Prevent deepcopy in subscript in for loops

Author: advikkabra

src/lpython/semantics/python_ast_to_asr.cpp

@@ -5871,6 +5871,7 @@ class BodyVisitor : public CommonVisitor<BodyVisitor> {
         std::string loop_src_var_name = "";
         ASR::expr_t *loop_end = nullptr, *loop_start = nullptr, *inc = nullptr;
         ASR::expr_t *for_iter_type = nullptr;
+        ASR::expr_t *loop_src_var = nullptr;
         if (AST::is_a<AST::Call_t>(*x.m_iter)) {
             AST::Call_t *c = AST::down_cast<AST::Call_t>(x.m_iter);
             std::string call_name;
@@ -5915,6 +5916,8 @@ class BodyVisitor : public CommonVisitor<BodyVisitor> {
 
             if (ASR::is_a<ASR::Dict_t>(*loop_src_var_ttype) ||
                 ASR::is_a<ASR::Set_t>(*loop_src_var_ttype)) {
+                loop_src_var = ASRUtils::EXPR(
+                    ASR::make_Var_t(al, x.base.base.loc, current_scope->resolve_symbol(loop_src_var_name)));
                 is_explicit_iterator_required = false;
                 for_each = true;
             } else {
@@ -5930,34 +5933,35 @@ class BodyVisitor : public CommonVisitor<BodyVisitor> {
                 visit_Subscript(*sbt);
                 ASR::expr_t *target = ASRUtils::EXPR(tmp);
                 ASR::ttype_t *loop_src_var_ttype = ASRUtils::expr_type(target);
-                // Create a temporary variable that will contain the evaluated value of Subscript
-                std::string tmp_assign_name = current_scope->get_unique_name("__tmp_assign_for_loop", false);
-                SetChar variable_dependencies_vec;
-                variable_dependencies_vec.reserve(al, 1);
-                ASRUtils::collect_variable_dependencies(al, variable_dependencies_vec, loop_src_var_ttype);
-                ASR::asr_t* tmp_assign_variable = ASR::make_Variable_t(al, sbt->base.base.loc, current_scope,
-                    s2c(al, tmp_assign_name), variable_dependencies_vec.p, variable_dependencies_vec.size(),
-                    ASR::intentType::Local, nullptr, nullptr, ASR::storage_typeType::Default,
-                    loop_src_var_ttype, nullptr, ASR::abiType::Source, ASR::accessType::Public, ASR::presenceType::Required, false
-                );
-                ASR::symbol_t *tmp_assign_variable_sym = ASR::down_cast<ASR::symbol_t>(tmp_assign_variable);
-                current_scope->add_symbol(tmp_assign_name, tmp_assign_variable_sym);
-
-                // Assign the Subscript expr to temporary variable
-                ASR::asr_t* assign = ASR::make_Assignment_t(al, x.base.base.loc,
-                                ASRUtils::EXPR(ASR::make_Var_t(al, x.base.base.loc, tmp_assign_variable_sym)),
-                                target, nullptr);
-                if (current_body != nullptr) {
-                    current_body->push_back(al, ASRUtils::STMT(assign));
-                } else {
-                    global_init.push_back(al, assign);
-                }
-                loop_src_var_name = tmp_assign_name;
                 if (ASR::is_a<ASR::Dict_t>(*loop_src_var_ttype) ||
                     ASR::is_a<ASR::Set_t>(*loop_src_var_ttype)) {
+                    loop_src_var = target;
                     is_explicit_iterator_required = false;
                     for_each = true;
                 } else {
+                    // Create a temporary variable that will contain the evaluated value of Subscript
+                    std::string tmp_assign_name = current_scope->get_unique_name("__tmp_assign_for_loop", false);
+                    SetChar variable_dependencies_vec;
+                    variable_dependencies_vec.reserve(al, 1);
+                    ASRUtils::collect_variable_dependencies(al, variable_dependencies_vec, loop_src_var_ttype);
+                    ASR::asr_t* tmp_assign_variable = ASR::make_Variable_t(al, sbt->base.base.loc, current_scope,
+                        s2c(al, tmp_assign_name), variable_dependencies_vec.p, variable_dependencies_vec.size(),
+                        ASR::intentType::Local, nullptr, nullptr, ASR::storage_typeType::Default,
+                        loop_src_var_ttype, nullptr, ASR::abiType::Source, ASR::accessType::Public, ASR::presenceType::Required, false
+                    );
+                    ASR::symbol_t *tmp_assign_variable_sym = ASR::down_cast<ASR::symbol_t>(tmp_assign_variable);
+                    current_scope->add_symbol(tmp_assign_name, tmp_assign_variable_sym);
+
+                    // Assign the Subscript expr to temporary variable
+                    ASR::asr_t* assign = ASR::make_Assignment_t(al, x.base.base.loc,
+                                    ASRUtils::EXPR(ASR::make_Var_t(al, x.base.base.loc, tmp_assign_variable_sym)),
+                                    target, nullptr);
+                    if (current_body != nullptr) {
+                        current_body->push_back(al, ASRUtils::STMT(assign));
+                    } else {
+                        global_init.push_back(al, assign);
+                    }
+                    loop_src_var_name = tmp_assign_name;
                     loop_end = for_iterable_helper(loop_src_var_name, x.base.base.loc, explicit_iter_name);
                     for_iter_type = loop_end;
                     LCOMPILERS_ASSERT(loop_end);
@@ -6070,7 +6074,6 @@ class BodyVisitor : public CommonVisitor<BodyVisitor> {
 
         if (for_each) {
             current_scope = parent_scope;
-            ASR::expr_t* loop_src_var = ASRUtils::EXPR(ASR::make_Var_t(al, x.base.base.loc, current_scope->resolve_symbol(loop_src_var_name)));
             tmp = ASR::make_ForEach_t(al, x.base.base.loc, target, loop_src_var, body.p, body.size());
             for_each = false;
             return;