Rust error E0461: couldn't find crate `..` with expected target triple `..`

The compiler team's explanation

Couldn't find crate .. with expected target triple ...

Example of erroneous code:

a.rs

#![crate_type = "lib"]

fn foo() {}

main.rs

extern crate a;

fn main() {
    a::foo();
}

a.rs is then compiled with --target powerpc-unknown-linux-gnu and b.rs with --target x86_64-unknown-linux-gnu. a.rs is compiled into a binary format incompatible with b.rs; PowerPC and x86 are totally different architectures. This issue also extends to any difference in target triples, as std is operating-system specific.

This error can be fixed by:

• Using Cargo, the Rust package manager, automatically fixing this issue.
• Recompiling either crate so that they target a consistent target triple.

From rustc --explain E0461 (1.99.0), part of the Rust project, MIT or Apache-2.0. Official page.