diff --git a/compiler/rustc_feature/src/builtin_attrs.rs b/compiler/rustc_feature/src/builtin_attrs.rs index f25b2d8f566..6f119d5ab88 100644 --- a/compiler/rustc_feature/src/builtin_attrs.rs +++ b/compiler/rustc_feature/src/builtin_attrs.rs @@ -677,6 +677,12 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[ "the `#[rustc_skip_array_during_method_dispatch]` attribute is used to exclude a trait \ from method dispatch when the receiver is an array, for compatibility in editions < 2021." ), + rustc_attr!( + rustc_must_implement_one_of, Normal, template!(List: "method1, method2, ..."), ErrorFollowing, + "the `#[rustc_must_implement_one_of]` attribute is used to change minimal complete \ + definition of a trait, it's currently in experimental form and should be changed before \ + being exposed outside of the std" + ), // ========================================================================== // Internal attributes, Testing: diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs index 603b21d4005..2cdbdfdd99b 100644 --- a/compiler/rustc_metadata/src/rmeta/decoder.rs +++ b/compiler/rustc_metadata/src/rmeta/decoder.rs @@ -820,6 +820,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> { data.skip_array_during_method_dispatch, data.specialization_kind, self.def_path_hash(item_id), + data.must_implement_one_of, ) } EntryKind::TraitAlias => ty::TraitDef::new( @@ -831,6 +832,7 @@ impl<'a, 'tcx> CrateMetadataRef<'a> { false, ty::trait_def::TraitSpecializationKind::None, self.def_path_hash(item_id), + None, ), _ => bug!("def-index does not refer to trait or trait alias"), } diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs index 8a74aef60dd..c2c231d5cf9 100644 --- a/compiler/rustc_metadata/src/rmeta/encoder.rs +++ b/compiler/rustc_metadata/src/rmeta/encoder.rs @@ -1514,6 +1514,7 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> { is_marker: trait_def.is_marker, skip_array_during_method_dispatch: trait_def.skip_array_during_method_dispatch, specialization_kind: trait_def.specialization_kind, + must_implement_one_of: trait_def.must_implement_one_of.clone(), }; EntryKind::Trait(self.lazy(data)) diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs index 432ca547de6..c7e5a7c5d2c 100644 --- a/compiler/rustc_metadata/src/rmeta/mod.rs +++ b/compiler/rustc_metadata/src/rmeta/mod.rs @@ -378,6 +378,7 @@ struct TraitData { is_marker: bool, skip_array_during_method_dispatch: bool, specialization_kind: ty::trait_def::TraitSpecializationKind, + must_implement_one_of: Option>, } #[derive(TyEncodable, TyDecodable)] diff --git a/compiler/rustc_middle/src/ty/trait_def.rs b/compiler/rustc_middle/src/ty/trait_def.rs index 34d059f4ec8..c4c75434980 100644 --- a/compiler/rustc_middle/src/ty/trait_def.rs +++ b/compiler/rustc_middle/src/ty/trait_def.rs @@ -1,7 +1,7 @@ use crate::traits::specialization_graph; use crate::ty::fast_reject::{self, SimplifiedType, SimplifyParams, StripReferences}; use crate::ty::fold::TypeFoldable; -use crate::ty::{Ty, TyCtxt}; +use crate::ty::{Ident, Ty, TyCtxt}; use rustc_hir as hir; use rustc_hir::def_id::DefId; use rustc_hir::definitions::DefPathHash; @@ -44,6 +44,10 @@ pub struct TraitDef { /// The ICH of this trait's DefPath, cached here so it doesn't have to be /// recomputed all the time. pub def_path_hash: DefPathHash, + + /// List of methods from `#[rustc_must_implement_one_of]` attribute one of which + /// must be implemented. + pub must_implement_one_of: Option>, } /// Whether this trait is treated specially by the standard library @@ -87,6 +91,7 @@ impl<'tcx> TraitDef { skip_array_during_method_dispatch: bool, specialization_kind: TraitSpecializationKind, def_path_hash: DefPathHash, + must_implement_one_of: Option>, ) -> TraitDef { TraitDef { def_id, @@ -97,6 +102,7 @@ impl<'tcx> TraitDef { skip_array_during_method_dispatch, specialization_kind, def_path_hash, + must_implement_one_of, } } diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs index 84cf8878af8..483171917dd 100644 --- a/compiler/rustc_span/src/symbol.rs +++ b/compiler/rustc_span/src/symbol.rs @@ -1136,6 +1136,7 @@ symbols! { rustc_macro_transparency, rustc_main, rustc_mir, + rustc_must_implement_one_of, rustc_nonnull_optimization_guaranteed, rustc_object_lifetime_default, rustc_on_unimplemented, diff --git a/compiler/rustc_typeck/src/check/check.rs b/compiler/rustc_typeck/src/check/check.rs index dcf42e1aefe..ff103159566 100644 --- a/compiler/rustc_typeck/src/check/check.rs +++ b/compiler/rustc_typeck/src/check/check.rs @@ -979,6 +979,10 @@ fn check_impl_items_against_trait<'tcx>( if let Ok(ancestors) = trait_def.ancestors(tcx, impl_id.to_def_id()) { // Check for missing items from trait let mut missing_items = Vec::new(); + + let mut must_implement_one_of: Option> = + trait_def.must_implement_one_of.as_deref().map(|slice| slice.iter().copied().collect()); + for &trait_item_id in tcx.associated_item_def_ids(impl_trait_ref.def_id) { let is_implemented = ancestors .leaf_def(tcx, trait_item_id) @@ -987,12 +991,31 @@ fn check_impl_items_against_trait<'tcx>( if !is_implemented && tcx.impl_defaultness(impl_id).is_final() { missing_items.push(tcx.associated_item(trait_item_id)); } + + if let Some(required_items) = &must_implement_one_of { + let trait_item = tcx.associated_item(trait_item_id); + + if is_implemented && required_items.contains(&trait_item.ident) { + must_implement_one_of = None; + } + } } if !missing_items.is_empty() { let impl_span = tcx.sess.source_map().guess_head_span(full_impl_span); missing_items_err(tcx, impl_span, &missing_items, full_impl_span); } + + if let Some(missing_items) = must_implement_one_of { + let impl_span = tcx.sess.source_map().guess_head_span(full_impl_span); + let attr_span = tcx + .get_attrs(impl_trait_ref.def_id) + .iter() + .find(|attr| attr.has_name(sym::rustc_must_implement_one_of)) + .map(|attr| attr.span); + + missing_items_must_implement_one_of_err(tcx, impl_span, &missing_items, attr_span); + } } } diff --git a/compiler/rustc_typeck/src/check/mod.rs b/compiler/rustc_typeck/src/check/mod.rs index d576154ff90..17c4bc1b301 100644 --- a/compiler/rustc_typeck/src/check/mod.rs +++ b/compiler/rustc_typeck/src/check/mod.rs @@ -641,6 +641,31 @@ fn missing_items_err( err.emit(); } +fn missing_items_must_implement_one_of_err( + tcx: TyCtxt<'_>, + impl_span: Span, + missing_items: &FxHashSet, + annotation_span: Option, +) { + let missing_items_msg = + missing_items.iter().map(Ident::to_string).collect::>().join("`, `"); + + let mut err = struct_span_err!( + tcx.sess, + impl_span, + E0046, + "not all trait items implemented, missing one of: `{}`", + missing_items_msg + ); + err.span_label(impl_span, format!("missing one of `{}` in implementation", missing_items_msg)); + + if let Some(annotation_span) = annotation_span { + err.span_note(annotation_span, "required because of this annotation"); + } + + err.emit(); +} + /// Resugar `ty::GenericPredicates` in a way suitable to be used in structured suggestions. fn bounds_from_generic_predicates<'tcx>( tcx: TyCtxt<'tcx>, diff --git a/compiler/rustc_typeck/src/collect.rs b/compiler/rustc_typeck/src/collect.rs index d4d4baa3f71..50613ef7104 100644 --- a/compiler/rustc_typeck/src/collect.rs +++ b/compiler/rustc_typeck/src/collect.rs @@ -1198,9 +1198,11 @@ fn super_predicates_that_define_assoc_type( fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef { let item = tcx.hir().expect_item(def_id.expect_local()); - let (is_auto, unsafety) = match item.kind { - hir::ItemKind::Trait(is_auto, unsafety, ..) => (is_auto == hir::IsAuto::Yes, unsafety), - hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal), + let (is_auto, unsafety, items) = match item.kind { + hir::ItemKind::Trait(is_auto, unsafety, .., items) => { + (is_auto == hir::IsAuto::Yes, unsafety, items) + } + hir::ItemKind::TraitAlias(..) => (false, hir::Unsafety::Normal, &[][..]), _ => span_bug!(item.span, "trait_def_of_item invoked on non-trait"), }; @@ -1227,6 +1229,80 @@ fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef { ty::trait_def::TraitSpecializationKind::None }; let def_path_hash = tcx.def_path_hash(def_id); + + let must_implement_one_of = tcx + .get_attrs(def_id) + .iter() + .find(|attr| attr.has_name(sym::rustc_must_implement_one_of)) + // Check that there are at least 2 arguments of `#[rustc_must_implement_one_of]` + // and that they are all identifiers + .and_then(|attr| match attr.meta_item_list() { + Some(items) if items.len() < 2 => { + tcx.sess + .struct_span_err( + attr.span, + "the `#[rustc_must_implement_one_of]` attribute must be \ + used with at least 2 args", + ) + .emit(); + + None + } + Some(items) => items + .into_iter() + .map(|item| item.ident().ok_or(item.span())) + .collect::, _>>() + .map_err(|span| { + tcx.sess.struct_span_err(span, "must be an identifier of a method").emit(); + }) + .ok() + .zip(Some(attr.span)), + // Error is reported by `rustc_attr!` + None => None, + }) + // Check that all arguments of `#[rustc_must_implement_one_of]` reference + // methods in the trait with default implementations + .and_then(|(list, attr_span)| { + let errors = list.iter().filter_map(|ident| { + let item = items.iter().find(|item| item.ident == *ident); + + match item { + Some(item) if matches!(item.kind, hir::AssocItemKind::Fn { .. }) => { + if !item.defaultness.has_value() { + tcx.sess + .struct_span_err( + item.span, + "This method doesn't have a default implementation", + ) + .span_note(attr_span, "required by this annotation") + .emit(); + + return Some(()); + } + + return None; + } + Some(item) => tcx + .sess + .struct_span_err(item.span, "Not a method") + .span_note(attr_span, "required by this annotation") + .note( + "All `#[rustc_must_implement_one_of]` arguments \ + must be method identifiers", + ) + .emit(), + None => tcx + .sess + .struct_span_err(ident.span, "Method not found in this trait") + .emit(), + } + + Some(()) + }); + + (errors.count() == 0).then_some(list) + }); + ty::TraitDef::new( def_id, unsafety, @@ -1236,6 +1312,7 @@ fn trait_def(tcx: TyCtxt<'_>, def_id: DefId) -> ty::TraitDef { skip_array_during_method_dispatch, spec_kind, def_path_hash, + must_implement_one_of, ) } diff --git a/src/test/ui/rustc_must_implement_one_of.rs b/src/test/ui/rustc_must_implement_one_of.rs new file mode 100644 index 00000000000..f98d3bdc3fa --- /dev/null +++ b/src/test/ui/rustc_must_implement_one_of.rs @@ -0,0 +1,44 @@ +#![feature(rustc_attrs)] + +#[rustc_must_implement_one_of(eq, neq)] +trait Equal { + fn eq(&self, other: &Self) -> bool { + !self.neq(other) + } + + fn neq(&self, other: &Self) -> bool { + !self.eq(other) + } +} + +struct T0; +struct T1; +struct T2; +struct T3; + +impl Equal for T0 { + fn eq(&self, _other: &Self) -> bool { + true + } +} + +impl Equal for T1 { + fn neq(&self, _other: &Self) -> bool { + false + } +} + +impl Equal for T2 { + fn eq(&self, _other: &Self) -> bool { + true + } + + fn neq(&self, _other: &Self) -> bool { + false + } +} + +impl Equal for T3 {} +//~^ not all trait items implemented, missing one of: `neq`, `eq` + +fn main() {} diff --git a/src/test/ui/rustc_must_implement_one_of.stderr b/src/test/ui/rustc_must_implement_one_of.stderr new file mode 100644 index 00000000000..53c4e71cf8b --- /dev/null +++ b/src/test/ui/rustc_must_implement_one_of.stderr @@ -0,0 +1,15 @@ +error[E0046]: not all trait items implemented, missing one of: `neq`, `eq` + --> $DIR/rustc_must_implement_one_of.rs:41:1 + | +LL | impl Equal for T3 {} + | ^^^^^^^^^^^^^^^^^ missing one of `neq`, `eq` in implementation + | +note: required because of this annotation + --> $DIR/rustc_must_implement_one_of.rs:3:1 + | +LL | #[rustc_must_implement_one_of(eq, neq)] + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + +error: aborting due to previous error + +For more information about this error, try `rustc --explain E0046`.