Merge pull request #9417 from joroKr21/hk-skolems

Correct bounds for higher-kinded GADT skolems
scala · Jan 6, 2021 · b049775 · b049775
2 parents 2e79383 + cd13abc
commit b049775
Show file tree

Hide file tree

Showing 5 changed files with 43 additions and 10 deletions.
diff --git a/src/compiler/scala/tools/nsc/typechecker/PatternTypers.scala b/src/compiler/scala/tools/nsc/typechecker/PatternTypers.scala
@@ -195,16 +195,16 @@ trait PatternTypers {
 
       def skolems = try skolemBuffer.toList finally skolemBuffer.clear()
       def apply(tp: Type): Type = mapOver(tp) match {
-        case tp @ TypeRef(NoPrefix, tpSym, Nil) if eligible(tpSym) =>
-          val bounds = (
-            if (variance.isInvariant) tpSym.tpeHK.bounds
-            else if (variance.isPositive) TypeBounds.upper(tpSym.tpeHK)
-            else TypeBounds.lower(tpSym.tpeHK)
+        case TypeRef(NoPrefix, tpSym, Nil) if eligible(tpSym) =>
+          val bounds = genPolyType(tpSym.typeParams,
+            if (variance.isInvariant) tpSym.tpe.bounds
+            else if (variance.isPositive) TypeBounds.upper(tpSym.tpe)
+            else TypeBounds.lower(tpSym.tpe)
           )
           // origin must be the type param so we can deskolemize
           val skolem = context.owner.newGADTSkolem(freshTypeName("?" + tpSym.name), tpSym, bounds)
           skolemBuffer += skolem
-          logResult(s"Created gadt skolem $skolem: ${skolem.tpe_*} to stand in for $tpSym")(skolem.tpe_*)
+          logResult(s"Created gadt skolem $skolem: ${skolem.tpeHK} to stand in for $tpSym")(skolem.tpeHK)
         case tp1 => tp1
       }
     }

diff --git a/src/reflect/scala/reflect/internal/Types.scala b/src/reflect/scala/reflect/internal/Types.scala
@@ -2438,7 +2438,7 @@ trait Types
 
 
     // interpret symbol's info in terms of the type's prefix and type args
-    protected def relativeInfo: Type = appliedType(sym.info.asSeenFrom(pre, sym.owner), argsOrDummies)
+    protected def relativeInfo: Type = appliedType(sym.info.asSeenFrom(pre, sym.owner), args)
 
     // @M: propagate actual type params (args) to `tp`, by replacing
     // formal type parameters with actual ones. If tp is higher kinded,

diff --git a/test/files/neg/hk-existential-lb.check b/test/files/neg/hk-existential-lb.check
@@ -1,7 +1,7 @@
 hk-existential-lb.scala:5: error: type mismatch;
  found   : Functor[Option]
  required: Functor[_[x] >: List[x]]
-Note: Option <: Any, but class Functor is invariant in type F.
+Note: Option <: [x]Any, but class Functor is invariant in type F.
 You may wish to define F as +F instead. (SLS 4.5)
   val someF: Functor[F] forSome { type F[x] >: List[x] } = new Functor[Option]
                                                            ^

diff --git a/test/files/pos/t12295.scala b/test/files/pos/t12295.scala
@@ -0,0 +1,33 @@
+object Test {
+  sealed trait Foo[+A] // sealed or not doesn't matter
+  case class ImplA[A](a: A) extends Foo[A]
+  case class ImplAny[A](a: Any) extends Foo[A]
+
+  trait Bar[+G[_]] // must be covariant
+
+  def err[F[_]](): Unit = {
+    val x: Foo[Foo[Bar[F]]] = ???
+
+    x match {
+      case ImplAny(ImplAny(_)) => ???
+      case ImplAny(ImplA(_)) => ???
+      case ImplA(_) => ???
+      case ImplAny(_) => ???
+      case _ => ???
+    }
+
+    x match {
+      case ImplA(ImplA(_)) => ???
+      case ImplA(ImplAny(_)) => ???
+      case ImplA(y) => y.toString
+      case ImplA(y) => y match {
+        case ImplA(_) => ???
+        case _ => ???
+      }
+      case ImplA(y) => y
+      case _ => ???
+    }
+
+    ()
+  }
+}
diff --git a/test/files/run/repl-kind.check b/test/files/run/repl-kind.check
@@ -14,8 +14,8 @@ Either's kind is F[+A1,+A2]
 This is a type constructor: a 1st-order-kinded type.
 
 scala> :k -v scala.collection.SortedMapOps
-scala.collection.SortedMapOps's kind is X[K,+V,+CC[X,Y] <: scala.collection.Map[X,Y] with scala.collection.SortedMapOps[X, Y, CC, _],+C <: scala.collection.SortedMapOps[K,V,CC,C]]
-* -> * -(+)-> (* -> * -> *(scala.collection.Map[X,Y] with scala.collection.SortedMapOps[X, Y, CC, _])) -(+)-> *(scala.collection.SortedMapOps[K,V,CC,C]) -(+)-> *
+scala.collection.SortedMapOps's kind is X[K,+V,+CC[X,Y] <: [X, Y]scala.collection.Map[X,Y] with scala.collection.SortedMapOps[X, Y, CC, _],+C <: scala.collection.SortedMapOps[K,V,CC,C]]
+* -> * -(+)-> (* -> * -> *([X, Y]scala.collection.Map[X,Y] with scala.collection.SortedMapOps[X, Y, CC, _])) -(+)-> *(scala.collection.SortedMapOps[K,V,CC,C]) -(+)-> *
 This is a type constructor that takes type constructor(s): a higher-kinded type.
 
 scala> :kind -v Tuple2