mv compiler to compiler/

compiler/rustc_passes/src/lib_features.rs

@@ -0,0 +1,145 @@
+// 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, MetaItem, MetaItemKind};
+use rustc_errors::struct_span_err;
+use rustc_hir::def_id::LOCAL_CRATE;
+use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
+use rustc_middle::hir::map::Map;
+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 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_unstable];
+
+        // Find a stability attribute (i.e., `#[stable (..)]`, `#[unstable (..)]`,
+        // `#[rustc_const_unstable (..)]`).
+        if let Some(stab_attr) =
+            stab_attrs.iter().find(|stab_attr| self.tcx.sess.check_name(attr, **stab_attr))
+        {
+            let meta_item = attr.meta();
+            if let Some(MetaItem { kind: MetaItemKind::List(ref metas), .. }) = meta_item {
+                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.
+                    if *stab_attr != sym::stable || since.is_some() {
+                        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(&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);
+            }
+            (None, false, _) => {
+                self.lib_features.unstable.insert(feature);
+            }
+            (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 Visitor<'tcx> for LibFeatureCollector<'tcx> {
+    type Map = Map<'tcx>;
+
+    fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
+        NestedVisitorMap::All(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 collect(tcx: TyCtxt<'_>) -> LibFeatures {
+    let mut collector = LibFeatureCollector::new(tcx);
+    let krate = tcx.hir().krate();
+    for attr in krate.non_exported_macro_attrs {
+        collector.visit_attribute(attr);
+    }
+    intravisit::walk_crate(&mut collector, krate);
+    collector.lib_features
+}
+
+pub fn provide(providers: &mut Providers) {
+    providers.get_lib_features = |tcx, id| {
+        assert_eq!(id, LOCAL_CRATE);
+        collect(tcx)
+    };
+}