mirror of
https://github.com/rust-lang/rust.git
synced 2024-10-30 14:01:51 +00:00
2540070fd4
Documents that `BikeshedIntrinsicFrom` models transmute-via-union, which is slightly more expressive than the transmute-via-cast implemented by `transmute_copy`. Additionally, we provide an implementation of transmute-via-union as a method on the `BikeshedIntrinsicFrom` trait with additional documentation on the boundary between trait invariants and caller obligations. Whether or not transmute-via-union is the right kind of transmute to model remains up for discussion [1]. Regardless, it seems wise to document the present behavior. [1] https://rust-lang.zulipchat.com/#narrow/stream/216762-project-safe-transmute/topic/What.20'kind'.20of.20transmute.20to.20model.3F/near/426331967
31 lines
1.5 KiB
Plaintext
31 lines
1.5 KiB
Plaintext
error[E0308]: cannot coerce intrinsics to function pointers
|
|
--> $DIR/reify-intrinsic.rs:6:64
|
|
|
|
|
LL | let _: unsafe extern "rust-intrinsic" fn(isize) -> usize = std::mem::transmute;
|
|
| ------------------------------------------------- ^^^^^^^^^^^^^^^^^^^ cannot coerce intrinsics to function pointers
|
|
| |
|
|
| expected due to this
|
|
|
|
|
= note: expected fn pointer `unsafe extern "rust-intrinsic" fn(isize) -> usize`
|
|
found fn item `unsafe extern "rust-intrinsic" fn(_) -> _ {std::intrinsics::transmute::<_, _>}`
|
|
|
|
error[E0606]: casting `unsafe extern "rust-intrinsic" fn(_) -> _ {std::intrinsics::transmute::<_, _>}` as `unsafe extern "rust-intrinsic" fn(isize) -> usize` is invalid
|
|
--> $DIR/reify-intrinsic.rs:11:13
|
|
|
|
|
LL | let _ = std::mem::transmute as unsafe extern "rust-intrinsic" fn(isize) -> usize;
|
|
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
|
|
|
error[E0308]: cannot coerce intrinsics to function pointers
|
|
--> $DIR/reify-intrinsic.rs:17:9
|
|
|
|
|
LL | std::intrinsics::likely,
|
|
| ^^^^^^^^^^^^^^^^^^^^^^^ cannot coerce intrinsics to function pointers
|
|
|
|
|
= note: expected fn pointer `unsafe extern "rust-intrinsic" fn(_) -> _`
|
|
found fn item `fn(_) -> _ {likely}`
|
|
|
|
error: aborting due to 3 previous errors
|
|
|
|
Some errors have detailed explanations: E0308, E0606.
|
|
For more information about an error, try `rustc --explain E0308`.
|