* add ascii incompatible case.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@15577 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

string.c

@@ -220,7 +220,8 @@ rb_enc_cr_str_copy(VALUE dest, VALUE src)
 	ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);
 	break;
     case ENC_CODERANGE_VALID:
-	if (search_nonascii(RSTRING_PTR(dest), RSTRING_END(dest)))
+	if (!rb_enc_asciicompat(enc) ||
+	    search_nonascii(RSTRING_PTR(dest), RSTRING_END(dest)))
 	    ENC_CODERANGE_SET(dest, ENC_CODERANGE_VALID);
 	else
 	    ENC_CODERANGE_SET(dest, ENC_CODERANGE_7BIT);