[Feature #21572] Syntax error at capture in alternation pattern

Should fail even with `-c` option.

Author: nobu

language/pattern_matching_spec.rb

@@ -493,7 +493,7 @@
           in [0, 0] | [0, a]
           end
         RUBY
-      }.should raise_error(SyntaxError, /illegal variable in alternative pattern/)
+      }.should raise_error(SyntaxError)
     end
 
     it "support underscore prefixed variables in alternation" do