SI-5788 correct test and symbol update

Previously I thought it's fixed because I didn't include the correct
testcase. Now it's the correct testcase and this prompted me to
change the code a bit to make it work properly.

Author: VladUreche

src/compiler/scala/tools/nsc/typechecker/Duplicators.scala

@@ -283,14 +283,15 @@ abstract class Duplicators extends Analyzer {
 
           // the typer does not create the symbols for a LabelDef's params, so unless they were created before we need
           // to do it manually here -- but for the tailcalls-generated labels, ValDefs are created before the LabelDef,
-          // so we just need to plug in the name
+          // so we just need to change the tree to point to the updated symbols
           def newParam(p: Tree): Ident =
             if (isTailLabel)
-              Ident(p.symbol.name) // let the typer pick up the right symbol
+              Ident(updateSym(p.symbol))
             else {
               val newsym = p.symbol.cloneSymbol //(context.owner) // TODO owner?
               Ident(newsym.setInfo(fixType(p.symbol.info)))
             }
+
           val params1 = params map newParam
           val rhs1 = (new TreeSubstituter(params map (_.symbol), params1) transform rhs) // TODO: duplicate?
           rhs1.tpe = null

test/files/pos/SI-5788.scala

@@ -1,4 +1,3 @@
-trait Test {
-  trait B[T]
-  private final def grow[T](): B[T] = grow[T]()
+trait Foo[@specialized(Int) A] {
+  final def bar(a:A):A = bar(a)
 }