Merge pull request #1620 from dotty-staging/fix-1614

Fix #1614 tailrec.

Author: felixmulder

src/dotty/tools/dotc/transform/TailRec.scala

@@ -143,7 +143,11 @@ class TailRec extends MiniPhaseTransform with DenotTransformer with FullParamete
                     newOwners = label :: Nil
                   ).transform(rhsSemiTransformed)
                 })
-                Block(List(labelDef), ref(label).appliedToArgss(vparamss0.map(_.map(x=> ref(x.symbol)))))
+                val callIntoLabel = (
+                    if (dd.tparams.isEmpty) ref(label)
+                    else ref(label).appliedToTypes(dd.tparams.map(_.tpe))
+                  ).appliedToArgss(vparamss0.map(_.map(x=> ref(x.symbol))))
+                Block(List(labelDef), callIntoLabel)
             }} else {
               if (mandatory) ctx.error(
                 "TailRec optimisation not applicable, method not tail recursive",

tests/pos/tailcall/i1614.scala

@@ -0,0 +1,9 @@
+object Foobar {
+  def apply(): Option[String] = { 
+    def foobar[A](f: (String, String) => A): List[A] = List[String]() match { 
+      case _ :: ls => foobar(f) 
+    } 
+    foobar((a1, a2) => (a1 + a2)).headOption 
+  } 
+}
+