cgen: fix variadic arg var passed to another call which expects varia…

…dic (fix #22315) (#22317)

vlib/v/gen/c/fn.v

@@ -2607,16 +2607,23 @@ fn (mut g Gen) call_args(node ast.CallExpr) {
 						}
 					}
 				} else {
-					noscan := g.check_noscan(arr_info.elem_type)
-					g.write('new_array_from_c_array${noscan}(${variadic_count}, ${variadic_count}, sizeof(${elem_type}), _MOV((${elem_type}[${variadic_count}]){')
-					for j in arg_nr .. args.len {
-						g.ref_or_deref_arg(args[j], arr_info.elem_type, node.language,
+					// passing variadic arg to another call which expects same array type
+					if args.len == 1 && args[arg_nr].typ.has_flag(.variadic)
+						&& args[arg_nr].typ == varg_type {
+						g.ref_or_deref_arg(args[arg_nr], arr_info.elem_type, node.language,
 							false)
-						if j < args.len - 1 {
-							g.write(', ')
+					} else {
+						noscan := g.check_noscan(arr_info.elem_type)
+						g.write('new_array_from_c_array${noscan}(${variadic_count}, ${variadic_count}, sizeof(${elem_type}), _MOV((${elem_type}[${variadic_count}]){')
+						for j in arg_nr .. args.len {
+							g.ref_or_deref_arg(args[j], arr_info.elem_type, node.language,
+								false)
+							if j < args.len - 1 {
+								g.write(', ')
+							}
 						}
+						g.write('}))')
 					}
-					g.write('}))')
 				}
 			} else {
 				g.write('__new_array(0, 0, sizeof(${elem_type}))')

vlib/v/tests/fns/variadic_sumtype_test.v

@@ -0,0 +1,19 @@
+type Either = string | int
+
+fn tag(params ...Either) int {
+	mut c := 0
+	for p in params {
+		if p is int {
+			c += p
+		}
+	}
+	return c
+}
+
+fn div(params ...Either) int {
+	return tag(params)
+}
+
+fn test_main() {
+	assert dump(div('foo', 1, 2)) == 3
+}