error[E0658]: use of unstable library feature `transmutability`
  --> $DIR/feature-missing.rs:5:5
   |
LL | use std::mem::TransmuteFrom;
   |     ^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #99571 <https://github.com/rust-lang/rust/issues/99571> for more information
   = help: add `#![feature(transmutability)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: use of unstable library feature `transmutability`
  --> $DIR/feature-missing.rs:8:5
   |
LL | use std::mem::Assume;
   |     ^^^^^^^^^^^^^^^^
   |
   = note: see issue #99571 <https://github.com/rust-lang/rust/issues/99571> for more information
   = help: add `#![feature(transmutability)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0658`.