[Universal parser] Decouple IMEMO from rb_ast_t

This patch removes the `VALUE flags` member from the `rb_ast_t` structure making `rb_ast_t` no longer an IMEMO object.

## Background

We are trying to make the Ruby parser generated from parse.y a universal parser that can be used by other implementations such as mruby.
To achieve this, it is necessary to exclude VALUE and IMEMO from parse.y, AST, and NODE.

## Summary (file by file)

- `rubyparser.h`
  - Remove the `VALUE flags` member from `rb_ast_t`
- `ruby_parser.c` and `internal/ruby_parser.h`
  - Use TypedData_Make_Struct VALUE which wraps `rb_ast_t` `in ast_alloc()` so that GC can manage it
    - You can retrieve `rb_ast_t` from the VALUE by `rb_ruby_ast_data_get()`
  - Change the return type of `rb_parser_compile_XXXX()` functions from `rb_ast_t *` to `VALUE`
  - rb_ruby_ast_new() which internally `calls ast_alloc()` is to create VALUE vast outside ruby_parser.c
- `iseq.c` and `vm_core.h`
  - Amend the first parameter of `rb_iseq_new_XXXX()` functions from `rb_ast_body_t *` to `VALUE`
  - This keeps the VALUE of AST on the machine stack to prevent being removed by GC
- `ast.c`
  - Almost all change is replacement `rb_ast_t *ast` with `VALUE vast` (sorry for the big diff)
  - Fix `node_memsize()`
    - Now it includes `rb_ast_local_table_link`, `tokens` and script_lines
- `compile.c`, `load.c`, `node.c`, `parse.y`, `proc.c`, `ruby.c`, `template/prelude.c.tmpl`, `vm.c` and `vm_eval.c`
  - Follow-up due to the above changes
- `imemo.{c|h}`
  - If an object with `imemo_ast` appears, considers it a bug

Co-authored-by: Nobuyoshi Nakada <[email protected]>

1 files changed, 6 insertions, 2 deletions

diff --git a/vm_eval.c b/vm_eval.c
index 542f8d0b3a..4dfff02f6b 100644
--- a/vm_eval.c
+++ b/vm_eval.c
@@ -1753,6 +1753,7 @@ eval_make_iseq(VALUE src, VALUE fname, int line,
     const VALUE parser = rb_parser_new();
     const rb_iseq_t *const parent = vm_block_iseq(base_block);
     rb_iseq_t *iseq = NULL;
+    VALUE vast;
     rb_ast_t *ast;
     int isolated_depth = 0;
 
@@ -1790,10 +1791,13 @@ eval_make_iseq(VALUE src, VALUE fname, int line,
 
     rb_parser_set_context(parser, parent, FALSE);
     if (ruby_vm_keep_script_lines) rb_parser_set_script_lines(parser);
-    ast = rb_parser_compile_string_path(parser, fname, src, line);
+    vast = rb_parser_compile_string_path(parser, fname, src, line);
+
+    ast = rb_ruby_ast_data_get(vast);
+
     if (ast->body.root) {
         ast->body.coverage_enabled = coverage_enabled;
-        iseq = rb_iseq_new_eval(&ast->body,
+        iseq = rb_iseq_new_eval(vast,
                                 ISEQ_BODY(parent)->location.label,
                                 fname, Qnil, line,
                                 parent, isolated_depth);