SI-8743 Fix crasher with poly-methods annotated with @varargs

The code that generated the Java varargs forwarder was basing
things on the `ValDef-s` of the parameters of the source method.
But, their types refer to a type parameter skolems of the enclosing
method, which led to a type mismatch when typechecking the forwarder.

Instead, I've reworked the code to simply use the `DefDef`-s symbol's
info, which *doesn't* refer to skolems. This actually simplifies the
surrounding code somewhat; rather than repeated symbols in a map
we can just time travel the pre-uncurry method signatures to figure
out which params are releated.

3 files changed, 4 insertions, 2 deletions

diff --git a/test/files/jvm/varargs.check b/test/files/jvm/varargs.check
index 8379befe93..986f98896a 100644
--- a/test/files/jvm/varargs.check
+++ b/test/files/jvm/varargs.check
@@ -1,3 +1,4 @@
 7
 10
-19
\ No newline at end of file
+19
+a
diff --git a/test/files/jvm/varargs/JavaClass.java b/test/files/jvm/varargs/JavaClass.java
index 9851e1b78b..6928ee5adc 100644
--- a/test/files/jvm/varargs/JavaClass.java
+++ b/test/files/jvm/varargs/JavaClass.java
@@ -11,5 +11,6 @@ public class JavaClass {
 	va.vi(1, 2, 3, 4);
         varargz(5, 1.0, 2.0, 3.0);
 	va.vt(16, "", "", "");
+	System.out.println(va.vt1(16, "a", "b", "c"));
     }
 }
\ No newline at end of file
diff --git a/test/files/jvm/varargs/VaClass.scala b/test/files/jvm/varargs/VaClass.scala
index 6343f9c6f6..e94e8a625a 100644
--- a/test/files/jvm/varargs/VaClass.scala
+++ b/test/files/jvm/varargs/VaClass.scala
@@ -9,5 +9,5 @@ class VaClass {
   @varargs def vs(a: Int, b: String*) = println(a + b.length)
   @varargs def vi(a: Int, b: Int*) = println(a + b.sum)
   @varargs def vt[T](a: Int, b: T*) = println(a + b.length)
-
+  @varargs def vt1[T](a: Int, b: T*): T = b.head
 }