Refactored used_mut_nodes

src/librustc/ty/context.rs

@@ -811,11 +811,6 @@ pub struct GlobalCtxt<'tcx> {
     /// present in this set can be warned about.
     pub used_unsafe: RefCell<NodeSet>,
 
-    /// Set of nodes which mark locals as mutable which end up getting used at
-    /// some point. Local variable definitions not in this set can be warned
-    /// about.
-    pub used_mut_nodes: RefCell<NodeSet>,
-
     /// Maps any item's def-id to its stability index.
     pub stability: RefCell<stability::Index<'tcx>>,
 
@@ -1043,7 +1038,6 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             inhabitedness_cache: RefCell::new(FxHashMap()),
             lang_items,
             used_unsafe: RefCell::new(NodeSet()),
-            used_mut_nodes: RefCell::new(NodeSet()),
             stability: RefCell::new(stability),
             selection_cache: traits::SelectionCache::new(),
             evaluation_cache: traits::EvaluationCache::new(),

src/librustc/ty/maps.rs

@@ -21,7 +21,7 @@ use mir;
 use mir::transform::{MirSuite, MirPassIndex};
 use session::CompileResult;
 use traits::specialization_graph;
-use ty::{self, CrateInherentImpls, Ty, TyCtxt};
+use ty::{self, BorrowCheckResult, CrateInherentImpls, Ty, TyCtxt};
 use ty::layout::{Layout, LayoutError};
 use ty::item_path;
 use ty::steal::Steal;
@@ -922,7 +922,7 @@ define_maps! { <'tcx>
 
     [] coherent_trait: coherent_trait_dep_node((CrateNum, DefId)) -> (),
 
-    [] borrowck: BorrowCheck(DefId) -> (),
+    [] borrowck: BorrowCheck(DefId) -> Rc<BorrowCheckResult>,
 
     /// Gets a complete map from all types to their inherent impls.
     /// Not meant to be used directly outside of coherence.

src/librustc/ty/mod.rs

@@ -2599,3 +2599,10 @@ impl fmt::Display for SymbolName {
         fmt::Display::fmt(&self.name, fmt)
     }
 }
+
+pub struct BorrowCheckResult {
+    /// contains the node-ids for variables within this function where the `mut`
+    /// declaration was used in some way (e.g., by modifying the variable's value,
+    /// or taking an `&mut` borrow of it).
+    used_mut_nodes: NodeSet
+}

src/librustc_borrowck/borrowck/check_loans.rs

@@ -189,7 +189,7 @@ pub fn check_loans<'a, 'b, 'c, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
                                      dfcx_loans: &LoanDataFlow<'b, 'tcx>,
                                      move_data: &move_data::FlowedMoveData<'c, 'tcx>,
                                      all_loans: &[Loan<'tcx>],
-                                     body: &hir::Body) {
+                                     body: &hir::Body) -> BorrowCheckResult {
     debug!("check_loans(body id={})", body.value.id);
 
     let def_id = bccx.tcx.hir.body_owner_def_id(body.id());
@@ -203,6 +203,7 @@ pub fn check_loans<'a, 'b, 'c, 'tcx>(bccx: &BorrowckCtxt<'a, 'tcx>,
     };
     euv::ExprUseVisitor::new(&mut clcx, bccx.tcx, param_env, &bccx.region_maps, bccx.tables)
         .consume_body(body);
+    clcx.bccx.borrowck_result.borrow()
 }
 
 #[derive(PartialEq)]
@@ -843,7 +844,7 @@ impl<'a, 'tcx> CheckLoanCtxt<'a, 'tcx> {
             let lp = opt_loan_path(&assignee_cmt).unwrap();
             self.move_data.each_assignment_of(assignment_id, &lp, |assign| {
                 if assignee_cmt.mutbl.is_mutable() {
-                    self.tcx().used_mut_nodes.borrow_mut().insert(local_id);
+                    self.bccx.borrowck_result.borrow_mut().used_mut_nodes.insert(local_id);
                 } else {
                     self.bccx.report_reassigned_immutable_variable(
                         assignment_span,

src/librustc_borrowck/borrowck/gather_loans/mod.rs

@@ -451,7 +451,7 @@ impl<'a, 'tcx> GatherLoanCtxt<'a, 'tcx> {
                 }
                 LpUpvar(ty::UpvarId{ var_id, closure_expr_id: _ }) => {
                     let local_id = self.tcx().hir.def_index_to_node_id(var_id);
-                    self.tcx().used_mut_nodes.borrow_mut().insert(local_id);
+                    self.bccx.borrowck_result.borrow_mut().used_mut_nodes.insert(local_id);
                     None
                 }
                 LpExtend(ref base, mc::McInherited, LpDeref(pointer_kind)) |

src/librustc_borrowck/borrowck/mod.rs

@@ -34,7 +34,7 @@ use rustc::middle::mem_categorization::Categorization;
 use rustc::middle::mem_categorization::ImmutabilityBlame;
 use rustc::middle::region::{self, RegionMaps};
 use rustc::middle::free_region::RegionRelations;
-use rustc::ty::{self, TyCtxt};
+use rustc::ty::{self, BorrowCheckResult, TyCtxt};
 use rustc::ty::maps::Providers;
 
 use rustc_mir::util::borrowck_errors::{BorrowckErrors, Origin};
@@ -80,7 +80,7 @@ pub struct AnalysisData<'a, 'tcx: 'a> {
     pub move_data: move_data::FlowedMoveData<'a, 'tcx>,
 }
 
-fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId) {
+fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId) -> BorrowCheckResult {
     debug!("borrowck(body_owner_def_id={:?})", owner_def_id);
 
     let owner_id = tcx.hir.as_local_node_id(owner_def_id).unwrap();
@@ -128,6 +128,8 @@ fn borrowck<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, owner_def_id: DefId) {
     {
         check_loans::check_loans(bccx, &loan_dfcx, &flowed_moves, &all_loans, body);
     }
+
+    check_loans::check_loans(bccx, &loan_dfcx, &flowed_moves, &all_loans, body)
 }
 
 fn build_borrowck_dataflow_data<'a, 'c, 'tcx, F>(this: &mut BorrowckCtxt<'a, 'tcx>,
@@ -217,6 +219,8 @@ pub struct BorrowckCtxt<'a, 'tcx: 'a> {
 
     region_maps: Rc<RegionMaps>,
 
+    borrowck_result: Rc<BorrowCheckResult>,
+
     owner_def_id: DefId,
 }
 

src/librustc_lint/unused.rs

@@ -35,7 +35,9 @@ declare_lint! {
 }
 
 #[derive(Copy, Clone)]
-pub struct UnusedMut;
+pub struct UnusedMut {
+    borrowck_results: Vec<Rc<BorrowCheckResult>>
+}
 
 impl UnusedMut {
     fn check_unused_mut_pat(&self, cx: &LateContext, pats: &[P<hir::Pat>]) {
@@ -84,6 +86,15 @@ impl LintPass for UnusedMut {
 }
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedMut {
+    fn check_body(&mut self, cx: &LateContext, body: &'tcx hir::Body) {
+        let body_owner_def_id = cx.tcx().hir.body_owner_def_id(body.id());
+        self.borrowck_results.push(cx.tcx().borrowck(body_owner_def_id));
+    }
+
+    fn check_body_post(&mut self, cx: &LateContext, body: &'tcx hir::Body) {
+        self.borrowck_results.pop();
+    }
+
     fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
         if let hir::ExprMatch(_, ref arms, _) = e.node {
             for a in arms {