Move fn safety out of the subtyping relationship and into coercions #23452
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nikomatsakis
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Safe fns are no longer subtypes of unsafe fns, but you can coerce from one to the other. This is a [breaking-change] in that impl fns must now be declared `unsafe` if the trait is declared `unsafe`. In some rare cases, the subtyping change may also direct affect you, but no such cases were encountered in practice. Fixes #23449. r? @nrc
| @@ -282,6 +282,7 @@ pub enum Variance { | |||
| #[derive(Clone, Debug)] | |||
| pub enum AutoAdjustment<'tcx> { | |||
| AdjustReifyFnPointer(ast::DefId), // go from a fn-item type to a fn-pointer type | |||
| AdjustUnsafeFnPointer, // go from a safe fn pointer to an unsafe fn pointer | |||
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Whoa, you can match against this with ty::AdjustUnsafeFnPointer(..), that's an interesting... feature.
lilyball
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Mar 23, 2015
rust-lang/rust#23452 makes safe functions no longer a subtype of unsafe functions. For consistency, change the definitions of `raw::lua_Reader`, `raw::lua_Writer`, and `raw::lua_Alloc` to be `unsafe` and update all places where we provide these functions. Also update the `lua_extern!` and `lua_extern_pub!` macros to produce `unsafe` functions.
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Safe fns are no longer subtypes of unsafe fns, but you can coerce from one to the other.
This is a [breaking-change] in that impl fns must now be declared
unsafeif the trait is declaredunsafe. In some rare cases, the subtyping change may also direct affect you, but no such cases were encountered in practice.Fixes #23449.
r? @nrc