error[E0433]: failed to resolve: maybe a missing crate `core`? --> $DIR/issue-102156.rs:4:5 | LL | use core::convert::{From, TryFrom}; | ^^^^ maybe a missing crate `core`? | = help: consider adding `extern crate core` to use the `core` crate error[E0433]: failed to resolve: maybe a missing crate `core`? --> $DIR/issue-102156.rs:4:5 | LL | use core::convert::{From, TryFrom}; | ^^^^ maybe a missing crate `core`? | = help: consider adding `extern crate core` to use the `core` crate error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0433`.