I hope to implement newline support within fix-it hints at some point,
but currently it's not supported, and leads to misleading diagnostic
output, so for now, fail gracefully.
gcc/ChangeLog:
* diagnostic-show-locus.c
(selftest::test_fixit_insert_containing_newline): New function.
(selftest::test_fixit_replace_containing_newline): New function.
(selftest::diagnostic_show_locus_c_tests): Call the above.
libcpp/ChangeLog:
* include/line-map.h (class rich_location): Note that newlines
aren't supported in fix-it text.
* line-map.c (rich_location::add_fixit_insert_before): Reject
attempts to add fix-its containing newlines.
(rich_location::add_fixit_replace): Likewise.
From-SVN: r240169
