Treat Refinements more like AndTypes #12317
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Fixes scala#12306 When comparing with an AndType on the left and a RefinedType on the right, decompose the right hand side into an AndType of types that have a single refinement each. This makes sure we lose the least information in the necessary subsequent `either` call.
abgruszecki approved these changes May 4, 2021
| case tp: AndType => true | ||
| case OrType(tp1, tp2) => containsAnd(tp1) || containsAnd(tp2) | ||
| case tp: TypeParamRef => containsAnd(bounds(tp).hi) | ||
| case tp: TypeRef => containsAnd(tp.info.hiBound) || tp.symbol.onGadtBounds(gbounds => containsAnd(gbounds.hi)) |
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Ah, interesting. We always compare with GADT bounds in frozen constraint, but that doesn't end up mattering, right? That is: do I understand correctly that even if we're not inferring constraints, we need to break down structural types on the RHS to properly check if there's subtyping between the left- and right-hand sides?
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I think the same reasoning applies: If we end up comparing GADT constraints we need necessaryEither, and that means we need to decompose the RHS as much as possible so that necesssaryEither is sound.
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Fixes #12306
When comparing with an AndType on the left and a RefinedType on the right,
decompose the right hand side into an AndType of types that have a single
refinement each. This makes sure we lose the least possible information in the
necessary subsequent
eithercall.This is a much better fix than #12316.