Merge attrs, better validation

Author: compiler-errors

compiler/rustc_feature/src/builtin_attrs.rs

@@ -705,14 +705,13 @@ pub const BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
  "#[rustc_allow_incoherent_impl] has to be added to all impl items of an incoherent inherent impl."
  ),
  rustc_attr!(
- rustc_deny_explicit_impl, AttributeType::Normal, template!(Word), ErrorFollowing, @only_local: true,
+ rustc_deny_explicit_impl,
+ AttributeType::Normal,
+ template!(List: "implement_via_object = (true|false)"),
+ ErrorFollowing,
+ @only_local: true,
  "#[rustc_deny_explicit_impl] enforces that a trait can have no user-provided impls"
  ),
- rustc_attr!(
- rustc_do_not_implement_via_object, AttributeType::Normal, template!(Word), ErrorFollowing, @only_local: true,
- "#[rustc_do_not_implement_via_object] marks a trait so that `dyn Trait` does not \
- implement `Trait` (without requiring `Sized` as a supertrait)"
- ),
  rustc_attr!(
  rustc_has_incoherent_inherent_impls, AttributeType::Normal, template!(Word), ErrorFollowing,
  "#[rustc_has_incoherent_inherent_impls] allows the addition of incoherent inherent impls for \

compiler/rustc_hir_analysis/src/collect.rs

@@ -985,8 +985,50 @@ fn trait_def(tcx: TyCtxt<'_>, def_id: LocalDefId) -> ty::TraitDef {
 
  no_dups.then_some(list)
  });
- let do_not_implement_via_object = tcx.has_attr(def_id, sym::rustc_do_not_implement_via_object);
- let deny_explicit_impl = tcx.has_attr(def_id, sym::rustc_deny_explicit_impl);
+
+ let mut deny_explicit_impl = false;
+ let mut implement_via_object = true;
+ if let Some(attr) = tcx.get_attr(def_id, sym::rustc_deny_explicit_impl) {
+ deny_explicit_impl = true;
+ let mut seen_attr = false;
+ for meta in attr.meta_item_list().iter().flatten() {
+ if let Some(meta) = meta.meta_item()
+ && meta.name_or_empty() == sym::implement_via_object
+ && let Some(lit) = meta.name_value_literal()
+ {
+ if seen_attr {
+ tcx.sess.span_err(
+ meta.span,
+ "duplicated `implement_via_object` meta item",
+ );
+ }
+ seen_attr = true;
+
+ match lit.symbol {
+ kw::True => {
+ implement_via_object = true;
+ }
+ kw::False => {
+ implement_via_object = false;
+ }
+ _ => {
+ tcx.sess.span_err(
+ meta.span,
+ format!("unknown literal passed to `implement_via_object` attribute: {}", lit.symbol),
+ );
+ }
+ }
+ } else {
+ tcx.sess.span_err(
+ meta.span(),
+ format!("unknown meta item passed to `rustc_deny_explicit_impl` {:?}", meta),
+ );
+ }
+ }
+ if !seen_attr {
+ tcx.sess.span_err(attr.span, "missing `implement_via_object` meta item");
+ }
+ }
 
  ty::TraitDef {
  def_id: def_id.to_def_id(),

compiler/rustc_middle/src/ty/trait_def.rs

@@ -53,12 +53,14 @@ pub struct TraitDef {
  /// must be implemented.
  pub must_implement_one_of: Option<Box<[Ident]>>,
 
- /// Whether a type's built-in `dyn Trait: Trait` implementation is explicitly
- /// denied. This only applies to built-in trait, and is marked via
- /// `#[rustc_do_not_implement_via_object]`.
- pub do_not_implement_via_object: bool,
+ /// Whether to add a builtin `dyn Trait: Trait` implementation.
+ /// This is enabled for all traits except ones marked with
+ /// `#[rustc_deny_explicit_impl(implement_via_object = false)]`.
+ pub implement_via_object: bool,
 
  /// Whether a trait is fully built-in, and any implementation is disallowed.
+ /// This only applies to built-in traits, and is marked via
+ /// `#[rustc_deny_explicit_impl(implement_via_object = ...)]`.
  pub deny_explicit_impl: bool,
 }
 

compiler/rustc_passes/messages.ftl

@@ -102,9 +102,6 @@ passes_const_impl_const_trait =
  const `impl`s must be for traits marked with `#[const_trait]`
  .note = this trait must be annotated with `#[const_trait]`
 
-passes_const_trait =
- attribute should be applied to a trait
-
 passes_continue_labeled_block =
  `continue` pointing to a labeled block
  .label = labeled blocks cannot be `continue`'d

compiler/rustc_passes/src/check_attr.rs

@@ -110,9 +110,6 @@ impl CheckAttrVisitor<'_> {
  sym::no_coverage => self.check_no_coverage(hir_id, attr, span, target),
  sym::non_exhaustive => self.check_non_exhaustive(hir_id, attr, span, target),
  sym::marker => self.check_marker(hir_id, attr, span, target),
- sym::rustc_must_implement_one_of => {
- self.check_rustc_must_implement_one_of(attr, span, target)
- }
  sym::target_feature => self.check_target_feature(hir_id, attr, span, target),
  sym::thread_local => self.check_thread_local(attr, span, target),
  sym::track_caller => {
@@ -159,12 +156,14 @@ impl CheckAttrVisitor<'_> {
  | sym::rustc_dirty
  | sym::rustc_if_this_changed
  | sym::rustc_then_this_would_need => self.check_rustc_dirty_clean(&attr),
- sym::rustc_coinductive => self.check_rustc_coinductive(&attr, span, target),
+ sym::rustc_coinductive
+ | sym::rustc_must_implement_one_of
+ | sym::rustc_deny_explicit_impl
+ | sym::const_trait => self.check_must_be_applied_to_trait(&attr, span, target),
  sym::cmse_nonsecure_entry => {
  self.check_cmse_nonsecure_entry(hir_id, attr, span, target)
  }
  sym::collapse_debuginfo => self.check_collapse_debuginfo(attr, span, target),
- sym::const_trait => self.check_const_trait(attr, span, target),
  sym::must_not_suspend => self.check_must_not_suspend(&attr, span, target),
  sym::must_use => self.check_must_use(hir_id, &attr, target),
  sym::rustc_pass_by_value => self.check_pass_by_value(&attr, span, target),
@@ -567,25 +566,6 @@ impl CheckAttrVisitor<'_> {
  }
  }
 
- /// Checks if the `#[rustc_must_implement_one_of]` attribute on a `target` is valid. Returns `true` if valid.
- fn check_rustc_must_implement_one_of(
- &self,
- attr: &Attribute,
- span: Span,
- target: Target,
- ) -> bool {
- match target {
- Target::Trait => true,
- _ => {
- self.tcx.sess.emit_err(errors::AttrShouldBeAppliedToTrait {
- attr_span: attr.span,
- defn_span: span,
- });
- false
- }
- }
- }
-
  /// Checks if the `#[target_feature]` attribute on `item` is valid. Returns `true` if valid.
  fn check_target_feature(
  &self,
@@ -1591,8 +1571,8 @@ impl CheckAttrVisitor<'_> {
  }
  }
 
- /// Checks if the `#[rustc_coinductive]` attribute is applied to a trait.
- fn check_rustc_coinductive(&self, attr: &Attribute, span: Span, target: Target) -> bool {
+ /// Checks if the attribute is applied to a trait.
+ fn check_must_be_applied_to_trait(&self, attr: &Attribute, span: Span, target: Target) -> bool {
  match target {
  Target::Trait => true,
  _ => {
@@ -1986,17 +1966,6 @@ impl CheckAttrVisitor<'_> {
  }
  }
 
- /// `#[const_trait]` only applies to traits.
- fn check_const_trait(&self, attr: &Attribute, _span: Span, target: Target) -> bool {
- match target {
- Target::Trait => true,
- _ => {
- self.tcx.sess.emit_err(errors::ConstTrait { attr_span: attr.span });
- false
- }
- }
- }
-
  fn check_stability_promotable(&self, attr: &Attribute, _span: Span, target: Target) -> bool {
  match target {
  Target::Expression => {

compiler/rustc_passes/src/errors.rs

@@ -610,13 +610,6 @@ pub struct RustcStdInternalSymbol {
  pub span: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(passes_const_trait)]
-pub struct ConstTrait {
- #[primary_span]
- pub attr_span: Span,
-}
-
 #[derive(Diagnostic)]
 #[diag(passes_link_ordinal)]
 pub struct LinkOrdinal {

compiler/rustc_span/src/symbol.rs

@@ -817,6 +817,7 @@ symbols! {
  impl_trait_in_bindings,
  impl_trait_in_fn_trait_return,
  impl_trait_projections,
+ implement_via_object,
  implied_by,
  import,
  import_name_type,
@@ -1270,7 +1271,6 @@ symbols! {
  rustc_diagnostic_macros,
  rustc_dirty,
  rustc_do_not_const_check,
- rustc_do_not_implement_via_object,
  rustc_doc_primitive,
  rustc_dummy,
  rustc_dump_env_program_clauses,

compiler/rustc_trait_selection/src/traits/project.rs

@@ -1586,6 +1586,10 @@ fn assemble_candidates_from_object_ty<'cx, 'tcx>(
 
  let tcx = selcx.tcx();
 
+ if !tcx.trait_def(obligation.predicate.trait_def_id(tcx)).implement_via_object {
+ return;
+ }
+
  let self_ty = obligation.predicate.self_ty();
  let object_ty = selcx.infcx.shallow_resolve(self_ty);
  let data = match object_ty.kind() {

compiler/rustc_trait_selection/src/traits/select/candidate_assembly.rs

@@ -554,6 +554,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
  "assemble_candidates_from_object_ty",
  );
 
+ if !self.tcx().trait_def(obligation.predicate.def_id()).implement_via_object {
+ return;
+ }
+
  self.infcx.probe(|_snapshot| {
  if obligation.has_non_region_late_bound() {
  return;

library/core/src/marker.rs

@@ -140,7 +140,8 @@ unsafe impl<T: Sync + ?Sized> Send for &T {}
 )]
 #[fundamental] // for Default, for example, which requires that `[T]: !Default` be evaluatable
 #[rustc_specialization_trait]
-#[rustc_deny_explicit_impl]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 #[rustc_coinductive]
 pub trait Sized {
  // Empty.
@@ -173,8 +174,8 @@ pub trait Sized {
 /// [nomicon-coerce]: ../../nomicon/coercions.html
 #[unstable(feature = "unsize", issue = "18598")]
 #[lang = "unsize"]
-#[rustc_deny_explicit_impl]
-#[cfg_attr(not(bootstrap), rustc_do_not_implement_via_object)]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 pub trait Unsize<T: ?Sized> {
  // Empty.
 }
@@ -855,8 +856,8 @@ impl<T: ?Sized> StructuralEq for PhantomData<T> {}
  reason = "this trait is unlikely to ever be stabilized, use `mem::discriminant` instead"
 )]
 #[lang = "discriminant_kind"]
-#[rustc_deny_explicit_impl]
-#[cfg_attr(not(bootstrap), rustc_do_not_implement_via_object)]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 pub trait DiscriminantKind {
  /// The type of the discriminant, which must satisfy the trait
  /// bounds required by `mem::Discriminant`.
@@ -961,8 +962,8 @@ marker_impls! {
 #[unstable(feature = "const_trait_impl", issue = "67792")]
 #[lang = "destruct"]
 #[rustc_on_unimplemented(message = "can't drop `{Self}`", append_const_msg)]
-#[rustc_deny_explicit_impl]
-#[cfg_attr(not(bootstrap), rustc_do_not_implement_via_object)]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 #[const_trait]
 pub trait Destruct {}
 
@@ -973,8 +974,8 @@ pub trait Destruct {}
 #[unstable(feature = "tuple_trait", issue = "none")]
 #[lang = "tuple_trait"]
 #[rustc_on_unimplemented(message = "`{Self}` is not a tuple")]
-#[rustc_deny_explicit_impl]
-#[cfg_attr(not(bootstrap), rustc_do_not_implement_via_object)]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 pub trait Tuple {}
 
 /// A marker for pointer-like types.
@@ -1029,7 +1030,8 @@ impl ConstParamTy for () {}
  reason = "internal trait for implementing various traits for all function pointers"
 )]
 #[lang = "fn_ptr_trait"]
-#[rustc_deny_explicit_impl]
+#[cfg_attr(not(bootstrap), rustc_deny_explicit_impl(implement_via_object = false))]
+#[cfg_attr(bootstrap, rustc_deny_explicit_impl)]
 pub trait FnPtr: Copy + Clone {
  /// Returns the address of the function pointer.
  #[lang = "fn_ptr_addr"]