gen: fix sumtype custom str (#6534)

vlib/v/gen/auto_str_methods.v

@@ -383,16 +383,13 @@ fn struct_auto_str_func(sym table.TypeSymbol, field_type table.Type, fn_name, fi
 		}
 		if has_custom_str {
 			return '${fn_name}($obj)'
-		} else {
-			return 'indent_${fn_name}($obj, indent_count + 1)'
 		}
-	} else if sym.kind in [.array, .array_fixed, .map] {
+		return 'indent_${fn_name}($obj, indent_count + 1)'
+	} else if sym.kind in [.array, .array_fixed, .map, .sum_type] {
 		if has_custom_str {
 			return '${fn_name}(it->${c_name(field_name)})'
 		}
 		return 'indent_${fn_name}(it->${c_name(field_name)}, indent_count + 1)'
-	} else if sym.kind == .sum_type {
-		return 'indent_${fn_name}(it->${c_name(field_name)}, indent_count + 1)'
 	} else {
 		mut method_str := 'it->${c_name(field_name)}'
 		if sym.kind == .bool {

vlib/v/tests/sumtype_str_test.v

@@ -57,3 +57,21 @@ fn test_pointer() {
 	st := ST(0)
 	assert '${&st}' == '&ST(0)'
 }
+
+struct Xyz {}
+
+type Hola = Abc | Xyz
+
+fn (h Hola) str() string {
+	return 'Hola'
+}
+
+struct HolaContainer {
+	h Hola
+}
+
+fn test_custom_str_method() {
+	h := HolaContainer{}
+	assert h.str() == 'HolaContainer {\n    h: Hola\n}'
+	assert '$h' == 'HolaContainer {\n    h: Hola\n}'
+}