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Add explanation about taking the minimum of the two lints

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LeSeulArtichaut 2020-05-23 22:32:40 +02:00
parent 4a538d31e0
commit e3d27ec1c8
1 changed files with 11 additions and 0 deletions
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11
src/librustc_mir/transform/check_unsafety.rs
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@ -726,6 +726,17 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def_id: DefId) {
},
),
UnsafetyViolationKind::UnsafeFnBorrowPacked => {
// When `unsafe_op_in_unsafe_fn` is disallowed, the behavior of safe and unsafe functions
// should be the same in terms of warnings and errors. Therefore, with `#[warn(safe_packed_borrows)]`,
// a safe packed borrow should emit a warning *but not an error* in an unsafe function,
// just like in a safe function, even if `unsafe_op_in_unsafe_fn` is `deny`.
//
// Also, `#[warn(unsafe_op_in_unsafe_fn)]` can't cause any new errors. Therefore, with
// `#[deny(safe_packed_borrows)]` and `#[warn(unsafe_op_in_unsafe_fn)]`, a packed borrow
// should only issue a warning for the sake of backwards compatibility.
//
// The solution those 2 expectations is to always take the minimum of both lints.
// This prevent any new errors (unless both lints are explicitely set to `deny`).
let lint = if tcx.lint_level_at_node(SAFE_PACKED_BORROWS, lint_root).0
<= tcx.lint_level_at_node(UNSAFE_OP_IN_UNSAFE_FN, lint_root).0
{