+/// Enforce some basic invariants on layouts.
+fn sanity_check_layout<'tcx>(
+ tcx: TyCtxt<'tcx>,
+ param_env: ty::ParamEnv<'tcx>,
+ layout: &TyAndLayout<'tcx>,
+) {
+ // Type-level uninhabitedness should always imply ABI uninhabitedness.
+ if tcx.conservative_is_privately_uninhabited(param_env.and(layout.ty)) {
+ assert!(layout.abi.is_uninhabited());
+ }
+
+ if cfg!(debug_assertions) {
+ fn check_layout_abi<'tcx>(tcx: TyCtxt<'tcx>, layout: Layout<'tcx>) {
+ match layout.abi() {
+ Abi::Scalar(_scalar) => {
+ // No padding in scalars.
+ /* FIXME(#96185):
+ assert_eq!(
+ layout.align().abi,
+ scalar.align(&tcx).abi,
+ "alignment mismatch between ABI and layout in {layout:#?}"
+ );
+ assert_eq!(
+ layout.size(),
+ scalar.size(&tcx),
+ "size mismatch between ABI and layout in {layout:#?}"
+ );*/
+ }
+ Abi::Vector { count, element } => {
+ // No padding in vectors. Alignment can be strengthened, though.
+ assert!(
+ layout.align().abi >= element.align(&tcx).abi,
+ "alignment mismatch between ABI and layout in {layout:#?}"
+ );
+ let size = element.size(&tcx) * count;
+ assert_eq!(
+ layout.size(),
+ size.align_to(tcx.data_layout().vector_align(size).abi),
+ "size mismatch between ABI and layout in {layout:#?}"
+ );
+ }
+ Abi::ScalarPair(scalar1, scalar2) => {
+ // Sanity-check scalar pairs. These are a bit more flexible and support
+ // padding, but we can at least ensure both fields actually fit into the layout
+ // and the alignment requirement has not been weakened.
+ let align1 = scalar1.align(&tcx).abi;
+ let align2 = scalar2.align(&tcx).abi;
+ assert!(
+ layout.align().abi >= cmp::max(align1, align2),
+ "alignment mismatch between ABI and layout in {layout:#?}",
+ );
+ let field2_offset = scalar1.size(&tcx).align_to(align2);
+ assert!(
+ layout.size() >= field2_offset + scalar2.size(&tcx),
+ "size mismatch between ABI and layout in {layout:#?}"
+ );
+ }
+ Abi::Uninhabited | Abi::Aggregate { .. } => {} // Nothing to check.
+ }
+ }
+
+ check_layout_abi(tcx, layout.layout);
+
+ if let Variants::Multiple { variants, .. } = &layout.variants {
+ for variant in variants {
+ check_layout_abi(tcx, *variant);
+ // No nested "multiple".
+ assert!(matches!(variant.variants(), Variants::Single { .. }));
+ // Skip empty variants.
+ if variant.size() == Size::ZERO
+ || variant.fields().count() == 0
+ || variant.abi().is_uninhabited()
+ {
+ // These are never actually accessed anyway, so we can skip them. (Note that
+ // sometimes, variants with fields have size 0, and sometimes, variants without
+ // fields have non-0 size.)
+ continue;
+ }
+ // Variants should have the same or a smaller size as the full thing.
+ if variant.size() > layout.size {
+ bug!(
+ "Type with size {} bytes has variant with size {} bytes: {layout:#?}",
+ layout.size.bytes(),
+ variant.size().bytes(),
+ )
+ }
+ // The top-level ABI and the ABI of the variants should be coherent.
+ let abi_coherent = match (layout.abi, variant.abi()) {
+ (Abi::Scalar(..), Abi::Scalar(..)) => true,
+ (Abi::ScalarPair(..), Abi::ScalarPair(..)) => true,
+ (Abi::Uninhabited, _) => true,
+ (Abi::Aggregate { .. }, _) => true,
+ _ => false,
+ };
+ if !abi_coherent {
+ bug!(
+ "Variant ABI is incompatible with top-level ABI:\nvariant={:#?}\nTop-level: {layout:#?}",
+ variant
+ );
+ }
+ }
+ }
+ }
+}
+