error[E0308]: mismatched types --> tests/ui-nightly/transmute-mut-src-immutable.rs:17:37 | 17 | let _: &mut u8 = transmute_mut!(&0u8); | ---------------^^^^- | | | | | types differ in mutability | expected due to this | = note: expected mutable reference `&mut _` found reference `&u8` warning: this function depends on never type fallback being `()` --> tests/ui-nightly/transmute-mut-src-immutable.rs:15:1 | 15 | fn ref_src_immutable() { | ^^^^^^^^^^^^^^^^^^^^^^ | = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release! = note: for more information, see issue #123748 = help: specify the types explicitly note: in edition 2024, the requirement `!: FromBytes` will fail --> tests/ui-nightly/transmute-mut-src-immutable.rs:17:22 | 17 | let _: &mut u8 = transmute_mut!(&0u8); | ^^^^^^^^^^^^^^^^^^^^ = note: `#[warn(dependency_on_unit_never_type_fallback)]` on by default = note: this warning originates in the macro `transmute_mut` (in Nightly builds, run with -Z macro-backtrace for more info) help: use `()` annotations to avoid fallback changes --> src/macros.rs | | let e: &mut () = $e; | ~~ warning: never type fallback affects this call to an `unsafe` function --> tests/ui-nightly/transmute-mut-src-immutable.rs:17:22 | 17 | let _: &mut u8 = transmute_mut!(&0u8); | ^^^^^^^^^^^^^^^^^^^^ | = warning: this will change its meaning in a future release! = note: for more information, see issue #123748 = help: specify the type explicitly = note: `#[warn(never_type_fallback_flowing_into_unsafe)]` on by default = note: this warning originates in the macro `$crate::assert_size_eq` which comes from the expansion of the macro `transmute_mut` (in Nightly builds, run with -Z macro-backtrace for more info)