parse.y: allow value omission in Hash literals introduced in Ruby3.1.

`{x:, y:}` now is a syntax sugar of `{x: x, y: y}`.

This fix also includes the update of #4815 fix.

1 files changed, 6 insertions, 0 deletions

diff --git a/test/t/hash.rb b/test/t/hash.rb
index 9bc2668ae..1b4db056e 100644
--- a/test/t/hash.rb
+++ b/test/t/hash.rb
@@ -1006,3 +1006,9 @@ assert('#== receiver should be specified value') do
     %i[has_value? value?].each{|m| assert_nothing_raised{h.__send__(m, v1)}}
   end
 end
+
+assert('test value ommision') do
+  x = 1
+  y = 2
+  assert_equal({x:1, y:2}, {x:, y:})
+end