Fix bug in printing a list (#2654)

* Fix bug in printing a list

* Update tests

* Add integration test

* Fix bugs

* Update references

* Fix tests for C backend

Author: advikkabra

integration_tests/test_list_11.py

@@ -1,5 +1,12 @@
 from lpython import i32
 
+l: list[i32] = [1, 2]
+
+def add_item(i: i32) -> list[i32]:
+    l.append(i)
+    return l
+
+
 def return_empty_list_of_tuples() -> list[i32]:
     return []
 
@@ -19,12 +26,21 @@ def test_iterate_over_string():
         assert s == temp[i]
         i+=1
 
+def test_issue_2639():
+    print(add_item(3))
+
+    assert len(l) == 3
+    assert l[0] == 1
+    assert l[1] == 2
+    assert l[2] == 3
+
 def main0():
     x: list[i32] = return_empty_list_of_tuples()
     print(len(x))
 
     assert len(x) == 0
     test_issue_1882()
     test_iterate_over_string()
+    test_issue_2639()
 
 main0()

src/libasr/pass/print_list_tuple.cpp

@@ -114,11 +114,23 @@ class PrintListTupleVisitor
                 list_iter_var_name, al, current_scope, int_type);
         }
 
+        std::string list_var_name;
+        ASR::expr_t *list_var;
+        {
+            list_var_name = 
+                current_scope->get_unique_name("__list_var", false);
+            list_var = PassUtils::create_auxiliary_variable(loc,
+                list_var_name, al, current_scope, ASRUtils::expr_type(list_expr));
+        }
+
+        ASR::stmt_t *assign_stmt = ASRUtils::STMT(
+            ASR::make_Assignment_t(al, loc, list_var, list_expr, nullptr));
+
         ASR::expr_t *list_item = ASRUtils::EXPR(
-            ASR::make_ListItem_t(al, loc, list_expr,
+            ASR::make_ListItem_t(al, loc, list_var,
                                     list_iter_var, listC->m_type, nullptr));
         ASR::expr_t *list_len = ASRUtils::EXPR(ASR::make_ListLen_t(
-            al, loc, list_expr, int_type, nullptr));
+            al, loc, list_var, int_type, nullptr));
         ASR::expr_t *constant_one = ASRUtils::EXPR(
             ASR::make_IntegerConstant_t(al, loc, 1, int_type));
         ASR::expr_t *list_len_minus_one =
@@ -199,6 +211,7 @@ class PrintListTupleVisitor
             al, loc, nullptr, loop_head, loop_body.p, loop_body.size(), nullptr, 0));
 
         {
+            print_pass_result_tmp.push_back(al, assign_stmt);
             print_pass_result_tmp.push_back(al, print_open_bracket);
             print_pass_result_tmp.push_back(al, loop);
             print_pass_result_tmp.push_back(al, print_close_bracket);

tests/reference/pass_print_list_tuple-print_02-09600eb.json

@@ -6,7 +6,7 @@
     "outfile": null,
     "outfile_hash": null,
     "stdout": "pass_print_list_tuple-print_02-09600eb.stdout",
-    "stdout_hash": "b518803746ffd1666ff29f4bfa2347eb621d81af5e52dc36964cd249",
+    "stdout_hash": "2831d417b5508b57e5e64c51339eb96f4d9aaf3559ee19c31dd0bb3c",
     "stderr": null,
     "stderr_hash": null,
     "returncode": 0