merge revision(s) 7ff1bf317887c0d7b21e91ad548d07b9f05c540c,e89d80702bd98a8276243a7fcaa2a158b3bfb659: [Backport #18516]

	An alias can suppress method redefinition warning

	---
	 test/ruby/test_alias.rb | 11 +++++++++++
	 1 file changed, 11 insertions(+)

	Fix memory leak at the same named alias [Bug #18516]

	When aliasing a method to the same name method, set a separate bit
	flag on that method definition, instead of the reference count
	increment.  Although this kind of alias has no actual effect at
	runtime, is used as the hack to suppress the method re-definition
	warning.
	---
	 method.h                |  1 +
	 test/ruby/test_alias.rb | 18 ++++++++++++++++++
	 vm_method.c             |  9 ++++++++-
	 3 files changed, 27 insertions(+), 1 deletion(-)

1 files changed, 1 insertions, 0 deletions

diff --git a/method.h b/method.h
index 5b6fe2d800..16a48ccf88 100644
--- a/method.h
+++ b/method.h
@@ -173,6 +173,7 @@ struct rb_method_definition_struct {
     BITFIELD(rb_method_type_t, type, VM_METHOD_TYPE_MINIMUM_BITS);
     int alias_count : 28;
     int complemented_count : 28;
+    unsigned int no_redef_warning: 1;
 
     union {
         rb_method_iseq_t iseq;