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] 426331967
30 lines
1.5 KiB
Text
30 lines
1.5 KiB
Text
error[E0308]: cannot coerce intrinsics to function pointers
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--> $DIR/reify-intrinsic.rs:6:64
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LL | let _: unsafe extern "rust-intrinsic" fn(isize) -> usize = std::mem::transmute;
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| ------------------------------------------------- ^^^^^^^^^^^^^^^^^^^ cannot coerce intrinsics to function pointers
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| expected due to this
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= note: expected fn pointer `unsafe extern "rust-intrinsic" fn(isize) -> usize`
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found fn item `unsafe extern "rust-intrinsic" fn(_) -> _ {std::intrinsics::transmute::<_, _>}`
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error[E0606]: casting `unsafe extern "rust-intrinsic" fn(_) -> _ {std::intrinsics::transmute::<_, _>}` as `unsafe extern "rust-intrinsic" fn(isize) -> usize` is invalid
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--> $DIR/reify-intrinsic.rs:11:13
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LL | let _ = std::mem::transmute as unsafe extern "rust-intrinsic" fn(isize) -> usize;
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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error[E0308]: cannot coerce intrinsics to function pointers
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--> $DIR/reify-intrinsic.rs:17:9
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LL | std::intrinsics::likely,
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| ^^^^^^^^^^^^^^^^^^^^^^^ cannot coerce intrinsics to function pointers
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= note: expected fn pointer `unsafe extern "rust-intrinsic" fn(_) -> _`
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found fn item `fn(_) -> _ {likely}`
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error: aborting due to 3 previous errors
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Some errors have detailed explanations: E0308, E0606.
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For more information about an error, try `rustc --explain E0308`.
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