Auto merge of #59540 - Zoxc:the-arena-2, r=<try>

[WIP] Use arenas to avoid Lrc in queries #1

Based on #59536.

Author: bors

src/librustc/arena.rs

@@ -16,6 +16,7 @@ macro_rules! arena_types {
             )>,
             [few] mir_keys: rustc::util::nodemap::DefIdSet,
             [decode] specialization_graph: rustc::traits::specialization_graph::Graph,
+            [decode] borrowck: rustc::middle::borrowck::BorrowCheckResult,
         ], $tcx);
     )
 }

src/librustc/query/mod.rs

@@ -368,7 +368,7 @@ rustc_queries! {
     }
 
     BorrowChecking {
-        query borrowck(_: DefId) -> Lrc<BorrowCheckResult> {}
+        query borrowck(_: DefId) -> &'tcx BorrowCheckResult {}
 
         /// Borrow checks the function body. If this is a closure, returns
         /// additional requirements that the closure's creator must verify.

src/librustc_borrowck/borrowck/mod.rs

@@ -77,7 +77,7 @@ pub struct AnalysisData<'a, 'tcx: 'a> {
 }
 
 fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId)
-    -> Lrc<BorrowCheckResult>
+    -> &'tcx BorrowCheckResult
 {
     assert!(tcx.use_ast_borrowck() || tcx.migrate_borrowck());
 
@@ -91,7 +91,7 @@ fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId)
             // those things (notably the synthesized constructors from
             // tuple structs/variants) do not have an associated body
             // and do not need borrowchecking.
-            return Lrc::new(BorrowCheckResult {
+            return tcx.arena.alloc(BorrowCheckResult {
                 used_mut_nodes: Default::default(),
                 signalled_any_error: SignalledError::NoErrorsSeen,
             })
@@ -142,7 +142,7 @@ fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId)
         unused::check(&mut bccx, body);
     }
 
-    Lrc::new(BorrowCheckResult {
+    tcx.arena.alloc(BorrowCheckResult {
         used_mut_nodes: bccx.used_mut_nodes.into_inner(),
         signalled_any_error: bccx.signalled_any_error.into_inner(),
     })