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Don't lint transmute_undefined_repr when the the first field of a repr(C) type is compatible with the other type

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This commit is contained in:
Jason Newcomb 2022-08-03 13:16:04 -04:00
parent 71777465cc
commit b426bd52a1
3 changed files with 44 additions and 15 deletions
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29
clippy_lints/src/transmute/transmute_undefined_repr.rs
View file

@ -164,9 +164,18 @@ pub(super) fn check<'tcx>(
);
return true;
},
// `Repr(C)` <-> unordered type.
// If the first field of the `Repr(C)` type matches then the transmute is ok
(ReducedTy::OrderedFields(_, Some(from_sub_ty)), ReducedTy::UnorderedFields(to_sub_ty))
| (ReducedTy::UnorderedFields(from_sub_ty), ReducedTy::OrderedFields(_, Some(to_sub_ty)))
| (ReducedTy::Ref(from_sub_ty), ReducedTy::Ref(to_sub_ty)) => {
from_ty = from_sub_ty;
to_ty = to_sub_ty;
continue;
},
(
ReducedTy::UnorderedFields(from_ty),
ReducedTy::Other(_) | ReducedTy::OrderedFields(_) | ReducedTy::Ref(_),
ReducedTy::Other(_) | ReducedTy::OrderedFields(..) | ReducedTy::Ref(_),
) => {
span_lint_and_then(
cx,
@ -182,7 +191,7 @@ pub(super) fn check<'tcx>(
return true;
},
(
ReducedTy::Other(_) | ReducedTy::OrderedFields(_) | ReducedTy::Ref(_),
ReducedTy::Other(_) | ReducedTy::OrderedFields(..) | ReducedTy::Ref(_),
ReducedTy::UnorderedFields(to_ty),
) => {
span_lint_and_then(
@ -198,14 +207,9 @@ pub(super) fn check<'tcx>(
);
return true;
},
(ReducedTy::Ref(from_sub_ty), ReducedTy::Ref(to_sub_ty)) => {
from_ty = from_sub_ty;
to_ty = to_sub_ty;
continue;
},
(
ReducedTy::OrderedFields(_) | ReducedTy::Ref(_) | ReducedTy::Other(_) | ReducedTy::Param,
ReducedTy::OrderedFields(_) | ReducedTy::Ref(_) | ReducedTy::Other(_) | ReducedTy::Param,
ReducedTy::OrderedFields(..) | ReducedTy::Ref(_) | ReducedTy::Other(_) | ReducedTy::Param,
ReducedTy::OrderedFields(..) | ReducedTy::Ref(_) | ReducedTy::Other(_) | ReducedTy::Param,
)
| (
ReducedTy::UnorderedFields(_) | ReducedTy::Param,
@ -269,7 +273,8 @@ enum ReducedTy<'tcx> {
TypeErasure,
/// The type is a struct containing either zero non-zero sized fields, or multiple non-zero
/// sized fields with a defined order.
OrderedFields(Ty<'tcx>),
/// The second value is the first non-zero sized type.
OrderedFields(Ty<'tcx>, Option<Ty<'tcx>>),
/// The type is a struct containing multiple non-zero sized fields with no defined order.
UnorderedFields(Ty<'tcx>),
/// The type is a reference to the contained type.
@ -294,7 +299,7 @@ fn reduce_ty<'tcx>(cx: &LateContext<'tcx>, mut ty: Ty<'tcx>) -> ReducedTy<'tcx>
ty::Tuple(args) => {
let mut iter = args.iter();
let Some(sized_ty) = iter.find(|&ty| !is_zero_sized_ty(cx, ty)) else {
return ReducedTy::OrderedFields(ty);
return ReducedTy::OrderedFields(ty, None);
};
if iter.all(|ty| is_zero_sized_ty(cx, ty)) {
ty = sized_ty;
@ -316,7 +321,7 @@ fn reduce_ty<'tcx>(cx: &LateContext<'tcx>, mut ty: Ty<'tcx>) -> ReducedTy<'tcx>
continue;
}
if def.repr().inhibit_struct_field_reordering_opt() {
ReducedTy::OrderedFields(ty)
ReducedTy::OrderedFields(ty, Some(sized_ty))
} else {
ReducedTy::UnorderedFields(ty)
}