[PRISM] Implement regex encoding flags

Added the  correct encoding to the allocated regex. This required making
a new method to set the encoding and pass that to `rb_enc_reg_new`
instead of `rb_reg_new`. The former `rb_reg_new` would set the encoding
to ASCII8BIT regardless of encoding flag.

1 files changed, 8 insertions, 0 deletions

diff --git a/test/ruby/test_compile_prism.rb b/test/ruby/test_compile_prism.rb
index b62bac4132..60b669eb0e 100644
--- a/test/ruby/test_compile_prism.rb
+++ b/test/ruby/test_compile_prism.rb
@@ -390,6 +390,14 @@ module Prism
       assert_prism_eval('/pit/mx')
       assert_prism_eval('/pit/xi')
       assert_prism_eval('/pit/ixm')
+
+      assert_prism_eval('/pit/u')
+      assert_prism_eval('/pit/e')
+      assert_prism_eval('/pit/s')
+      assert_prism_eval('/pit/n')
+
+      assert_prism_eval('/pit/me')
+      assert_prism_eval('/pit/ne')
     end
 
     def test_StringConcatNode