Error code E0463
A crate was declared but cannot be found.
Erroneous code example:
#![allow(unused)] fn main() { extern crate foo; // error: can't find crate }
You need to link your code to the relevant crate in order to be able to use it
(through Cargo or the -L
option of rustc, for example).
Common causes
- The crate is not present at all. If using Cargo, add it to
[dependencies]
in Cargo.toml. - The crate is present, but under a different name. If using Cargo, look for
package =
under[dependencies]
in Cargo.toml.
Common causes for missing std
or core
- You are cross-compiling for a target which doesn't have
std
prepackaged. Consider one of the following:- Adding a pre-compiled version of std with
rustup target add
- Building std from source with
cargo build -Z build-std
- Using
#![no_std]
at the crate root, so you won't needstd
in the first place.
- Adding a pre-compiled version of std with
- You are developing the compiler itself and haven't built libstd from source.
You can usually build it with
x.py build library/std
. More information about x.py is available in the rustc-dev-guide.