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Fix a fp in transmute_ptr_to_ptr #5999

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merged 1 commit into from
Sep 1, 2020
Merged

Fix a fp in transmute_ptr_to_ptr #5999

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6 changes: 4 additions & 2 deletions clippy_lints/src/transmute.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -331,8 +331,9 @@ impl<'tcx> LateLintPass<'tcx> for Transmute {
if let Some(def_id) = cx.qpath_res(qpath, path_expr.hir_id).opt_def_id();
if match_def_path(cx, def_id, &paths::TRANSMUTE);
then {
// Avoid suggesting from/to bits in const contexts.
// Avoid suggesting from/to bits and dereferencing raw pointers in const contexts.
// See https://github.com/rust-lang/rust/issues/73736 for progress on making them `const fn`.
// And see https://github.com/rust-lang/rust/issues/51911 for dereferencing raw pointers.
let const_context = in_constant(cx, e.hir_id);

let from_ty = cx.typeck_results().expr_ty(&args[0]);
Expand Down Expand Up @@ -486,7 +487,8 @@ impl<'tcx> LateLintPass<'tcx> for Transmute {
Applicability::Unspecified,
);
} else {
if cx.tcx.erase_regions(&from_ty) != cx.tcx.erase_regions(&to_ty) {
if (cx.tcx.erase_regions(&from_ty) != cx.tcx.erase_regions(&to_ty))
&& !const_context {
span_lint_and_then(
cx,
TRANSMUTE_PTR_TO_PTR,
Expand Down
8 changes: 8 additions & 0 deletions tests/ui/transmute_ptr_to_ptr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -51,4 +51,12 @@ fn transmute_ptr_to_ptr() {
let _: &GenericParam<&LifetimeParam<'static>> = unsafe { std::mem::transmute(&GenericParam { t: &lp }) };
}

// dereferencing raw pointers in const contexts, should not lint as it's unstable (issue 5959)
const _: &() = {
struct ZST;
let zst = &ZST;

unsafe { std::mem::transmute::<&'static ZST, &'static ()>(zst) }
};

fn main() {}