From cb08e087221ba0263a338e959264520a8ed8080e Mon Sep 17 00:00:00 2001
From: Adwin White <adwinw01@gmail.com>
Date: Thu, 12 Sep 2024 11:32:39 +0800
Subject: [PATCH 1/3] Lower AST node id only once

---
 compiler/rustc_ast_lowering/src/block.rs      |  14 ++-
 compiler/rustc_ast_lowering/src/delegation.rs |   5 +-
 compiler/rustc_ast_lowering/src/expr.rs       | 113 +++++++++++-------
 compiler/rustc_ast_lowering/src/item.rs       |  14 ++-
 compiler/rustc_ast_lowering/src/lib.rs        |  65 +++++-----
 compiler/rustc_ast_lowering/src/pat.rs        |  58 ++++++---
 tests/ui/thir-print/thir-tree-match.stdout    |  46 +++----
 7 files changed, 184 insertions(+), 131 deletions(-)

diff --git a/compiler/rustc_ast_lowering/src/block.rs b/compiler/rustc_ast_lowering/src/block.rs
index 9d2b5690c23d9..8e02cbfd2ca81 100644
--- a/compiler/rustc_ast_lowering/src/block.rs
+++ b/compiler/rustc_ast_lowering/src/block.rs
@@ -10,17 +10,27 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         b: &Block,
         targeted_by_break: bool,
     ) -> &'hir hir::Block<'hir> {
-        self.arena.alloc(self.lower_block_noalloc(b, targeted_by_break))
+        let hir_id = self.lower_node_id(b.id);
+        self.arena.alloc(self.lower_block_noalloc(hir_id, b, targeted_by_break))
+    }
+
+    pub(super) fn lower_block_with_hir_id(
+        &mut self,
+        b: &Block,
+        hir_id: hir::HirId,
+        targeted_by_break: bool,
+    ) -> &'hir hir::Block<'hir> {
+        self.arena.alloc(self.lower_block_noalloc(hir_id, b, targeted_by_break))
     }
 
     pub(super) fn lower_block_noalloc(
         &mut self,
+        hir_id: hir::HirId,
         b: &Block,
         targeted_by_break: bool,
     ) -> hir::Block<'hir> {
         let (stmts, expr) = self.lower_stmts(&b.stmts);
         let rules = self.lower_block_check_mode(&b.rules);
-        let hir_id = self.lower_node_id(b.id);
         hir::Block { hir_id, stmts, expr, rules, span: self.lower_span(b.span), targeted_by_break }
     }
 
diff --git a/compiler/rustc_ast_lowering/src/delegation.rs b/compiler/rustc_ast_lowering/src/delegation.rs
index 3b85f1737bdd9..37eea707929e7 100644
--- a/compiler/rustc_ast_lowering/src/delegation.rs
+++ b/compiler/rustc_ast_lowering/src/delegation.rs
@@ -259,10 +259,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         self_param_id: pat_node_id,
                     };
                     self_resolver.visit_block(block);
+                    // Target expr needs to lower `self` path.
+                    this.ident_to_local_id.insert(pat_node_id, param.pat.hir_id.local_id);
                     this.lower_target_expr(&block)
                 } else {
-                    let pat_hir_id = this.lower_node_id(pat_node_id);
-                    this.generate_arg(pat_hir_id, span)
+                    this.generate_arg(param.pat.hir_id, span)
                 };
                 args.push(arg);
             }
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index a1a16d0ca2632..3df945a18e80a 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -70,8 +70,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 _ => (),
             }
 
-            let hir_id = self.lower_node_id(e.id);
-            self.lower_attrs(hir_id, &e.attrs);
+            let expr_hir_id = self.lower_node_id(e.id);
+            self.lower_attrs(expr_hir_id, &e.attrs);
 
             let kind = match &e.kind {
                 ExprKind::Array(exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
@@ -175,18 +175,25 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 ExprKind::If(cond, then, else_opt) => {
                     self.lower_expr_if(cond, then, else_opt.as_deref())
                 }
-                ExprKind::While(cond, body, opt_label) => self.with_loop_scope(e.id, |this| {
-                    let span = this.mark_span_with_reason(DesugaringKind::WhileLoop, e.span, None);
-                    this.lower_expr_while_in_loop_scope(span, cond, body, *opt_label)
-                }),
-                ExprKind::Loop(body, opt_label, span) => self.with_loop_scope(e.id, |this| {
-                    hir::ExprKind::Loop(
-                        this.lower_block(body, false),
-                        this.lower_label(*opt_label),
-                        hir::LoopSource::Loop,
-                        this.lower_span(*span),
-                    )
-                }),
+                ExprKind::While(cond, body, opt_label) => {
+                    self.with_loop_scope(expr_hir_id, |this| {
+                        let span =
+                            this.mark_span_with_reason(DesugaringKind::WhileLoop, e.span, None);
+                        let opt_label = this.lower_label(*opt_label, e.id, expr_hir_id);
+                        this.lower_expr_while_in_loop_scope(span, cond, body, opt_label)
+                    })
+                }
+                ExprKind::Loop(body, opt_label, span) => {
+                    self.with_loop_scope(expr_hir_id, |this| {
+                        let opt_label = this.lower_label(*opt_label, e.id, expr_hir_id);
+                        hir::ExprKind::Loop(
+                            this.lower_block(body, false),
+                            opt_label,
+                            hir::LoopSource::Loop,
+                            this.lower_span(*span),
+                        )
+                    })
+                }
                 ExprKind::TryBlock(body) => self.lower_expr_try_block(body),
                 ExprKind::Match(expr, arms, kind) => hir::ExprKind::Match(
                     self.lower_expr(expr),
@@ -212,7 +219,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         binder,
                         *capture_clause,
                         e.id,
-                        hir_id,
+                        expr_hir_id,
                         *coroutine_kind,
                         fn_decl,
                         body,
@@ -223,7 +230,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         binder,
                         *capture_clause,
                         e.id,
-                        hir_id,
+                        expr_hir_id,
                         *constness,
                         *movability,
                         fn_decl,
@@ -250,8 +257,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     )
                 }
                 ExprKind::Block(blk, opt_label) => {
-                    let opt_label = self.lower_label(*opt_label);
-                    hir::ExprKind::Block(self.lower_block(blk, opt_label.is_some()), opt_label)
+                    // Different from loops, label of block resolves to block id rather than
+                    // expr node id.
+                    let block_hir_id = self.lower_node_id(blk.id);
+                    let opt_label = self.lower_label(*opt_label, blk.id, block_hir_id);
+                    hir::ExprKind::Block(
+                        self.lower_block_with_hir_id(blk, block_hir_id, opt_label.is_some()),
+                        opt_label,
+                    )
                 }
                 ExprKind::Assign(el, er, span) => self.lower_expr_assign(el, er, *span, e.span),
                 ExprKind::AssignOp(op, el, er) => hir::ExprKind::AssignOp(
@@ -354,7 +367,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 ExprKind::MacCall(_) => panic!("{:?} shouldn't exist here", e.span),
             };
 
-            hir::Expr { hir_id, kind, span: self.lower_span(e.span) }
+            hir::Expr { hir_id: expr_hir_id, kind, span: self.lower_span(e.span) }
         })
     }
 
@@ -504,7 +517,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let if_expr = self.expr(span, if_kind);
         let block = self.block_expr(self.arena.alloc(if_expr));
         let span = self.lower_span(span.with_hi(cond.span.hi()));
-        let opt_label = self.lower_label(opt_label);
         hir::ExprKind::Loop(block, opt_label, hir::LoopSource::While, span)
     }
 
@@ -512,8 +524,9 @@ impl<'hir> LoweringContext<'_, 'hir> {
     /// `try { <stmts>; }` into `{ <stmts>; ::std::ops::Try::from_output(()) }`
     /// and save the block id to use it as a break target for desugaring of the `?` operator.
     fn lower_expr_try_block(&mut self, body: &Block) -> hir::ExprKind<'hir> {
-        self.with_catch_scope(body.id, |this| {
-            let mut block = this.lower_block_noalloc(body, true);
+        let body_hir_id = self.lower_node_id(body.id);
+        self.with_catch_scope(body_hir_id, |this| {
+            let mut block = this.lower_block_noalloc(body_hir_id, body, true);
 
             // Final expression of the block (if present) or `()` with span at the end of block
             let (try_span, tail_expr) = if let Some(expr) = block.expr.take() {
@@ -869,7 +882,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             let x_expr = self.expr_ident(gen_future_span, x_ident, x_pat_hid);
             let ready_field = self.single_pat_field(gen_future_span, x_pat);
             let ready_pat = self.pat_lang_item_variant(span, hir::LangItem::PollReady, ready_field);
-            let break_x = self.with_loop_scope(loop_node_id, move |this| {
+            let break_x = self.with_loop_scope(loop_hir_id, move |this| {
                 let expr_break =
                     hir::ExprKind::Break(this.lower_loop_destination(None), Some(x_expr));
                 this.arena.alloc(this.expr(gen_future_span, expr_break))
@@ -1101,8 +1114,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         hir::CoroutineSource::Closure,
                     );
 
-                    let hir_id = this.lower_node_id(coroutine_kind.closure_id());
-                    this.maybe_forward_track_caller(body.span, closure_hir_id, hir_id);
+                    this.maybe_forward_track_caller(body.span, closure_hir_id, expr.hir_id);
 
                     (parameters, expr)
                 });
@@ -1465,8 +1477,16 @@ impl<'hir> LoweringContext<'_, 'hir> {
         )
     }
 
-    fn lower_label(&self, opt_label: Option<Label>) -> Option<Label> {
+    // Record labelled expr's HirId so that we can retrieve it in `lower_jump_destination` without
+    // lowering node id again.
+    fn lower_label(
+        &mut self,
+        opt_label: Option<Label>,
+        dest_id: NodeId,
+        dest_hir_id: hir::HirId,
+    ) -> Option<Label> {
         let label = opt_label?;
+        self.labelled_node_id_to_local_id.insert(dest_id, dest_hir_id.local_id);
         Some(Label { ident: self.lower_ident(label.ident) })
     }
 
@@ -1474,17 +1494,20 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let target_id = match destination {
             Some((id, _)) => {
                 if let Some(loop_id) = self.resolver.get_label_res(id) {
-                    Ok(self.lower_node_id(loop_id))
+                    let local_id = self.labelled_node_id_to_local_id[&loop_id];
+                    let loop_hir_id = HirId { owner: self.current_hir_id_owner, local_id };
+                    Ok(loop_hir_id)
                 } else {
                     Err(hir::LoopIdError::UnresolvedLabel)
                 }
             }
-            None => self
-                .loop_scope
-                .map(|id| Ok(self.lower_node_id(id)))
-                .unwrap_or(Err(hir::LoopIdError::OutsideLoopScope)),
+            None => {
+                self.loop_scope.map(|id| Ok(id)).unwrap_or(Err(hir::LoopIdError::OutsideLoopScope))
+            }
         };
-        let label = self.lower_label(destination.map(|(_, label)| label));
+        let label = destination
+            .map(|(_, label)| label)
+            .map(|label| Label { ident: self.lower_ident(label.ident) });
         hir::Destination { label, target_id }
     }
 
@@ -1499,14 +1522,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
         }
     }
 
-    fn with_catch_scope<T>(&mut self, catch_id: NodeId, f: impl FnOnce(&mut Self) -> T) -> T {
+    fn with_catch_scope<T>(&mut self, catch_id: hir::HirId, f: impl FnOnce(&mut Self) -> T) -> T {
         let old_scope = self.catch_scope.replace(catch_id);
         let result = f(self);
         self.catch_scope = old_scope;
         result
     }
 
-    fn with_loop_scope<T>(&mut self, loop_id: NodeId, f: impl FnOnce(&mut Self) -> T) -> T {
+    fn with_loop_scope<T>(&mut self, loop_id: hir::HirId, f: impl FnOnce(&mut Self) -> T) -> T {
         // We're no longer in the base loop's condition; we're in another loop.
         let was_in_loop_condition = self.is_in_loop_condition;
         self.is_in_loop_condition = false;
@@ -1658,9 +1681,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let head_span = self.mark_span_with_reason(DesugaringKind::ForLoop, head.span, None);
         let pat_span = self.mark_span_with_reason(DesugaringKind::ForLoop, pat.span, None);
 
+        let loop_hir_id = self.lower_node_id(e.id);
+        let label = self.lower_label(opt_label, e.id, loop_hir_id);
+
         // `None => break`
         let none_arm = {
-            let break_expr = self.with_loop_scope(e.id, |this| this.expr_break_alloc(for_span));
+            let break_expr =
+                self.with_loop_scope(loop_hir_id, |this| this.expr_break_alloc(for_span));
             let pat = self.pat_none(for_span);
             self.arm(pat, break_expr)
         };
@@ -1668,7 +1695,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // Some(<pat>) => <body>,
         let some_arm = {
             let some_pat = self.pat_some(pat_span, pat);
-            let body_block = self.with_loop_scope(e.id, |this| this.lower_block(body, false));
+            let body_block =
+                self.with_loop_scope(loop_hir_id, |this| this.lower_block(body, false));
             let body_expr = self.arena.alloc(self.expr_block(body_block));
             self.arm(some_pat, body_expr)
         };
@@ -1722,12 +1750,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // `[opt_ident]: loop { ... }`
         let kind = hir::ExprKind::Loop(
             loop_block,
-            self.lower_label(opt_label),
+            label,
             hir::LoopSource::ForLoop,
             self.lower_span(for_span.with_hi(head.span.hi())),
         );
-        let loop_expr =
-            self.arena.alloc(hir::Expr { hir_id: self.lower_node_id(e.id), kind, span: for_span });
+        let loop_expr = self.arena.alloc(hir::Expr { hir_id: loop_hir_id, kind, span: for_span });
 
         // `mut iter => { ... }`
         let iter_arm = self.arm(iter_pat, loop_expr);
@@ -1867,8 +1894,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 self.arena.alloc(residual_expr),
                 unstable_span,
             );
-            let ret_expr = if let Some(catch_node) = self.catch_scope {
-                let target_id = Ok(self.lower_node_id(catch_node));
+            let ret_expr = if let Some(catch_id) = self.catch_scope {
+                let target_id = Ok(catch_id);
                 self.arena.alloc(self.expr(
                     try_span,
                     hir::ExprKind::Break(
@@ -1922,8 +1949,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
             yeeted_span,
         );
 
-        if let Some(catch_node) = self.catch_scope {
-            let target_id = Ok(self.lower_node_id(catch_node));
+        if let Some(catch_id) = self.catch_scope {
+            let target_id = Ok(catch_id);
             hir::ExprKind::Break(hir::Destination { label: None, target_id }, Some(from_yeet_expr))
         } else {
             hir::ExprKind::Ret(Some(from_yeet_expr))
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 97fa90d340ea2..9cad03ae4034b 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -154,7 +154,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
     fn lower_item(&mut self, i: &Item) -> &'hir hir::Item<'hir> {
         let mut ident = i.ident;
         let vis_span = self.lower_span(i.vis.span);
-        let hir_id = self.lower_node_id(i.id);
+        let hir_id =
+            hir::HirId { owner: self.current_hir_id_owner, local_id: hir::ItemLocalId::ZERO };
         let attrs = self.lower_attrs(hir_id, &i.attrs);
         let kind = self.lower_item_kind(i.span, i.id, hir_id, &mut ident, attrs, vis_span, &i.kind);
         let item = hir::Item {
@@ -604,7 +605,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
     }
 
     fn lower_foreign_item(&mut self, i: &ForeignItem) -> &'hir hir::ForeignItem<'hir> {
-        let hir_id = self.lower_node_id(i.id);
+        let hir_id =
+            hir::HirId { owner: self.current_hir_id_owner, local_id: hir::ItemLocalId::ZERO };
         let owner_id = hir_id.expect_owner();
         self.lower_attrs(hir_id, &i.attrs);
         let item = hir::ForeignItem {
@@ -728,7 +730,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
     }
 
     fn lower_trait_item(&mut self, i: &AssocItem) -> &'hir hir::TraitItem<'hir> {
-        let hir_id = self.lower_node_id(i.id);
+        let hir_id =
+            hir::HirId { owner: self.current_hir_id_owner, local_id: hir::ItemLocalId::ZERO };
         self.lower_attrs(hir_id, &i.attrs);
         let trait_item_def_id = hir_id.expect_owner();
 
@@ -858,7 +861,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // Since `default impl` is not yet implemented, this is always true in impls.
         let has_value = true;
         let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
-        let hir_id = self.lower_node_id(i.id);
+        let hir_id =
+            hir::HirId { owner: self.current_hir_id_owner, local_id: hir::ItemLocalId::ZERO };
         self.lower_attrs(hir_id, &i.attrs);
 
         let (generics, kind) = match &i.kind {
@@ -1086,7 +1090,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             );
 
             // FIXME(async_fn_track_caller): Can this be moved above?
-            let hir_id = this.lower_node_id(coroutine_kind.closure_id());
+            let hir_id = expr.hir_id;
             this.maybe_forward_track_caller(body.span, fn_id, hir_id);
 
             (parameters, expr)
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 34b8137aea8ef..3067cb7ccf24f 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -40,8 +40,6 @@
 #![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
-use std::collections::hash_map::Entry;
-
 use rustc_ast::node_id::NodeMap;
 use rustc_ast::ptr::P;
 use rustc_ast::{self as ast, *};
@@ -115,8 +113,8 @@ struct LoweringContext<'a, 'hir> {
     /// outside of an `async fn`.
     current_item: Option<Span>,
 
-    catch_scope: Option<NodeId>,
-    loop_scope: Option<NodeId>,
+    catch_scope: Option<HirId>,
+    loop_scope: Option<HirId>,
     is_in_loop_condition: bool,
     is_in_trait_impl: bool,
     is_in_dyn_type: bool,
@@ -140,8 +138,10 @@ struct LoweringContext<'a, 'hir> {
     impl_trait_defs: Vec<hir::GenericParam<'hir>>,
     impl_trait_bounds: Vec<hir::WherePredicate<'hir>>,
 
-    /// NodeIds that are lowered inside the current HIR owner.
-    node_id_to_local_id: NodeMap<hir::ItemLocalId>,
+    /// NodeIds of labelled nodes that are lowered inside the current HIR owner.
+    labelled_node_id_to_local_id: NodeMap<hir::ItemLocalId>,
+    /// NodeIds of identifier that are lowered inside the current HIR owner.
+    ident_to_local_id: NodeMap<hir::ItemLocalId>,
 
     allow_try_trait: Lrc<[Symbol]>,
     allow_gen_future: Lrc<[Symbol]>,
@@ -171,7 +171,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             current_hir_id_owner: hir::CRATE_OWNER_ID,
             current_def_id_parent: CRATE_DEF_ID,
             item_local_id_counter: hir::ItemLocalId::ZERO,
-            node_id_to_local_id: Default::default(),
+            labelled_node_id_to_local_id: Default::default(),
+            ident_to_local_id: Default::default(),
             trait_map: Default::default(),
 
             // Lowering state.
@@ -588,7 +589,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         let current_attrs = std::mem::take(&mut self.attrs);
         let current_bodies = std::mem::take(&mut self.bodies);
-        let current_node_ids = std::mem::take(&mut self.node_id_to_local_id);
+        let current_labelled_node_id_to_local_id =
+            std::mem::take(&mut self.labelled_node_id_to_local_id);
+        let current_ident_to_local_id = std::mem::take(&mut self.ident_to_local_id);
         let current_trait_map = std::mem::take(&mut self.trait_map);
         let current_owner =
             std::mem::replace(&mut self.current_hir_id_owner, hir::OwnerId { def_id });
@@ -601,10 +604,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         // we want `f` to be able to refer to the `LocalDefId`s that the caller created.
         // and the caller to refer to some of the subdefinitions' nodes' `LocalDefId`s.
 
-        // Always allocate the first `HirId` for the owner itself.
-        let _old = self.node_id_to_local_id.insert(owner, hir::ItemLocalId::ZERO);
-        debug_assert_eq!(_old, None);
-
         let item = self.with_def_id_parent(def_id, f);
         debug_assert_eq!(def_id, item.def_id().def_id);
         // `f` should have consumed all the elements in these vectors when constructing `item`.
@@ -614,7 +613,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         self.attrs = current_attrs;
         self.bodies = current_bodies;
-        self.node_id_to_local_id = current_node_ids;
+        self.labelled_node_id_to_local_id = current_labelled_node_id_to_local_id;
+        self.ident_to_local_id = current_ident_to_local_id;
         self.trait_map = current_trait_map;
         self.current_hir_id_owner = current_owner;
         self.item_local_id_counter = current_local_counter;
@@ -680,39 +680,30 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.arena.alloc(hir::OwnerInfo { nodes, parenting, attrs, trait_map })
     }
 
-    /// This method allocates a new `HirId` for the given `NodeId` and stores it in
-    /// the `LoweringContext`'s `NodeId => HirId` map.
+    /// This method allocates a new `HirId` for the given `NodeId`.
     /// Take care not to call this method if the resulting `HirId` is then not
     /// actually used in the HIR, as that would trigger an assertion in the
     /// `HirIdValidator` later on, which makes sure that all `NodeId`s got mapped
-    /// properly. Calling the method twice with the same `NodeId` is fine though.
+    /// properly. Calling the method twice with the same `NodeId` is also forbidden.
     #[instrument(level = "debug", skip(self), ret)]
     fn lower_node_id(&mut self, ast_node_id: NodeId) -> HirId {
         assert_ne!(ast_node_id, DUMMY_NODE_ID);
 
-        match self.node_id_to_local_id.entry(ast_node_id) {
-            Entry::Occupied(o) => HirId { owner: self.current_hir_id_owner, local_id: *o.get() },
-            Entry::Vacant(v) => {
-                // Generate a new `HirId`.
-                let owner = self.current_hir_id_owner;
-                let local_id = self.item_local_id_counter;
-                let hir_id = HirId { owner, local_id };
-
-                v.insert(local_id);
-                self.item_local_id_counter.increment_by(1);
-
-                assert_ne!(local_id, hir::ItemLocalId::ZERO);
-                if let Some(def_id) = self.opt_local_def_id(ast_node_id) {
-                    self.children.push((def_id, hir::MaybeOwner::NonOwner(hir_id)));
-                }
+        let owner = self.current_hir_id_owner;
+        let local_id = self.item_local_id_counter;
+        assert_ne!(local_id, hir::ItemLocalId::ZERO);
+        self.item_local_id_counter.increment_by(1);
+        let hir_id = HirId { owner, local_id };
 
-                if let Some(traits) = self.resolver.trait_map.remove(&ast_node_id) {
-                    self.trait_map.insert(hir_id.local_id, traits.into_boxed_slice());
-                }
+        if let Some(def_id) = self.opt_local_def_id(ast_node_id) {
+            self.children.push((def_id, hir::MaybeOwner::NonOwner(hir_id)));
+        }
 
-                hir_id
-            }
+        if let Some(traits) = self.resolver.trait_map.remove(&ast_node_id) {
+            self.trait_map.insert(hir_id.local_id, traits.into_boxed_slice());
         }
+
+        hir_id
     }
 
     /// Generate a new `HirId` without a backing `NodeId`.
@@ -729,7 +720,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_res(&mut self, res: Res<NodeId>) -> Res {
         let res: Result<Res, ()> = res.apply_id(|id| {
             let owner = self.current_hir_id_owner;
-            let local_id = self.node_id_to_local_id.get(&id).copied().ok_or(())?;
+            let local_id = self.ident_to_local_id.get(&id).copied().ok_or(())?;
             Ok(HirId { owner, local_id })
         });
         trace!(?res);
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
index 760f84564f1a2..21829ea25a9bd 100644
--- a/compiler/rustc_ast_lowering/src/pat.rs
+++ b/compiler/rustc_ast_lowering/src/pat.rs
@@ -21,13 +21,20 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_pat_mut(&mut self, mut pattern: &Pat) -> hir::Pat<'hir> {
         ensure_sufficient_stack(|| {
             // loop here to avoid recursion
+            let pat_hir_id = self.lower_node_id(pattern.id);
             let node = loop {
                 match &pattern.kind {
                     PatKind::Wild => break hir::PatKind::Wild,
                     PatKind::Never => break hir::PatKind::Never,
                     PatKind::Ident(binding_mode, ident, sub) => {
                         let lower_sub = |this: &mut Self| sub.as_ref().map(|s| this.lower_pat(s));
-                        break self.lower_pat_ident(pattern, *binding_mode, *ident, lower_sub);
+                        break self.lower_pat_ident(
+                            pattern,
+                            *binding_mode,
+                            *ident,
+                            pat_hir_id,
+                            lower_sub,
+                        );
                     }
                     PatKind::Lit(e) => {
                         break hir::PatKind::Lit(self.lower_expr_within_pat(e, false));
@@ -119,7 +126,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 }
             };
 
-            self.pat_with_node_id_of(pattern, node)
+            self.pat_with_node_id_of(pattern, node, pat_hir_id)
         })
     }
 
@@ -187,10 +194,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let mut prev_rest_span = None;
 
         // Lowers `$bm $ident @ ..` to `$bm $ident @ _`.
-        let lower_rest_sub = |this: &mut Self, pat, &ann, &ident, sub| {
-            let lower_sub = |this: &mut Self| Some(this.pat_wild_with_node_id_of(sub));
-            let node = this.lower_pat_ident(pat, ann, ident, lower_sub);
-            this.pat_with_node_id_of(pat, node)
+        let lower_rest_sub = |this: &mut Self, pat: &Pat, &ann, &ident, sub: &Pat| {
+            let sub_hir_id = this.lower_node_id(sub.id);
+            let lower_sub = |this: &mut Self| Some(this.pat_wild_with_node_id_of(sub, sub_hir_id));
+            let pat_hir_id = this.lower_node_id(pat.id);
+            let node = this.lower_pat_ident(pat, ann, ident, pat_hir_id, lower_sub);
+            this.pat_with_node_id_of(pat, node, pat_hir_id)
         };
 
         let mut iter = pats.iter();
@@ -200,7 +209,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 // Found a sub-slice pattern `..`. Record, lower it to `_`, and stop here.
                 PatKind::Rest => {
                     prev_rest_span = Some(pat.span);
-                    slice = Some(self.pat_wild_with_node_id_of(pat));
+                    let hir_id = self.lower_node_id(pat.id);
+                    slice = Some(self.pat_wild_with_node_id_of(pat, hir_id));
                     break;
                 }
                 // Found a sub-slice pattern `$binding_mode $ident @ ..`.
@@ -248,6 +258,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         p: &Pat,
         annotation: BindingMode,
         ident: Ident,
+        hir_id: hir::HirId,
         lower_sub: impl FnOnce(&mut Self) -> Option<&'hir hir::Pat<'hir>>,
     ) -> hir::PatKind<'hir> {
         match self.resolver.get_partial_res(p.id).map(|d| d.expect_full_res()) {
@@ -257,10 +268,19 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     Some(Res::Local(id)) => id,
                     _ => p.id,
                 };
-
+                // All identifiers resolves to this canonical identifier share its `HirId`.
+                let binding_id = if canonical_id == p.id {
+                    self.ident_to_local_id.insert(canonical_id, hir_id.local_id);
+                    hir_id
+                } else {
+                    hir::HirId {
+                        owner: self.current_hir_id_owner,
+                        local_id: self.ident_to_local_id[&canonical_id],
+                    }
+                };
                 hir::PatKind::Binding(
                     annotation,
-                    self.lower_node_id(canonical_id),
+                    binding_id,
                     self.lower_ident(ident),
                     lower_sub(self),
                 )
@@ -280,18 +300,18 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         }
     }
 
-    fn pat_wild_with_node_id_of(&mut self, p: &Pat) -> &'hir hir::Pat<'hir> {
-        self.arena.alloc(self.pat_with_node_id_of(p, hir::PatKind::Wild))
+    fn pat_wild_with_node_id_of(&mut self, p: &Pat, hir_id: hir::HirId) -> &'hir hir::Pat<'hir> {
+        self.arena.alloc(self.pat_with_node_id_of(p, hir::PatKind::Wild, hir_id))
     }
 
-    /// Construct a `Pat` with the `HirId` of `p.id` lowered.
-    fn pat_with_node_id_of(&mut self, p: &Pat, kind: hir::PatKind<'hir>) -> hir::Pat<'hir> {
-        hir::Pat {
-            hir_id: self.lower_node_id(p.id),
-            kind,
-            span: self.lower_span(p.span),
-            default_binding_modes: true,
-        }
+    /// Construct a `Pat` with the `HirId` of `p.id` already lowered.
+    fn pat_with_node_id_of(
+        &mut self,
+        p: &Pat,
+        kind: hir::PatKind<'hir>,
+        hir_id: hir::HirId,
+    ) -> hir::Pat<'hir> {
+        hir::Pat { hir_id, kind, span: self.lower_span(p.span), default_binding_modes: true }
     }
 
     /// Emit a friendly error for extra `..` patterns in a tuple/tuple struct/slice pattern.
diff --git a/tests/ui/thir-print/thir-tree-match.stdout b/tests/ui/thir-print/thir-tree-match.stdout
index b2431698cc645..8cff788766189 100644
--- a/tests/ui/thir-print/thir-tree-match.stdout
+++ b/tests/ui/thir-print/thir-tree-match.stdout
@@ -41,7 +41,7 @@ body:
                             Block {
                                 targeted_by_break: false
                                 span: $DIR/thir-tree-match.rs:15:32: 21:2 (#0)
-                                region_scope: Node(25)
+                                region_scope: Node(3)
                                 safety_mode: Safe
                                 stmts: []
                                 expr:
@@ -51,8 +51,8 @@ body:
                                         span: $DIR/thir-tree-match.rs:16:5: 20:6 (#0)
                                         kind: 
                                             Scope {
-                                                region_scope: Node(3)
-                                                lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).3))
+                                                region_scope: Node(4)
+                                                lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).4))
                                                 value:
                                                     Expr {
                                                         ty: bool
@@ -67,8 +67,8 @@ body:
                                                                         span: $DIR/thir-tree-match.rs:16:11: 16:14 (#0)
                                                                         kind: 
                                                                             Scope {
-                                                                                region_scope: Node(4)
-                                                                                lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).4))
+                                                                                region_scope: Node(5)
+                                                                                lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).5))
                                                                                 value:
                                                                                     Expr {
                                                                                         ty: Foo
@@ -123,16 +123,16 @@ body:
                                                                         body: 
                                                                             Expr {
                                                                                 ty: bool
-                                                                                temp_lifetime: Some(Node(12))
+                                                                                temp_lifetime: Some(Node(13))
                                                                                 span: $DIR/thir-tree-match.rs:17:36: 17:40 (#0)
                                                                                 kind: 
                                                                                     Scope {
-                                                                                        region_scope: Node(13)
-                                                                                        lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).13))
+                                                                                        region_scope: Node(14)
+                                                                                        lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).14))
                                                                                         value:
                                                                                             Expr {
                                                                                                 ty: bool
-                                                                                                temp_lifetime: Some(Node(12))
+                                                                                                temp_lifetime: Some(Node(13))
                                                                                                 span: $DIR/thir-tree-match.rs:17:36: 17:40 (#0)
                                                                                                 kind: 
                                                                                                     Literal( lit: Spanned { node: Bool(true), span: $DIR/thir-tree-match.rs:17:36: 17:40 (#0) }, neg: false)
@@ -140,8 +140,8 @@ body:
                                                                                             }
                                                                                     }
                                                                             }
-                                                                        lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).12))
-                                                                        scope: Node(12)
+                                                                        lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).13))
+                                                                        scope: Node(13)
                                                                         span: $DIR/thir-tree-match.rs:17:9: 17:40 (#0)
                                                                     }
                                                                     Arm {
@@ -175,16 +175,16 @@ body:
                                                                         body: 
                                                                             Expr {
                                                                                 ty: bool
-                                                                                temp_lifetime: Some(Node(18))
+                                                                                temp_lifetime: Some(Node(19))
                                                                                 span: $DIR/thir-tree-match.rs:18:27: 18:32 (#0)
                                                                                 kind: 
                                                                                     Scope {
-                                                                                        region_scope: Node(19)
-                                                                                        lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).19))
+                                                                                        region_scope: Node(20)
+                                                                                        lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).20))
                                                                                         value:
                                                                                             Expr {
                                                                                                 ty: bool
-                                                                                                temp_lifetime: Some(Node(18))
+                                                                                                temp_lifetime: Some(Node(19))
                                                                                                 span: $DIR/thir-tree-match.rs:18:27: 18:32 (#0)
                                                                                                 kind: 
                                                                                                     Literal( lit: Spanned { node: Bool(false), span: $DIR/thir-tree-match.rs:18:27: 18:32 (#0) }, neg: false)
@@ -192,8 +192,8 @@ body:
                                                                                             }
                                                                                     }
                                                                             }
-                                                                        lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).18))
-                                                                        scope: Node(18)
+                                                                        lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).19))
+                                                                        scope: Node(19)
                                                                         span: $DIR/thir-tree-match.rs:18:9: 18:32 (#0)
                                                                     }
                                                                     Arm {
@@ -219,16 +219,16 @@ body:
                                                                         body: 
                                                                             Expr {
                                                                                 ty: bool
-                                                                                temp_lifetime: Some(Node(23))
+                                                                                temp_lifetime: Some(Node(24))
                                                                                 span: $DIR/thir-tree-match.rs:19:24: 19:28 (#0)
                                                                                 kind: 
                                                                                     Scope {
-                                                                                        region_scope: Node(24)
-                                                                                        lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).24))
+                                                                                        region_scope: Node(25)
+                                                                                        lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).25))
                                                                                         value:
                                                                                             Expr {
                                                                                                 ty: bool
-                                                                                                temp_lifetime: Some(Node(23))
+                                                                                                temp_lifetime: Some(Node(24))
                                                                                                 span: $DIR/thir-tree-match.rs:19:24: 19:28 (#0)
                                                                                                 kind: 
                                                                                                     Literal( lit: Spanned { node: Bool(true), span: $DIR/thir-tree-match.rs:19:24: 19:28 (#0) }, neg: false)
@@ -236,8 +236,8 @@ body:
                                                                                             }
                                                                                     }
                                                                             }
-                                                                        lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).23))
-                                                                        scope: Node(23)
+                                                                        lint_level: Explicit(HirId(DefId(0:16 ~ thir_tree_match[fcf8]::has_match).24))
+                                                                        scope: Node(24)
                                                                         span: $DIR/thir-tree-match.rs:19:9: 19:28 (#0)
                                                                     }
                                                                 ]

From 1a39247d8dce70554964368046abcae9722675b6 Mon Sep 17 00:00:00 2001
From: Adwin White <adwinw01@gmail.com>
Date: Sun, 15 Sep 2024 11:10:16 +0800
Subject: [PATCH 2/3] Add duplicate lowering check

---
 compiler/rustc_ast_lowering/src/block.rs      |  9 -----
 compiler/rustc_ast_lowering/src/delegation.rs |  2 +-
 compiler/rustc_ast_lowering/src/expr.rs       | 14 ++++----
 compiler/rustc_ast_lowering/src/item.rs       | 12 +++----
 compiler/rustc_ast_lowering/src/lib.rs        | 35 ++++++++++++-------
 compiler/rustc_ast_lowering/src/pat.rs        |  4 +--
 6 files changed, 38 insertions(+), 38 deletions(-)

diff --git a/compiler/rustc_ast_lowering/src/block.rs b/compiler/rustc_ast_lowering/src/block.rs
index 8e02cbfd2ca81..20d3ce65facc7 100644
--- a/compiler/rustc_ast_lowering/src/block.rs
+++ b/compiler/rustc_ast_lowering/src/block.rs
@@ -14,15 +14,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.arena.alloc(self.lower_block_noalloc(hir_id, b, targeted_by_break))
     }
 
-    pub(super) fn lower_block_with_hir_id(
-        &mut self,
-        b: &Block,
-        hir_id: hir::HirId,
-        targeted_by_break: bool,
-    ) -> &'hir hir::Block<'hir> {
-        self.arena.alloc(self.lower_block_noalloc(hir_id, b, targeted_by_break))
-    }
-
     pub(super) fn lower_block_noalloc(
         &mut self,
         hir_id: hir::HirId,
diff --git a/compiler/rustc_ast_lowering/src/delegation.rs b/compiler/rustc_ast_lowering/src/delegation.rs
index 37eea707929e7..70c94f4019ae2 100644
--- a/compiler/rustc_ast_lowering/src/delegation.rs
+++ b/compiler/rustc_ast_lowering/src/delegation.rs
@@ -260,7 +260,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     };
                     self_resolver.visit_block(block);
                     // Target expr needs to lower `self` path.
-                    this.ident_to_local_id.insert(pat_node_id, param.pat.hir_id.local_id);
+                    this.ident_and_label_to_local_id.insert(pat_node_id, param.pat.hir_id.local_id);
                     this.lower_target_expr(&block)
                 } else {
                     this.generate_arg(param.pat.hir_id, span)
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
index 3df945a18e80a..d986c4b412fe7 100644
--- a/compiler/rustc_ast_lowering/src/expr.rs
+++ b/compiler/rustc_ast_lowering/src/expr.rs
@@ -261,10 +261,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     // expr node id.
                     let block_hir_id = self.lower_node_id(blk.id);
                     let opt_label = self.lower_label(*opt_label, blk.id, block_hir_id);
-                    hir::ExprKind::Block(
-                        self.lower_block_with_hir_id(blk, block_hir_id, opt_label.is_some()),
-                        opt_label,
-                    )
+                    let hir_block = self.arena.alloc(self.lower_block_noalloc(
+                        block_hir_id,
+                        blk,
+                        opt_label.is_some(),
+                    ));
+                    hir::ExprKind::Block(hir_block, opt_label)
                 }
                 ExprKind::Assign(el, er, span) => self.lower_expr_assign(el, er, *span, e.span),
                 ExprKind::AssignOp(op, el, er) => hir::ExprKind::AssignOp(
@@ -1486,7 +1488,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         dest_hir_id: hir::HirId,
     ) -> Option<Label> {
         let label = opt_label?;
-        self.labelled_node_id_to_local_id.insert(dest_id, dest_hir_id.local_id);
+        self.ident_and_label_to_local_id.insert(dest_id, dest_hir_id.local_id);
         Some(Label { ident: self.lower_ident(label.ident) })
     }
 
@@ -1494,7 +1496,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let target_id = match destination {
             Some((id, _)) => {
                 if let Some(loop_id) = self.resolver.get_label_res(id) {
-                    let local_id = self.labelled_node_id_to_local_id[&loop_id];
+                    let local_id = self.ident_and_label_to_local_id[&loop_id];
                     let loop_hir_id = HirId { owner: self.current_hir_id_owner, local_id };
                     Ok(loop_hir_id)
                 } else {
diff --git a/compiler/rustc_ast_lowering/src/item.rs b/compiler/rustc_ast_lowering/src/item.rs
index 9cad03ae4034b..d724560750114 100644
--- a/compiler/rustc_ast_lowering/src/item.rs
+++ b/compiler/rustc_ast_lowering/src/item.rs
@@ -154,8 +154,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     fn lower_item(&mut self, i: &Item) -> &'hir hir::Item<'hir> {
         let mut ident = i.ident;
         let vis_span = self.lower_span(i.vis.span);
-        let hir_id =
-            hir::HirId { owner: self.current_hir_id_owner, local_id: hir::ItemLocalId::ZERO };
+        let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
         let attrs = self.lower_attrs(hir_id, &i.attrs);
         let kind = self.lower_item_kind(i.span, i.id, hir_id, &mut ident, attrs, vis_span, &i.kind);
         let item = hir::Item {
@@ -605,8 +604,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     }
 
     fn lower_foreign_item(&mut self, i: &ForeignItem) -> &'hir hir::ForeignItem<'hir> {
-        let hir_id =
-            hir::HirId { owner: self.current_hir_id_owner, local_id: hir::ItemLocalId::ZERO };
+        let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
         let owner_id = hir_id.expect_owner();
         self.lower_attrs(hir_id, &i.attrs);
         let item = hir::ForeignItem {
@@ -730,8 +728,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
     }
 
     fn lower_trait_item(&mut self, i: &AssocItem) -> &'hir hir::TraitItem<'hir> {
-        let hir_id =
-            hir::HirId { owner: self.current_hir_id_owner, local_id: hir::ItemLocalId::ZERO };
+        let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
         self.lower_attrs(hir_id, &i.attrs);
         let trait_item_def_id = hir_id.expect_owner();
 
@@ -861,8 +858,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         // Since `default impl` is not yet implemented, this is always true in impls.
         let has_value = true;
         let (defaultness, _) = self.lower_defaultness(i.kind.defaultness(), has_value);
-        let hir_id =
-            hir::HirId { owner: self.current_hir_id_owner, local_id: hir::ItemLocalId::ZERO };
+        let hir_id = hir::HirId::make_owner(self.current_hir_id_owner.def_id);
         self.lower_attrs(hir_id, &i.attrs);
 
         let (generics, kind) = match &i.kind {
diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 3067cb7ccf24f..4ca878a1be0da 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -138,10 +138,10 @@ struct LoweringContext<'a, 'hir> {
     impl_trait_defs: Vec<hir::GenericParam<'hir>>,
     impl_trait_bounds: Vec<hir::WherePredicate<'hir>>,
 
-    /// NodeIds of labelled nodes that are lowered inside the current HIR owner.
-    labelled_node_id_to_local_id: NodeMap<hir::ItemLocalId>,
-    /// NodeIds of identifier that are lowered inside the current HIR owner.
-    ident_to_local_id: NodeMap<hir::ItemLocalId>,
+    /// NodeIds of pattern identifiers and labelled nodes that are lowered inside the current HIR owner.
+    ident_and_label_to_local_id: NodeMap<hir::ItemLocalId>,
+    /// NodeIds that are lowered inside the current HIR owner. Only used for duplicate lowering check.
+    node_id_to_local_id: NodeMap<hir::ItemLocalId>,
 
     allow_try_trait: Lrc<[Symbol]>,
     allow_gen_future: Lrc<[Symbol]>,
@@ -171,8 +171,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             current_hir_id_owner: hir::CRATE_OWNER_ID,
             current_def_id_parent: CRATE_DEF_ID,
             item_local_id_counter: hir::ItemLocalId::ZERO,
-            labelled_node_id_to_local_id: Default::default(),
-            ident_to_local_id: Default::default(),
+            ident_and_label_to_local_id: Default::default(),
+            node_id_to_local_id: Default::default(),
             trait_map: Default::default(),
 
             // Lowering state.
@@ -589,9 +589,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         let current_attrs = std::mem::take(&mut self.attrs);
         let current_bodies = std::mem::take(&mut self.bodies);
-        let current_labelled_node_id_to_local_id =
-            std::mem::take(&mut self.labelled_node_id_to_local_id);
-        let current_ident_to_local_id = std::mem::take(&mut self.ident_to_local_id);
+        let current_ident_and_label_to_local_id =
+            std::mem::take(&mut self.ident_and_label_to_local_id);
+        let current_node_id_to_local_id = std::mem::take(&mut self.node_id_to_local_id);
         let current_trait_map = std::mem::take(&mut self.trait_map);
         let current_owner =
             std::mem::replace(&mut self.current_hir_id_owner, hir::OwnerId { def_id });
@@ -604,6 +604,10 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         // we want `f` to be able to refer to the `LocalDefId`s that the caller created.
         // and the caller to refer to some of the subdefinitions' nodes' `LocalDefId`s.
 
+        // Always allocate the first `HirId` for the owner itself.
+        let _old = self.node_id_to_local_id.insert(owner, hir::ItemLocalId::ZERO);
+        debug_assert_eq!(_old, None);
+
         let item = self.with_def_id_parent(def_id, f);
         debug_assert_eq!(def_id, item.def_id().def_id);
         // `f` should have consumed all the elements in these vectors when constructing `item`.
@@ -613,8 +617,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
 
         self.attrs = current_attrs;
         self.bodies = current_bodies;
-        self.labelled_node_id_to_local_id = current_labelled_node_id_to_local_id;
-        self.ident_to_local_id = current_ident_to_local_id;
+        self.ident_and_label_to_local_id = current_ident_and_label_to_local_id;
+        self.node_id_to_local_id = current_node_id_to_local_id;
         self.trait_map = current_trait_map;
         self.current_hir_id_owner = current_owner;
         self.item_local_id_counter = current_local_counter;
@@ -703,6 +707,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             self.trait_map.insert(hir_id.local_id, traits.into_boxed_slice());
         }
 
+        // Check whether the same `NodeId` is lowered more than once.
+        #[cfg(debug_assertions)]
+        {
+            let old = self.node_id_to_local_id.insert(ast_node_id, local_id);
+            assert_eq!(old, None);
+        }
+
         hir_id
     }
 
@@ -720,7 +731,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     fn lower_res(&mut self, res: Res<NodeId>) -> Res {
         let res: Result<Res, ()> = res.apply_id(|id| {
             let owner = self.current_hir_id_owner;
-            let local_id = self.ident_to_local_id.get(&id).copied().ok_or(())?;
+            let local_id = self.ident_and_label_to_local_id.get(&id).copied().ok_or(())?;
             Ok(HirId { owner, local_id })
         });
         trace!(?res);
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
index 21829ea25a9bd..59c0e24479a09 100644
--- a/compiler/rustc_ast_lowering/src/pat.rs
+++ b/compiler/rustc_ast_lowering/src/pat.rs
@@ -270,12 +270,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 };
                 // All identifiers resolves to this canonical identifier share its `HirId`.
                 let binding_id = if canonical_id == p.id {
-                    self.ident_to_local_id.insert(canonical_id, hir_id.local_id);
+                    self.ident_and_label_to_local_id.insert(canonical_id, hir_id.local_id);
                     hir_id
                 } else {
                     hir::HirId {
                         owner: self.current_hir_id_owner,
-                        local_id: self.ident_to_local_id[&canonical_id],
+                        local_id: self.ident_and_label_to_local_id[&canonical_id],
                     }
                 };
                 hir::PatKind::Binding(

From e3bf50ede281ffd88ac70b65eb2df6b4352f3737 Mon Sep 17 00:00:00 2001
From: Adwin White <adwinw01@gmail.com>
Date: Mon, 14 Oct 2024 12:38:59 +0800
Subject: [PATCH 3/3] more consistent debug_assertions

---
 compiler/rustc_ast_lowering/src/lib.rs | 17 ++++++++++++---
 compiler/rustc_ast_lowering/src/pat.rs | 30 +++++++++++++++-----------
 2 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index 4ca878a1be0da..59dc369fe17f7 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -141,6 +141,7 @@ struct LoweringContext<'a, 'hir> {
     /// NodeIds of pattern identifiers and labelled nodes that are lowered inside the current HIR owner.
     ident_and_label_to_local_id: NodeMap<hir::ItemLocalId>,
     /// NodeIds that are lowered inside the current HIR owner. Only used for duplicate lowering check.
+    #[cfg(debug_assertions)]
     node_id_to_local_id: NodeMap<hir::ItemLocalId>,
 
     allow_try_trait: Lrc<[Symbol]>,
@@ -172,6 +173,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             current_def_id_parent: CRATE_DEF_ID,
             item_local_id_counter: hir::ItemLocalId::ZERO,
             ident_and_label_to_local_id: Default::default(),
+            #[cfg(debug_assertions)]
             node_id_to_local_id: Default::default(),
             trait_map: Default::default(),
 
@@ -591,6 +593,8 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let current_bodies = std::mem::take(&mut self.bodies);
         let current_ident_and_label_to_local_id =
             std::mem::take(&mut self.ident_and_label_to_local_id);
+
+        #[cfg(debug_assertions)]
         let current_node_id_to_local_id = std::mem::take(&mut self.node_id_to_local_id);
         let current_trait_map = std::mem::take(&mut self.trait_map);
         let current_owner =
@@ -605,8 +609,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         // and the caller to refer to some of the subdefinitions' nodes' `LocalDefId`s.
 
         // Always allocate the first `HirId` for the owner itself.
-        let _old = self.node_id_to_local_id.insert(owner, hir::ItemLocalId::ZERO);
-        debug_assert_eq!(_old, None);
+        #[cfg(debug_assertions)]
+        {
+            let _old = self.node_id_to_local_id.insert(owner, hir::ItemLocalId::ZERO);
+            debug_assert_eq!(_old, None);
+        }
 
         let item = self.with_def_id_parent(def_id, f);
         debug_assert_eq!(def_id, item.def_id().def_id);
@@ -618,7 +625,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         self.attrs = current_attrs;
         self.bodies = current_bodies;
         self.ident_and_label_to_local_id = current_ident_and_label_to_local_id;
-        self.node_id_to_local_id = current_node_id_to_local_id;
+
+        #[cfg(debug_assertions)]
+        {
+            self.node_id_to_local_id = current_node_id_to_local_id;
+        }
         self.trait_map = current_trait_map;
         self.current_hir_id_owner = current_owner;
         self.item_local_id_counter = current_local_counter;
diff --git a/compiler/rustc_ast_lowering/src/pat.rs b/compiler/rustc_ast_lowering/src/pat.rs
index 59c0e24479a09..ace7bfb5c73f2 100644
--- a/compiler/rustc_ast_lowering/src/pat.rs
+++ b/compiler/rustc_ast_lowering/src/pat.rs
@@ -264,18 +264,24 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         match self.resolver.get_partial_res(p.id).map(|d| d.expect_full_res()) {
             // `None` can occur in body-less function signatures
             res @ (None | Some(Res::Local(_))) => {
-                let canonical_id = match res {
-                    Some(Res::Local(id)) => id,
-                    _ => p.id,
-                };
-                // All identifiers resolves to this canonical identifier share its `HirId`.
-                let binding_id = if canonical_id == p.id {
-                    self.ident_and_label_to_local_id.insert(canonical_id, hir_id.local_id);
-                    hir_id
-                } else {
-                    hir::HirId {
-                        owner: self.current_hir_id_owner,
-                        local_id: self.ident_and_label_to_local_id[&canonical_id],
+                let binding_id = match res {
+                    Some(Res::Local(id)) => {
+                        // In `Or` patterns like `VariantA(s) | VariantB(s, _)`, multiple identifier patterns
+                        // will be resolved to the same `Res::Local`. Thus they just share a single
+                        // `HirId`.
+                        if id == p.id {
+                            self.ident_and_label_to_local_id.insert(id, hir_id.local_id);
+                            hir_id
+                        } else {
+                            hir::HirId {
+                                owner: self.current_hir_id_owner,
+                                local_id: self.ident_and_label_to_local_id[&id],
+                            }
+                        }
+                    }
+                    _ => {
+                        self.ident_and_label_to_local_id.insert(p.id, hir_id.local_id);
+                        hir_id
                     }
                 };
                 hir::PatKind::Binding(