Simplify forSome statements into wildcard existentials (fix #471) #483
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olafurpg
reviewed
Oct 1, 2019
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| val box: Box[_] = null.asInstanceOf[Box[_]] | ||
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| val boxes1: Seq[Box[_]] = Seq(new Box[A], new Box[B]) |
Collaborator
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Can we add a test case for wildcard bounds? For example “Box[_ <: Path]”
| opt(utpe)(normal) | ||
| rep(" forSome { ", decls.infos, "; ", " }")(pprint) | ||
| if (config.better) { | ||
| val wildcardInfos = decls.infos.map(_.withDisplayName("_")) |
Collaborator
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There are cases where it’s not safe to convert existentials into wildcards, for example “Map[T, T] forSome { type T }”. I think the rule is that existential types can only be converted into wildcards if they’re referenced once.
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Also fixes #353
This will prevent unreadable existential types from being ascribed, as well as circumventing a bug where an existential type might be qualified:
Box[MyScope._1] forSome { type _1 ... }.