Use the upper bound of type skolems to enumerate subtypes

scala · Feb 1, 2021 · 0733455 · 0733455
1 parent 99a6820
commit 0733455
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diff --git a/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala b/src/compiler/scala/tools/nsc/transform/patmat/MatchAnalysis.scala
@@ -164,6 +164,8 @@ trait TreeAndTypeAnalysis extends Debugging {
         case sym if sym.isCase =>
           List(List(tp))
 
+        case sym if sym.isTypeSkolem => enumerateSubtypes(sym.info.upperBound, grouped) // pos/t12277
+
         case sym =>
           debug.patmat("enum unsealed "+ ((tp, sym, sym.isSealed, isPrimitiveValueClass(sym))))
           Nil

diff --git a/test/files/pos/t12277.scala b/test/files/pos/t12277.scala
@@ -0,0 +1,12 @@
+// scalac: -Xlint:strict-unsealed-patmat -Werror
+sealed trait A
+final case class B() extends A
+final case class C() extends A
+
+object x extends App {
+
+  def matcher[A1 <: A](a1: A1) = a1 match {
+    case x @ (_: B | _: C) => println("B")
+  }
+
+}