merge revision(s) d0ba4abf1a00339ebbb5d405db3240a8bdb7b68b,54eac83b2ad77ddea84fa6d66c09e0bb014cf61e: [Backport #15786]

	Add RB_ID_SERIAL_MAX
	
	
	Hide internal IDs
	
	* parse.y (internal_id): number the ID serial for internal use by
	  counting down from the neary maximum value, not to accidentally
	  match permanent IDs.
	
	[Bug #15768]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67758 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 2 insertions, 1 deletions

diff --git a/parse.y b/parse.y
index 682fc28fcf..62428c92a7 100644
--- a/parse.y
+++ b/parse.y
@@ -11583,8 +11583,9 @@ rb_init_parse(void)
 static ID
 internal_id_gen(struct parser_params *parser)
 {
+    const ID max_id = RB_ID_SERIAL_MAX & ~0xffff;
     ID id = (ID)vtable_size(lvtbl->args) + (ID)vtable_size(lvtbl->vars);
-    id += ((tLAST_TOKEN - ID_INTERNAL) >> ID_SCOPE_SHIFT) + 1;
+    id = max_id - id;
     return ID_STATIC_SYM | ID_INTERNAL | (id << ID_SCOPE_SHIFT);
 }