Space: Fix decomposable, dont recurse on Java enums

Author: dwijnand

compiler/src/dotty/tools/dotc/transform/patmat/Space.scala

@@ -613,9 +613,9 @@ object SpaceEngine {
       case OrType(tp1, tp2)                            => List(tp1, tp2)
       case tp if tp.isRef(defn.BooleanClass)           => List(ConstantType(Constant(true)), ConstantType(Constant(false)))
       case tp if tp.isRef(defn.UnitClass)              => ConstantType(Constant(())) :: Nil
-      case tp if tp.classSymbol.isAllOf(JavaEnumTrait) => tp.classSymbol.children.map(_.termRef)
       case tp @ NamedType(Parts(parts), _)             => parts.map(tp.derivedSelect)
       case _: SingletonType                            => ListOfNoType
+      case tp if tp.classSymbol.isAllOf(JavaEnumTrait) => tp.classSymbol.children.map(_.termRef)
 
       case tp @ AppliedType(Parts(parts), targs) if tp.classSymbol.children.isEmpty =>
         // It might not obvious that it's OK to apply the type arguments of a parent type to child types.

tests/patmat/java-enum1/ParameterModifier.java

@@ -0,0 +1,8 @@
+public enum ParameterModifier {
+    Repeated,
+    Plain,
+    ByName;
+
+    private ParameterModifier() {
+    }
+}

tests/patmat/java-enum1/Test.scala

@@ -0,0 +1,6 @@
+class Test:
+  private def showParameterModifier(base: String, pm: ParameterModifier): String = pm match {
+    case ParameterModifier.Plain    => base
+    case ParameterModifier.Repeated => base + "*"
+    case ParameterModifier.ByName   => "=> " + base
+  }