Track lifetime_elision_allowed per owner, and discard fn ptr and Fn() syntax registrations of it, they are never used

Author: oli-obk

compiler/rustc_ast_lowering/src/lib.rs

@@ -321,10 +321,6 @@ impl<'tcx> ResolverAstLowering<'tcx> {
     fn owner_def_id(&self, id: NodeId) -> LocalDefId {
         self.owners[&id].def_id
     }
-
-    fn lifetime_elision_allowed(&self, id: NodeId) -> bool {
-        self.lifetime_elision_allowed.contains(&id)
-    }
 }
 
 /// How relaxed bounds `?Trait` should be treated.
@@ -1866,7 +1862,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     _ => hir::ImplicitSelfKind::None,
                 }
             }))
-            .set_lifetime_elision_allowed(self.resolver.lifetime_elision_allowed(fn_node_id))
+            .set_lifetime_elision_allowed(
+                self.owner.id == fn_node_id && self.owner.lifetime_elision_allowed,
+            )
             .set_c_variadic(c_variadic);
 
         self.arena.alloc(hir::FnDecl { inputs, output, fn_decl_kind })

compiler/rustc_middle/src/ty/mod.rs

@@ -31,7 +31,7 @@ use rustc_ast as ast;
 use rustc_ast::expand::typetree::{FncTree, Kind, Type, TypeTree};
 use rustc_ast::node_id::NodeMap;
 pub use rustc_ast_ir::{Movability, Mutability, try_visit};
-use rustc_data_structures::fx::{FxHashSet, FxIndexMap, FxIndexSet};
+use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
 use rustc_data_structures::intern::Interned;
 use rustc_data_structures::stable_hash::{StableHash, StableHashCtxt, StableHasher};
 use rustc_data_structures::steal::Steal;
@@ -207,6 +207,9 @@ pub struct ResolverGlobalCtxt {
 #[derive(Debug)]
 pub struct PerOwnerResolverData {
     pub node_id_to_def_id: NodeMap<LocalDefId> = Default::default(),
+    /// Whether lifetime elision was successful.
+    pub lifetime_elision_allowed: bool = false,
+
     /// The id of the owner
     pub id: ast::NodeId,
     /// The `DefId` of the owner, can't be found in `node_id_to_def_id`.
@@ -239,8 +242,6 @@ pub struct ResolverAstLowering<'tcx> {
     pub owners: NodeMap<PerOwnerResolverData>,
 
     pub trait_map: NodeMap<&'tcx [hir::TraitCandidate<'tcx>]>,
-    /// List functions and methods for which lifetime elision was successful.
-    pub lifetime_elision_allowed: FxHashSet<ast::NodeId>,
 
     /// Lints that were emitted by the resolver and early lints.
     pub lint_buffer: Steal<LintBuffer>,

compiler/rustc_resolve/src/late.rs

@@ -2456,7 +2456,9 @@ impl<'a, 'ast, 'ra, 'tcx> LateResolutionVisitor<'a, 'ast, 'ra, 'tcx> {
 
             let outer_failures = take(&mut this.diag_metadata.current_elision_failures);
             let output_rib = if let Ok(res) = elision_lifetime.as_ref() {
-                this.r.lifetime_elision_allowed.insert(fn_id);
+                if fn_id == this.r.current_owner.id {
+                    this.r.current_owner.lifetime_elision_allowed = true;
+                }
                 LifetimeRibKind::Elided(*res)
             } else {
                 LifetimeRibKind::ElisionFailure

compiler/rustc_resolve/src/lib.rs

@@ -1533,8 +1533,6 @@ pub struct Resolver<'ra, 'tcx> {
     /// they are declared in the static array generated by proc_macro_harness.
     proc_macros: Vec<LocalDefId> = Vec::new(),
     confused_type_with_std_module: FxIndexMap<Span, Span>,
-    /// Whether lifetime elision was successful.
-    lifetime_elision_allowed: FxHashSet<NodeId> = default::fx_hash_set(),
 
     /// Names of items that were stripped out via cfg with their corresponding cfg meta item.
     stripped_cfg_items: Vec<StrippedCfgItem<NodeId>> = Vec::new(),
@@ -2023,7 +2021,6 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             next_node_id: self.next_node_id,
             owners: self.owners,
             trait_map: self.trait_map,
-            lifetime_elision_allowed: self.lifetime_elision_allowed,
             lint_buffer: Steal::new(self.lint_buffer),
             delegation_infos: self.delegation_infos,
             disambiguators,