This code does not belong in libstd, and rather belongs in a dedicated crate. In
the future, the syntax::ext::format module should move to the fmt_macros crate
(hence the name of the crate), but for now the fmt_macros crate will only
contain the format string parser.
The entire fmt_macros crate is marked #[experimental] because it is not meant
for general consumption, only the format!() interface is officially supported,
not the internals.
This is a breaking change for anyone using the internals of std::fmt::parse.
Some of the flags have moved to std::fmt::rt, while the actual parsing support
has all moved to the fmt_macros library.
[breaking-change]
* Allow named parameters to specify width/precision
* Intepret the format string '0$' as "width is the 0th argument" instead of
thinking the lone '0' was the sign-aware-zero-padding flag. To get both you'd
need to put '00$' which makes more sense if you want both to happen.
Closes#9669
