaseNoLater than ElimOpaque #20017
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EugeneFlesselle
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odersky
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Mar 27, 2024
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Nice fix |
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If a match type pattern is an opaque type, we use its bounds when checking the validity of the pattern.
Following the
ElimOpaquephase however, the pattern is beta-reduced (as normal applied type aliases), which may result in an illegal pattern, and hence an ErrorType.We initially discussed doing the changes in the TypeComparer
reduceMatchWith, but I think theatPhaseNoLater(elimOpaquePhase)should be in the reduced method of MatchType, for the footprint computation to happen in the same context.Fixes #19434
Also allows to keep
bad-footprint.scalain #19954