Implement filesystem_error::what() and improve reporting.

This patch implements the `what()` for filesystem errors. The message
includes the 'what_arg', any paths that were specified, and the
error code message.

Additionally this patch refactors how errors are created, making it easier
to report them correctly.

llvm-svn: 337664

1 files changed, 2 insertions, 1 deletions

diff --git a/libcxx/test/libcxx/experimental/filesystem/class.directory_entry/directory_entry.mods/last_write_time.sh.cpp b/libcxx/test/libcxx/experimental/filesystem/class.directory_entry/directory_entry.mods/last_write_time.sh.cpp
index 30b44b877c5..2305f54f5cb 100644
--- a/libcxx/test/libcxx/experimental/filesystem/class.directory_entry/directory_entry.mods/last_write_time.sh.cpp
+++ b/libcxx/test/libcxx/experimental/filesystem/class.directory_entry/directory_entry.mods/last_write_time.sh.cpp
@@ -80,7 +80,8 @@ TEST_CASE(last_write_time_not_representable_error) {
     TEST_CHECK(last_write_time(file, ec) == file_time_type::min());
     TEST_CHECK(ErrorIs(ec, expected_err));
 
-    ExceptionChecker CheckExcept(file, expected_err);
+    ExceptionChecker CheckExcept(file, expected_err,
+                                 "directory_entry::last_write_time");
     TEST_CHECK_THROW_RESULT(fs::filesystem_error, CheckExcept,
                             ent.last_write_time());