Add a rust-toolchain.toml

[mistydemeo]

I normally have rustup set to use the latest stable release, so having this was helpful for me to give rustup a hint that it should switch to nightly for this project.

[hikari-no-yume]

Wait, this needs nightly? I thought I was using stable, but maybe I was only doing that for the native builds for some reason. What problem did you hit?

[mistydemeo]

There's two build errors on stable:

error[E0658]: use of unstable library feature 'int_roundings'
   --> src/wasm_ffi.rs:193:65
    |
193 |         last_event_time + ((ticks_per_quarter_note * 120) / 60).div_ceil(1000 / 50)
    |                                                                 ^^^^^^^^
    |
    = note: see issue #88581 <https://github.com/rust-lang/rust/issues/88581> for more information

error[E0277]: the trait bound `std::io::Empty: std::io::Write` is not satisfied
   --> src/wasm_ffi.rs:221:9
    |
218 |     crate::midi::write_midi(
    |     ----------------------- required by a bound introduced by this call
...
221 |         &mut std::io::empty(),
    |         ^^^^^^^^^^^^^^^^^^^^^ the trait `std::io::Write` is not implemented for `std::io::Empty`
    |
note: required by a bound in `write_midi`
   --> src/midi.rs:426:8
    |
419 | pub fn write_midi<F, L>(
    |        ---------- required by a bound in this function
...
426 |     L: Write,
    |        ^^^^^ required by this bound in `write_midi`

[mistydemeo]

Hm, no, it actually looks like I was just on a slightly outdated stable. I was on 1.72.1, updating to 1.74.1 fixes it.