Replace transmute! macro with transmute fn
#190
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jswrenn
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As a consequence of this change, the phase in which some invalid transmutes are detected differs. The `transmute!` macro depended internally on `mem::transmute`, which cannot be used in generic contexts but provides pre-monomorphization errors if the source and destination types have different sizes. By contrast, the `transmute` function can be used in generic contexts, but does not report size errors until monomorphization. This increase in expressivity comes at the cost of some usability: size errors are currently only reported by invocations of `cargo build`; not `cargo check`.
kupiakos
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Jul 21, 2023
| #[doc(hidden)] | ||
| pub use core::mem::transmute as __real_transmute; | ||
| pub trait TransmuteFrom<Src>: Sized { |
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This trait does not need to be (and shouldn't be) pub, because it has a blanket implementation on T: Sized that transmute can use without declaring it in its where bounds.
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As a consequence of this change, the phase in which some invalid transmutes are detected differs. The
transmute!macro depended internally onmem::transmute, which cannot be used in generic contexts but provides pre-monomorphization errors if the source and destination types have different sizes. By contrast, thetransmutefunction can be used in generic contexts, but does not report size errors until monomorphization.This increase in expressivity comes at the cost of some usability: size errors are currently only reported by invocations of
cargo build; notcargo check.