Fix #4382: Disallow wildcard arguments for higher-kinded types #4423
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…ents Four existing test cases had to be reclassified to require -language:Scala2.
This previous encoding used a higher-kinded type applied to a wildcard argument, which is no longer supported. The new encoding is a temporary fix. To get it right, it's best if we can base it on the future typeclass derivation mechanism.
I don't have a test, but it makes more sense this way.
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@Blaisorblade Between #4423 and #4422 that makes a co-ordinated swatting of wildcards. Great to have this! |
smarter
approved these changes
Apr 30, 2018
| @@ -366,6 +366,12 @@ object desugar { | |||
| (if (args.isEmpty) tycon else AppliedTypeTree(tycon, args)) | |||
| .withPos(cdef.pos.startPos) | |||
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| def isHK(tparam: Tree): Boolean = tparam match { | |||
| case TypeDef(_, LambdaTypeTree(tparams, body)) => true | |||
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I don't think that's enough in general, e.g. enum Foo[F <: [X] => Any], but maybe we're ok with that since that's only a temporary solution.
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Yes, I think the right solution cannot be done at Desugar, it needs full type information.
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This needed some follow-on work on how we encode
Eqfor enums, which could still be improved once we have typeclass derivation.