[Universal parser] Decouple IMEMO from rb_ast_tHEADmaster

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 <nobu@ruby-lang.org>

1 files changed, 17 insertions, 13 deletions

diff --git a/template/prelude.c.tmpl b/template/prelude.c.tmpl
index dc0a143004..386511f20c 100644
--- a/template/prelude.c.tmpl
+++ b/template/prelude.c.tmpl
@@ -141,37 +141,39 @@ COMPILER_WARNING_POP
 #define PRELUDE_NAME(n) rb_usascii_str_new_static(prelude_name##n, sizeof(prelude_name##n)-1)
 #define PRELUDE_CODE(n) rb_utf8_str_new_static(prelude_code##n.L0, sizeof(prelude_code##n))
 
-static rb_ast_t *
-prelude_ast(VALUE name, VALUE code, int line)
+static VALUE
+prelude_vast(VALUE name, VALUE code, int line)
 {
-    rb_ast_t *ast = rb_parser_compile_string_path(rb_parser_new(), name, code, line);
+    rb_ast_t *ast;
+    VALUE vast = rb_parser_compile_string_path(rb_parser_new(), name, code, line);
+    ast = rb_ruby_ast_data_get(vast);
     if (!ast || !ast->body.root) {
         if (ast) rb_ast_dispose(ast);
         rb_exc_raise(rb_errinfo());
     }
-    return ast;
+    return vast;
 }
 
 % end
 % if @builtin_count > 0
-#define PRELUDE_AST(n, name_str, start_line) \
+#define PRELUDE_VAST(n, name_str, start_line) \
     (((sizeof(prelude_name<%='##'%><%=%>n) - prefix_len - 2) == namelen) && \
      (strncmp(prelude_name<%='##'%><%=%>n + prefix_len, feature_name, namelen) == 0) ? \
-     prelude_ast((name_str) = PRELUDE_NAME(n), PRELUDE_CODE(n), start_line) : 0)
+     prelude_vast((name_str) = PRELUDE_NAME(n), PRELUDE_CODE(n), start_line) : Qnil)
 
-rb_ast_t *
-rb_builtin_ast(const char *feature_name, VALUE *name_str)
+VALUE
+rb_builtin_vast(const char *feature_name, VALUE *name_str)
 {
     const size_t prefix_len = rb_strlen_lit("<internal:");
     size_t namelen = strlen(feature_name);
-    rb_ast_t *ast = 0;
+    VALUE vast = Qnil;
 
 %   @preludes.each_value do |i, prelude, lines, sub, start_line|
 %     if sub
-    if ((ast = PRELUDE_AST(<%=i%><%=%>, *name_str, <%=start_line%>)) != 0) return ast;
+    if (!NIL_P(vast = PRELUDE_VAST(<%=i%><%=%>, *name_str, <%=start_line%>))) return vast;
 %     end
 %   end
-    return ast;
+    return vast;
 }
 
 % end
@@ -196,8 +198,10 @@ prelude_eval(VALUE code, VALUE name, int line)
         0, /* int debug_level; */
     };
 
-    rb_ast_t *ast = prelude_ast(name, code, line);
-    rb_iseq_eval(rb_iseq_new_with_opt(&ast->body, name, name, Qnil, line,
+    rb_ast_t *ast;
+    VALUE vast = prelude_vast(name, code, line);
+    ast = rb_ruby_ast_data_get(vast);
+    rb_iseq_eval(rb_iseq_new_with_opt(vast, name, name, Qnil, line,
                                       NULL, 0, ISEQ_TYPE_TOP, &optimization,
                                       Qnil));
     rb_ast_dispose(ast);