Fix #3343: Make baseType work properly with type lambdas #3345
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odersky
previously requested changes
Oct 18, 2017
| val tparams = clsd.typeParams | ||
| if (tparams.hasSameLengthAs(args)) baseTypeOf(tycon).subst(tparams, args) | ||
| else NoType | ||
| baseTypeOf(tycon).substTypeParams(tycon, args) |
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I think the real fault is the condition. It was meant to check that we have an application of a class instead of a type lambda but failed at that. So I'd fix that first. One candidate is the condition of substTypeParams, that the typeParams of subsym are symbols. If that's the case, proceed as before, if not do a baseTypeOf(superType), again as before.
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Makes sense. PR updated.
Previously,
`C[Char]`.baseTypeOf(`Traversable[Char]`)
where C := `[X] => List[X]`
returned `Traversable[ParamRef(A)]` instead of `Traversable[Char]`,
because the substitution was done on the type parameters of the class
symbol instead of the type parameters of the type, these are different
when type lambdas are involved. This is fixed by always going through
`AppliedType#superType` when the tycon is not a class.
|
I can confirm it fixes the issue I reported from scalacheck |
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Previously,
`C[Char]`.baseTypeOf(`Traversable[Char]`) where C := `[X] => List[X]`returned
Traversable[ParamRef(A)]instead ofTraversable[Char],because the substitution was done on the type parameters of the class
symbol instead of the type parameters of the type, these are different
when type lambdas are involved.