diff options
| -rw-r--r-- | compiler/rustc_lint/src/types.rs | 85 |
1 files changed, 60 insertions, 25 deletions
diff --git a/compiler/rustc_lint/src/types.rs b/compiler/rustc_lint/src/types.rs index 842dc2baae4..49fa312fe13 100644 --- a/compiler/rustc_lint/src/types.rs +++ b/compiler/rustc_lint/src/types.rs @@ -740,35 +740,49 @@ enum FfiResult<'tcx> { }, } -pub(crate) fn is_unsized_because_foreign<'tcx, 'a>( - cx: &'a LateContext<'tcx>, - ty: Ty<'tcx>, -) -> Result<bool, ()> { +/// Determine if a type is sized or not, and wether it affects references/pointers/boxes to it +#[derive(Clone, Copy)] +enum TypeSizedness { + /// sized type (pointers are C-compatible) + Sized, + /// unsized type because it includes an opaque/foreign type (pointers are C-compatible) + UnsizedBecauseForeign, + /// unsized type for other reasons (slice, string, dyn Trait, closure, ...) (pointers are not C-compatible) + UnsizedWithMetadata, +} + +/// Is this type unsized because it contains (or is) a foreign type? +/// (Returns Err if the type happens to be sized after all) +fn get_type_sizedness<'tcx, 'a>(cx: &'a LateContext<'tcx>, ty: Ty<'tcx>) -> TypeSizedness { let tcx = cx.tcx; if ty.is_sized(tcx, cx.typing_env()) { - Err(()) + TypeSizedness::Sized } else { - Ok(match ty.kind() { - ty::Slice(_) => false, - ty::Str => false, - ty::Dynamic(..) => false, - ty::Foreign(..) => true, - ty::Alias(ty::Opaque, ..) => todo!("why"), + match ty.kind() { + ty::Slice(_) => TypeSizedness::UnsizedWithMetadata, + ty::Str => TypeSizedness::UnsizedWithMetadata, + ty::Dynamic(..) => TypeSizedness::UnsizedWithMetadata, + ty::Foreign(..) => TypeSizedness::UnsizedBecauseForeign, + // While opaque types are checked for earlier, if a projection in a struct field + // normalizes to an opaque type, then it will reach this branch. + ty::Alias(ty::Opaque, ..) => todo!("We... don't know enough about this type yet?"), ty::Adt(def, args) => { // for now assume: boxes and phantoms don't mess with this match def.adt_kind() { - AdtKind::Union | AdtKind::Enum => true, + AdtKind::Union | AdtKind::Enum => { + bug!("unions and enums are necessarily sized") + } AdtKind::Struct => { if let Some(sym::cstring_type | sym::cstr_type) = tcx.get_diagnostic_name(def.did()) { - return Ok(false); + return TypeSizedness::UnsizedWithMetadata; } // FIXME: how do we deal with non-exhaustive unsized structs/unions? if def.non_enum_variant().fields.is_empty() { - bug!("empty unsized struct/union. what?"); + bug!("an empty struct is necessarily sized"); } let variant = def.non_enum_variant(); @@ -781,7 +795,13 @@ pub(crate) fn is_unsized_because_foreign<'tcx, 'a>( .tcx .try_normalize_erasing_regions(cx.typing_env(), field_ty) .unwrap_or(field_ty); - return Ok(is_unsized_because_foreign(cx, field_ty).unwrap()); + match get_type_sizedness(cx, field_ty) { + s @ (TypeSizedness::UnsizedWithMetadata + | TypeSizedness::UnsizedBecauseForeign) => s, + TypeSizedness::Sized => { + bug!("failed to find the reason why struct `{:?}` is unsized", ty) + } + } } } } @@ -794,12 +814,21 @@ pub(crate) fn is_unsized_because_foreign<'tcx, 'a>( .tcx .try_normalize_erasing_regions(cx.typing_env(), field_ty) .unwrap_or(field_ty); - is_unsized_because_foreign(cx, field_ty).unwrap() + match get_type_sizedness(cx, field_ty) { + s @ (TypeSizedness::UnsizedWithMetadata + | TypeSizedness::UnsizedBecauseForeign) => s, + TypeSizedness::Sized => { + bug!("failed to find the reason why tuple `{:?}` is unsized", ty) + } + } } t => { - bug!("we shouldn't be looking if this is unsized for a reason or another: {:?}", t) + bug!( + "we shouldn't be trying to determine if this is unsized for a reason or another: `{:?}`", + t + ) } - }) + } } } @@ -1106,8 +1135,8 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> { match *ty.kind() { ty::Adt(def, args) => { if let Some(inner_ty) = ty.boxed_ty() { - if inner_ty.is_sized(tcx, self.cx.typing_env()) - || is_unsized_because_foreign(self.cx, inner_ty).unwrap() + if let TypeSizedness::UnsizedBecauseForeign | TypeSizedness::Sized = + get_type_sizedness(self.cx, inner_ty) { // discussion on declaration vs definition: // see the `ty::RawPtr(inner_ty, _) | ty::Ref(_, inner_ty, _)` arm @@ -1311,13 +1340,14 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> { } ty::RawPtr(inner_ty, _) | ty::Ref(_, inner_ty, _) => { - if inner_ty.is_sized(tcx, self.cx.typing_env()) - || is_unsized_because_foreign(self.cx, inner_ty).unwrap() + if let TypeSizedness::UnsizedBecauseForeign | TypeSizedness::Sized = + get_type_sizedness(self.cx, inner_ty) { // there's a nuance on what this lint should do for function definitions - // (touched upon in https://github.com/rust-lang/rust/issues/66220 and https://github.com/rust-lang/rust/pull/72700) - // // (`extern "C" fn fn_name(...) {...}`) versus declarations (`extern "C" {fn fn_name(...);}`). + // (this is touched upon in https://github.com/rust-lang/rust/issues/66220 + // and https://github.com/rust-lang/rust/pull/72700) + // // The big question is: what does "ABI safety" mean? if you have something translated to a C pointer // (which has a stable layout) but points to FFI-unsafe type, is it safe? // on one hand, the function's ABI will match that of a similar C-declared function API, @@ -1609,7 +1639,12 @@ impl<'a, 'tcx> ImproperCTypesVisitor<'a, 'tcx> { } }; } - let last_ty = last_ty.unwrap(); // populated by any run of the `while` block + let last_ty = match last_ty { + Some(last_ty) => last_ty, + None => bug!( + "This option should definitely have been filled by the loop that just finished" + ), + }; self.emit_ffi_unsafe_type_lint(last_ty, sp, cimproper_layers); } } |