Check bounds in match type case bodies #17602
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dwijnand
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@sjrd will you review if I rebase this? 😄 |
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Oh yes, sorry. |
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sjrd
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Feb 27, 2024
| @@ -21,6 +21,7 @@ object TypeEval: | |||
| case tp: TypeProxy => | |||
| val tp1 = tp.superType | |||
| if tp1.isStable then tp1.fixForEvaluation else tp | |||
| case AndType(tp1: ConstantType, tp2) if tp1.frozen_<:<(tp2) => tp1 | |||
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AndType is supposed to be commutative, so if we do this we must also do the mirror:
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| case AndType(tp1: ConstantType, tp2) if tp1.frozen_<:<(tp2) => tp1 | |
| case AndType(tp1: ConstantType, tp2) if tp1.frozen_<:<(tp2) => tp1 | |
| case AndType(tp1, tp2: ConstantType) if tp2.frozen_<:<(tp1) => tp2 |
| withMode(Mode.Pattern)(super.transform(x)).asInstanceOf[CaseDef] | ||
| def transformCase(x: CaseDef): CaseDef = | ||
| val gadtCtx = x.pat.removeAttachment(typer.Typer.InferredGadtConstraints) match | ||
| case Some(gadt) => ctx.fresh.setGadtState(GadtState(gadt)) |
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Is this enough to ensure that, after PostTyper, the trees are well-kinded without resorting to GADT reasoning? I'm not familiar with what are the consequences of doing setGadtState.
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I'm not inserting any casts, if that's what you're asking. And I'm hoping we can handle things like:
class Foo
class Bar
class Res[X <: Bar]
type MT[X <: Foo | Bar] = X match
case Foo => Unit
case Bar => Res[X] // X vs bounds check <: Bar in part also because I've found adding a type intersection (for types) doesn't fix errors like adding a type casting (for terms) fixes errors...
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So we can either:
- disallow such reasoning, force users to insert type intersections, and then decide how much to work on the limitations of those intersections
- allow these things to require GADT reasoning
- deal with how to force types to honour bounds, and perhaps in a way that is accessible to users too
- return to the AssumeInfo tree idea
😭
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Fixes #13741