fixes a varargs of untyped regression

tests/macros/tvarargsuntyped.nim

@@ -0,0 +1,79 @@
+discard """
+  output: '''Let's go!
+(left: 2, r: 7, x: 8, height: 4, s: test, width: 3, y: 9, top: 1, g: 7, b: 8)
+(left: 2, r: 7, x: 8, height: 4, s: text, width: 3, y: 9, top: 1, g: 7, b: 8)
+(left: 2, r: 7, x: 8, height: 4, s: text, width: 3, y: 9, top: 4, g: 7, b: 8)
+(left: 2, r: 7, x: 8, height: 4, s: test, width: 3, y: 9, top: 1, g: 7, b: 8)'''
+"""
+
+import macros
+
+proc internalBar(top, left, width, height: cint, s: string, x, y: int, r,g,b: int) =
+  echo locals()
+
+# we need these dummy constructors due to the wrong implementation
+# of 'varargs[untyped]' in the compiler:
+
+proc point(x, y: int): int = discard
+proc color(r, g, b: int): int = discard
+proc rect(a, b, c, d: int): int = discard
+
+template declareUnpackingMacro(nimname,extname) =
+  macro nimname(n: varargs[untyped]): untyped =
+    var s: string = astToStr(extname) & "("
+    var first = true
+    echo repr n
+    for x in n.children:
+      var unpack = false
+      if x.kind in nnkCallKinds:
+        case $x[0]
+        of "point":
+          expectLen(x, 3)
+          unpack = true
+        of "rect":
+          expectLen(x, 5)
+          unpack = true
+        of "color":
+          expectLen(x, 4)
+          unpack = true
+        else: discard
+      if unpack:
+        for i in 1..<x.len:
+          if first:
+            first = false
+          else:
+            add(s, ", ")
+          add(s, repr(x[i]))
+      else:
+        if first:
+          first = false
+        else:
+          add(s, ", ")
+        add(s, repr(x))
+
+    add(s, ")")
+    echo s
+    result = parseStmt(s)
+
+declareUnpackingMacro(bar,internalBar)
+
+type MyInt = distinct int
+
+proc myInt(i: int): MyInt = cast[MyInt](i)
+
+converter toCInt(mi: MyInt): cint = cast[cint](mi)
+
+echo "Let's go!"
+
+bar(rect(1, 2, 3, 4), "test", point(8, 9), color(7,7,8))
+
+bar(1,2,3,4,"text",8,9,7,7,8)
+
+bar(myInt(4),2,3,4,"text",8,9,7,7,8)
+
+let top: cint = 1
+let left: cint = 2
+let width: cint = 3
+let height: cint = 4
+
+bar(rect(top, left, width, height), "test", point(8, 9), color(7,7,8))