Handle enums that have multiple parents

Author: liufengyun

compiler/src/dotty/tools/dotc/core/TypeComparer.scala

@@ -2586,9 +2586,10 @@ class TypeComparer(@constructorOnly initctx: Context) extends ConstraintHandling
         provablyDisjoint(tp1, gadtBounds(tp2.symbol).hi) || provablyDisjoint(tp1, tp2.superType)
       case (tp1: TermRef, tp2: TermRef) if isEnumValueOrModule(tp1) && isEnumValueOrModule(tp2) =>
         tp1.termSymbol != tp2.termSymbol
-      case (tp1: TermRef, tp2: TypeRef) if isEnumValueOrModule(tp1) && !tp1.symbol.moduleClass.derivesFrom(tp2.classSymbol) =>
+      case (tp1: TermRef, tp2: TypeRef) if isEnumValueOrModule(tp1) && !tp1.classSymbols.exists(_.derivesFrom(tp2.classSymbol)) =>
+        // Note: enum values may have multiple parents
         true
-      case (tp1: TypeRef, tp2: TermRef) if isEnumValueOrModule(tp2) && !tp2.symbol.moduleClass.derivesFrom(tp1.classSymbol) =>
+      case (tp1: TypeRef, tp2: TermRef) if isEnumValueOrModule(tp2) && !tp2.classSymbols.exists(_.derivesFrom(tp1.classSymbol)) =>
         true
       case (tp1: Type, tp2: Type) if defn.isTupleType(tp1) =>
         provablyDisjoint(tp1.toNestedPairs, tp2)

tests/patmat/i12475b.scala

@@ -0,0 +1,14 @@
+trait SomeRestriction
+
+enum ADT {
+  case A
+  case B extends ADT with SomeRestriction
+}
+
+object MinimalExample {
+  val b: ADT & SomeRestriction = ADT.B
+
+  b match {
+    case ADT.B => ???
+  }
+}