Merge pull request #4898 from soc/SI-8700

SI-8700 Exhaustiveness warning for enums from Java source

4 files changed, 10 insertions, 13 deletions

diff --git a/src/compiler/scala/tools/nsc/backend/jvm/BTypesFromSymbols.scala b/src/compiler/scala/tools/nsc/backend/jvm/BTypesFromSymbols.scala
index 3696bb3daf..53304d137f 100644
--- a/src/compiler/scala/tools/nsc/backend/jvm/BTypesFromSymbols.scala
+++ b/src/compiler/scala/tools/nsc/backend/jvm/BTypesFromSymbols.scala
@@ -671,7 +671,7 @@ class BTypesFromSymbols[G <: Global](val global: G) extends BTypes {
     // Primitives are "abstract final" to prohibit instantiation
     // without having to provide any implementations, but that is an
     // illegal combination of modifiers at the bytecode level so
-    // suppress final if abstract if present.
+    // suppress final if abstract is present.
     import asm.Opcodes._
     GenBCode.mkFlags(
       if (privateFlag) ACC_PRIVATE else ACC_PUBLIC,
diff --git a/src/compiler/scala/tools/nsc/javac/JavaParsers.scala b/src/compiler/scala/tools/nsc/javac/JavaParsers.scala
index eb25eb6e06..7224523a41 100644
--- a/src/compiler/scala/tools/nsc/javac/JavaParsers.scala
+++ b/src/compiler/scala/tools/nsc/javac/JavaParsers.scala
@@ -800,16 +800,10 @@ trait JavaParsers extends ast.parser.ParsersCommon with JavaScanners {
       val superclazz =
         AppliedTypeTree(javaLangDot(tpnme.Enum), List(enumType))
       val finalFlag = if (enumIsFinal) Flags.FINAL else 0l
-      val abstractFlag = {
-        // javac adds `ACC_ABSTRACT` to enum classes with deferred members
-        val hasAbstractMember = body exists {
-          case d: DefDef => d.mods.isDeferred
-          case _         => false
-        }
-        if (hasAbstractMember) Flags.ABSTRACT else 0l
-      }
       addCompanionObject(consts ::: statics ::: predefs, atPos(pos) {
-        ClassDef(mods | Flags.JAVA_ENUM | finalFlag | abstractFlag, name, List(),
+        // Marking the enum class SEALED | ABSTRACT enables exhaustiveness checking. See also ClassfileParser.
+        // This is a bit of a hack and requires excluding the ABSTRACT flag in the backend, see method javaClassfileFlags.
+        ClassDef(mods | Flags.JAVA_ENUM | Flags.SEALED | Flags.ABSTRACT | finalFlag, name, List(),
                  makeTemplate(superclazz :: interfaces, body))
       })
     }
diff --git a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
index 99e61d2482..406411f21f 100644
--- a/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
+++ b/src/compiler/scala/tools/nsc/symtab/classfile/ClassfileParser.scala
@@ -542,7 +542,7 @@ abstract class ClassfileParser {
             devWarning(s"no linked class for java enum $sym in ${sym.owner}. A referencing class file might be missing an InnerClasses entry.")
           case linked =>
             if (!linked.isSealed)
-              // Marking the enum class SEALED | ABSTRACT enables exhaustiveness checking.
+              // Marking the enum class SEALED | ABSTRACT enables exhaustiveness checking. See also JavaParsers.
               // This is a bit of a hack and requires excluding the ABSTRACT flag in the backend, see method javaClassfileFlags.
               linked setFlag (SEALED | ABSTRACT)
             linked addChild sym
diff --git a/src/compiler/scala/tools/nsc/typechecker/Namers.scala b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
index e01edd196e..0b6b6065f3 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Namers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Namers.scala
@@ -653,8 +653,10 @@ trait Namers extends MethodSynthesis {
       if (isScala && deriveAccessors(tree)) enterGetterSetter(tree)
       else assignAndEnterFinishedSymbol(tree)
 
-      if (isEnumConstant(tree))
+      if (isEnumConstant(tree)) {
         tree.symbol setInfo ConstantType(Constant(tree.symbol))
+        tree.symbol.owner.linkedClassOfClass addChild tree.symbol
+      }
     }
 
     def enterLazyVal(tree: ValDef, lazyAccessor: Symbol): TermSymbol = {
@@ -1657,7 +1659,8 @@ trait Namers extends MethodSynthesis {
         checkWithDeferred(FINAL)
       }
 
-      checkNoConflict(FINAL, SEALED)
+      if (!sym.isJavaEnum)
+        checkNoConflict(FINAL, SEALED)
       checkNoConflict(PRIVATE, PROTECTED)
       // checkNoConflict(PRIVATE, OVERRIDE) // this one leads to bad error messages like #4174, so catch in refchecks
       // checkNoConflict(PRIVATE, FINAL)    // can't do this because FINAL also means compile-time constant