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use rustc_hir::Expr;
use rustc_lint::LateContext;
use rustc_middle::ty::{cast::CastKind, Ty};
use rustc_span::DUMMY_SP;
use rustc_typeck::check::{cast::CastCheck, FnCtxt, Inherited};
// check if the component types of the transmuted collection and the result have different ABI,
// size or alignment
pub(super) fn is_layout_incompatible<'tcx>(cx: &LateContext<'tcx>, from: Ty<'tcx>, to: Ty<'tcx>) -> bool {
if let Ok(from) = cx.tcx.try_normalize_erasing_regions(cx.param_env, from)
&& let Ok(to) = cx.tcx.try_normalize_erasing_regions(cx.param_env, to)
&& let Ok(from_layout) = cx.tcx.layout_of(cx.param_env.and(from))
&& let Ok(to_layout) = cx.tcx.layout_of(cx.param_env.and(to))
{
from_layout.size != to_layout.size || from_layout.align.abi != to_layout.align.abi
} else {
// no idea about layout, so don't lint
false
}
}
/// Check if the type conversion can be expressed as a pointer cast, instead of
/// a transmute. In certain cases, including some invalid casts from array
/// references to pointers, this may cause additional errors to be emitted and/or
/// ICE error messages. This function will panic if that occurs.
pub(super) fn can_be_expressed_as_pointer_cast<'tcx>(
cx: &LateContext<'tcx>,
e: &'tcx Expr<'_>,
from_ty: Ty<'tcx>,
to_ty: Ty<'tcx>,
) -> bool {
use CastKind::{AddrPtrCast, ArrayPtrCast, FnPtrAddrCast, FnPtrPtrCast, PtrAddrCast, PtrPtrCast};
matches!(
check_cast(cx, e, from_ty, to_ty),
Some(PtrPtrCast | PtrAddrCast | AddrPtrCast | ArrayPtrCast | FnPtrPtrCast | FnPtrAddrCast)
)
}
/// If a cast from `from_ty` to `to_ty` is valid, returns an Ok containing the kind of
/// the cast. In certain cases, including some invalid casts from array references
/// to pointers, this may cause additional errors to be emitted and/or ICE error
/// messages. This function will panic if that occurs.
fn check_cast<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>, from_ty: Ty<'tcx>, to_ty: Ty<'tcx>) -> Option<CastKind> {
let hir_id = e.hir_id;
let local_def_id = hir_id.owner;
Inherited::build(cx.tcx, local_def_id).enter(|inherited| {
let fn_ctxt = FnCtxt::new(&inherited, cx.param_env, hir_id);
// If we already have errors, we can't be sure we can pointer cast.
assert!(
!fn_ctxt.errors_reported_since_creation(),
"Newly created FnCtxt contained errors"
);
if let Ok(check) = CastCheck::new(
&fn_ctxt, e, from_ty, to_ty,
// We won't show any error to the user, so we don't care what the span is here.
DUMMY_SP, DUMMY_SP,
) {
let res = check.do_check(&fn_ctxt);
// do_check's documentation says that it might return Ok and create
// errors in the fcx instead of returning Err in some cases. Those cases
// should be filtered out before getting here.
assert!(
!fn_ctxt.errors_reported_since_creation(),
"`fn_ctxt` contained errors after cast check!"
);
res.ok()
} else {
None
}
})
}
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