* Check only for automatic argument indexing.
* Tests not included as I am not sure how compile failures should be tested (I haven't seen any death test in the repo).
All the following lines fail to compile after applying this patch:
```
fmt::print(FMT_STRING(""), 1); // too many
fmt::print(FMT_STRING("too many\n"), 1);
fmt::print(FMT_STRING("too many {}\n"), 1, 2);
fmt::print(FMT_STRING("too many {}\n"), 1, 2, 3);
fmt::print(FMT_STRING("too few {}-{}-{}bal\n"), 1, 2);
```
Tested on GCC and clang (https://wandbox.org/permlink/f7Pf9ERBskTWfFQx).
To avoid clang warning:
fmtlib/include/fmt/chrono.h:753:32: error: declaration shadows a field of 'formatter<duration<type-parameter-0-0, type-parameter-0-1>, type-parameter-0-2, void>' [-Werror,-Wshadow]
gcc-9 gives the following shadow warning:
```
In file included from /Users/libraries/ioss/src/fmt/ostream.h:12,
from /Users/libraries/ioss/src/Ioss_DatabaseIO.C:59:
/Users/libraries/ioss/src/fmt/format.h: In function 'void fmt::v6::internal::parse_format_string(fmt::v6::basic_string_view<Char>, Handler&&)':
/Users/libraries/ioss/src/fmt/format.h:2442:10: warning: declaration of 'struct fmt::v6::internal::parse_format_string(fmt::v6::basic_string_view<Char>, Handler&&)::writer' shadows a global declaration [-Wshadow]
2442 | struct writer {
| ^~~~~~
/Users/libraries/ioss/src/fmt/format.h:1703:7: note: shadowed declaration is here
1703 | using writer = basic_writer<buffer_range<char>>;
| ^~~~~~
```
Since the `writer` struct is only used internally in the `parse_format_string` function, its name can be changed somewhat aribtrarily to avoid conflicts with names in an outer scope.
Note that this warning is also present in the 6.0.0 release.
