Refactor rustc_resolve::late::lifetimes to resolve per-item

compiler/rustc_middle/src/middle/resolve_lifetime.rs

@@ -78,9 +78,4 @@ pub struct ResolveLifetimes {
     /// be late-bound if (a) it does NOT appear in a where-clause and
     /// (b) it DOES appear in the arguments.
     pub late_bound: FxHashMap<LocalDefId, FxHashSet<ItemLocalId>>,
-
-    /// For each type and trait definition, maps type parameters
-    /// to the trait object lifetime defaults computed from them.
-    pub object_lifetime_defaults:
-        FxHashMap<LocalDefId, FxHashMap<ItemLocalId, Vec<ObjectLifetimeDefault>>>,
 }

compiler/rustc_middle/src/query/mod.rs

@@ -1252,8 +1252,19 @@ rustc_queries! {
         desc { "looking up link arguments for a crate" }
     }
 
-    /// Lifetime resolution. See `middle::resolve_lifetimes`.
-    query resolve_lifetimes(_: CrateNum) -> ResolveLifetimes {
+    /// Does lifetime resolution, but does not descend into trait items. This
+    /// should only be used for resolving lifetimes of on trait definitions,
+    /// and is used to avoid cycles. Importantly, `resolve_lifetimes` still visits
+    /// the same lifetimes and is responsible for diagnostics.
+    /// See `rustc_resolve::late::lifetimes for details.
+    query resolve_lifetimes_trait_definition(_: LocalDefId) -> ResolveLifetimes {
+        storage(ArenaCacheSelector<'tcx>)
+        desc { "resolving lifetimes for a trait definition" }
+    }
+    /// Does lifetime resolution on items. Importantly, we can't resolve
+    /// lifetimes directly on things like trait methods, because of trait params.
+    /// See `rustc_resolve::late::lifetimes for details.
+    query resolve_lifetimes(_: LocalDefId) -> ResolveLifetimes {
         storage(ArenaCacheSelector<'tcx>)
         desc { "resolving lifetimes" }
     }
@@ -1265,9 +1276,13 @@ rustc_queries! {
         Option<(LocalDefId, &'tcx FxHashSet<ItemLocalId>)> {
         desc { "testing if a region is late bound" }
     }
+    /// For a given item (like a struct), gets the default lifetimes to be used
+    /// for each paramter if a trait object were to be passed for that parameter.
+    /// For example, for `struct Foo<'a, T, U>`, this would be `['static, 'static]`.
+    /// For `struct Foo<'a, T: 'a, U>`, this would instead be `['a, 'static]`.
     query object_lifetime_defaults_map(_: LocalDefId)
-        -> Option<&'tcx FxHashMap<ItemLocalId, Vec<ObjectLifetimeDefault>>> {
-        desc { "looking up lifetime defaults for a region" }
+        -> Option<Vec<ObjectLifetimeDefault>> {
+        desc { "looking up lifetime defaults for a region on an item" }
     }
 
     query visibility(def_id: DefId) -> ty::Visibility {

compiler/rustc_middle/src/ty/context.rs

@@ -2641,6 +2641,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     pub fn named_region(self, id: HirId) -> Option<resolve_lifetime::Region> {
+        debug!(?id, "named_region");
         self.named_region_map(id.owner).and_then(|map| map.get(&id.local_id).cloned())
     }
 
@@ -2649,9 +2650,8 @@ impl<'tcx> TyCtxt<'tcx> {
             .map_or(false, |(owner, set)| owner == id.owner && set.contains(&id.local_id))
     }
 
-    pub fn object_lifetime_defaults(self, id: HirId) -> Option<&'tcx [ObjectLifetimeDefault]> {
+    pub fn object_lifetime_defaults(self, id: HirId) -> Option<Vec<ObjectLifetimeDefault>> {
         self.object_lifetime_defaults_map(id.owner)
-            .and_then(|map| map.get(&id.local_id).map(|v| &**v))
     }
 }