From 850cc34da2ec86ae5b84e48a03d6b451b1dcd4d7 Mon Sep 17 00:00:00 2001 From: Michael Goulet Date: Thu, 7 Mar 2024 01:32:01 +0000 Subject: [PATCH] Don't require specifying unrelated assoc types when trait alias is in dyn type --- .../src/astconv/object_safety.rs | 80 +++++++++---------- .../rustc_trait_selection/src/traits/util.rs | 2 +- .../overlaping-bound-suggestion.stderr | 7 +- .../only-require-assocs-from-supertraits.rs | 16 ++++ 4 files changed, 55 insertions(+), 50 deletions(-) create mode 100644 tests/ui/traits/alias/only-require-assocs-from-supertraits.rs diff --git a/compiler/rustc_hir_analysis/src/astconv/object_safety.rs b/compiler/rustc_hir_analysis/src/astconv/object_safety.rs index 7705445ffaa..b9543c7a29b 100644 --- a/compiler/rustc_hir_analysis/src/astconv/object_safety.rs +++ b/compiler/rustc_hir_analysis/src/astconv/object_safety.rs @@ -45,10 +45,9 @@ pub(super) fn conv_object_ty_poly_trait_ref( dummy_self, &mut bounds, false, - // FIXME: This should be `true`, but we don't really handle - // associated type bounds or type aliases in objects in a way - // that makes this meaningful, I think. - OnlySelfBounds(false), + // True so we don't populate `bounds` with associated type bounds, even + // though they're disallowed from object types. + OnlySelfBounds(true), ) { potential_assoc_types.extend(cur_potential_assoc_types); } @@ -83,9 +82,8 @@ pub(super) fn conv_object_ty_poly_trait_ref( let expanded_traits = traits::expand_trait_aliases(tcx, trait_bounds.iter().map(|&(a, b)| (a, b))); - let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) = expanded_traits - .filter(|i| i.trait_ref().self_ty().skip_binder() == dummy_self) - .partition(|i| tcx.trait_is_auto(i.trait_ref().def_id())); + let (mut auto_traits, regular_traits): (Vec<_>, Vec<_>) = + expanded_traits.partition(|i| tcx.trait_is_auto(i.trait_ref().def_id())); if regular_traits.len() > 1 { let first_trait = ®ular_traits[0]; let additional_trait = ®ular_traits[1]; @@ -158,7 +156,7 @@ trait here instead: `trait NewTrait: {} {{}}`", for (base_trait_ref, span) in regular_traits_refs_spans { let base_pred: ty::Predicate<'tcx> = base_trait_ref.to_predicate(tcx); - for pred in traits::elaborate(tcx, [base_pred]) { + for pred in traits::elaborate(tcx, [base_pred]).filter_only_self() { debug!("conv_object_ty_poly_trait_ref: observing object predicate `{:?}`", pred); let bound_predicate = pred.kind(); @@ -312,45 +310,39 @@ trait here instead: `trait NewTrait: {} {{}}`", }) }); - let existential_projections = projection_bounds - .iter() - // We filter out traits that don't have `Self` as their self type above, - // we need to do the same for projections. - .filter(|(bound, _)| bound.skip_binder().self_ty() == dummy_self) - .map(|(bound, _)| { - bound.map_bound(|mut b| { - assert_eq!(b.projection_ty.self_ty(), dummy_self); + let existential_projections = projection_bounds.iter().map(|(bound, _)| { + bound.map_bound(|mut b| { + assert_eq!(b.projection_ty.self_ty(), dummy_self); - // Like for trait refs, verify that `dummy_self` did not leak inside default type - // parameters. - let references_self = b.projection_ty.args.iter().skip(1).any(|arg| { - if arg.walk().any(|arg| arg == dummy_self.into()) { - return true; - } - false - }); - if references_self { - let guar = tcx.dcx().span_delayed_bug( - span, - "trait object projection bounds reference `Self`", - ); - let args: Vec<_> = b - .projection_ty - .args - .iter() - .map(|arg| { - if arg.walk().any(|arg| arg == dummy_self.into()) { - return Ty::new_error(tcx, guar).into(); - } - arg - }) - .collect(); - b.projection_ty.args = tcx.mk_args(&args); + // Like for trait refs, verify that `dummy_self` did not leak inside default type + // parameters. + let references_self = b.projection_ty.args.iter().skip(1).any(|arg| { + if arg.walk().any(|arg| arg == dummy_self.into()) { + return true; } + false + }); + if references_self { + let guar = tcx + .dcx() + .span_delayed_bug(span, "trait object projection bounds reference `Self`"); + let args: Vec<_> = b + .projection_ty + .args + .iter() + .map(|arg| { + if arg.walk().any(|arg| arg == dummy_self.into()) { + return Ty::new_error(tcx, guar).into(); + } + arg + }) + .collect(); + b.projection_ty.args = tcx.mk_args(&args); + } - ty::ExistentialProjection::erase_self_ty(tcx, b) - }) - }); + ty::ExistentialProjection::erase_self_ty(tcx, b) + }) + }); let regular_trait_predicates = existential_trait_refs .map(|trait_ref| trait_ref.map_bound(ty::ExistentialPredicate::Trait)); diff --git a/compiler/rustc_trait_selection/src/traits/util.rs b/compiler/rustc_trait_selection/src/traits/util.rs index 6e01e0b76aa..3f433a9e919 100644 --- a/compiler/rustc_trait_selection/src/traits/util.rs +++ b/compiler/rustc_trait_selection/src/traits/util.rs @@ -127,7 +127,7 @@ fn expand(&mut self, item: &TraitAliasExpansionInfo<'tcx>) -> bool { } // Get components of trait alias. - let predicates = tcx.implied_predicates_of(trait_ref.def_id()); + let predicates = tcx.super_predicates_of(trait_ref.def_id()); debug!(?predicates); let items = predicates.predicates.iter().rev().filter_map(|(pred, span)| { diff --git a/tests/ui/associated-type-bounds/overlaping-bound-suggestion.stderr b/tests/ui/associated-type-bounds/overlaping-bound-suggestion.stderr index 2a308f83731..03d72f2ae2c 100644 --- a/tests/ui/associated-type-bounds/overlaping-bound-suggestion.stderr +++ b/tests/ui/associated-type-bounds/overlaping-bound-suggestion.stderr @@ -1,11 +1,8 @@ -error[E0191]: the value of the associated types `Item`, `Item`, `IntoIter` and `IntoIter` in `IntoIterator` must be specified +error[E0191]: the value of the associated types `Item` and `IntoIter` in `IntoIterator` must be specified --> $DIR/overlaping-bound-suggestion.rs:7:13 | LL | inner: >::IntoIterator as Item>::Core, - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ - | | | - | | associated types `Item`, `IntoIter` must be specified - | associated types `Item`, `IntoIter` must be specified + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: specify the associated types: `IntoIterator, Item = Type, IntoIter = Type>` error[E0223]: ambiguous associated type --> $DIR/overlaping-bound-suggestion.rs:7:13 diff --git a/tests/ui/traits/alias/only-require-assocs-from-supertraits.rs b/tests/ui/traits/alias/only-require-assocs-from-supertraits.rs new file mode 100644 index 00000000000..35149fdfba0 --- /dev/null +++ b/tests/ui/traits/alias/only-require-assocs-from-supertraits.rs @@ -0,0 +1,16 @@ +//@ check-pass + +#![feature(trait_alias)] + +trait Foo {} +trait Bar { type Assoc; } + +trait Alias = Foo; + +// Check that an alias only requires us to specify the associated types +// of the principal's supertraits. For example, we shouldn't require +// specifying the type `Assoc` on trait `Bar` just because we have some +// `T: Bar` where clause on the alias... because that makes no sense. +fn use_alias(x: &dyn Alias) {} + +fn main() {}