Make enum values static at Erasure

If an enum value is static (i.e. part of a globally reachable object),
set the JavaStatic flag at erasure.

Author: odersky

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

@@ -75,8 +75,12 @@ class Erasure extends Phase with DenotTransformer {
         val newInfo = transformInfo(oldSymbol, oldInfo)
         val oldFlags = ref.flags
         val newFlags =
-          if (oldSymbol.is(Flags.TermParam) && isCompacted(oldSymbol.owner)) oldFlags &~ Flags.Param
-          else oldFlags &~ Flags.HasDefaultParamsFlags // HasDefaultParamsFlags needs to be dropped because overriding might become overloading
+          if oldSymbol.is(Flags.TermParam) && isCompacted(oldSymbol.owner) then
+            oldFlags &~ Flags.Param
+          else if oldSymbol.isAllOf(Flags.EnumValue) && oldSymbol.isStatic then
+            oldFlags | Flags.JavaStatic
+          else
+            oldFlags &~ Flags.HasDefaultParamsFlags // HasDefaultParamsFlags needs to be dropped because overriding might become overloading
 
         // TODO: define derivedSymDenotation?
         if ((oldSymbol eq newSymbol) && (oldOwner eq newOwner) && (oldName eq newName) && (oldInfo eq newInfo) && (oldFlags == newFlags))

tests/pos/i7428.scala

@@ -1,4 +1,4 @@
-object ABug
+class ABug
   enum Tag
     case first
   import Tag.first