[libcxx] Correctly handle invalid regex character class names

[miyuki]

Summary

Currently when a regular expression contains an invalid character
class name std::regex constructors throw an std::regex_error with
std::regex_constants::error_brack code.

This patch changes the code to std::regex_constants::error_ctype and
adds a test.

[mclow.lists]

This looks fine to me. Thanks!

test/std/re/re.regex/re.regex.construct/bad_ctype.pass.cpp

29

I'm a big fan of the "return NOW" style of programming.
But this matches the other tests, so I'm ok with it.
(If I care enough, I'll change them all later)

try { std::regex re(pat); }
catch catch (const std::regex_error &ex) { return ex.code() == std::regex_constants::error_ctype; }
return false;

include/regex

_ForwardIterator __temp = _VSTD::search(__first, __last, _Colon_close,
                                                             _Colon_close+2);
     if (__temp == __last)
         __throw_regex_error<regex_constants::error_brack>();
     // [__first, __temp) contains all text in [: ... :]
     typedef typename _Traits::char_class_type char_class_type;
     char_class_type __class_type =
         __traits_.lookup_classname(__first, __temp, __flags_ & icase);
     if (__class_type == 0)
-        __throw_regex_error<regex_constants::error_brack>();
+        __throw_regex_error<regex_constants::error_ctype>();
     __ml->__add_class(__class_type);
     __first = _VSTD::next(__temp, 2);
     return __first;
 }
 
 template <class _CharT, class _Traits>
 template <class _ForwardIterator>
 _ForwardIterator

test/std/re/re.regex/re.regex.construct/bad_ctype.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: libcpp-no-exceptions
+// <regex>
+
+// template <class charT, class traits = regex_traits<charT>> class basic_regex;
+
+// template <class ST, class SA>
+//    basic_regex(const basic_string<charT, ST, SA>& s);
+
+#include <regex>
+#include <cassert>
+#include "test_macros.h"
+
+static bool error_ctype_thrown(const char *pat)
+{
+    bool result = false;
+    try {
+        std::regex re(pat);
+    } catch (const std::regex_error &ex) {
+        result = (ex.code() == std::regex_constants::error_ctype);
+    }
+    return result;
+}
+
+int main()
+{
+    assert(error_ctype_thrown("[[::]]"));
+    assert(error_ctype_thrown("[[:error:]]"));
+}