mruby-compiler: replace NODE_LITERAL_DELIM with (0 . 0) pattern

NODE_LITERAL_DELIM was only used as a marker in literal arrays.
Replace it with a (0 . 0) pattern which cannot conflict with
empty strings (which would be (0 . ptr) with non-NULL ptr).
This allows removing NODE_LITERAL_DELIM from the node type enum.

Co-authored-by: Claude <noreply@anthropic.com>

mrbgems/mruby-compiler/core/codegen.c

@@ -68,10 +68,10 @@
 /* Maximum number of arguments for some opcodes like OP_SUPER or OP_ARGARY. */
 #define MAXARG_S (1<<16)
 
-/* Macro to detect NODE_LITERAL_DELIM separators in literal arrays */
+/* Macro to detect (0 . 0) separators in literal arrays */
 #define IS_LITERAL_DELIM(node) \
   ((node) && (node)->car && \
-   node_to_int((node)->car->car) == NODE_LITERAL_DELIM && \
+   (node)->car->car == NULL && \
    (node)->car->cdr == NULL)
 
 typedef mrb_ast_node node;

mrbgems/mruby-compiler/core/node.h

@@ -88,7 +88,6 @@ enum node_type {
   NODE_POSTEXE,
   NODE_DSYM,
   NODE_HEREDOC,
-  NODE_LITERAL_DELIM,
   NODE_WORDS,
   NODE_SYMBOLS,
   NODE_VARIABLE,

mrbgems/mruby-compiler/core/parse.y

@@ -2270,7 +2270,7 @@ new_bv(parser_state *p, mrb_sym id)
 static node*
 new_literal_delim(parser_state *p)
 {
-  return cons_head((node*)NODE_LITERAL_DELIM, 0);
+  return cons((node*)0, (node*)0);
 }
 
 /* (:words . a) */
@@ -8781,10 +8781,6 @@ mrb_parser_dump(mrb_state *mrb, node *tree, int offset)
     dump_recur(mrb, tree, offset+1);
     break;
 
-  case NODE_LITERAL_DELIM:
-    printf("NODE_LITERAL_DELIM\n");
-    break;
-
   case NODE_SELF:
     printf("NODE_SELF\n");
     break;