[PATCH olang v1 2/5] ast: remove redundancy on ast_node base fields

[Carlos Maniero <carlos@maniero.me>]

This solution was inspired on cython PyObject which uses macros to avoid
the redundancy.

Signed-off-by: Carlos Maniero <carlos@maniero.me>
---
 src/ast.h | 54 ++++++++++++++++++++++++++++++------------------------
 1 file changed, 30 insertions(+), 24 deletions(-)

diff --git a/src/ast.h b/src/ast.h
index e7d8ed8..c7a25bf 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -26,6 +26,21 @@
 #include "string_view.h"
 #include "type.h"
 
+#define AST_NODE_BASE                                                          \
+    {                                                                          \
+        ast_node_kind_t kind;                                                  \
+        token_loc_t loc;                                                       \
+    }
+
+/**
+ * Every node within the *ast_node* union must include the base segment.
+ *
+ * This macro must be declared first within any node definition to ensure the
+ * ast_node base segment's integrity.
+ */
+
+#define AST_NODE_HEAD struct AST_NODE_BASE base
+
 typedef union ast_node ast_node_t;
 
 typedef enum
@@ -45,21 +60,17 @@ typedef enum
     AST_NODE_UNKNOWN
 } ast_node_kind_t;
 
-typedef struct ast_node_meta
-{
-    ast_node_kind_t kind;
-    token_loc_t loc;
-} ast_node_meta_t;
+typedef struct ast_node_base AST_NODE_BASE ast_node_base_t;
 
 typedef struct ast_block
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     list_t *nodes;
 } ast_block_t;
 
 typedef struct ast_translation_unit
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     list_t *decls;
 } ast_translation_unit_t;
 
@@ -71,7 +82,7 @@ typedef struct ast_fn_param
 
 typedef struct ast_fn_definition
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     string_view_t id;
     list_t *params;
     type_t *return_type;
@@ -82,7 +93,7 @@ typedef struct ast_fn_definition
 
 typedef struct ast_fn_call
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     string_view_t id;
     list_t *args;
     scope_t *scope;
@@ -90,7 +101,7 @@ typedef struct ast_fn_call
 
 typedef struct ast_var_definition
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     string_view_t id;
     type_t *type;
     ast_node_t *value;
@@ -104,7 +115,7 @@ typedef enum
 
 typedef struct ast_literal
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     ast_literal_kind_t kind;
     union
     {
@@ -114,7 +125,7 @@ typedef struct ast_literal
 
 typedef struct ast_ref
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     string_view_t id;
     scope_t *scope;
 } ast_ref_t;
@@ -144,7 +155,7 @@ typedef enum ast_binary_op_kind
 
 typedef struct ast_binary_op
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     ast_binary_op_kind_t kind;
     ast_node_t *lhs;
     ast_node_t *rhs;
@@ -162,27 +173,27 @@ typedef enum ast_unary_op_kind
 
 typedef struct ast_unary_op
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     ast_unary_op_kind_t kind;
     ast_node_t *expr;
 } ast_unary_op_t;
 
 typedef struct ast_var_assign_stmt
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     ast_node_t *ref;
     ast_node_t *expr;
 } ast_var_assign_stmt_t;
 
 typedef struct ast_return_stmt
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     ast_node_t *expr;
 } ast_return_stmt_t;
 
 typedef struct ast_if_stmt
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     ast_node_t *cond;
     ast_node_t *then;
     ast_node_t *_else;
@@ -190,19 +201,14 @@ typedef struct ast_if_stmt
 
 typedef struct ast_while_stmt
 {
-    ast_node_meta_t meta;
+    AST_NODE_HEAD;
     ast_node_t *cond;
     ast_node_t *then;
 } ast_while_stmt_t;
 
 typedef union ast_node
 {
-    // inlined ast_node_meta_t struct.
-    struct
-    {
-        ast_node_kind_t kind;
-        token_loc_t loc;
-    };
+    struct AST_NODE_BASE;
     ast_translation_unit_t as_translation_unit;
     ast_fn_definition_t as_fn_def;
     ast_fn_call_t as_fn_call;
-- 
2.46.1