Do we want to have a rust-toolchain.toml file in the repo?

[sunshowers]

Currently, this repo has a rust-toolchain.toml file in it, pinning the version to 1.75.0:

usdt/rust-toolchain.toml

Line 1 in d4b8090

[toolchain]

Is this something we'd still like to carry around?

• For binaries it makes sense to have such a file, but usdt is primarily a library.
• usdt needed nightly features for a long time, but it no longer does (and [meta] update MSRV to 1.75, turn on asm support unconditionally #267 removes all the nightly code).
• Rust is "append-only" and new versions very rarely break old code.

Would it make sense to remove the rust-toolchain.toml file, and let CI find issues with the MSRV?

[bnaecker]

One nice reason is to ensure that we're always testing locally with the CI version. That matters for the trybuild tests mostly, where there can be small variations in the compiler output that aren't that meaningful. I don't feel too strongly though, since practically-speaking most contributors will know how to read and diagnose those errors in CI, even if they don't see them locally without building against that specific toolchain.

[sunshowers]

Thank you! Okay, yeah, the trybuild tests are a great reason to pin the Rust toolchain. I think in that case I'll pin the version to 1.80, and also ensure that CI (minus the trybuild tests) runs on the MSRV.

[sunshowers]

Rationale added here:

usdt/rust-toolchain.toml

Lines 2 to 4 in 5a4bc0e

	# The Rust version is pinned because the repo has a number of trybuild tests,
	# and rustc's human-readable output is unstable across Rust versions. This
	# doesn't have to be the MSRV.