feat(ast): data as void* and basic helpers

src/utils/ast/ast.c

@@ -0,0 +1,23 @@
+#include "ast.h"
+
+#include <stdbool.h>
+
+bool ast_is_if(struct ast *node)
+{
+    return node->type == AST_IF;
+}
+
+bool ast_is_cmd(struct ast *node)
+{
+    return node->type == AST_CMD;
+}
+
+struct ast_if *ast_get_if(struct ast *node)
+{
+    return (struct ast_if *)node->data;
+}
+
+struct ast_cmd *ast_get_cmd(struct ast *node)
+{
+    return (struct ast_cmd *)node->data;
+}

src/utils/ast/ast.h

@@ -5,7 +5,7 @@
 
 enum ast_type
 {
-    AST_END = 0,
+    AST_END,
     AST_IF,
     AST_CMD
 };
@@ -15,14 +15,6 @@ struct ast_cmd
     struct list *cmd;
 };
 
-union ast_node;
-
-struct ast
-{
-    enum ast_type type;
-    union ast_node *data;
-};
-
 struct ast_if
 {
     struct ast *condition;
@@ -30,10 +22,17 @@ struct ast_if
     struct ast *else_clause;
 };
 
-union ast_node
+struct ast
 {
-    struct ast_if *ast_if;
-    struct ast_cmd *ast_cmd;
+    enum ast_type type;
+
+    /**
+     * Data associated with this AST node. It can be one of the following:
+     * - NULL (AST_END)
+     * - struct ast_if* (AST_IF)
+     * - struct ast_cmd* (AST_CMD)
+     */
+    void *data;
 };
 
 #endif /* ! AST_H */