part of #1589; error message for DesugarEnums.scala:47

Author: esarbe

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

@@ -6,6 +6,7 @@ import core._
 import util.Positions._, Types._, Contexts._, Constants._, Names._, NameOps._, Flags._
 import SymDenotations._, Symbols._, StdNames._, Annotations._, Trees._
 import Decorators._
+import dotty.tools.dotc.reporting.diagnostic.messages.EnumCaseDefinitionInNonEnumOwner
 import collection.mutable.ListBuffer
 import util.Property
 import typer.ErrorReporting._
@@ -32,7 +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(em"case not allowed here, since owner ${ctx.owner} is not an `enum' object", tree.pos)
+    || { ctx.error(EnumCaseDefinitionInNonEnumOwner(), tree.pos)
          false
        }
     )

compiler/src/dotty/tools/dotc/reporting/diagnostic/ErrorMessageID.java

@@ -100,6 +100,7 @@ public enum ErrorMessageID {
     NoReturnFromInlineID,
     ReturnOutsideMethodDefinitionID,
     UncheckedTypePatternID,
+    EnumCaseDefinitionInNonEnumOwnerID,
     ;
 
     public int errorNumber() {

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

@@ -1748,7 +1748,7 @@ object messages {
     val explanation =
       hl"you have to provide either ${"class"}, ${"trait"}, ${"object"}, or ${"enum"} definitions after qualifiers"
   }
-
+  
   case class NoReturnFromInline(owner: Symbol)(implicit ctx: Context)
     extends Message(NoReturnFromInlineID) {
     val kind = "Syntax"
@@ -1770,4 +1770,21 @@ object messages {
           |"""
   }
 
+  case class EnumCaseDefinitionInNonEnumOwner()(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 explanation = {
+
+        hl"""
+            | ${"case"} is only allowed at this place if the surrounding object is the companion object of an `enum class`.
+            | If you wanted to create an enumeration, make sure that the corresponding class has the `enum` keyword.
+            | Otherwise you might have forgotten `class` or `object` after this `enum`.
+            |
+            | See http://dotty.epfl.ch/docs/reference/enums/enums.html for more details on enumerations.
+          """.stripMargin
+      }
+
+    }
+
 }