Output parameter names

Partially ports scala/scala#4735

Author: Kordyjan

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

@@ -335,6 +335,14 @@ trait BCodeHelpers extends BCodeIdiomatic with BytecodeWriters {
         emitAssocs(av, assocs, BCodeHelpers.this)(this)
       }
 
+    /*
+     * must-single-thread
+     */
+    def emitParamNames(jmethod: asm.MethodVisitor, params: List[Symbol]) =
+      for param <- params do
+        var access = asm.Opcodes.ACC_FINAL
+        jmethod.visitParameter(param.name.mangledString, access)
+
     /*
      * must-single-thread
      */

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

@@ -615,7 +615,7 @@ trait BCodeSkelBuilder extends BCodeHelpers {
     /*
      * must-single-thread
      */
-    def initJMethod(flags: Int, paramAnnotations: List[List[Annotation]]): Unit = {
+    def initJMethod(flags: Int, params: List[Symbol]): Unit = {
 
       val jgensig = getGenericSignature(methSymbol, claszSymbol)
       val (excs, others) = methSymbol.annotations.partition(_.symbol eq defn.ThrowsAnnot)
@@ -637,7 +637,8 @@ trait BCodeSkelBuilder extends BCodeHelpers {
       // TODO param names: (m.params map (p => javaName(p.sym)))
 
       emitAnnotations(mnode, others)
-      emitParamAnnotations(mnode, paramAnnotations)
+      emitParamNames(mnode, params)
+      emitParamAnnotations(mnode, params.map(_.annotations))
 
     } // end of method initJMethod
 
@@ -749,7 +750,7 @@ trait BCodeSkelBuilder extends BCodeHelpers {
           .addFlagIf(isNative, asm.Opcodes.ACC_NATIVE) // native methods of objects are generated in mirror classes
 
       // TODO needed? for(ann <- m.symbol.annotations) { ann.symbol.initialize }
-      initJMethod(flags, params.map(p => p.symbol.annotations))
+      initJMethod(flags, params.map(_.symbol))
 
 
       if (!isAbstractMethod && !isNative) {

tests/run/i11486/Old_1.scala

@@ -0,0 +1,3 @@
+case class TestedOld(foo: Int, bar: String, baz: Double):
+  def target(abc: TestedOld, efg: TestedOld) = ()
+  def symbolic(`def`: Int, *** : Int, `unary_!`: Int) = ()

tests/run/i11486/Test_2.scala

@@ -0,0 +1,21 @@
+import java.lang.reflect.Executable
+
+case class Tested(foo: Int, bar: String, baz: Double):
+  def target(abc: Tested, efg: Tested) = ()
+  def symbolic(`def`: Int, *** : Int, `unary_!`: Int) = ()
+
+def run(cls: Class[_]) =
+  extension(m: Executable) def parameters: List[String] = m.getParameters.toList.map(_.getName)
+
+  val ctorParams = cls.getConstructors.head.parameters
+    assert(ctorParams == List("foo", "bar", "baz"))
+
+    val targetParams = cls.getMethods.toList.find(_.getName == "target").get.parameters
+    assert(targetParams == List("abc", "efg"))
+
+    val symbolicParams = cls.getMethods.toList.find(_.getName == "symbolic").get.parameters
+    assert(symbolicParams == List("def", "$times$times$times", "unary_$bang"))
+
+@main def Test =
+  run(classOf[TestedOld])
+  run(classOf[Tested])