Add a -Xmixin-force-forwarders ChoiceSetting

4 files changed, 22 insertions, 9 deletions

diff --git a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
index bb1d760d86..e10fa3a114 100644
--- a/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/ScalaSettings.scala
@@ -133,7 +133,22 @@ trait ScalaSettings extends AbsScalaSettings
 
   val XnoPatmatAnalysis = BooleanSetting ("-Xno-patmat-analysis", "Don't perform exhaustivity/unreachability analysis. Also, ignore @switch annotation.")
   val XfullLubs         = BooleanSetting ("-Xfull-lubs", "Retains pre 2.10 behavior of less aggressive truncation of least upper bounds.")
-  val XgenMixinForwarders = BooleanSetting("-Xgen-mixin-forwarders", "Generate forwarder methods in classes inhering concrete methods from traits.")
+
+  val XmixinForceForwarders = ChoiceSetting(
+    name    = "-Xmixin-force-forwarders",
+    helpArg = "mode",
+    descr   = "Generate forwarder methods in classes inhering concrete methods from traits.",
+    choices = List("true", "junit", "false"),
+    default = "junit",
+    choicesHelp = List(
+      "Always generate mixin forwarders.",
+      "Generate mixin forwarders for JUnit-annotated methods (JUnit 4 does not support default methods).",
+      "Only generate mixin forwarders required for program correctness."))
+
+  object mixinForwarderChoices {
+    def isTruthy = XmixinForceForwarders.value == "true"
+    def isJunit = isTruthy || XmixinForceForwarders.value == "junit"
+  }
 
   // XML parsing options
   object XxmlSettings extends MultiChoiceEnumeration {
diff --git a/src/compiler/scala/tools/nsc/settings/Warnings.scala b/src/compiler/scala/tools/nsc/settings/Warnings.scala
index 047ea3c751..839e734abc 100644
--- a/src/compiler/scala/tools/nsc/settings/Warnings.scala
+++ b/src/compiler/scala/tools/nsc/settings/Warnings.scala
@@ -25,8 +25,6 @@ trait Warnings {
   // currently considered too noisy for general use
   val warnUnusedImport     = BooleanSetting("-Ywarn-unused-import", "Warn when imports are unused.")
 
-  val junitTraitMethodsNoForwarders = BooleanSetting("-Yjunit-trait-methods-no-forwarders", "Don't generate forwarders for JUnit annotated trait methods (JUnit 4 does not support default methods).")
-
   // Experimental lint warnings that are turned off, but which could be turned on programmatically.
   // They are not activated by -Xlint and can't be enabled on the command line because they are not
   // created using the standard factory methods.
diff --git a/src/compiler/scala/tools/nsc/transform/Mixin.scala b/src/compiler/scala/tools/nsc/transform/Mixin.scala
index 58f32b9aca..af9ba7c300 100644
--- a/src/compiler/scala/tools/nsc/transform/Mixin.scala
+++ b/src/compiler/scala/tools/nsc/transform/Mixin.scala
@@ -287,14 +287,14 @@ abstract class Mixin extends InfoTransform with ast.TreeDSL {
               }
 
               def generateJUnitForwarder: Boolean = {
-                !settings.junitTraitMethodsNoForwarders &&
+                settings.mixinForwarderChoices.isJunit &&
                   member.annotations.nonEmpty &&
                   JUnitAnnotations.exists(annot => annot.exists && member.hasAnnotation(annot))
               }
 
               if (existsCompetingMethod(clazz.baseClasses) || generateJUnitForwarder)
                 genForwarder(required = true)
-              else if (settings.XgenMixinForwarders)
+              else if (settings.mixinForwarderChoices.isTruthy)
                 genForwarder(required = false)
             }
 
diff --git a/test/junit/scala/lang/traits/BytecodeTest.scala b/test/junit/scala/lang/traits/BytecodeTest.scala
index c20fae2500..7bfa3362d4 100644
--- a/test/junit/scala/lang/traits/BytecodeTest.scala
+++ b/test/junit/scala/lang/traits/BytecodeTest.scala
@@ -236,7 +236,7 @@ class BytecodeTest extends BytecodeTesting {
         |class C extends T
       """.stripMargin
     val List(c1, _) = compileClasses(code)
-    val List(c2, _) = newCompiler(extraArgs = "-Xgen-mixin-forwarders").compileClasses(code)
+    val List(c2, _) = newCompiler(extraArgs = "-Xmixin-force-forwarders:true").compileClasses(code)
     assert(getMethods(c1, "f").isEmpty)
     assertSameCode(getMethod(c2, "f"),
       List(VarOp(ALOAD, 0), Invoke(INVOKESTATIC, "T", "f$", "(LT;)I", true), Op(IRETURN)))
@@ -278,11 +278,11 @@ class BytecodeTest extends BytecodeTesting {
 
   @Test
   def sd210(): Unit = {
-    val forwardersCompiler = newCompiler(extraArgs = "-Xgen-mixin-forwarders")
+    val forwardersCompiler = newCompiler(extraArgs = "-Xmixin-force-forwarders:true")
     val jCode = List("interface A { default int m() { return 1; } }" -> "A.java")
 
 
-    // used to crash in the backend (SD-210) under `-Xgen-mixin-forwarders`
+    // used to crash in the backend (SD-210) under `-Xmixin-force-forwarders:true`
     val code1 =
       """trait B1 extends A // called "B1" not "B" due to scala-dev#214
         |class C extends B1
@@ -291,7 +291,7 @@ class BytecodeTest extends BytecodeTesting {
     val List(_, c1a) = compileClasses(code1, jCode)
     assert(getAsmMethods(c1a, "m").isEmpty) // ok, no forwarder
 
-    // here we test a warning. without `-Xgen-mixin-forwarders`, the forwarder would not be
+    // here we test a warning. without `-Xmixin-force-forwarders:true`, the forwarder would not be
     // generated, it is not necessary for correctness.
     val warn = "Unable to implement a mixin forwarder for method m in class C unless interface A is directly extended by class C"
     val List(_, c1b) = forwardersCompiler.compileClasses(code1, jCode, allowMessage = _.msg.contains(warn))