Generate ACC_ENUM flags for Java enums

Author: anatoliykmetyuk

compiler/src/dotty/tools/backend/jvm/BTypesFromSymbols.scala

@@ -223,7 +223,8 @@ class BTypesFromSymbols[I <: BackendInterface](val int: I) extends BTypes {
       if (sym.hasEnumFlag) ACC_ENUM else 0,
       if (sym.isVarargsMethod) ACC_VARARGS else 0,
       if (sym.isSynchronized) ACC_SYNCHRONIZED else 0,
-      if (sym.isDeprecated) asm.Opcodes.ACC_DEPRECATED else 0
+      if (sym.isDeprecated) asm.Opcodes.ACC_DEPRECATED else 0,
+      if (sym.isEnum) asm.Opcodes.ACC_ENUM else 0
     )
   }
 

compiler/src/dotty/tools/backend/jvm/BackendInterface.scala

@@ -512,6 +512,7 @@ abstract class BackendInterface extends BackendInterfaceDefinitions {
     def isJavaDefaultMethod: Boolean
     def isClassConstructor: Boolean
     def isSerializable: Boolean
+    def isEnum: Boolean
 
     /**
      * True for module classes of modules that are top-level or owned only by objects. Module classes

compiler/src/dotty/tools/backend/jvm/DottyBackendInterface.scala

@@ -703,6 +703,7 @@ class DottyBackendInterface(outputDirectory: AbstractFile, val superCallsMap: Ma
     def shouldEmitForwarders: Boolean =
       (sym is Flags.Module) && sym.isStatic
     def isJavaEntryPoint: Boolean = CollectEntryPoints.isJavaEntryPoint(sym)
+    def isEnum = sym.is(Flags.Enum, butNot = Flags.Case) && sym.info.parents.exists(p => p.typeSymbol == defn.JEnumClass)
 
     def isClassConstructor: Boolean = toDenot(sym).isClassConstructor
     def isSerializable: Boolean = toDenot(sym).isSerializable