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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
23 lines
557 B
Diff
23 lines
557 B
Diff
- // MIR for `transmute_ref_dst` before LowerIntrinsics
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+ // MIR for `transmute_ref_dst` after LowerIntrinsics
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fn transmute_ref_dst(_1: &T) -> *const T {
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debug u => _1;
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let mut _0: *const T;
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let mut _2: &T;
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bb0: {
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StorageLive(_2);
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_2 = copy _1;
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- _0 = std::intrinsics::transmute::<&T, *const T>(move _2) -> [return: bb1, unwind unreachable];
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+ _0 = move _2 as *const T (Transmute);
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+ goto -> bb1;
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}
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bb1: {
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StorageDead(_2);
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return;
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}
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}
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