Move @static immutable fields & methods to companion traits

The original code in addition adds the flag `Mutable` while moving, which does not respect Scala semantics.

Author: liufengyun

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

@@ -24,12 +24,11 @@ class MoveStatics extends MiniPhase with SymTransformer {
  override def phaseName: String = MoveStatics.name
 
  def transformSym(sym: SymDenotation)(implicit ctx: Context): SymDenotation = {
- if (sym.hasAnnotation(defn.ScalaStaticAnnot) && sym.owner.is(Flags.Module) &&
- sym.owner.companionClass.exists && !sym.owner.companionClass.is(Flags.Trait)) {
+ if (sym.hasAnnotation(defn.ScalaStaticAnnot) && sym.owner.is(Flags.Module) && sym.owner.companionClass.exists &&
+ (sym.is(Flags.Method) || !(sym.is(Flags.Mutable) && sym.owner.companionClass.is(Flags.Trait)))) {
  sym.owner.asClass.delete(sym.symbol)
  sym.owner.companionClass.asClass.enter(sym.symbol)
- val flags = if (sym.is(Flags.Method)) sym.flags else sym.flags | Flags.Mutable
- sym.copySymDenotation(owner = sym.owner.companionClass, initFlags = flags)
+ sym.copySymDenotation(owner = sym.owner.companionClass)
  }
  else sym
  }
@@ -59,9 +58,8 @@ class MoveStatics extends MiniPhase with SymTransformer {
  }
 
  def move(module: TypeDef, companion: TypeDef): List[Tree] = {
- assert(companion ne module)
+ assert(companion != module)
  if (!module.symbol.is(Flags.Module)) move(companion, module)
- else if (companion != null && companion.symbol.is(Flags.Trait)) List(module, companion)
  else {
  val allMembers =
  (if(companion != null) {companion.rhs.asInstanceOf[Template].body} else Nil) ++

compiler/test/dotty/tools/backend/jvm/DottyBytecodeTest.scala

@@ -73,6 +73,10 @@ trait DottyBytecodeTest {
  classNode.methods.asScala.find(_.name == name) getOrElse
  sys.error(s"Didn't find method '$name' in class '${classNode.name}'")
 
+ protected def getField(classNode: ClassNode, name: String): FieldNode =
+ classNode.fields.asScala.find(_.name == name) getOrElse
+ sys.error(s"Didn't find field '$name' in class '${classNode.name}'")
+
  def diffInstructions(isa: List[Instruction], isb: List[Instruction]): String = {
  val len = Math.max(isa.length, isb.length)
  val sb = new StringBuilder

compiler/test/dotty/tools/backend/jvm/DottyBytecodeTests.scala

@@ -695,4 +695,50 @@ class TestBCode extends DottyBytecodeTest {
  "`test` was not properly generated\n" + diffInstructions(instructions, expected))
  }
  }
+
+ @Test def i5924b = {
+ val source =
+ """|import scala.annotation.static
+ |trait Base
+ |
+ |object Base {
+ | @static val x = 10
+ | @static final val y = 10
+ | @static def f: Int = 30
+ |}
+ """.stripMargin
+
+ checkBCode(source) { dir =>
+ val clsIn = dir.lookupName("Base.class", directory = false).input
+ val clsNode = loadClassNode(clsIn)
+ getMethod(clsNode, "f")
+ getField(clsNode, "x")
+ getField(clsNode, "y")
+ }
+ }
+
+ @Test def i5924c = {
+ val source =
+ """|import scala.annotation.static
+ |class Base
+ |
+ |object Base {
+ | @static val x = 10
+ | @static final val y = 10
+ | @static var a = 10
+ | @static final var b = 10
+ | @static def f: Int = 30
+ |}
+ """.stripMargin
+
+ checkBCode(source) { dir =>
+ val clsIn = dir.lookupName("Base.class", directory = false).input
+ val clsNode = loadClassNode(clsIn)
+ getMethod(clsNode, "f")
+ getField(clsNode, "x")
+ getField(clsNode, "y")
+ getField(clsNode, "a")
+ getField(clsNode, "b")
+ }
+ }
 }

tests/run/i5924b.scala

@@ -0,0 +1,13 @@
+import scala.annotation.static
+
+trait Base
+
+object Base {
+ @static val x = 10
+ @static final val y = 10
+ @static def f: Int = 30
+}
+
+object Test {
+ def main(args: Array[String]): Unit = Base
+}

tests/run/i5924c.scala

@@ -0,0 +1,15 @@
+import scala.annotation.static
+
+class Base
+
+object Base {
+ @static val x = 10
+ @static final val y = 10
+ @static var a = 10
+ @static final var b = 10
+ @static def f: Int = 30
+}
+
+object Test {
+ def main(args: Array[String]): Unit = Base
+}