string.c: fix checking order

* string.c (str_undump): check for suffix before if Unicode escape
  conflicts with it.  the message "but used force_encoding" sounds
  strange when it is not used.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@63162 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

string.c

@@ -6289,15 +6289,15 @@ str_undump(VALUE str)
 		int encidx;
 		ptrdiff_t size;
 
-		if (utf8) {
-		    rb_raise(rb_eRuntimeError, "dumped string contained Unicode escape but used force_encoding");
-		}
-
 		size = rb_strlen_lit(".force_encoding(\"");
 		if (s_end - s <= size) goto invalid_format;
 		if (memcmp(s, ".force_encoding(\"", size) != 0) goto invalid_format;
 		s += size;
 
+		if (utf8) {
+		    rb_raise(rb_eRuntimeError, "dumped string contained Unicode escape but used force_encoding");
+		}
+
 		encname = s;
 		s = memchr(s, '"', s_end-s);
 		size = s - encname;

test/ruby/test_string.rb

@@ -814,6 +814,9 @@ CODE
     assert_raise(RuntimeError) { S('"\xA"').undump }
     assert_raise(RuntimeError) { S('"\\"').undump }
     assert_raise(RuntimeError) { S(%("\0")).undump }
+    assert_raise_with_message(RuntimeError, /invalid/) {
+      '"\\u{007F}".xxxxxx'.undump
+    }
   end
 
   def test_dup