add test and provide owner on message creation

Author: esarbe

compiler/src/dotty/tools/dotc/ast/DesugarEnums.scala

@@ -33,7 +33,7 @@ object DesugarEnums {
   /** Is enum case `tree` situated in a companion object of an enum class? */
   def enumCaseIsLegal(tree: Tree)(implicit ctx: Context): Boolean = (
     ctx.owner.is(ModuleClass) && enumClass.derivesFrom(defn.EnumClass)
-    || { ctx.error(EnumCaseDefinitionInNonEnumOwner(), tree.pos)
+    || { ctx.error(EnumCaseDefinitionInNonEnumOwner(ctx.owner), tree.pos)
          false
        }
     )

compiler/src/dotty/tools/dotc/reporting/diagnostic/messages.scala

@@ -1758,10 +1758,10 @@ object messages {
           |"""
   }
 
-  case class EnumCaseDefinitionInNonEnumOwner()(implicit ctx: Context)
+  case class EnumCaseDefinitionInNonEnumOwner(owner: Symbol)(implicit ctx: Context)
     extends Message(EnumCaseDefinitionInNonEnumOwnerID) {
       val kind = "Syntax"
-      val msg = em"case not allowed here, since owner ${ctx.owner} is not an `enum' object"
+      val msg = em"case not allowed here, since owner ${owner} is not an `enum' object"
       val explanation = {
 
         hl"""

compiler/test/dotty/tools/dotc/reporting/ErrorMessagesTests.scala

@@ -998,4 +998,17 @@ class ErrorMessagesTests extends ErrorMessagesTest {
       val ReturnOutsideMethodDefinition(owner) :: Nil = messages
       assertEquals("object A", owner.show)
     }
+
+  @Test def enumCaseDefinitionInNonEnumOwner =
+    checkMessagesAfter("frontend") {
+      """object Qux {
+        |  case Foo
+        |}
+      """.stripMargin
+    }.expect { (ictx, messages) =>
+      implicit val ctx: Context = ictx
+      assertMessageCount(1, messages)
+      val EnumCaseDefinitionInNonEnumOwner(owner) :: Nil = messages
+      assertEquals("object Qux", owner.show)
+    }
 }