//! A pass that annotates every item and method with its stability level, //! propagating default levels lexically from parent to children ast nodes. use rustc_ast::Attribute; use rustc_attr::{self as attr, ConstStability, Stability}; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_errors::struct_span_err; use rustc_hir as hir; use rustc_hir::def::{DefKind, Res}; use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_INDEX, LOCAL_CRATE}; use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor}; use rustc_hir::{Generics, HirId, Item, StructField, TraitRef, Ty, TyKind, Variant}; use rustc_middle::hir::map::Map; use rustc_middle::middle::privacy::AccessLevels; use rustc_middle::middle::stability::{DeprecationEntry, Index}; use rustc_middle::ty::{self, query::Providers, TyCtxt}; use rustc_session::lint; use rustc_session::lint::builtin::{INEFFECTIVE_UNSTABLE_TRAIT_IMPL, USELESS_DEPRECATED}; use rustc_session::parse::feature_err; use rustc_session::Session; use rustc_span::symbol::{sym, Symbol}; use rustc_span::{Span, DUMMY_SP}; use std::cmp::Ordering; use std::mem::replace; use std::num::NonZeroU32; #[derive(PartialEq)] enum AnnotationKind { // Annotation is required if not inherited from unstable parents Required, // Annotation is useless, reject it Prohibited, // Deprecation annotation is useless, reject it. (Stability attribute is still required.) DeprecationProhibited, // Annotation itself is useless, but it can be propagated to children Container, } /// Whether to inherit deprecation flags for nested items. In most cases, we do want to inherit /// deprecation, because nested items rarely have individual deprecation attributes, and so /// should be treated as deprecated if their parent is. However, default generic parameters /// have separate deprecation attributes from their parents, so we do not wish to inherit /// deprecation in this case. For example, inheriting deprecation for `T` in `Foo` /// would cause a duplicate warning arising from both `Foo` and `T` being deprecated. #[derive(Clone)] enum InheritDeprecation { Yes, No, } impl InheritDeprecation { fn yes(&self) -> bool { matches!(self, InheritDeprecation::Yes) } } // A private tree-walker for producing an Index. struct Annotator<'a, 'tcx> { tcx: TyCtxt<'tcx>, index: &'a mut Index<'tcx>, parent_stab: Option<&'tcx Stability>, parent_const_stab: Option<&'tcx ConstStability>, parent_depr: Option, in_trait_impl: bool, } impl<'a, 'tcx> Annotator<'a, 'tcx> { // Determine the stability for a node based on its attributes and inherited // stability. The stability is recorded in the index and used as the parent. fn annotate( &mut self, hir_id: HirId, attrs: &[Attribute], item_sp: Span, kind: AnnotationKind, inherit_deprecation: InheritDeprecation, visit_children: F, ) where F: FnOnce(&mut Self), { debug!("annotate(id = {:?}, attrs = {:?})", hir_id, attrs); let mut did_error = false; if !self.tcx.features().staged_api { did_error = self.forbid_staged_api_attrs(hir_id, attrs, inherit_deprecation.clone()); } let depr = if did_error { None } else { attr::find_deprecation(&self.tcx.sess, attrs) }; let mut is_deprecated = false; if let Some((depr, span)) = &depr { is_deprecated = true; if kind == AnnotationKind::Prohibited || kind == AnnotationKind::DeprecationProhibited { self.tcx.struct_span_lint_hir(USELESS_DEPRECATED, hir_id, *span, |lint| { lint.build("this `#[deprecated]` annotation has no effect") .span_suggestion_short( *span, "remove the unnecessary deprecation attribute", String::new(), rustc_errors::Applicability::MachineApplicable, ) .emit() }); } // `Deprecation` is just two pointers, no need to intern it let depr_entry = DeprecationEntry::local(depr.clone(), hir_id); self.index.depr_map.insert(hir_id, depr_entry); } else if let Some(parent_depr) = self.parent_depr.clone() { if inherit_deprecation.yes() { is_deprecated = true; info!("tagging child {:?} as deprecated from parent", hir_id); self.index.depr_map.insert(hir_id, parent_depr); } } if self.tcx.features().staged_api { if let Some(..) = attrs.iter().find(|a| self.tcx.sess.check_name(a, sym::deprecated)) { self.tcx.sess.span_err( item_sp, "`#[deprecated]` cannot be used in staged API; \ use `#[rustc_deprecated]` instead", ); } } else { self.recurse_with_stability_attrs( depr.map(|(d, _)| DeprecationEntry::local(d, hir_id)), None, None, visit_children, ); return; } let (stab, const_stab) = attr::find_stability(&self.tcx.sess, attrs, item_sp); let const_stab = const_stab.map(|const_stab| { let const_stab = self.tcx.intern_const_stability(const_stab); self.index.const_stab_map.insert(hir_id, const_stab); const_stab }); if const_stab.is_none() { debug!("annotate: const_stab not found, parent = {:?}", self.parent_const_stab); if let Some(parent) = self.parent_const_stab { if parent.level.is_unstable() { self.index.const_stab_map.insert(hir_id, parent); } } } if let Some((rustc_attr::Deprecation { is_since_rustc_version: true, .. }, span)) = &depr { if stab.is_none() { struct_span_err!( self.tcx.sess, *span, E0549, "rustc_deprecated attribute must be paired with \ either stable or unstable attribute" ) .emit(); } } let stab = stab.map(|stab| { // Error if prohibited, or can't inherit anything from a container. if kind == AnnotationKind::Prohibited || (kind == AnnotationKind::Container && stab.level.is_stable() && is_deprecated) { self.tcx.sess.span_err(item_sp, "This stability annotation is useless"); } debug!("annotate: found {:?}", stab); let stab = self.tcx.intern_stability(stab); // Check if deprecated_since < stable_since. If it is, // this is *almost surely* an accident. if let (&Some(dep_since), &attr::Stable { since: stab_since }) = (&depr.as_ref().and_then(|(d, _)| d.since), &stab.level) { // Explicit version of iter::order::lt to handle parse errors properly for (dep_v, stab_v) in dep_since.as_str().split('.').zip(stab_since.as_str().split('.')) { match stab_v.parse::() { Err(_) => { self.tcx.sess.span_err(item_sp, "Invalid stability version found"); break; } Ok(stab_vp) => match dep_v.parse::() { Ok(dep_vp) => match dep_vp.cmp(&stab_vp) { Ordering::Less => { self.tcx.sess.span_err( item_sp, "An API can't be stabilized after it is deprecated", ); break; } Ordering::Equal => continue, Ordering::Greater => break, }, Err(_) => { if dep_v != "TBD" { self.tcx .sess .span_err(item_sp, "Invalid deprecation version found"); } break; } }, } } } self.index.stab_map.insert(hir_id, stab); stab }); if stab.is_none() { debug!("annotate: stab not found, parent = {:?}", self.parent_stab); if let Some(stab) = self.parent_stab { if inherit_deprecation.yes() && stab.level.is_unstable() { self.index.stab_map.insert(hir_id, stab); } } } self.recurse_with_stability_attrs( depr.map(|(d, _)| DeprecationEntry::local(d, hir_id)), stab, const_stab, visit_children, ); } fn recurse_with_stability_attrs( &mut self, depr: Option, stab: Option<&'tcx Stability>, const_stab: Option<&'tcx ConstStability>, f: impl FnOnce(&mut Self), ) { // These will be `Some` if this item changes the corresponding stability attribute. let mut replaced_parent_depr = None; let mut replaced_parent_stab = None; let mut replaced_parent_const_stab = None; if let Some(depr) = depr { replaced_parent_depr = Some(replace(&mut self.parent_depr, Some(depr))); } if let Some(stab) = stab { replaced_parent_stab = Some(replace(&mut self.parent_stab, Some(stab))); } if let Some(const_stab) = const_stab { replaced_parent_const_stab = Some(replace(&mut self.parent_const_stab, Some(const_stab))); } f(self); if let Some(orig_parent_depr) = replaced_parent_depr { self.parent_depr = orig_parent_depr; } if let Some(orig_parent_stab) = replaced_parent_stab { self.parent_stab = orig_parent_stab; } if let Some(orig_parent_const_stab) = replaced_parent_const_stab { self.parent_const_stab = orig_parent_const_stab; } } // returns true if an error occurred, used to suppress some spurious errors fn forbid_staged_api_attrs( &mut self, hir_id: HirId, attrs: &[Attribute], inherit_deprecation: InheritDeprecation, ) -> bool { // Emit errors for non-staged-api crates. let unstable_attrs = [ sym::unstable, sym::stable, sym::rustc_deprecated, sym::rustc_const_unstable, sym::rustc_const_stable, ]; let mut has_error = false; for attr in attrs { let name = attr.name_or_empty(); if unstable_attrs.contains(&name) { self.tcx.sess.mark_attr_used(attr); struct_span_err!( self.tcx.sess, attr.span, E0734, "stability attributes may not be used outside of the standard library", ) .emit(); has_error = true; } } // Propagate unstability. This can happen even for non-staged-api crates in case // -Zforce-unstable-if-unmarked is set. if let Some(stab) = self.parent_stab { if inherit_deprecation.yes() && stab.level.is_unstable() { self.index.stab_map.insert(hir_id, stab); } } has_error } } impl<'a, 'tcx> Visitor<'tcx> for Annotator<'a, 'tcx> { /// Because stability levels are scoped lexically, we want to walk /// nested items in the context of the outer item, so enable /// deep-walking. type Map = Map<'tcx>; fn nested_visit_map(&mut self) -> NestedVisitorMap { NestedVisitorMap::All(self.tcx.hir()) } fn visit_item(&mut self, i: &'tcx Item<'tcx>) { let orig_in_trait_impl = self.in_trait_impl; let mut kind = AnnotationKind::Required; match i.kind { // Inherent impls and foreign modules serve only as containers for other items, // they don't have their own stability. They still can be annotated as unstable // and propagate this unstability to children, but this annotation is completely // optional. They inherit stability from their parents when unannotated. hir::ItemKind::Impl { of_trait: None, .. } | hir::ItemKind::ForeignMod { .. } => { self.in_trait_impl = false; kind = AnnotationKind::Container; } hir::ItemKind::Impl { of_trait: Some(_), .. } => { self.in_trait_impl = true; kind = AnnotationKind::DeprecationProhibited; } hir::ItemKind::Struct(ref sd, _) => { if let Some(ctor_hir_id) = sd.ctor_hir_id() { self.annotate( ctor_hir_id, &i.attrs, i.span, AnnotationKind::Required, InheritDeprecation::Yes, |_| {}, ) } } _ => {} } self.annotate(i.hir_id, &i.attrs, i.span, kind, InheritDeprecation::Yes, |v| { intravisit::walk_item(v, i) }); self.in_trait_impl = orig_in_trait_impl; } fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem<'tcx>) { self.annotate( ti.hir_id, &ti.attrs, ti.span, AnnotationKind::Required, InheritDeprecation::Yes, |v| { intravisit::walk_trait_item(v, ti); }, ); } fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem<'tcx>) { let kind = if self.in_trait_impl { AnnotationKind::Prohibited } else { AnnotationKind::Required }; self.annotate(ii.hir_id, &ii.attrs, ii.span, kind, InheritDeprecation::Yes, |v| { intravisit::walk_impl_item(v, ii); }); } fn visit_variant(&mut self, var: &'tcx Variant<'tcx>, g: &'tcx Generics<'tcx>, item_id: HirId) { self.annotate( var.id, &var.attrs, var.span, AnnotationKind::Required, InheritDeprecation::Yes, |v| { if let Some(ctor_hir_id) = var.data.ctor_hir_id() { v.annotate( ctor_hir_id, &var.attrs, var.span, AnnotationKind::Required, InheritDeprecation::Yes, |_| {}, ); } intravisit::walk_variant(v, var, g, item_id) }, ) } fn visit_struct_field(&mut self, s: &'tcx StructField<'tcx>) { self.annotate( s.hir_id, &s.attrs, s.span, AnnotationKind::Required, InheritDeprecation::Yes, |v| { intravisit::walk_struct_field(v, s); }, ); } fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem<'tcx>) { self.annotate( i.hir_id, &i.attrs, i.span, AnnotationKind::Required, InheritDeprecation::Yes, |v| { intravisit::walk_foreign_item(v, i); }, ); } fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef<'tcx>) { self.annotate( md.hir_id, &md.attrs, md.span, AnnotationKind::Required, InheritDeprecation::Yes, |_| {}, ); } fn visit_generic_param(&mut self, p: &'tcx hir::GenericParam<'tcx>) { let kind = match &p.kind { // FIXME(const_generics_defaults) hir::GenericParamKind::Type { default, .. } if default.is_some() => { AnnotationKind::Container } _ => AnnotationKind::Prohibited, }; self.annotate(p.hir_id, &p.attrs, p.span, kind, InheritDeprecation::No, |v| { intravisit::walk_generic_param(v, p); }); } } struct MissingStabilityAnnotations<'tcx> { tcx: TyCtxt<'tcx>, access_levels: &'tcx AccessLevels, } impl<'tcx> MissingStabilityAnnotations<'tcx> { fn check_missing_stability(&self, hir_id: HirId, span: Span) { let stab = self.tcx.stability().local_stability(hir_id); let is_error = !self.tcx.sess.opts.test && stab.is_none() && self.access_levels.is_reachable(hir_id); if is_error { let def_id = self.tcx.hir().local_def_id(hir_id); let descr = self.tcx.def_kind(def_id).descr(def_id.to_def_id()); self.tcx.sess.span_err(span, &format!("{} has missing stability attribute", descr)); } } fn check_missing_const_stability(&self, hir_id: HirId, span: Span) { let stab_map = self.tcx.stability(); let stab = stab_map.local_stability(hir_id); if stab.map_or(false, |stab| stab.level.is_stable()) { let const_stab = stab_map.local_const_stability(hir_id); if const_stab.is_none() { self.tcx.sess.span_err( span, "`#[stable]` const functions must also be either \ `#[rustc_const_stable]` or `#[rustc_const_unstable]`", ); } } } } impl<'tcx> Visitor<'tcx> for MissingStabilityAnnotations<'tcx> { type Map = Map<'tcx>; fn nested_visit_map(&mut self) -> NestedVisitorMap { NestedVisitorMap::OnlyBodies(self.tcx.hir()) } fn visit_item(&mut self, i: &'tcx Item<'tcx>) { // Inherent impls and foreign modules serve only as containers for other items, // they don't have their own stability. They still can be annotated as unstable // and propagate this unstability to children, but this annotation is completely // optional. They inherit stability from their parents when unannotated. if !matches!( i.kind, hir::ItemKind::Impl { of_trait: None, .. } | hir::ItemKind::ForeignMod { .. } ) { self.check_missing_stability(i.hir_id, i.span); } // Ensure `const fn` that are `stable` have one of `rustc_const_unstable` or // `rustc_const_stable`. if self.tcx.features().staged_api && matches!(&i.kind, hir::ItemKind::Fn(sig, ..) if sig.header.is_const()) { self.check_missing_const_stability(i.hir_id, i.span); } intravisit::walk_item(self, i) } fn visit_trait_item(&mut self, ti: &'tcx hir::TraitItem<'tcx>) { self.check_missing_stability(ti.hir_id, ti.span); intravisit::walk_trait_item(self, ti); } fn visit_impl_item(&mut self, ii: &'tcx hir::ImplItem<'tcx>) { let impl_def_id = self.tcx.hir().local_def_id(self.tcx.hir().get_parent_item(ii.hir_id)); if self.tcx.impl_trait_ref(impl_def_id).is_none() { self.check_missing_stability(ii.hir_id, ii.span); } intravisit::walk_impl_item(self, ii); } fn visit_variant(&mut self, var: &'tcx Variant<'tcx>, g: &'tcx Generics<'tcx>, item_id: HirId) { self.check_missing_stability(var.id, var.span); intravisit::walk_variant(self, var, g, item_id); } fn visit_struct_field(&mut self, s: &'tcx StructField<'tcx>) { self.check_missing_stability(s.hir_id, s.span); intravisit::walk_struct_field(self, s); } fn visit_foreign_item(&mut self, i: &'tcx hir::ForeignItem<'tcx>) { self.check_missing_stability(i.hir_id, i.span); intravisit::walk_foreign_item(self, i); } fn visit_macro_def(&mut self, md: &'tcx hir::MacroDef<'tcx>) { self.check_missing_stability(md.hir_id, md.span); } // Note that we don't need to `check_missing_stability` for default generic parameters, // as we assume that any default generic parameters without attributes are automatically // stable (assuming they have not inherited instability from their parent). } fn new_index(tcx: TyCtxt<'tcx>) -> Index<'tcx> { let is_staged_api = tcx.sess.opts.debugging_opts.force_unstable_if_unmarked || tcx.features().staged_api; let mut staged_api = FxHashMap::default(); staged_api.insert(LOCAL_CRATE, is_staged_api); let mut index = Index { staged_api, stab_map: Default::default(), const_stab_map: Default::default(), depr_map: Default::default(), active_features: Default::default(), }; let active_lib_features = &tcx.features().declared_lib_features; let active_lang_features = &tcx.features().declared_lang_features; // Put the active features into a map for quick lookup. index.active_features = active_lib_features .iter() .map(|&(s, ..)| s) .chain(active_lang_features.iter().map(|&(s, ..)| s)) .collect(); { let krate = tcx.hir().krate(); let mut annotator = Annotator { tcx, index: &mut index, parent_stab: None, parent_const_stab: None, parent_depr: None, in_trait_impl: false, }; // If the `-Z force-unstable-if-unmarked` flag is passed then we provide // a parent stability annotation which indicates that this is private // with the `rustc_private` feature. This is intended for use when // compiling `librustc_*` crates themselves so we can leverage crates.io // while maintaining the invariant that all sysroot crates are unstable // by default and are unable to be used. if tcx.sess.opts.debugging_opts.force_unstable_if_unmarked { let reason = "this crate is being loaded from the sysroot, an \ unstable location; did you mean to load this crate \ from crates.io via `Cargo.toml` instead?"; let stability = tcx.intern_stability(Stability { level: attr::StabilityLevel::Unstable { reason: Some(Symbol::intern(reason)), issue: NonZeroU32::new(27812), is_soft: false, }, feature: sym::rustc_private, }); annotator.parent_stab = Some(stability); } annotator.annotate( hir::CRATE_HIR_ID, &krate.item.attrs, krate.item.span, AnnotationKind::Required, InheritDeprecation::Yes, |v| intravisit::walk_crate(v, krate), ); } index } /// Cross-references the feature names of unstable APIs with enabled /// features and possibly prints errors. fn check_mod_unstable_api_usage(tcx: TyCtxt<'_>, module_def_id: LocalDefId) { tcx.hir().visit_item_likes_in_module(module_def_id, &mut Checker { tcx }.as_deep_visitor()); } pub(crate) fn provide(providers: &mut Providers) { *providers = Providers { check_mod_unstable_api_usage, ..*providers }; providers.stability_index = |tcx, cnum| { assert_eq!(cnum, LOCAL_CRATE); new_index(tcx) }; } struct Checker<'tcx> { tcx: TyCtxt<'tcx>, } impl Visitor<'tcx> for Checker<'tcx> { type Map = Map<'tcx>; /// Because stability levels are scoped lexically, we want to walk /// nested items in the context of the outer item, so enable /// deep-walking. fn nested_visit_map(&mut self) -> NestedVisitorMap { NestedVisitorMap::OnlyBodies(self.tcx.hir()) } fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) { match item.kind { hir::ItemKind::ExternCrate(_) => { // compiler-generated `extern crate` items have a dummy span. // `std` is still checked for the `restricted-std` feature. if item.span.is_dummy() && item.ident.as_str() != "std" { return; } let def_id = self.tcx.hir().local_def_id(item.hir_id); let cnum = match self.tcx.extern_mod_stmt_cnum(def_id) { Some(cnum) => cnum, None => return, }; let def_id = DefId { krate: cnum, index: CRATE_DEF_INDEX }; self.tcx.check_stability(def_id, Some(item.hir_id), item.span); } // For implementations of traits, check the stability of each item // individually as it's possible to have a stable trait with unstable // items. hir::ItemKind::Impl { of_trait: Some(ref t), self_ty, items, .. } => { if self.tcx.features().staged_api { // If this impl block has an #[unstable] attribute, give an // error if all involved types and traits are stable, because // it will have no effect. // See: https://github.com/rust-lang/rust/issues/55436 if let (Some(Stability { level: attr::Unstable { .. }, .. }), _) = attr::find_stability(&self.tcx.sess, &item.attrs, item.span) { let mut c = CheckTraitImplStable { tcx: self.tcx, fully_stable: true }; c.visit_ty(self_ty); c.visit_trait_ref(t); if c.fully_stable { let span = item .attrs .iter() .find(|a| a.has_name(sym::unstable)) .map_or(item.span, |a| a.span); self.tcx.struct_span_lint_hir( INEFFECTIVE_UNSTABLE_TRAIT_IMPL, item.hir_id, span, |lint| lint .build("an `#[unstable]` annotation here has no effect") .note("see issue #55436 for more information") .emit() ); } } } if let Res::Def(DefKind::Trait, trait_did) = t.path.res { for impl_item_ref in items { let impl_item = self.tcx.hir().impl_item(impl_item_ref.id); let trait_item_def_id = self .tcx .associated_items(trait_did) .filter_by_name_unhygienic(impl_item.ident.name) .next() .map(|item| item.def_id); if let Some(def_id) = trait_item_def_id { // Pass `None` to skip deprecation warnings. self.tcx.check_stability(def_id, None, impl_item.span); } } } } // There's no good place to insert stability check for non-Copy unions, // so semi-randomly perform it here in stability.rs hir::ItemKind::Union(..) if !self.tcx.features().untagged_unions => { let def_id = self.tcx.hir().local_def_id(item.hir_id); let ty = self.tcx.type_of(def_id); let (adt_def, substs) = match ty.kind() { ty::Adt(adt_def, substs) => (adt_def, substs), _ => bug!(), }; // Non-`Copy` fields are unstable, except for `ManuallyDrop`. let param_env = self.tcx.param_env(def_id); for field in &adt_def.non_enum_variant().fields { let field_ty = field.ty(self.tcx, substs); if !field_ty.ty_adt_def().map_or(false, |adt_def| adt_def.is_manually_drop()) && !field_ty.is_copy_modulo_regions(self.tcx.at(DUMMY_SP), param_env) { if field_ty.needs_drop(self.tcx, param_env) { // Avoid duplicate error: This will error later anyway because fields // that need drop are not allowed. self.tcx.sess.delay_span_bug( item.span, "union should have been rejected due to potentially dropping field", ); } else { feature_err( &self.tcx.sess.parse_sess, sym::untagged_unions, self.tcx.def_span(field.did), "unions with non-`Copy` fields other than `ManuallyDrop` are unstable", ) .emit(); } } } } _ => (/* pass */), } intravisit::walk_item(self, item); } fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, id: hir::HirId) { if let Some(def_id) = path.res.opt_def_id() { self.tcx.check_stability(def_id, Some(id), path.span) } intravisit::walk_path(self, path) } } struct CheckTraitImplStable<'tcx> { tcx: TyCtxt<'tcx>, fully_stable: bool, } impl Visitor<'tcx> for CheckTraitImplStable<'tcx> { type Map = Map<'tcx>; fn nested_visit_map(&mut self) -> NestedVisitorMap { NestedVisitorMap::None } fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, _id: hir::HirId) { if let Some(def_id) = path.res.opt_def_id() { if let Some(stab) = self.tcx.lookup_stability(def_id) { self.fully_stable &= stab.level.is_stable(); } } intravisit::walk_path(self, path) } fn visit_trait_ref(&mut self, t: &'tcx TraitRef<'tcx>) { if let Res::Def(DefKind::Trait, trait_did) = t.path.res { if let Some(stab) = self.tcx.lookup_stability(trait_did) { self.fully_stable &= stab.level.is_stable(); } } intravisit::walk_trait_ref(self, t) } fn visit_ty(&mut self, t: &'tcx Ty<'tcx>) { if let TyKind::Never = t.kind { self.fully_stable = false; } intravisit::walk_ty(self, t) } } /// Given the list of enabled features that were not language features (i.e., that /// were expected to be library features), and the list of features used from /// libraries, identify activated features that don't exist and error about them. pub fn check_unused_or_stable_features(tcx: TyCtxt<'_>) { let access_levels = &tcx.privacy_access_levels(LOCAL_CRATE); if tcx.stability().staged_api[&LOCAL_CRATE] { let krate = tcx.hir().krate(); let mut missing = MissingStabilityAnnotations { tcx, access_levels }; missing.check_missing_stability(hir::CRATE_HIR_ID, krate.item.span); intravisit::walk_crate(&mut missing, krate); krate.visit_all_item_likes(&mut missing.as_deep_visitor()); } let declared_lang_features = &tcx.features().declared_lang_features; let mut lang_features = FxHashSet::default(); for &(feature, span, since) in declared_lang_features { if let Some(since) = since { // Warn if the user has enabled an already-stable lang feature. unnecessary_stable_feature_lint(tcx, span, feature, since); } if !lang_features.insert(feature) { // Warn if the user enables a lang feature multiple times. duplicate_feature_err(tcx.sess, span, feature); } } let declared_lib_features = &tcx.features().declared_lib_features; let mut remaining_lib_features = FxHashMap::default(); for (feature, span) in declared_lib_features { if remaining_lib_features.contains_key(&feature) { // Warn if the user enables a lib feature multiple times. duplicate_feature_err(tcx.sess, *span, *feature); } remaining_lib_features.insert(feature, *span); } // `stdbuild` has special handling for `libc`, so we need to // recognise the feature when building std. // Likewise, libtest is handled specially, so `test` isn't // available as we'd like it to be. // FIXME: only remove `libc` when `stdbuild` is active. // FIXME: remove special casing for `test`. remaining_lib_features.remove(&sym::libc); remaining_lib_features.remove(&sym::test); let check_features = |remaining_lib_features: &mut FxHashMap<_, _>, defined_features: &[_]| { for &(feature, since) in defined_features { if let Some(since) = since { if let Some(span) = remaining_lib_features.get(&feature) { // Warn if the user has enabled an already-stable lib feature. unnecessary_stable_feature_lint(tcx, *span, feature, since); } } remaining_lib_features.remove(&feature); if remaining_lib_features.is_empty() { break; } } }; // We always collect the lib features declared in the current crate, even if there are // no unknown features, because the collection also does feature attribute validation. let local_defined_features = tcx.lib_features().to_vec(); if !remaining_lib_features.is_empty() { check_features(&mut remaining_lib_features, &local_defined_features); for &cnum in &*tcx.crates() { if remaining_lib_features.is_empty() { break; } check_features(&mut remaining_lib_features, tcx.defined_lib_features(cnum)); } } for (feature, span) in remaining_lib_features { struct_span_err!(tcx.sess, span, E0635, "unknown feature `{}`", feature).emit(); } // FIXME(#44232): the `used_features` table no longer exists, so we // don't lint about unused features. We should re-enable this one day! } fn unnecessary_stable_feature_lint(tcx: TyCtxt<'_>, span: Span, feature: Symbol, since: Symbol) { tcx.struct_span_lint_hir(lint::builtin::STABLE_FEATURES, hir::CRATE_HIR_ID, span, |lint| { lint.build(&format!( "the feature `{}` has been stable since {} and no longer requires \ an attribute to enable", feature, since )) .emit(); }); } fn duplicate_feature_err(sess: &Session, span: Span, feature: Symbol) { struct_span_err!(sess, span, E0636, "the feature `{}` has already been declared", feature) .emit(); }