table: fix alias of sumtype method_call (#11268)

vlib/v/ast/table.v

@@ -475,7 +475,7 @@ pub fn (t &Table) find_field(s &TypeSymbol, name string) ?StructField {
 				}
 			}
 			SumType {
-				t.resolve_common_sumtype_fields(s)
+				t.resolve_common_sumtype_fields(ts)
 				if field := ts.info.find_field(name) {
 					return field
 				}

vlib/v/tests/alias_sumtype_method_call_test.v

@@ -0,0 +1,16 @@
+import x.json2
+
+type MyType = json2.Any
+
+struct Data {
+	prop MyType
+}
+
+fn test_alias_sumtype_method_call() {
+	a := '{"a":"a","b":1}'
+	json := json2.raw_decode(a) or { panic(err) }
+	data := Data{json}
+	json_str := data.prop.str()
+	println(json_str)
+	assert json_str == '{"a":"a","b":1}'
+}