cgen: fix auto str for map with ptr str (#20741)

Author: felipensp

vlib/v/gen/c/auto_str_methods.v

@@ -806,9 +806,11 @@ fn (mut g Gen) gen_str_for_map(info ast.Map, styp string, str_fn_name string) {
 		tmp_str := str_intp_rune('${elem_str_fn_name}(*(${val_styp}*)DenseArray_value(&m.key_values, i))')
 		g.auto_str_funcs.writeln('\t\tstrings__Builder_write_string(&sb, ${tmp_str});')
 	} else {
-		ptr_str := '*'.repeat(if receiver_is_ptr { val_typ.nr_muls() - 1 } else { val_typ.nr_muls() })
+		ptr_str := '*'.repeat(val_typ.nr_muls())
 		if val_typ.has_flag(.option) {
 			g.auto_str_funcs.writeln('\t\tstrings__Builder_write_string(&sb, ${g.get_str_fn(val_typ)}(*${ptr_str}(${val_styp}*)DenseArray_value(&m.key_values, i)));')
+		} else if receiver_is_ptr {
+			g.auto_str_funcs.writeln('\t\tstrings__Builder_write_string(&sb, ${elem_str_fn_name}(${ptr_str}(${val_styp}*)DenseArray_value(&m.key_values, i)));')
 		} else {
 			g.auto_str_funcs.writeln('\t\tstrings__Builder_write_string(&sb, ${elem_str_fn_name}(*${ptr_str}(${val_styp}*)DenseArray_value(&m.key_values, i)));')
 		}

vlib/v/tests/map_auto_str_ptr_test.v

@@ -0,0 +1,23 @@
+module main
+
+struct Blob {
+	label int
+}
+
+fn (mut b Blob) str() string {
+	return ''
+}
+
+struct Labels {
+	blobs map[int]Blob
+}
+
+fn break_it() Labels {
+	mut a := Labels{}
+	return a
+}
+
+fn test_main() {
+	mut a := break_it()
+	assert a.blobs.len == 0
+}