Can clippy take into account --ignore-rust-version?

[Pat-Lafon]

With the ability of clippy to check rust-version from the Cargo.toml #8746, I was wondering about how this interacts with --ignore-rust-version. It looks like this flag is just passed along and ignored on the clippy side?

If that's the case I was wondering if it would make sense for clippy to have some handling for this flag to turn off the version check?

This came up in lalrpop/lalrpop#763 (comment) where for lalrpop, the suggestion is to set the msrv as somewhere <= stable -2 and then increase it within that constraint as new features are added. Here it would be nice if clippy could suggest lints that use these new features, even if they are not compatible with the current version.

[flip1995]

IIUC the --ignore-rust-version flag in cargo is only for cargo install. Clippy mostly only interacts with cargo check, so as long as cargo check doesn't support this, we'll probably won't add support for it to Clippy.

This is a cargo feature and Clippy should not re-implement cargo features.

[Pat-Lafon]

I believe cargo check does support --ignore-rust-version? https://doc.rust-lang.org/cargo/commands/cargo-check.html#compilation-options

[flip1995]

Awesome, then this should be supported out of the box. Clippy reads the rust-version specified in the Cargo.toml file from the CARGO_PKG_RUST_VERSION env var set by cargo. I think, the issue why it is not supported is, that cargo sets this env var (and the metadata), even though this flag is passed. So I don't think this needs any changes on the Clippy side, but rather on the cargo side.