| //! Detecting lib features (i.e., features that are not lang features). |
| //! |
| //! These are declared using stability attributes (e.g., `#[stable (..)]` and `#[unstable (..)]`), |
| //! but are not declared in one single location (unlike lang features), which means we need to |
| //! collect them instead. |
| |
| use rustc_ast::Attribute; |
| use rustc_attr::VERSION_PLACEHOLDER; |
| use rustc_hir::intravisit::Visitor; |
| use rustc_middle::hir::nested_filter; |
| use rustc_middle::middle::lib_features::{FeatureStability, LibFeatures}; |
| use rustc_middle::query::{LocalCrate, Providers}; |
| use rustc_middle::ty::TyCtxt; |
| use rustc_span::symbol::Symbol; |
| use rustc_span::{sym, Span}; |
| |
| use crate::errors::{FeaturePreviouslyDeclared, FeatureStableTwice}; |
| |
| pub struct LibFeatureCollector<'tcx> { |
| tcx: TyCtxt<'tcx>, |
| lib_features: LibFeatures, |
| } |
| |
| impl<'tcx> LibFeatureCollector<'tcx> { |
| fn new(tcx: TyCtxt<'tcx>) -> LibFeatureCollector<'tcx> { |
| LibFeatureCollector { tcx, lib_features: LibFeatures::default() } |
| } |
| |
| fn extract(&self, attr: &Attribute) -> Option<(Symbol, FeatureStability, Span)> { |
| let stab_attrs = [ |
| sym::stable, |
| sym::unstable, |
| sym::rustc_const_stable, |
| sym::rustc_const_unstable, |
| sym::rustc_default_body_unstable, |
| ]; |
| |
| // Find a stability attribute: one of #[stable(…)], #[unstable(…)], |
| // #[rustc_const_stable(…)], #[rustc_const_unstable(…)] or #[rustc_default_body_unstable]. |
| if let Some(stab_attr) = stab_attrs.iter().find(|stab_attr| attr.has_name(**stab_attr)) { |
| if let Some(metas) = attr.meta_item_list() { |
| let mut feature = None; |
| let mut since = None; |
| for meta in metas { |
| if let Some(mi) = meta.meta_item() { |
| // Find the `feature = ".."` meta-item. |
| match (mi.name_or_empty(), mi.value_str()) { |
| (sym::feature, val) => feature = val, |
| (sym::since, val) => since = val, |
| _ => {} |
| } |
| } |
| } |
| |
| if let Some(s) = since |
| && s.as_str() == VERSION_PLACEHOLDER |
| { |
| since = Some(sym::env_CFG_RELEASE); |
| } |
| |
| if let Some(feature) = feature { |
| // This additional check for stability is to make sure we |
| // don't emit additional, irrelevant errors for malformed |
| // attributes. |
| let is_unstable = matches!( |
| *stab_attr, |
| sym::unstable |
| | sym::rustc_const_unstable |
| | sym::rustc_default_body_unstable |
| ); |
| if is_unstable { |
| return Some((feature, FeatureStability::Unstable, attr.span)); |
| } |
| if let Some(since) = since { |
| return Some((feature, FeatureStability::AcceptedSince(since), attr.span)); |
| } |
| } |
| // We need to iterate over the other attributes, because |
| // `rustc_const_unstable` is not mutually exclusive with |
| // the other stability attributes, so we can't just `break` |
| // here. |
| } |
| } |
| |
| None |
| } |
| |
| fn collect_feature(&mut self, feature: Symbol, stability: FeatureStability, span: Span) { |
| let existing_stability = self.lib_features.stability.get(&feature).cloned(); |
| |
| match (stability, existing_stability) { |
| (_, None) => { |
| self.lib_features.stability.insert(feature, (stability, span)); |
| } |
| ( |
| FeatureStability::AcceptedSince(since), |
| Some((FeatureStability::AcceptedSince(prev_since), _)), |
| ) => { |
| if prev_since != since { |
| self.tcx.dcx().emit_err(FeatureStableTwice { |
| span, |
| feature, |
| since, |
| prev_since, |
| }); |
| } |
| } |
| (FeatureStability::AcceptedSince(_), Some((FeatureStability::Unstable, _))) => { |
| self.tcx.dcx().emit_err(FeaturePreviouslyDeclared { |
| span, |
| feature, |
| declared: "stable", |
| prev_declared: "unstable", |
| }); |
| } |
| (FeatureStability::Unstable, Some((FeatureStability::AcceptedSince(_), _))) => { |
| self.tcx.dcx().emit_err(FeaturePreviouslyDeclared { |
| span, |
| feature, |
| declared: "unstable", |
| prev_declared: "stable", |
| }); |
| } |
| // duplicate `unstable` feature is ok. |
| (FeatureStability::Unstable, Some((FeatureStability::Unstable, _))) => {} |
| } |
| } |
| } |
| |
| impl<'tcx> Visitor<'tcx> for LibFeatureCollector<'tcx> { |
| type NestedFilter = nested_filter::All; |
| |
| fn nested_visit_map(&mut self) -> Self::Map { |
| self.tcx.hir() |
| } |
| |
| fn visit_attribute(&mut self, attr: &'tcx Attribute) { |
| if let Some((feature, stable, span)) = self.extract(attr) { |
| self.collect_feature(feature, stable, span); |
| } |
| } |
| } |
| |
| fn lib_features(tcx: TyCtxt<'_>, LocalCrate: LocalCrate) -> LibFeatures { |
| // If `staged_api` is not enabled then we aren't allowed to define lib |
| // features; there is no point collecting them. |
| if !tcx.features().staged_api { |
| return LibFeatures::default(); |
| } |
| |
| let mut collector = LibFeatureCollector::new(tcx); |
| tcx.hir().walk_attributes(&mut collector); |
| collector.lib_features |
| } |
| |
| pub fn provide(providers: &mut Providers) { |
| providers.lib_features = lib_features; |
| } |