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Explain unsafety trickery of const functions

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This commit is contained in:
Oliver Scherer 2018-11-30 18:17:50 +01:00
parent b75d5f1867
commit 932dbe816e
1 changed files with 14 additions and 5 deletions
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19
src/librustc_mir/build/mod.rs
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@ -114,11 +114,20 @@ pub fn mir_build<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> Mir<'t
hir::Unsafety::Normal => Safety::Safe,
hir::Unsafety::Unsafe => Safety::FnUnsafe,
};
let safety = if implicit_argument.is_none() && tcx.is_min_const_fn(fn_def_id) {
// the body of `const unsafe fn`s is treated like the body of safe `const fn`s
Safety::Safe
} else {
safety
let safety = match fn_sig.unsafety {
hir::Unsafety::Normal => Safety::Safe,
hir::Unsafety::Unsafe => {
if tcx.is_min_const_fn(fn_def_id) => {
// As specified in #55607, a `const unsafe fn` differs
// from an `unsafe fn` in that its body is still considered
// safe code by default.
assert!(!implicit_argument.is_none());
Safety::Safe
} else {
Safety::Unsafe
}
}
};
let body = tcx.hir.body(body_id);