lub/glb for HKTs #6352
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lub/glb for HKTs #6352
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joroKr21
commented
Feb 26, 2018
| @@ -4713,19 +4713,22 @@ trait Types | |||
| NoType | |||
| } | |||
| else { | |||
| if (tparam.variance == variance) lub(as, depth.decr) | |||
| else if (tparam.variance == variance.flip) glb(as, depth.decr) | |||
| val hktParams = tparam.typeParams | |||
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Is reusing this gonna break anything?
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Also things like this are probably still broken: class Foo[F[G[_] <: F[G]]]
joroKr21
commented
Feb 26, 2018
test/files/neg/hk-bad-bounds.check
Outdated
| @@ -1,4 +1,4 @@ | |||
| hk-bad-bounds.scala:4: error: type arguments [Set] do not conform to class SeqFactory's type parameter bounds [CC[X] <: Seq[X] with scala.collection.generic.GenericTraversableTemplate[X,CC]] | |||
| hk-bad-bounds.scala:4: error: can't existentially abstract over parameterized type _1[X] | |||
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I have no memory of this place.
joroKr21
commented
Feb 26, 2018
test/files/neg/lub-from-hell-2.check
Outdated
| @@ -1,7 +1,7 @@ | |||
| lub-from-hell-2.scala:3: error: type arguments [Any,Iterable[Any] with Int => Any with scala.collection.generic.Subtractable[Any,Iterable[Any] with Int => Any with scala.collection.generic.Subtractable[Any,Iterable[Any] with Int => Any]{def seq: Iterable[Any] with Int => Any}]{def seq: Iterable[Any] with Int => Any{def seq: Iterable[Any] with Int => Any}}] do not conform to trait Subtractable's type parameter bounds [A,+Repr <: scala.collection.generic.Subtractable[A,Repr]] | |||
| def foo(a: Boolean, b: collection.mutable.Set[Any], c: collection.mutable.ListBuffer[Any]) = if (a) b else c | |||
| ^ | |||
| lub-from-hell-2.scala:4: error: type arguments [Any,scala.collection.mutable.Iterable[Any] with scala.collection.mutable.Cloneable[scala.collection.mutable.Iterable[Any] with scala.collection.mutable.Cloneable[scala.collection.mutable.Iterable[Any] with Cloneable with Int => Any] with Int => Any{def seq: scala.collection.mutable.Iterable[Any] with Cloneable with Int => Any}] with scala.collection.generic.Growable[Any] with Int => Any with scala.collection.generic.Shrinkable[Any] with scala.collection.generic.Subtractable[Any,Iterable[Any] with Int => Any with scala.collection.generic.Subtractable[Any,Iterable[Any] with Int => Any]{def seq: Iterable[Any] with Int => Any}] with scala.collection.script.Scriptable[Any]] do not conform to trait Subtractable's type parameter bounds [A,+Repr <: scala.collection.generic.Subtractable[A,Repr]] | |||
| lub-from-hell-2.scala:4: error: type arguments [Any,scala.collection.mutable.Iterable[Any] with scala.collection.mutable.Cloneable[scala.collection.mutable.Iterable[Any] with scala.collection.mutable.Cloneable[scala.collection.mutable.Iterable[Any] with Cloneable with Int => Any] with Int => Any{def seq: scala.collection.mutable.Iterable[Any] with Cloneable with Int => Any}] with scala.collection.generic.Growable[Any] with Int => Any with scala.collection.generic.Shrinkable[Any] with scala.collection.generic.Subtractable[Any,Iterable[Any] with Int => Any with scala.collection.generic.Subtractable[Any,Iterable[Any] with Int => Any]{def seq: Iterable[Any] with Int => Any}] with scala.collection.script.Scriptable[Any]{def clone(): scala.collection.mutable.Iterable[Any] with scala.collection.mutable.Cloneable[scala.collection.mutable.Iterable[Any] with Cloneable with Int => Any] with scala.collection.generic.Growable[Any] with Int => Any with scala.collection.generic.Shrinkable[Any] with scala.collection.generic.Subtractable[Any,Iterable[Any] with Int => Any] with scala.collection.script.Scriptable[Any]{def clone(): scala.collection.mutable.Iterable[Any] with Cloneable with scala.collection.generic.Growable[Any] with Int => Any with scala.collection.generic.Shrinkable[Any] with scala.collection.script.Scriptable[Any]; def seq: scala.collection.mutable.Iterable[Any] with Cloneable with Int => Any}; def seq: scala.collection.mutable.Iterable[Any] with scala.collection.mutable.Cloneable[scala.collection.mutable.Iterable[Any] with Cloneable with Int => Any] with Int => Any{def seq: scala.collection.mutable.Iterable[Any] with Cloneable with Int => Any}; def companion: scala.collection.generic.GenericCompanion[[X]scala.collection.mutable.Iterable[X] with Cloneable with scala.collection.generic.Growable[X] with scala.collection.generic.Shrinkable[X] with scala.collection.script.Scriptable[X]]}] do not conform to trait Subtractable's type parameter bounds [A,+Repr <: scala.collection.generic.Subtractable[A,Repr]] | |||
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I wonder if there is any use case for refining all of those members.
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How about not doing the refinements for F-bounded types, assuming there is any way to detect that?
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adriaanm
approved these changes
Aug 3, 2018
When computing the `lub/glb` of HKTs take care to produce well-kinded types when merging type constructor arguments that are supplied for a type constructor parameter. This improves type inference. A few tests with `-Xstrict-inference` were changed. Other tests reveal a limitation of higher-kinded existentials. Fixes scala/bug#8882 and promotes scala/bug#10700 to an error.
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When computing the
lub/glbof HKTs take care to producewell-kinded types. Improves type inference.
A few tests with
-Xstrict-inferencewere changed.Other tests reveal a limitation of higher-kinded existentials.
Fixes scala/bug#8882 and promotes scala/bug#10700 to an error.