Manipulate lifetimes by LocalDefId for region resolution.

Author: cjgillot

compiler/rustc_ast_lowering/src/lib.rs

@@ -672,9 +672,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             LifetimeRes::Param { .. } => {
                 (hir::ParamName::Plain(ident), hir::LifetimeParamKind::Explicit)
             }
-            LifetimeRes::Fresh { param, .. } => {
-                (hir::ParamName::Fresh(param), hir::LifetimeParamKind::Elided)
-            }
+            LifetimeRes::Fresh { .. } => (hir::ParamName::Fresh, hir::LifetimeParamKind::Elided),
             LifetimeRes::Static | LifetimeRes::Error => return None,
             res => panic!(
                 "Unexpected lifetime resolution {:?} for {:?} at {:?}",
@@ -1576,10 +1574,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     (hir::ParamName::Plain(ident), LifetimeRes::Param { param, binder: fn_node_id })
                 }
                 // Input lifetime like `'1`:
-                LifetimeRes::Fresh { param, .. } => (
-                    hir::ParamName::Fresh(outer_def_id),
-                    LifetimeRes::Fresh { param, binder: fn_node_id },
-                ),
+                LifetimeRes::Fresh { param, .. } => {
+                    (hir::ParamName::Fresh, LifetimeRes::Fresh { param, binder: fn_node_id })
+                }
                 LifetimeRes::Static | LifetimeRes::Error => continue,
                 res => {
                     panic!("Unexpected lifetime resolution {:?} for {:?} at {:?}", res, ident, span)
@@ -1749,18 +1746,18 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     ) -> hir::Lifetime {
         debug!(?self.captured_lifetimes);
         let name = match res {
-            LifetimeRes::Param { param, binder } => {
+            LifetimeRes::Param { mut param, binder } => {
                 debug_assert_ne!(ident.name, kw::UnderscoreLifetime);
                 let p_name = ParamName::Plain(ident);
                 if let Some(LifetimeCaptureContext { parent_def_id, captures, binders_to_ignore }) =
                     &mut self.captured_lifetimes
                     && !binders_to_ignore.contains(&binder)
                 {
                     match captures.entry(param) {
-                        Entry::Occupied(_) => {}
+                        Entry::Occupied(o) => param = self.resolver.local_def_id(o.get().1),
                         Entry::Vacant(v) => {
                             let p_id = self.resolver.next_node_id();
-                            self.resolver.create_def(
+                            let p_def_id = self.resolver.create_def(
                                 *parent_def_id,
                                 p_id,
                                 DefPathData::LifetimeNs(p_name.ident().name),
@@ -1769,10 +1766,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                             );
 
                             v.insert((span, p_id, p_name, res));
+                            param = p_def_id;
                         }
                     }
                 }
-                hir::LifetimeName::Param(p_name)
+                hir::LifetimeName::Param(param, p_name)
             }
             LifetimeRes::Fresh { mut param, binder } => {
                 debug_assert_eq!(ident.name, kw::UnderscoreLifetime);
@@ -1792,21 +1790,14 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                                 span.with_parent(None),
                             );
 
-                            let p_name = ParamName::Fresh(param);
-                            v.insert((span, p_id, p_name, res));
+                            v.insert((span, p_id, ParamName::Fresh, res));
                             param = p_def_id;
                         }
                     }
                 }
-                let p_name = ParamName::Fresh(param);
-                hir::LifetimeName::Param(p_name)
+                hir::LifetimeName::Param(param, ParamName::Fresh)
             }
             LifetimeRes::Anonymous { binder, elided } => {
-                let l_name = if elided {
-                    hir::LifetimeName::Implicit
-                } else {
-                    hir::LifetimeName::Underscore
-                };
                 if let Some(LifetimeCaptureContext { parent_def_id, captures, binders_to_ignore }) =
                     &mut self.captured_lifetimes
                     && !binders_to_ignore.contains(&binder)
@@ -1819,18 +1810,20 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         ExpnId::root(),
                         span.with_parent(None),
                     );
-                    let p_name = ParamName::Fresh(p_def_id);
-                    captures.insert(p_def_id, (span, p_id, p_name, res));
-                    hir::LifetimeName::Param(p_name)
+                    captures.insert(p_def_id, (span, p_id, ParamName::Fresh, res));
+                    hir::LifetimeName::Param(p_def_id, ParamName::Fresh)
+                } else if elided {
+                    hir::LifetimeName::Implicit
                 } else {
-                    l_name
+                    hir::LifetimeName::Underscore
                 }
             }
             LifetimeRes::Static => hir::LifetimeName::Static,
             LifetimeRes::Error => hir::LifetimeName::Error,
             res => panic!("Unexpected lifetime resolution {:?} for {:?} at {:?}", res, ident, span),
         };
         debug!(?self.captured_lifetimes);
+        debug!(?name);
         hir::Lifetime { hir_id: self.lower_node_id(id), span: self.lower_span(span), name }
     }
 

compiler/rustc_borrowck/src/diagnostics/region_name.rs

@@ -567,14 +567,14 @@ impl<'tcx> MirBorrowckCtxt<'_, 'tcx> {
         let lifetime =
             self.try_match_adt_and_generic_args(substs, needle_fr, args, search_stack)?;
         match lifetime.name {
-            hir::LifetimeName::Param(hir::ParamName::Plain(_) | hir::ParamName::Error)
+            hir::LifetimeName::Param(_, hir::ParamName::Plain(_) | hir::ParamName::Error)
             | hir::LifetimeName::Error
             | hir::LifetimeName::Static => {
                 let lifetime_span = lifetime.span;
                 Some(RegionNameHighlight::MatchedAdtAndSegment(lifetime_span))
             }
 
-            hir::LifetimeName::Param(hir::ParamName::Fresh(_))
+            hir::LifetimeName::Param(_, hir::ParamName::Fresh)
             | hir::LifetimeName::ImplicitObjectLifetimeDefault
             | hir::LifetimeName::Implicit
             | hir::LifetimeName::Underscore => {

compiler/rustc_hir/src/hir.rs

@@ -26,7 +26,7 @@ use rustc_target::spec::abi::Abi;
 use smallvec::SmallVec;
 use std::fmt;
 
-#[derive(Copy, Clone, Encodable, HashStable_Generic)]
+#[derive(Debug, Copy, Clone, Encodable, HashStable_Generic)]
 pub struct Lifetime {
     pub hir_id: HirId,
     pub span: Span,
@@ -60,7 +60,7 @@ pub enum ParamName {
     /// ```
     /// where `'f` is something like `Fresh(0)`. The indices are
     /// unique per impl, but not necessarily continuous.
-    Fresh(LocalDefId),
+    Fresh,
 
     /// Indicates an illegal name was given and an error has been
     /// reported (so we should squelch other derived errors). Occurs
@@ -72,9 +72,7 @@ impl ParamName {
     pub fn ident(&self) -> Ident {
         match *self {
             ParamName::Plain(ident) => ident,
-            ParamName::Fresh(_) | ParamName::Error => {
-                Ident::with_dummy_span(kw::UnderscoreLifetime)
-            }
+            ParamName::Fresh | ParamName::Error => Ident::with_dummy_span(kw::UnderscoreLifetime),
         }
     }
 
@@ -90,7 +88,7 @@ impl ParamName {
 #[derive(HashStable_Generic)]
 pub enum LifetimeName {
     /// User-given names or fresh (synthetic) names.
-    Param(ParamName),
+    Param(LocalDefId, ParamName),
 
     /// User wrote nothing (e.g., the lifetime in `&u32`).
     Implicit,
@@ -127,7 +125,7 @@ impl LifetimeName {
             | LifetimeName::Error => Ident::empty(),
             LifetimeName::Underscore => Ident::with_dummy_span(kw::UnderscoreLifetime),
             LifetimeName::Static => Ident::with_dummy_span(kw::StaticLifetime),
-            LifetimeName::Param(param_name) => param_name.ident(),
+            LifetimeName::Param(_, param_name) => param_name.ident(),
         }
     }
 
@@ -136,9 +134,9 @@ impl LifetimeName {
             LifetimeName::ImplicitObjectLifetimeDefault
             | LifetimeName::Implicit
             | LifetimeName::Underscore
-            | LifetimeName::Param(ParamName::Fresh(_))
+            | LifetimeName::Param(_, ParamName::Fresh)
             | LifetimeName::Error => true,
-            LifetimeName::Static | LifetimeName::Param(_) => false,
+            LifetimeName::Static | LifetimeName::Param(..) => false,
         }
     }
 
@@ -148,12 +146,12 @@ impl LifetimeName {
             | LifetimeName::Implicit
             | LifetimeName::Underscore => true,
 
-            // It might seem surprising that `Fresh(_)` counts as
+            // It might seem surprising that `Fresh` counts as
             // *not* elided -- but this is because, as far as the code
-            // in the compiler is concerned -- `Fresh(_)` variants act
+            // in the compiler is concerned -- `Fresh` variants act
             // equivalently to "some fresh name". They correspond to
             // early-bound regions on an impl, in other words.
-            LifetimeName::Error | LifetimeName::Param(_) | LifetimeName::Static => false,
+            LifetimeName::Error | LifetimeName::Param(..) | LifetimeName::Static => false,
         }
     }
 
@@ -163,8 +161,8 @@ impl LifetimeName {
 
     pub fn normalize_to_macros_2_0(&self) -> LifetimeName {
         match *self {
-            LifetimeName::Param(param_name) => {
-                LifetimeName::Param(param_name.normalize_to_macros_2_0())
+            LifetimeName::Param(def_id, param_name) => {
+                LifetimeName::Param(def_id, param_name.normalize_to_macros_2_0())
             }
             lifetime_name => lifetime_name,
         }
@@ -177,12 +175,6 @@ impl fmt::Display for Lifetime {
     }
 }
 
-impl fmt::Debug for Lifetime {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "lifetime({}: {})", self.hir_id, self.name.ident())
-    }
-}
-
 impl Lifetime {
     pub fn is_elided(&self) -> bool {
         self.name.is_elided()
@@ -628,6 +620,16 @@ impl<'hir> Generics<'hir> {
         })
     }
 
+    pub fn outlives_for_param(
+        &self,
+        param_def_id: LocalDefId,
+    ) -> impl Iterator<Item = &WhereRegionPredicate<'_>> {
+        self.predicates.iter().filter_map(move |pred| match pred {
+            WherePredicate::RegionPredicate(rp) if rp.is_param_bound(param_def_id) => Some(rp),
+            _ => None,
+        })
+    }
+
     pub fn bounds_span_for_suggestions(&self, param_def_id: LocalDefId) -> Option<Span> {
         self.bounds_for_param(param_def_id).flat_map(|bp| bp.bounds.iter().rev()).find_map(
             |bound| {
@@ -769,6 +771,16 @@ pub struct WhereRegionPredicate<'hir> {
     pub bounds: GenericBounds<'hir>,
 }
 
+impl<'hir> WhereRegionPredicate<'hir> {
+    /// Returns `true` if `param_def_id` matches the `lifetime` of this predicate.
+    pub fn is_param_bound(&self, param_def_id: LocalDefId) -> bool {
+        match self.lifetime.name {
+            LifetimeName::Param(id, _) => id == param_def_id,
+            _ => false,
+        }
+    }
+}
+
 /// An equality predicate (e.g., `T = int`); currently unsupported.
 #[derive(Debug, HashStable_Generic)]
 pub struct WhereEqPredicate<'hir> {

compiler/rustc_hir/src/intravisit.rs

@@ -510,11 +510,11 @@ pub fn walk_label<'v, V: Visitor<'v>>(visitor: &mut V, label: &'v Label) {
 pub fn walk_lifetime<'v, V: Visitor<'v>>(visitor: &mut V, lifetime: &'v Lifetime) {
     visitor.visit_id(lifetime.hir_id);
     match lifetime.name {
-        LifetimeName::Param(ParamName::Plain(ident)) => {
+        LifetimeName::Param(_, ParamName::Plain(ident)) => {
             visitor.visit_ident(ident);
         }
-        LifetimeName::Param(ParamName::Fresh(_))
-        | LifetimeName::Param(ParamName::Error)
+        LifetimeName::Param(_, ParamName::Fresh)
+        | LifetimeName::Param(_, ParamName::Error)
         | LifetimeName::Static
         | LifetimeName::Error
         | LifetimeName::Implicit
@@ -879,7 +879,7 @@ pub fn walk_generic_param<'v, V: Visitor<'v>>(visitor: &mut V, param: &'v Generi
     visitor.visit_id(param.hir_id);
     match param.name {
         ParamName::Plain(ident) => visitor.visit_ident(ident),
-        ParamName::Error | ParamName::Fresh(_) => {}
+        ParamName::Error | ParamName::Fresh => {}
     }
     match param.kind {
         GenericParamKind::Lifetime { .. } => {}

compiler/rustc_middle/src/middle/resolve_lifetime.rs

@@ -6,7 +6,6 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::ItemLocalId;
 use rustc_macros::HashStable;
-use rustc_span::symbol::Symbol;
 
 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, HashStable)]
 pub enum Region {
@@ -22,12 +21,12 @@ pub enum Region {
 /// so that we can e.g. suggest elided-lifetimes-in-paths of the form <'_, '_> e.g.
 #[derive(Clone, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, HashStable)]
 pub enum LifetimeScopeForPath {
-    // Contains all lifetime names that are in scope and could possibly be used in generics
-    // arguments of path.
-    NonElided(Vec<Symbol>),
+    /// Contains all lifetime names that are in scope and could possibly be used in generics
+    /// arguments of path.
+    NonElided(Vec<LocalDefId>),
 
-    // Information that allows us to suggest args of the form `<'_>` in case
-    // no generic arguments were provided for a path.
+    /// Information that allows us to suggest args of the form `<'_>` in case
+    /// no generic arguments were provided for a path.
     Elided,
 }
 

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -13,15 +13,15 @@ use rustc_ast::{
 };
 use rustc_ast_lowering::ResolverAstLowering;
 use rustc_ast_pretty::pprust::path_segment_to_string;
-use rustc_data_structures::fx::FxHashSet;
+use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
 use rustc_errors::{
     pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
     MultiSpan,
 };
 use rustc_hir as hir;
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, CtorOf, DefKind};
-use rustc_hir::def_id::{DefId, CRATE_DEF_ID, LOCAL_CRATE};
+use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID, LOCAL_CRATE};
 use rustc_hir::PrimTy;
 use rustc_session::lint;
 use rustc_session::parse::feature_err;
@@ -2082,7 +2082,7 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
 
     /// Returns whether to add `'static` lifetime to the suggested lifetime list.
     pub(crate) fn report_elision_failure(
-        &mut self,
+        &self,
         diag: &mut Diagnostic,
         params: &[ElisionFailureInfo],
     ) -> bool {
@@ -2187,10 +2187,27 @@ impl<'tcx> LifetimeContext<'_, 'tcx> {
         &self,
         err: &mut Diagnostic,
         mut spans_with_counts: Vec<(Span, usize)>,
-        lifetime_names: &FxHashSet<Symbol>,
-        lifetime_spans: Vec<Span>,
-        params: &[ElisionFailureInfo],
+        in_scope_lifetimes: FxIndexSet<LocalDefId>,
+        params: Option<&[ElisionFailureInfo]>,
     ) {
+        let (mut lifetime_names, lifetime_spans): (FxHashSet<_>, Vec<_>) = in_scope_lifetimes
+            .iter()
+            .filter_map(|def_id| {
+                let name = self.tcx.item_name(def_id.to_def_id());
+                let span = self.tcx.def_ident_span(def_id.to_def_id())?;
+                Some((name, span))
+            })
+            .filter(|&(n, _)| n != kw::UnderscoreLifetime)
+            .unzip();
+
+        if let Some(params) = params {
+            // If there's no lifetime available, suggest `'static`.
+            if self.report_elision_failure(err, params) && lifetime_names.is_empty() {
+                lifetime_names.insert(kw::StaticLifetime);
+            }
+        }
+        let params = params.unwrap_or(&[]);
+
         let snippets: Vec<Option<String>> = spans_with_counts
             .iter()
             .map(|(span, _)| self.tcx.sess.source_map().span_to_snippet(*span).ok())