diff options
Diffstat (limited to '')
-rw-r--r-- | compiler/rustc_passes/src/lib_features.rs | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/compiler/rustc_passes/src/lib_features.rs b/compiler/rustc_passes/src/lib_features.rs new file mode 100644 index 000000000..e05994f13 --- /dev/null +++ b/compiler/rustc_passes/src/lib_features.rs @@ -0,0 +1,138 @@ +//! 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, MetaItemKind}; +use rustc_errors::struct_span_err; +use rustc_hir::intravisit::Visitor; +use rustc_middle::hir::nested_filter; +use rustc_middle::middle::lib_features::LibFeatures; +use rustc_middle::ty::query::Providers; +use rustc_middle::ty::TyCtxt; +use rustc_span::symbol::Symbol; +use rustc_span::{sym, Span}; + +fn new_lib_features() -> LibFeatures { + LibFeatures { stable: Default::default(), unstable: Default::default() } +} + +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: new_lib_features() } + } + + fn extract(&self, attr: &Attribute) -> Option<(Symbol, Option<Symbol>, Span)> { + let stab_attrs = + [sym::stable, sym::unstable, sym::rustc_const_stable, sym::rustc_const_unstable]; + + // Find a stability attribute: one of #[stable(…)], #[unstable(…)], + // #[rustc_const_stable(…)], or #[rustc_const_unstable(…)]. + if let Some(stab_attr) = stab_attrs.iter().find(|stab_attr| attr.has_name(**stab_attr)) { + let meta_kind = attr.meta_kind(); + if let Some(MetaItemKind::List(ref metas)) = meta_kind { + 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(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); + if since.is_some() || is_unstable { + return Some((feature, 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, since: Option<Symbol>, span: Span) { + let already_in_stable = self.lib_features.stable.contains_key(&feature); + let already_in_unstable = self.lib_features.unstable.contains_key(&feature); + + match (since, already_in_stable, already_in_unstable) { + (Some(since), _, false) => { + if let Some((prev_since, _)) = self.lib_features.stable.get(&feature) { + if *prev_since != since { + self.span_feature_error( + span, + &format!( + "feature `{}` is declared stable since {}, \ + but was previously declared stable since {}", + feature, since, prev_since, + ), + ); + return; + } + } + + self.lib_features.stable.insert(feature, (since, span)); + } + (None, false, _) => { + self.lib_features.unstable.insert(feature, span); + } + (Some(_), _, true) | (None, true, _) => { + self.span_feature_error( + span, + &format!( + "feature `{}` is declared {}, but was previously declared {}", + feature, + if since.is_some() { "stable" } else { "unstable" }, + if since.is_none() { "stable" } else { "unstable" }, + ), + ); + } + } + } + + fn span_feature_error(&self, span: Span, msg: &str) { + struct_span_err!(self.tcx.sess, span, E0711, "{}", &msg).emit(); + } +} + +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<'_>, (): ()) -> LibFeatures { + 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; +} |