---

yaml
---
r: 116723
b: refs/heads/snap-stage3
c: 45a1b97
h: refs/heads/master
i:
  116721: 92577d1
  116719: 1df9534
v: v3

Author: Cameron Zwarich

[refs]

@@ -1,7 +1,7 @@
 ---
 refs/heads/master: bee4e6adac17f87b1cdc26ab69f8c0f5d82575a3
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
-refs/heads/snap-stage3: 8c0e1ce6c9410f4d928923ee93e7b5a4674ae2ed
+refs/heads/snap-stage3: 45a1b977643456ceacfc81183e2d5743f7c61ce9
 refs/heads/try: 009d898a9422ac04c1aa60c0e9aff3abc5fa4672
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/heads/ndm: f3868061cd7988080c30d6d5bf352a5a5fe2460b

branches/snap-stage3/src/librustc/middle/borrowck/check_loans.rs

@@ -871,33 +871,55 @@ impl<'a> CheckLoanCtxt<'a> {
                self.tcx().map.node_to_str(expr_id),
                move_path.repr(self.tcx()));
 
-        // We must check every element of a move path. See
-        // `borrowck-move-subcomponent.rs` for a test case.
-
         let mut ret = MoveOk;
+
+        // First, we check for a restriction on the path P being used. This
+        // accounts for borrows of P but also borrows of subpaths, like P.a.b.
+        // Consider the following example:
+        //
+        //     let x = &mut a.b.c; // Restricts a, a.b, and a.b.c
+        //     let y = a;          // Conflicts with restriction
+
+        self.each_in_scope_restriction(expr_id, move_path, |loan, _restr| {
+            // Any restriction prevents moves.
+            ret = MoveWhileBorrowed(loan.loan_path.clone(), loan.span);
+            false
+        });
+
+        // Next, we must check for *loans* (not restrictions) on the path P or
+        // any base path. This rejects examples like the following:
+        //
+        //     let x = &mut a.b;
+        //     let y = a.b.c;
+        //
+        // Limiting this search to *loans* and not *restrictions* means that
+        // examples like the following continue to work:
+        //
+        //     let x = &mut a.b;
+        //     let y = a.c;
+
         let mut loan_path = move_path;
         loop {
-            // check for a conflicting loan:
-            self.each_in_scope_restriction(expr_id, loan_path, |loan, _| {
+            self.each_in_scope_loan(expr_id, |loan| {
                 // Any restriction prevents moves.
-                ret = MoveWhileBorrowed(loan.loan_path.clone(), loan.span);
-                false
+                if *loan.loan_path == *loan_path {
+                    ret = MoveWhileBorrowed(loan.loan_path.clone(), loan.span);
+                    false
+                } else {
+                    true
+                }
             });
 
-            if ret != MoveOk {
-                return ret
-            }
-
             match *loan_path {
                 LpVar(_) => {
-                    ret = MoveOk;
                     break;
                 }
                 LpExtend(ref lp_base, _, _) => {
                     loan_path = &**lp_base;
                 }
             }
         }
-        ret
+
+        return ret;
     }
 }

branches/snap-stage3/src/test/compile-fail/borrowck-field-sensitivity.rs

@@ -84,20 +84,6 @@ fn fu_move_after_fu_move() {
 
 // The following functions aren't yet accepted, but they should be.
 
-fn move_after_borrow_correct() {
-    let x = A { a: 1, b: box 2 };
-    let p = &x.a;
-    drop(x.b); //~ ERROR cannot move out of `x.b` because it is borrowed
-    drop(*p);
-}
-
-fn fu_move_after_borrow_correct() {
-    let x = A { a: 1, b: box 2 };
-    let p = &x.a;
-    let _y = A { a: 3, .. x }; //~ ERROR cannot move out of `x.b` because it is borrowed
-    drop(*p);
-}
-
 fn copy_after_field_assign_after_uninit() {
     let mut x: A;
     x.a = 1;
@@ -132,9 +118,6 @@ fn main() {
     fu_move_after_move();
     fu_move_after_fu_move();
 
-    move_after_borrow_correct();
-    fu_move_after_borrow_correct();
-
     copy_after_field_assign_after_uninit();
     borrow_after_field_assign_after_uninit();
     move_after_field_assign_after_uninit();

branches/snap-stage3/src/test/run-pass/borrowck-field-sensitivity.rs

@@ -73,6 +73,20 @@ fn borrow_after_fu_move() {
     drop(*p);
 }
 
+fn move_after_borrow() {
+    let x = A { a: 1, b: box 2 };
+    let p = &x.a;
+    drop(x.b);
+    drop(*p);
+}
+
+fn fu_move_after_borrow() {
+    let x = A { a: 1, b: box 2 };
+    let p = &x.a;
+    let _y = A { a: 3, .. x };
+    drop(*p);
+}
+
 fn mut_borrow_after_mut_borrow() {
     let mut x = A { a: 1, b: box 2 };
     let p = &mut x.a;
@@ -225,6 +239,8 @@ fn main() {
 
     borrow_after_move();
     borrow_after_fu_move();
+    move_after_borrow();
+    fu_move_after_borrow();
     mut_borrow_after_mut_borrow();
 
     move_after_move();