ast: fix formatting fn variadic of reference param (#11130)

vlib/v/ast/types.v

@@ -1064,7 +1064,7 @@ pub fn (t &Table) type_to_str_using_aliases(typ Type, import_aliases map[string]
 		nr_muls--
 		res = 'shared ' + res
 	}
-	if nr_muls > 0 {
+	if nr_muls > 0 && !typ.has_flag(.variadic) {
 		res = strings.repeat(`&`, nr_muls) + res
 	}
 	if typ.has_flag(.optional) {

vlib/v/fmt/tests/vargs_reference_param_keep.vv

@@ -0,0 +1,27 @@
+[heap]
+struct Foo {
+	name string
+}
+
+fn agg_stuff(stuffs ...&Foo) []&Foo {
+	stuffs2 := stuffs.clone()
+	return stuffs2
+}
+
+fn arr_stuff(stuffs []&Foo) []&Foo {
+	stuffs2 := stuffs.clone()
+	return stuffs2
+}
+
+fn main() {
+	foo1 := &Foo{'foo'}
+	foo2 := &Foo{'bar'}
+
+	foo11 := agg_stuff(foo1, foo2)
+	println(foo11)
+
+	foo22 := arr_stuff([foo1, foo2])
+	println(foo22)
+
+	assert '$foo11' == '$foo22'
+}