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Preserve tvar bounds that represent kinds #6156

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Merged
merged 4 commits into from
Mar 26, 2019
Merged

Preserve tvar bounds that represent kinds #6156

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7387da3
Preserve tvar bounds that represent kinds
milessabin Mar 24, 2019
bee6ff7
Relaxed constraint on lower bound and added tests
milessabin Mar 25, 2019
b9165fe
Renamed test
milessabin Mar 25, 2019
2e1428d
Merge branch 'master' into topic/i6014
abgruszecki Mar 26, 2019
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5 changes: 4 additions & 1 deletion compiler/src/dotty/tools/dotc/core/Contexts.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -929,7 +929,10 @@ object Contexts {
// - we don't want TyperState instantiating these TypeVars
// - we don't want TypeComparer constraining these TypeVars
val poly = PolyType(DepParamName.fresh(sym.name.toTypeName) :: Nil)(
pt => TypeBounds.empty :: Nil,
pt => (sym.info match {
case tb @ TypeBounds(_, hi) if hi.isLambdaSub => tb
case _ => TypeBounds.empty
}) :: Nil,
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This code looks a bit suspicious (we should already record the info as bounds in newPatternBoundSymbol), so I checked why does it make a difference. It seems that when adding bounds to Constraint, it checks whether they fit in the TypeParamRefs original bounds. This turns out to actually fail when dealing with HK types.

This'll do for now, but I'd like to touch up this code in the future - in general when inserting a symbol into GADTMap, we probably should just use the initial bounds as the fake TypeParamRefs bounds.

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OK, then can you open an issue and add a TODO in the code that points to the issue so we can keep track of this ?

pt => defn.AnyType)
new TypeVar(poly.paramRefs.head, creatorState = null)
}
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2 changes: 1 addition & 1 deletion compiler/src/dotty/tools/dotc/core/TypeComparer.scala
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Expand Up @@ -559,7 +559,7 @@ class TypeComparer(initctx: Context) extends ConstraintHandling[AbsentContext] {
if (tparams1.nonEmpty)
return recur(
HKTypeLambda.fromParams(tparams1, tp1.appliedTo(tparams1.map(_.paramRef))),
tp2)
tp2) || fourthTry
else tp2 match {
case EtaExpansion(tycon2) if tycon2.symbol.isClass =>
return recur(tp1, tycon2)
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2 changes: 1 addition & 1 deletion compiler/test/dotc/pos-from-tasty.blacklist
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Expand Up @@ -23,4 +23,4 @@ i4006c.scala

# Not sure what's wring here
i4203.scala
t6278-synth-def.scala
t6278-synth-def.scala
57 changes: 57 additions & 0 deletions tests/pos/i6014-gadt.scala
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@@ -0,0 +1,57 @@
import scala.compiletime._

object Test1 {
type Foo[F[_]]
type Bar[T] = T match {
case Foo[f] => f[Int]
}

val li: Bar[Foo[List]] = List(1, 2, 3)
}

object Test2 {
inline def summon[T] = implicit match {
case t: T => t
}

class Foo[F[_]]

inline def bar[T] = inline erasedValue[T] match {
case _: Foo[f] => summon[f[Int]]
}

implicit val li: List[Int] = List(1, 2, 3)
val lii = bar[Foo[List]]
}

object Test3 {
inline def summon[T] = implicit match {
case t: T => t
}

type K1Top = [t] => Any

class Foo[F <: K1Top]

inline def bar[T] = inline erasedValue[T] match {
case _: Foo[f] => summon[f[Int]]
}

implicit val li: List[Int] = List(1, 2, 3)
val lii = bar[Foo[List]]
}

object Test4 {
inline def summon[T] = implicit match {
case t: T => t
}

class Foo[F[t] >: List[t]]

inline def bar[T] = inline erasedValue[T] match {
case _: Foo[f] => summon[f[Int]]
}

implicit val li: List[Int] = List(1, 2, 3)
val lii = bar[Foo[List]]
}