Simplify compile-time evaluation logic

Author: kmr-srbh

src/libasr/pass/intrinsic_functions.h

@@ -4677,14 +4677,17 @@ static inline ASR::expr_t *eval_list_pop(Allocator &/*al*/,
             return nullptr;
         }
         ASR::ListConstant_t* clist = ASR::down_cast<ASR::ListConstant_t>(args[0]);
+        int64_t index;
 
         if (args.n == 1) {
-            return clist->m_args[clist->n_args - 1];
+            index = clist->n_args - 1;
+            return clist->m_args[index];
         } else {
             if (args[1] == nullptr) {
                 return nullptr;
             }
-            return clist->m_args[ASR::down_cast<ASR::IntegerConstant_t>(ASRUtils::expr_value(args[1]))->m_n];
+            index = ASR::down_cast<ASR::IntegerConstant_t>(ASRUtils::expr_value(args[1]))->m_n;
+            return clist->m_args[index];
         }
 
 }