diff options
Diffstat (limited to 'compiler/rustc_middle/src/ty/layout.rs')
| -rw-r--r-- | compiler/rustc_middle/src/ty/layout.rs | 67 |
1 files changed, 44 insertions, 23 deletions
diff --git a/compiler/rustc_middle/src/ty/layout.rs b/compiler/rustc_middle/src/ty/layout.rs index 7f66b993646..00f53afd663 100644 --- a/compiler/rustc_middle/src/ty/layout.rs +++ b/compiler/rustc_middle/src/ty/layout.rs @@ -670,29 +670,50 @@ where }); } - match tcx.struct_tail_erasing_lifetimes(pointee, cx.param_env()).kind() { - ty::Slice(_) | ty::Str => TyMaybeWithLayout::Ty(tcx.types.usize), - ty::Dynamic(_, _, ty::Dyn) => { - TyMaybeWithLayout::Ty(tcx.mk_imm_ref( - tcx.lifetimes.re_static, - tcx.mk_array(tcx.types.usize, 3), - )) - /* FIXME: use actual fn pointers - Warning: naively computing the number of entries in the - vtable by counting the methods on the trait + methods on - all parent traits does not work, because some methods can - be not object safe and thus excluded from the vtable. - Increase this counter if you tried to implement this but - failed to do it without duplicating a lot of code from - other places in the compiler: 2 - tcx.mk_tup(&[ - tcx.mk_array(tcx.types.usize, 3), - tcx.mk_array(Option<fn()>), - ]) - */ + let mk_dyn_vtable = || { + tcx.mk_imm_ref(tcx.lifetimes.re_static, tcx.mk_array(tcx.types.usize, 3)) + /* FIXME: use actual fn pointers + Warning: naively computing the number of entries in the + vtable by counting the methods on the trait + methods on + all parent traits does not work, because some methods can + be not object safe and thus excluded from the vtable. + Increase this counter if you tried to implement this but + failed to do it without duplicating a lot of code from + other places in the compiler: 2 + tcx.mk_tup(&[ + tcx.mk_array(tcx.types.usize, 3), + tcx.mk_array(Option<fn()>), + ]) + */ + }; + + let metadata = if let Some(metadata_def_id) = tcx.lang_items().metadata_type() { + let metadata = tcx.normalize_erasing_regions( + cx.param_env(), + tcx.mk_projection(metadata_def_id, [pointee]), + ); + + // Map `Metadata = DynMetadata<dyn Trait>` back to a vtable, since it + // offers better information than `std::ptr::metadata::VTable`, + // and we rely on this layout information to trigger a panic in + // `std::mem::uninitialized::<&dyn Trait>()`, for example. + if let ty::Adt(def, substs) = metadata.kind() + && Some(def.did()) == tcx.lang_items().dyn_metadata() + && substs.type_at(0).is_trait() + { + mk_dyn_vtable() + } else { + metadata } - _ => bug!("TyAndLayout::field({:?}): not applicable", this), - } + } else { + match tcx.struct_tail_erasing_lifetimes(pointee, cx.param_env()).kind() { + ty::Slice(_) | ty::Str => tcx.types.usize, + ty::Dynamic(_, _, ty::Dyn) => mk_dyn_vtable(), + _ => bug!("TyAndLayout::field({:?}): not applicable", this), + } + }; + + TyMaybeWithLayout::Ty(metadata) } // Arrays and slices. @@ -993,7 +1014,7 @@ where /// might (from a foreign exception or similar). #[inline] #[tracing::instrument(level = "debug", skip(tcx))] -pub fn fn_can_unwind<'tcx>(tcx: TyCtxt<'tcx>, fn_def_id: Option<DefId>, abi: SpecAbi) -> bool { +pub fn fn_can_unwind(tcx: TyCtxt<'_>, fn_def_id: Option<DefId>, abi: SpecAbi) -> bool { if let Some(did) = fn_def_id { // Special attribute for functions which can't unwind. if tcx.codegen_fn_attrs(did).flags.contains(CodegenFnAttrFlags::NEVER_UNWIND) { |