error[E0658]: the `#[compiler_builtins]` attribute is used to identify the `compiler_builtins` crate which contains compiler-rt intrinsics and will never be stable --> $DIR/feature-gate-compiler-builtins.rs:1:1 | LL | #![compiler_builtins] | ^^^^^^^^^^^^^^^^^^^^^ | = help: add #![feature(compiler_builtins)] to the crate attributes to enable error: aborting due to previous error For more information about this error, try `rustc --explain E0658`.