diff options
Diffstat (limited to 'compiler/rustc_middle')
| -rw-r--r-- | compiler/rustc_middle/src/ty/instance.rs | 37 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/mod.rs | 1 | ||||
| -rw-r--r-- | compiler/rustc_middle/src/ty/return_position_impl_trait_in_trait.rs | 95 |
3 files changed, 116 insertions, 17 deletions
diff --git a/compiler/rustc_middle/src/ty/instance.rs b/compiler/rustc_middle/src/ty/instance.rs index 65c909e70f6..1dd564d9798 100644 --- a/compiler/rustc_middle/src/ty/instance.rs +++ b/compiler/rustc_middle/src/ty/instance.rs @@ -677,23 +677,26 @@ impl<'tcx> Instance<'tcx> { // // 1) The underlying method expects a caller location parameter // in the ABI - if resolved.def.requires_caller_location(tcx) - // 2) The caller location parameter comes from having `#[track_caller]` - // on the implementation, and *not* on the trait method. - && !tcx.should_inherit_track_caller(def) - // If the method implementation comes from the trait definition itself - // (e.g. `trait Foo { #[track_caller] my_fn() { /* impl */ } }`), - // then we don't need to generate a shim. This check is needed because - // `should_inherit_track_caller` returns `false` if our method - // implementation comes from the trait block, and not an impl block - && !matches!( - tcx.opt_associated_item(def), - Some(ty::AssocItem { - container: ty::AssocItemContainer::Trait, - .. - }) - ) - { + let needs_track_caller_shim = resolved.def.requires_caller_location(tcx) + // 2) The caller location parameter comes from having `#[track_caller]` + // on the implementation, and *not* on the trait method. + && !tcx.should_inherit_track_caller(def) + // If the method implementation comes from the trait definition itself + // (e.g. `trait Foo { #[track_caller] my_fn() { /* impl */ } }`), + // then we don't need to generate a shim. This check is needed because + // `should_inherit_track_caller` returns `false` if our method + // implementation comes from the trait block, and not an impl block + && !matches!( + tcx.opt_associated_item(def), + Some(ty::AssocItem { + container: ty::AssocItemContainer::Trait, + .. + }) + ); + // We also need to generate a shim if this is an AFIT. + let needs_rpitit_shim = + tcx.return_position_impl_trait_in_trait_shim_data(def).is_some(); + if needs_track_caller_shim || needs_rpitit_shim { if tcx.is_closure_like(def) { debug!( " => vtable fn pointer created for closure with #[track_caller]: {:?} for method {:?} {:?}", diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs index 70e0568b202..80b11892a42 100644 --- a/compiler/rustc_middle/src/ty/mod.rs +++ b/compiler/rustc_middle/src/ty/mod.rs @@ -146,6 +146,7 @@ mod opaque_types; mod parameterized; mod predicate; mod region; +mod return_position_impl_trait_in_trait; mod rvalue_scopes; mod structural_impls; #[allow(hidden_glob_reexports)] diff --git a/compiler/rustc_middle/src/ty/return_position_impl_trait_in_trait.rs b/compiler/rustc_middle/src/ty/return_position_impl_trait_in_trait.rs new file mode 100644 index 00000000000..21c605f8296 --- /dev/null +++ b/compiler/rustc_middle/src/ty/return_position_impl_trait_in_trait.rs @@ -0,0 +1,95 @@ +use rustc_hir::def_id::DefId; + +use crate::ty::{self, ExistentialPredicateStableCmpExt, TyCtxt}; + +impl<'tcx> TyCtxt<'tcx> { + /// Given a `def_id` of a trait or impl method, compute whether that method needs to + /// have an RPITIT shim applied to it for it to be object safe. If so, return the + /// `def_id` of the RPITIT, and also the args of trait method that returns the RPITIT. + /// + /// NOTE that these args are not, in general, the same as than the RPITIT's args. They + /// are a subset of those args, since they do not include the late-bound lifetimes of + /// the RPITIT. Depending on the context, these will need to be dealt with in different + /// ways -- in codegen, it's okay to fill them with ReErased. + pub fn return_position_impl_trait_in_trait_shim_data( + self, + def_id: DefId, + ) -> Option<(DefId, ty::EarlyBinder<'tcx, ty::GenericArgsRef<'tcx>>)> { + let assoc_item = self.opt_associated_item(def_id)?; + + let (trait_item_def_id, opt_impl_def_id) = match assoc_item.container { + ty::AssocItemContainer::Impl => { + (assoc_item.trait_item_def_id?, Some(self.parent(def_id))) + } + ty::AssocItemContainer::Trait => (def_id, None), + }; + + let sig = self.fn_sig(trait_item_def_id); + + // Check if the trait returns an RPITIT. + let ty::Alias(ty::Projection, ty::AliasTy { def_id, .. }) = + *sig.skip_binder().skip_binder().output().kind() + else { + return None; + }; + if !self.is_impl_trait_in_trait(def_id) { + return None; + } + + let args = if let Some(impl_def_id) = opt_impl_def_id { + // Rebase the args from the RPITIT onto the impl trait ref, so we can later + // substitute them with the method args of the *impl* method, since that's + // the instance we're building a vtable shim for. + ty::GenericArgs::identity_for_item(self, trait_item_def_id).rebase_onto( + self, + self.parent(trait_item_def_id), + self.impl_trait_ref(impl_def_id) + .expect("expected impl trait ref from parent of impl item") + .instantiate_identity() + .args, + ) + } else { + // This is when we have a default trait implementation. + ty::GenericArgs::identity_for_item(self, trait_item_def_id) + }; + + Some((def_id, ty::EarlyBinder::bind(args))) + } + + /// Given a `DefId` of an RPITIT and its args, return the existential predicates + /// that corresponds to the RPITIT's bounds with the self type erased. + pub fn item_bounds_to_existential_predicates( + self, + def_id: DefId, + args: ty::GenericArgsRef<'tcx>, + ) -> &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> { + let mut bounds: Vec<_> = self + .item_super_predicates(def_id) + .iter_instantiated(self, args) + .filter_map(|clause| { + clause + .kind() + .map_bound(|clause| match clause { + ty::ClauseKind::Trait(trait_pred) => Some(ty::ExistentialPredicate::Trait( + ty::ExistentialTraitRef::erase_self_ty(self, trait_pred.trait_ref), + )), + ty::ClauseKind::Projection(projection_pred) => { + Some(ty::ExistentialPredicate::Projection( + ty::ExistentialProjection::erase_self_ty(self, projection_pred), + )) + } + ty::ClauseKind::TypeOutlives(_) => { + // Type outlives bounds don't really turn into anything, + // since we must use an intersection region for the `dyn*`'s + // region anyways. + None + } + _ => unreachable!("unexpected clause in item bounds: {clause:?}"), + }) + .transpose() + }) + .collect(); + bounds.sort_by(|a, b| a.skip_binder().stable_cmp(self, &b.skip_binder())); + self.mk_poly_existential_predicates(&bounds) + } +} |