Don't set throw data as cause [Bug #15282]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65554 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

eval.c

@@ -531,7 +531,7 @@ setup_exception(rb_execution_context_t *ec, int tag, volatile VALUE mesg, VALUE
 		    mesg = rb_obj_dup(mesg);
 		}
 	    }
-	    if (cause != Qundef) {
+	    if (cause != Qundef && !THROW_DATA_P(cause)) {
 		exc_setup_cause(mesg, cause);
 	    }
 	    if (NIL_P(bt)) {

test/ruby/test_exception.rb

@@ -699,6 +699,12 @@ end.join
     assert_same(a, e.cause.cause)
   end
 
+  def test_cause_at_end
+    assert_in_out_err([], <<-'end;', [], [/-: unexpected return\n/, /.*undefined local variable or method `n'.*\n/])
+      END{n}; END{return}
+    end;
+  end
+
   def test_raise_with_cause
     msg = "[Feature #8257]"
     cause = ArgumentError.new("foobar")