fix: merging all the code

src/utils/ast/ast_base.h

@@ -8,6 +8,7 @@ enum ast_type
     AST_END,
     AST_LIST,
     AST_IF,
+    AST_VOID,
     AST_CMD
 };
 
@@ -24,4 +25,15 @@ struct ast
     void *data;
 };
 
+/* @brief: returns an ast* with corresponding data and type.
+ *
+ * @note: this function should only be called by ast_create_[TYPE] functions.
+ */
+struct ast *ast_create(enum ast_type type, void *data);
+
+/* @brief: frees the given ast. If ast is NULL, does nothing.
+ *
+ */
+void ast_free(struct ast **node);
+
 #endif /* ! AST_BASE_H */