`cargo check` passes where `cargo build` fails

[amling]

The code is obviously silly, but I did run into the essential problem genuinely:

fn foo(f: impl Fn()) {
    f();

    foo(&f);
}

fn main() {
    foo(|| {});
}

cargo check does mention unconditional recursion although that's not the real problem and that warning can be dodged (without fixing cargo build) by making the code a little more complicated.

I had assumed that cargo check passing where cargo build failed was a bug, but I've been told by @dtolnay that that's not quite true. He did say to file the bug anyway?

cargo 1.42.1, rustc 1.42.0

[ehuss]

Thanks for the report! This gets reported occasionally, but is unfortunately the nature of how cargo check works. It does all compilation steps except for code generation. Some diagnostics and errors are only emitted during code generation, so they inherently won't be reported with cargo check.

This is a rustc issue (see rust-lang/rust#49292, rust-lang/rust#61330, rust-lang/rust#70923, etc.).

I'm going to leave this open to at least add a note to Cargo's documentation that not all errors are reported via cargo check.

[0xPoe]

Can I working on this?

[ehuss]

@Rustin-Liu Go ahead! Just needs a sentence added to the end of the Description in the cargo-check man page. There is documentation at https://github.com/rust-lang/cargo/tree/master/src/doc on how to rebuild the man pages.

[RalfJung]

Also see rust-lang/rust#99682