support & in mirrorCompanionRef

Author: bishabosha

compiler/src/dotty/tools/dotc/transform/TypeUtils.scala

@@ -92,6 +92,11 @@ object TypeUtils {
         val r2 = tp2.mirrorCompanionRef
         assert(r1.symbol == r2.symbol, em"mirrorCompanionRef mismatch for $self: $r1, $r2 did not have the same symbol")
         r1
+      case AndType(tp1, tp2) =>
+        val c1 = tp1.classSymbol
+        val c2 = tp2.classSymbol
+        if c1.isSubClass(c2) then tp1.mirrorCompanionRef
+        else tp2.mirrorCompanionRef // precondition: the parts of the AndType have already been checked to be non-overlapping
       case self @ TypeRef(prefix, _) if self.symbol.isClass =>
         prefix.select(self.symbol.companionModule).asInstanceOf[TermRef]
       case self: TypeProxy =>

tests/neg/i15190.scala

@@ -0,0 +1,17 @@
+import scala.deriving.Mirror
+
+trait Mixin
+object Mixin
+
+trait Parent
+object Parent
+
+sealed trait Fruit extends Parent
+object Fruit {
+  case object Apple extends Fruit
+  case object Orange extends Fruit
+}
+
+@main def Test = {
+  summon[Mirror.SumOf[Fruit & Mixin]] // error: not a sum type
+}

tests/run/i15190.scala

@@ -0,0 +1,19 @@
+import scala.deriving.Mirror
+
+trait Mixin
+object Mixin
+
+trait Parent
+object Parent
+
+sealed trait Fruit extends Parent
+object Fruit {
+  case object Apple extends Fruit
+  case object Orange extends Fruit
+}
+
+@main def Test = {
+  val mFruit = summon[Mirror.SumOf[Fruit & Parent]]
+  assert(mFruit.ordinal(Fruit.Apple) == 0)
+  assert(mFruit.ordinal(Fruit.Orange) == 1)
+}