Macro todo!() is unstable

[CowsertheKoopahog]

Even after updating to a nightly release of rustup, I still wasn't able to compile simply due to the todo macro.

Compiling toonmux v0.0.2 (/home/cowser/toonmux/toonmux) error[E0658]: macro todo! is unstable --> src/main.rs:89:51 | 89 | Action::Talk(_key) => todo!(), | ^^^^^^^ | = note: for more information, see https://github.com/rust-lang/rust/issues/59277

error[E0658]: macro todo! is unstable --> src/main.rs:131:47 | 131 | Action::Talk(_key) => todo!(), | ^^^^^^^ | = note: for more information, see https://github.com/rust-lang/rust/issues/59277

error: aborting due to 2 previous errors

For more information about this error, tryrustc --explain E0658. error: Could not compile ``toonmux.`

To learn more, run the command again with --verbose.

[JonathanHelianthicusDoe]

todo! is in the standard library on stable Rust version >=1.40.0:

https://blog.rust-lang.org/2019/12/19/Rust-1.40.0.html#additions-to-the-standard-library