Merge pull request #2225 from retronym/ticket/7234

SI-7234 Make named args play nice with dep. method types

1 files changed, 10 insertions, 7 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/NamesDefaults.scala b/src/compiler/scala/tools/nsc/typechecker/NamesDefaults.scala
index 2340c78f8c..525a67a923 100644
--- a/src/compiler/scala/tools/nsc/typechecker/NamesDefaults.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/NamesDefaults.scala
@@ -273,22 +273,25 @@ trait NamesDefaults { self: Analyzer =>
      */
     def argValDefs(args: List[Tree], paramTypes: List[Type], blockTyper: Typer): List[Option[ValDef]] = {
       val context = blockTyper.context
-      val symPs = map2(args, paramTypes)((arg, tpe) => arg match {
+      val symPs = map2(args, paramTypes)((arg, paramTpe) => arg match {
         case Ident(nme.SELECTOR_DUMMY) =>
           None // don't create a local ValDef if the argument is <unapply-selector>
         case _ =>
-          val byName   = isByNameParamType(tpe)
-          val repeated = isScalaRepeatedParamType(tpe)
+          val byName   = isByNameParamType(paramTpe)
+          val repeated = isScalaRepeatedParamType(paramTpe)
           val argTpe = (
             if (repeated) arg match {
               case Typed(expr, Ident(tpnme.WILDCARD_STAR)) => expr.tpe
               case _                                       => seqType(arg.tpe)
             }
-            else arg.tpe
-            ).widen // have to widen or types inferred from literal defaults will be singletons
+            else
+              // Note stabilizing can lead to a non-conformant argument when existentials are involved, e.g. neg/t3507-old.scala, hence the filter.
+              // We have to deconst or types inferred from literal arguments will be Constant(_), e.g. pos/z1730.scala.
+              gen.stableTypeFor(arg).filter(_ <:< paramTpe).getOrElse(arg.tpe).deconst
+          )
           val s = context.owner.newValue(unit.freshTermName("x$"), arg.pos) setInfo (
-              if (byName) functionType(Nil, argTpe) else argTpe
-              )
+            if (byName) functionType(Nil, argTpe) else argTpe
+          )
           Some((context.scope.enter(s), byName, repeated))
       })
       map2(symPs, args) {