fixes #888

compiler/sigmatch.nim

@@ -1451,7 +1451,7 @@ proc paramTypesMatchAux(m: var TCandidate, f, argType: PType,
     if skipTypes(f, abstractVar-{tyTypeDesc}).kind in {tyTuple}:
       result = implicitConv(nkHiddenSubConv, f, arg, m, c)
   of isNone:
-    # do not do this in ``typeRel`` as it then can't infere T in ``ref T``:
+    # do not do this in ``typeRel`` as it then can't infer T in ``ref T``:
     if a.kind in {tyProxy, tyUnknown}:
       inc(m.genericMatches)
       m.fauxMatch = a.kind
@@ -1472,6 +1472,7 @@ proc paramTypesMatchAux(m: var TCandidate, f, argType: PType,
           m.baseTypeMatch = true
         else:
           result = userConvMatch(c, m, base(f), a, arg)
+          if result != nil: m.baseTypeMatch = true
 
 proc paramTypesMatch*(m: var TCandidate, f, a: PType,
                       arg, argOrig: PNode): PNode =

tests/converter/tconverter_with_varargs.nim

@@ -0,0 +1,18 @@
+
+# bug #888
+
+type
+  PyRef = object
+  PPyRef* = ref PyRef
+
+converter to_py*(i: int) : PPyRef = nil
+
+when false:
+  proc to_tuple*(vals: openarray[PPyRef]): PPyRef =
+    discard
+
+proc abc(args: varargs[PPyRef]) =
+  #let args_tup = to_tuple(args)
+  discard
+
+abc(1, 2)