Rollup merge of #120214 - Nadrieril:fix-120210, r=pnkfelix

match lowering: consistently lower bindings deepest-first

Currently when lowering match expressions to MIR, we do a funny little dance with the order of bindings. I attempt to explain it in the third commit: we handle refutable (i.e. needing a test) patterns differently than irrefutable ones. This leads to inconsistencies, as reported in https://github.com/rust-lang/rust/issues/120210. The reason we need a dance at all is for situations like:

```rust
fn foo1(x: NonCopyStruct) {
    let y @ NonCopyStruct { copy_field: z } = x;
    // the above should turn into
    let z = x.copy_field;
    let y = x;
}
```

Here the `y ```````@```````` binding will move out of `x`, so we need to copy the field first.

I believe that the inconsistency came about when we fixed https://github.com/rust-lang/rust/issues/69971, and didn't notice that the fix didn't extend to refutable patterns. My guess then is that ordering bindings by "deepest-first, otherwise source order" is a sound choice. This PR implements that (at least I hope, match lowering is hard to follow 🥲).

Fixes https://github.com/rust-lang/rust/issues/120210

r? ```````@oli-obk``````` since you merged the original fix to https://github.com/rust-lang/rust/issues/69971
cc ```````@matthewjasper```````

compiler/rustc_mir_build/src/build/matches/simplify.rs

@@ -40,55 +40,10 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         &mut self,
         candidate: &mut Candidate<'pat, 'tcx>,
     ) -> bool {
-        // repeatedly simplify match pairs until fixed point is reached
         debug!("{candidate:#?}");
-
+        // In order to please the borrow checker, in a pattern like `x @ pat` we must lower the
-        // existing_bindings and new_bindings exists to keep the semantics in order.
+        // bindings in `pat` before `x`. E.g. (#69971):
-        // Reversing the binding order for bindings after `@` changes the binding order in places
-        // it shouldn't be changed, for example `let (Some(a), Some(b)) = (x, y)`
         //
-        // To avoid this, the binding occurs in the following manner:
-        // * the bindings for one iteration of the following loop occurs in order (i.e. left to
-        // right)
-        // * the bindings from the previous iteration of the loop is prepended to the bindings from
-        // the current iteration (in the implementation this is done by mem::swap and extend)
-        // * after all iterations, these new bindings are then appended to the bindings that were
-        // preexisting (i.e. `candidate.binding` when the function was called).
-        //
-        // example:
-        // candidate.bindings = [1, 2, 3]
-        // binding in iter 1: [4, 5]
-        // binding in iter 2: [6, 7]
-        //
-        // final binding: [1, 2, 3, 6, 7, 4, 5]
-        let mut existing_bindings = mem::take(&mut candidate.bindings);
-        let mut new_bindings = Vec::new();
-        loop {
-            let match_pairs = mem::take(&mut candidate.match_pairs);
-
-            if let [MatchPair { pattern: Pat { kind: PatKind::Or { pats }, .. }, place }] =
-                &*match_pairs
-            {
-                existing_bindings.extend_from_slice(&new_bindings);
-                mem::swap(&mut candidate.bindings, &mut existing_bindings);
-                candidate.subcandidates = self.create_or_subcandidates(candidate, place, pats);
-                return true;
-            }
-
-            let mut changed = false;
-            for match_pair in match_pairs {
-                match self.simplify_match_pair(match_pair, candidate) {
-                    Ok(()) => {
-                        changed = true;
-                    }
-                    Err(match_pair) => {
-                        candidate.match_pairs.push(match_pair);
-                    }
-                }
-            }
-            // Avoid issue #69971: the binding order should be right to left if there are more
-            // bindings after `@` to please the borrow checker
-            // Ex
         // struct NonCopyStruct {
         //     copy_field: u32,
         // }
@@ -99,23 +54,67 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         //     let z = x.copy_field;
         //     let y = x;
         // }
-            candidate.bindings.extend_from_slice(&new_bindings);
+        //
-            mem::swap(&mut candidate.bindings, &mut new_bindings);
+        // We can't just reverse the binding order, because we must preserve pattern-order
+        // otherwise, e.g. in `let (Some(a), Some(b)) = (x, y)`. Our rule then is: deepest-first,
+        // and bindings at the same depth stay in source order.
+        //
+        // To do this, every time around the loop we prepend the newly found bindings to the
+        // bindings we already had.
+        //
+        // example:
+        // candidate.bindings = [1, 2, 3]
+        // bindings in iter 1: [4, 5]
+        // bindings in iter 2: [6, 7]
+        //
+        // final bindings: [6, 7, 4, 5, 1, 2, 3]
+        let mut accumulated_bindings = mem::take(&mut candidate.bindings);
+        // Repeatedly simplify match pairs until fixed point is reached
+        loop {
+            let mut changed = false;
+            for match_pair in mem::take(&mut candidate.match_pairs) {
+                match self.simplify_match_pair(match_pair, candidate) {
+                    Ok(()) => {
+                        changed = true;
+                    }
+                    Err(match_pair) => {
+                        candidate.match_pairs.push(match_pair);
+                    }
+                }
+            }
+
+            // This does: accumulated_bindings = candidate.bindings.take() ++ accumulated_bindings
+            candidate.bindings.extend_from_slice(&accumulated_bindings);
+            mem::swap(&mut candidate.bindings, &mut accumulated_bindings);
             candidate.bindings.clear();
 
             if !changed {
-                existing_bindings.extend_from_slice(&new_bindings);
+                // If we were not able to simplify anymore, done.
-                mem::swap(&mut candidate.bindings, &mut existing_bindings);
+                break;
+            }
+        }
+
+        // Store computed bindings back in `candidate`.
+        mem::swap(&mut candidate.bindings, &mut accumulated_bindings);
+
+        let did_expand_or =
+            if let [MatchPair { pattern: Pat { kind: PatKind::Or { pats }, .. }, place }] =
+                &*candidate.match_pairs
+            {
+                candidate.subcandidates = self.create_or_subcandidates(candidate, place, pats);
+                candidate.match_pairs.clear();
+                true
+            } else {
+                false
+            };
+
         // Move or-patterns to the end, because they can result in us
         // creating additional candidates, so we want to test them as
         // late as possible.
-                candidate
+        candidate.match_pairs.sort_by_key(|pair| matches!(pair.pattern.kind, PatKind::Or { .. }));
-                    .match_pairs
-                    .sort_by_key(|pair| matches!(pair.pattern.kind, PatKind::Or { .. }));
         debug!(simplified = ?candidate, "simplify_candidate");
-                return false; // if we were not able to simplify any, done.
+
-            }
+        did_expand_or
-        }
     }
 
     /// Given `candidate` that has a single or-pattern for its match-pairs,

tests/mir-opt/early_otherwise_branch.opt1.EarlyOtherwiseBranch.diff

@@ -51,13 +51,13 @@
 -     }
 - 
 -     bb3: {
-          StorageLive(_8);
-          _8 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
           StorageLive(_9);
           _9 = (((_3.1: std::option::Option<u32>) as Some).0: u32);
+          StorageLive(_8);
+          _8 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
           _0 = const 0_u32;
-          StorageDead(_9);
           StorageDead(_8);
+          StorageDead(_9);
 -         goto -> bb4;
 +         goto -> bb3;
       }

tests/mir-opt/early_otherwise_branch.opt2.EarlyOtherwiseBranch.diff

@@ -58,13 +58,13 @@
 - 
 -     bb4: {
 +     bb2: {
-          StorageLive(_9);
-          _9 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
           StorageLive(_10);
           _10 = (((_3.1: std::option::Option<u32>) as Some).0: u32);
+          StorageLive(_9);
+          _9 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
           _0 = const 0_u32;
-          StorageDead(_10);
           StorageDead(_9);
+          StorageDead(_10);
 -         goto -> bb6;
 +         goto -> bb4;
       }

tests/mir-opt/early_otherwise_branch.opt3.EarlyOtherwiseBranch.diff

@@ -51,13 +51,13 @@
 -     }
 - 
 -     bb3: {
-          StorageLive(_8);
-          _8 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
           StorageLive(_9);
           _9 = (((_3.1: std::option::Option<bool>) as Some).0: bool);
+          StorageLive(_8);
+          _8 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
           _0 = const 0_u32;
-          StorageDead(_9);
           StorageDead(_8);
+          StorageDead(_9);
 -         goto -> bb4;
 +         goto -> bb3;
       }

tests/mir-opt/early_otherwise_branch_3_element_tuple.opt1.EarlyOtherwiseBranch.diff

@@ -69,16 +69,16 @@
   
 -     bb4: {
 +     bb3: {
-          StorageLive(_11);
-          _11 = (((_4.0: std::option::Option<u32>) as Some).0: u32);
-          StorageLive(_12);
-          _12 = (((_4.1: std::option::Option<u32>) as Some).0: u32);
           StorageLive(_13);
           _13 = (((_4.2: std::option::Option<u32>) as Some).0: u32);
+          StorageLive(_12);
+          _12 = (((_4.1: std::option::Option<u32>) as Some).0: u32);
+          StorageLive(_11);
+          _11 = (((_4.0: std::option::Option<u32>) as Some).0: u32);
           _0 = const 0_u32;
-          StorageDead(_13);
-          StorageDead(_12);
           StorageDead(_11);
+          StorageDead(_12);
+          StorageDead(_13);
 -         goto -> bb5;
 +         goto -> bb4;
       }

tests/mir-opt/early_otherwise_branch_68867.try_sum.EarlyOtherwiseBranch.diff

@@ -116,12 +116,12 @@
       }
   
       bb6: {
-          StorageLive(_12);
-          _39 = deref_copy (_4.0: &ViewportPercentageLength);
-          _12 = (((*_39) as Vw).0: f32);
           StorageLive(_13);
-          _40 = deref_copy (_4.1: &ViewportPercentageLength);
+          _39 = deref_copy (_4.1: &ViewportPercentageLength);
-          _13 = (((*_40) as Vw).0: f32);
+          _13 = (((*_39) as Vw).0: f32);
+          StorageLive(_12);
+          _40 = deref_copy (_4.0: &ViewportPercentageLength);
+          _12 = (((*_40) as Vw).0: f32);
           StorageLive(_14);
           StorageLive(_15);
           _15 = _12;
@@ -132,18 +132,18 @@
           StorageDead(_15);
           _3 = ViewportPercentageLength::Vw(move _14);
           StorageDead(_14);
-          StorageDead(_13);
           StorageDead(_12);
+          StorageDead(_13);
           goto -> bb10;
       }
   
       bb7: {
-          StorageLive(_17);
-          _41 = deref_copy (_4.0: &ViewportPercentageLength);
-          _17 = (((*_41) as Vh).0: f32);
           StorageLive(_18);
-          _42 = deref_copy (_4.1: &ViewportPercentageLength);
+          _41 = deref_copy (_4.1: &ViewportPercentageLength);
-          _18 = (((*_42) as Vh).0: f32);
+          _18 = (((*_41) as Vh).0: f32);
+          StorageLive(_17);
+          _42 = deref_copy (_4.0: &ViewportPercentageLength);
+          _17 = (((*_42) as Vh).0: f32);
           StorageLive(_19);
           StorageLive(_20);
           _20 = _17;
@@ -154,18 +154,18 @@
           StorageDead(_20);
           _3 = ViewportPercentageLength::Vh(move _19);
           StorageDead(_19);
-          StorageDead(_18);
           StorageDead(_17);
+          StorageDead(_18);
           goto -> bb10;
       }
   
       bb8: {
-          StorageLive(_22);
-          _43 = deref_copy (_4.0: &ViewportPercentageLength);
-          _22 = (((*_43) as Vmin).0: f32);
           StorageLive(_23);
-          _44 = deref_copy (_4.1: &ViewportPercentageLength);
+          _43 = deref_copy (_4.1: &ViewportPercentageLength);
-          _23 = (((*_44) as Vmin).0: f32);
+          _23 = (((*_43) as Vmin).0: f32);
+          StorageLive(_22);
+          _44 = deref_copy (_4.0: &ViewportPercentageLength);
+          _22 = (((*_44) as Vmin).0: f32);
           StorageLive(_24);
           StorageLive(_25);
           _25 = _22;
@@ -176,18 +176,18 @@
           StorageDead(_25);
           _3 = ViewportPercentageLength::Vmin(move _24);
           StorageDead(_24);
-          StorageDead(_23);
           StorageDead(_22);
+          StorageDead(_23);
           goto -> bb10;
       }
   
       bb9: {
-          StorageLive(_27);
-          _45 = deref_copy (_4.0: &ViewportPercentageLength);
-          _27 = (((*_45) as Vmax).0: f32);
           StorageLive(_28);
-          _46 = deref_copy (_4.1: &ViewportPercentageLength);
+          _45 = deref_copy (_4.1: &ViewportPercentageLength);
-          _28 = (((*_46) as Vmax).0: f32);
+          _28 = (((*_45) as Vmax).0: f32);
+          StorageLive(_27);
+          _46 = deref_copy (_4.0: &ViewportPercentageLength);
+          _27 = (((*_46) as Vmax).0: f32);
           StorageLive(_29);
           StorageLive(_30);
           _30 = _27;
@@ -198,8 +198,8 @@
           StorageDead(_30);
           _3 = ViewportPercentageLength::Vmax(move _29);
           StorageDead(_29);
-          StorageDead(_28);
           StorageDead(_27);
+          StorageDead(_28);
           goto -> bb10;
       }
   

tests/mir-opt/early_otherwise_branch_noopt.noopt1.EarlyOtherwiseBranch.diff

@@ -59,13 +59,13 @@
       }
   
       bb5: {
-          StorageLive(_9);
-          _9 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
           StorageLive(_10);
           _10 = (((_3.1: std::option::Option<u32>) as Some).0: u32);
+          StorageLive(_9);
+          _9 = (((_3.0: std::option::Option<u32>) as Some).0: u32);
           _0 = const 0_u32;
-          StorageDead(_10);
           StorageDead(_9);
+          StorageDead(_10);
           goto -> bb8;
       }
   

tests/ui/pattern/bindings-after-at/bind-by-copy.rs

@@ -1,13 +1,30 @@
 // run-pass
+#![allow(unused)]
 
 // Test copy
 
-struct A { a: i32, b: i32 }
+struct A {
-struct B { a: i32, b: C }
+    a: i32,
-struct D { a: i32, d: C }
+    b: i32,
-#[derive(Copy,Clone)]
+}
-struct C { c: i32 }
+struct B {
+    a: i32,
+    b: C,
+}
+struct D {
+    a: i32,
+    d: C,
+}
+#[derive(Copy, Clone)]
+struct C {
+    c: i32,
+}
+enum E {
+    E { a: i32, e: C },
+    NotE,
+}
 
+#[rustfmt::skip]
 pub fn main() {
     match (A {a: 10, b: 20}) {
         x@A {a, b: 20} => { assert!(x.a == 10); assert!(a == 10); }
@@ -23,6 +40,23 @@ pub fn main() {
     y.d.c = 30;
     assert_eq!(d.c, 20);
 
+    match (E::E { a: 10, e: C { c: 20 } }) {
+        x @ E::E{ a, e: C { c } } => {
+            assert!(matches!(x, E::E { a: 10, e: C { c: 20 } }));
+            assert!(a == 10);
+            assert!(c == 20);
+        }
+        _ => panic!(),
+    }
+    match (E::E { a: 10, e: C { c: 20 } }) {
+        mut x @ E::E{ a, e: C { mut c } } => {
+            x = E::NotE;
+            c += 30;
+            assert_eq!(c, 50);
+        }
+        _ => panic!(),
+    }
+
     let some_b = Some(B { a: 10, b: C { c: 20 } });
 
     // in irrefutable pattern

tests/ui/pattern/bindings-after-at/borrowck-move-and-move.rs

@@ -15,8 +15,8 @@ fn main() {
     let a @ (b, c) = (u(), u()); //~ ERROR use of partially moved value
 
     match Ok(U) {
-        a @ Ok(b) | a @ Err(b) => {} //~ ERROR use of moved value
+        a @ Ok(b) | a @ Err(b) => {} //~ ERROR use of partially moved value
-                                     //~^ ERROR use of moved value
+                                     //~^ ERROR use of partially moved value
     }
 
     fn fun(a @ b: U) {} //~ ERROR use of moved value

tests/ui/pattern/bindings-after-at/borrowck-move-and-move.stderr

@@ -40,35 +40,33 @@ help: borrow this binding in the pattern to avoid moving the value
 LL |     let ref a @ (b, ref c) = (u(), u());
    |         +++         +++
 
-error[E0382]: use of moved value
+error[E0382]: use of partially moved value
-  --> $DIR/borrowck-move-and-move.rs:18:16
+  --> $DIR/borrowck-move-and-move.rs:18:9
    |
-LL |     match Ok(U) {
-   |           ----- move occurs because value has type `Result<U, U>`, which does not implement the `Copy` trait
 LL |         a @ Ok(b) | a @ Err(b) => {}
-   |         -      ^ value used here after move
+   |         ^      - value partially moved here
    |         |
-   |         value moved here
+   |         value used here after partial move
    |
+   = note: partial move occurs because value has type `U`, which does not implement the `Copy` trait
 help: borrow this binding in the pattern to avoid moving the value
    |
-LL |         ref a @ Ok(b) | a @ Err(b) => {}
+LL |         ref a @ Ok(ref b) | a @ Err(b) => {}
-   |         +++
+   |         +++        +++
 
-error[E0382]: use of moved value
+error[E0382]: use of partially moved value
-  --> $DIR/borrowck-move-and-move.rs:18:29
+  --> $DIR/borrowck-move-and-move.rs:18:21
    |
-LL |     match Ok(U) {
-   |           ----- move occurs because value has type `Result<U, U>`, which does not implement the `Copy` trait
 LL |         a @ Ok(b) | a @ Err(b) => {}
-   |                     -       ^ value used here after move
+   |                     ^       - value partially moved here
    |                     |
-   |                     value moved here
+   |                     value used here after partial move
    |
+   = note: partial move occurs because value has type `U`, which does not implement the `Copy` trait
 help: borrow this binding in the pattern to avoid moving the value
    |
-LL |         a @ Ok(b) | ref a @ Err(b) => {}
+LL |         a @ Ok(b) | ref a @ Err(ref b) => {}
-   |                     +++
+   |                     +++         +++
 
 error[E0382]: use of partially moved value
   --> $DIR/borrowck-move-and-move.rs:25:9

tests/ui/pattern/bindings-after-at/borrowck-pat-by-move-and-ref-inverse.rs

@@ -48,19 +48,17 @@ fn main() {
         //~^ ERROR borrow of moved value
         //~| ERROR borrow of moved value
         //~| ERROR borrow of moved value
-        //~| ERROR use of moved value
+        //~| ERROR use of partially moved value
         None => {}
     }
     match Some([U, U]) {
         mut a @ Some([ref b, ref mut c]) => {}
         //~^ ERROR borrow of moved value
-        //~| ERROR borrow of moved value
         None => {}
     }
     match Some(u()) {
         a @ Some(ref b) => {}
         //~^ ERROR borrow of moved value
-        //~| ERROR borrow of moved value
         None => {}
     }
     match Some((u(), u())) {
@@ -68,13 +66,12 @@ fn main() {
         //~^ ERROR borrow of moved value
         //~| ERROR borrow of moved value
         //~| ERROR borrow of moved value
-        //~| ERROR use of moved value
+        //~| ERROR use of partially moved value
         None => {}
     }
     match Some([u(), u()]) {
         mut a @ Some([ref b, ref mut c]) => {}
         //~^ ERROR borrow of moved value
-        //~| ERROR borrow of moved value
         None => {}
     }
 }

tests/ui/pattern/bindings-after-at/borrowck-pat-by-move-and-ref-inverse.stderr

@@ -215,7 +215,7 @@ LL |         ref mut a @ Some([ref b, ref mut c]) => {}
    |         +++
 
 error: borrow of moved value
-  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:61:9
+  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:60:9
    |
 LL |         a @ Some(ref b) => {}
    |         ^        ----- value borrowed here after move
@@ -229,7 +229,7 @@ LL |         ref a @ Some(ref b) => {}
    |         +++
 
 error: borrow of moved value
-  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:67:9
+  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:65:9
    |
 LL |         a @ Some((mut b @ ref mut c, d @ ref e)) => {}
    |         ^                 ---------      ----- value borrowed here after move
@@ -244,7 +244,7 @@ LL |         ref a @ Some((mut b @ ref mut c, d @ ref e)) => {}
    |         +++
 
 error: borrow of moved value
-  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:67:19
+  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:65:19
    |
 LL |         a @ Some((mut b @ ref mut c, d @ ref e)) => {}
    |                   ^^^^^   --------- value borrowed here after move
@@ -258,7 +258,7 @@ LL |         a @ Some((ref mut b @ ref mut c, d @ ref e)) => {}
    |                   +++
 
 error: borrow of moved value
-  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:67:38
+  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:65:38
    |
 LL |         a @ Some((mut b @ ref mut c, d @ ref e)) => {}
    |                                      ^   ----- value borrowed here after move
@@ -272,7 +272,7 @@ LL |         a @ Some((mut b @ ref mut c, ref d @ ref e)) => {}
    |                                      +++
 
 error: borrow of moved value
-  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:75:9
+  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:73:9
    |
 LL |         mut a @ Some([ref b, ref mut c]) => {}
    |         ^^^^^         -----  --------- value borrowed here after move
@@ -314,66 +314,33 @@ help: borrow this binding in the pattern to avoid moving the value
 LL |     let ref a @ (mut b @ ref mut c, ref d @ ref e) = (u(), u());
    |         +++                         +++
 
-error[E0382]: use of moved value
+error[E0382]: use of partially moved value
-  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:47:38
+  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:47:9
    |
-LL |     match Some((U, U)) {
-   |           ------------ move occurs because value has type `Option<(U, U)>`, which does not implement the `Copy` trait
 LL |         a @ Some((mut b @ ref mut c, d @ ref e)) => {}
-   |         - value moved here           ^ value used here after move
+   |         ^                            - value partially moved here
+   |         |
+   |         value used here after partial move
    |
+   = note: partial move occurs because value has type `U`, which does not implement the `Copy` trait
 help: borrow this binding in the pattern to avoid moving the value
    |
-LL |         ref a @ Some((mut b @ ref mut c, d @ ref e)) => {}
+LL |         ref a @ Some((mut b @ ref mut c, ref d @ ref e)) => {}
-   |         +++
+   |         +++                              +++
 
-error[E0382]: borrow of moved value
+error[E0382]: use of partially moved value
-  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:55:30
+  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:65:9
    |
-LL |     match Some([U, U]) {
-   |           ------------ move occurs because value has type `Option<[U; 2]>`, which does not implement the `Copy` trait
-LL |         mut a @ Some([ref b, ref mut c]) => {}
-   |         -----                ^^^^^^^^^ value borrowed here after move
-   |         |
-   |         value moved here
-
-error[E0382]: borrow of moved value
-  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:61:18
-   |
-LL |     match Some(u()) {
-   |           --------- move occurs because value has type `Option<U>`, which does not implement the `Copy` trait
-LL |         a @ Some(ref b) => {}
-   |         -        ^^^^^ value borrowed here after move
-   |         |
-   |         value moved here
-   |
-help: borrow this binding in the pattern to avoid moving the value
-   |
-LL |         ref a @ Some(ref b) => {}
-   |         +++
-
-error[E0382]: use of moved value
-  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:67:38
-   |
-LL |     match Some((u(), u())) {
-   |           ---------------- move occurs because value has type `Option<(U, U)>`, which does not implement the `Copy` trait
 LL |         a @ Some((mut b @ ref mut c, d @ ref e)) => {}
-   |         - value moved here           ^ value used here after move
+   |         ^                            - value partially moved here
+   |         |
+   |         value used here after partial move
    |
+   = note: partial move occurs because value has type `U`, which does not implement the `Copy` trait
 help: borrow this binding in the pattern to avoid moving the value
    |
-LL |         ref a @ Some((mut b @ ref mut c, d @ ref e)) => {}
+LL |         ref a @ Some((mut b @ ref mut c, ref d @ ref e)) => {}
-   |         +++
+   |         +++                              +++
-
-error[E0382]: borrow of moved value
-  --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:75:30
-   |
-LL |     match Some([u(), u()]) {
-   |           ---------------- move occurs because value has type `Option<[U; 2]>`, which does not implement the `Copy` trait
-LL |         mut a @ Some([ref b, ref mut c]) => {}
-   |         -----                ^^^^^^^^^ value borrowed here after move
-   |         |
-   |         value moved here
 
 error: borrow of moved value
   --> $DIR/borrowck-pat-by-move-and-ref-inverse.rs:11:11
@@ -457,6 +424,6 @@ help: borrow this binding in the pattern to avoid moving the value
 LL |     fn f3(ref a @ [ref mut b, ref c]: [U; 2]) {}
    |           +++
 
-error: aborting due to 33 previous errors
+error: aborting due to 30 previous errors
 
 For more information about this error, try `rustc --explain E0382`.

tests/ui/pattern/bindings-after-at/borrowck-pat-by-move-and-ref.rs

@@ -58,11 +58,13 @@ fn main() {
     match Some([U, U]) {
         ref mut a @ Some([b, mut c]) => {}
         //~^ ERROR cannot move out of value because it is borrowed
+        //~| ERROR borrow of partially moved value
         None => {}
     }
     match Some(u()) {
         ref a @ Some(b) => {}
         //~^ ERROR cannot move out of value because it is borrowed
+        //~| ERROR borrow of partially moved value
         None => {}
     }
     match Some((u(), u())) {
@@ -77,6 +79,7 @@ fn main() {
     match Some([u(), u()]) {
         ref mut a @ Some([b, mut c]) => {}
         //~^ ERROR cannot move out of value because it is borrowed
+        //~| ERROR borrow of partially moved value
         None => {}
     }
 }

tests/ui/pattern/bindings-after-at/borrowck-pat-by-move-and-ref.stderr

@@ -125,7 +125,7 @@ LL |         ref mut a @ Some([b, mut c]) => {}
    |         value is mutably borrowed by `a` here
 
 error: cannot move out of value because it is borrowed
-  --> $DIR/borrowck-pat-by-move-and-ref.rs:64:9
+  --> $DIR/borrowck-pat-by-move-and-ref.rs:65:9
    |
 LL |         ref a @ Some(b) => {}
    |         ^^^^^        - value is moved into `b` here
@@ -133,7 +133,7 @@ LL |         ref a @ Some(b) => {}
    |         value is borrowed by `a` here
 
 error: cannot move out of value because it is borrowed
-  --> $DIR/borrowck-pat-by-move-and-ref.rs:69:9
+  --> $DIR/borrowck-pat-by-move-and-ref.rs:71:9
    |
 LL |         ref a @ Some((ref b @ mut c, ref d @ e)) => {}
    |         ^^^^^                 -----          - value is moved into `e` here
@@ -142,7 +142,7 @@ LL |         ref a @ Some((ref b @ mut c, ref d @ e)) => {}
    |         value is borrowed by `a` here
 
 error: cannot move out of value because it is borrowed
-  --> $DIR/borrowck-pat-by-move-and-ref.rs:69:23
+  --> $DIR/borrowck-pat-by-move-and-ref.rs:71:23
    |
 LL |         ref a @ Some((ref b @ mut c, ref d @ e)) => {}
    |                       ^^^^^   ----- value is moved into `c` here
@@ -150,7 +150,7 @@ LL |         ref a @ Some((ref b @ mut c, ref d @ e)) => {}
    |                       value is borrowed by `b` here
 
 error: cannot move out of value because it is borrowed
-  --> $DIR/borrowck-pat-by-move-and-ref.rs:69:38
+  --> $DIR/borrowck-pat-by-move-and-ref.rs:71:38
    |
 LL |         ref a @ Some((ref b @ mut c, ref d @ e)) => {}
    |                                      ^^^^^   - value is moved into `e` here
@@ -158,7 +158,7 @@ LL |         ref a @ Some((ref b @ mut c, ref d @ e)) => {}
    |                                      value is borrowed by `d` here
 
 error: cannot move out of value because it is borrowed
-  --> $DIR/borrowck-pat-by-move-and-ref.rs:78:9
+  --> $DIR/borrowck-pat-by-move-and-ref.rs:80:9
    |
 LL |         ref mut a @ Some([b, mut c]) => {}
    |         ^^^^^^^^^         -  ----- value is moved into `c` here
@@ -236,8 +236,36 @@ help: borrow this binding in the pattern to avoid moving the value
 LL |     let ref mut a @ [b, ref mut c] = [u(), u()];
    |                         +++
 
+error[E0382]: borrow of partially moved value
+  --> $DIR/borrowck-pat-by-move-and-ref.rs:59:9
+   |
+LL |         ref mut a @ Some([b, mut c]) => {}
+   |         ^^^^^^^^^            ----- value partially moved here
+   |         |
+   |         value borrowed here after partial move
+   |
+   = note: partial move occurs because value has type `U`, which does not implement the `Copy` trait
+help: borrow this binding in the pattern to avoid moving the value
+   |
+LL |         ref mut a @ Some([b, ref mut c]) => {}
+   |                              +++
+
+error[E0382]: borrow of partially moved value
+  --> $DIR/borrowck-pat-by-move-and-ref.rs:65:9
+   |
+LL |         ref a @ Some(b) => {}
+   |         ^^^^^        - value partially moved here
+   |         |
+   |         value borrowed here after partial move
+   |
+   = note: partial move occurs because value has type `U`, which does not implement the `Copy` trait
+help: borrow this binding in the pattern to avoid moving the value
+   |
+LL |         ref a @ Some(ref b) => {}
+   |                      +++
+
 error[E0382]: borrow of moved value
-  --> $DIR/borrowck-pat-by-move-and-ref.rs:69:23
+  --> $DIR/borrowck-pat-by-move-and-ref.rs:71:23
    |
 LL |         ref a @ Some((ref b @ mut c, ref d @ e)) => {}
    |                       ^^^^^   ----- value moved here
@@ -251,7 +279,7 @@ LL |         ref a @ Some((ref b @ ref mut c, ref d @ e)) => {}
    |                               +++
 
 error[E0382]: borrow of moved value
-  --> $DIR/borrowck-pat-by-move-and-ref.rs:69:38
+  --> $DIR/borrowck-pat-by-move-and-ref.rs:71:38
    |
 LL |         ref a @ Some((ref b @ mut c, ref d @ e)) => {}
    |                                      ^^^^^   - value moved here
@@ -264,6 +292,20 @@ help: borrow this binding in the pattern to avoid moving the value
 LL |         ref a @ Some((ref b @ mut c, ref d @ ref e)) => {}
    |                                              +++
 
+error[E0382]: borrow of partially moved value
+  --> $DIR/borrowck-pat-by-move-and-ref.rs:80:9
+   |
+LL |         ref mut a @ Some([b, mut c]) => {}
+   |         ^^^^^^^^^            ----- value partially moved here
+   |         |
+   |         value borrowed here after partial move
+   |
+   = note: partial move occurs because value has type `U`, which does not implement the `Copy` trait
+help: borrow this binding in the pattern to avoid moving the value
+   |
+LL |         ref mut a @ Some([b, ref mut c]) => {}
+   |                              +++
+
 error: cannot move out of value because it is borrowed
   --> $DIR/borrowck-pat-by-move-and-ref.rs:11:11
    |
@@ -345,6 +387,6 @@ LL |     fn f3(ref mut a @ [b, mut c]: [U; 2]) {}
    |
    = note: partial move occurs because value has type `U`, which does not implement the `Copy` trait
 
-error: aborting due to 36 previous errors
+error: aborting due to 39 previous errors
 
 For more information about this error, try `rustc --explain E0382`.

tests/ui/pattern/bindings-after-at/borrowck-pat-ref-mut-and-ref.rs

@@ -7,7 +7,7 @@ fn main() {
     match &mut Some(1) {
         ref mut z @ &mut Some(ref a) => {
         //~^ ERROR cannot borrow value as immutable because it is also borrowed as mutable
-        //~| ERROR cannot borrow value as immutable because it is also borrowed as mutable
+        //~| ERROR cannot borrow value as mutable because it is also borrowed as immutable
             **z = None;
             println!("{}", *a);
         }
@@ -76,8 +76,8 @@ fn main() {
         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) => {
             //~^ ERROR cannot borrow value as mutable because it is also borrowed as immutable
             //~| ERROR cannot borrow value as mutable because it is also borrowed as immutable
-            //~| ERROR cannot borrow value as mutable because it is also borrowed as immutable
+            //~| ERROR cannot borrow value as immutable because it is also borrowed as mutable
-            //~| ERROR cannot borrow value as mutable because it is also borrowed as immutable
+            //~| ERROR cannot borrow value as immutable because it is also borrowed as mutable
             *b = U;
             drop(a);
         }
@@ -87,6 +87,8 @@ fn main() {
         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { *b = U; false } => {}
         //~^ ERROR cannot borrow value as mutable because it is also borrowed as immutable
         //~| ERROR cannot borrow value as mutable because it is also borrowed as immutable
+        //~| ERROR cannot borrow value as immutable because it is also borrowed as mutable
+        //~| ERROR cannot borrow value as immutable because it is also borrowed as mutable
         //~| ERROR cannot assign to `*b`, as it is immutable for the pattern guard
         _ => {}
     }
@@ -101,6 +103,8 @@ fn main() {
         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { drop(b); false } => {}
         //~^ ERROR cannot borrow value as mutable because it is also borrowed as immutable
         //~| ERROR cannot borrow value as mutable because it is also borrowed as immutable
+        //~| ERROR cannot borrow value as immutable because it is also borrowed as mutable
+        //~| ERROR cannot borrow value as immutable because it is also borrowed as mutable
         //~| ERROR cannot move out of `b` in pattern guard
         //~| ERROR cannot move out of `b` in pattern guard
         _ => {}

tests/ui/pattern/bindings-after-at/borrowck-pat-ref-mut-and-ref.stderr

@@ -138,7 +138,7 @@ LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { *b = U; false }
    |                                 value is borrowed by `a` here
 
 error: cannot borrow value as immutable because it is also borrowed as mutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:94:9
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:96:9
    |
 LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { *a = Err(U); false } => {}
    |         ^^^^^^^^^      ----- value is borrowed by `b` here
@@ -146,7 +146,7 @@ LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { *a = Err(U); fa
    |         value is mutably borrowed by `a` here
 
 error: cannot borrow value as immutable because it is also borrowed as mutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:94:33
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:96:33
    |
 LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { *a = Err(U); false } => {}
    |                                 ^^^^^^^^^       ----- value is borrowed by `b` here
@@ -154,7 +154,7 @@ LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { *a = Err(U); fa
    |                                 value is mutably borrowed by `a` here
 
 error: cannot borrow value as mutable because it is also borrowed as immutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:101:9
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:103:9
    |
 LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { drop(b); false } => {}
    |         ^^^^^      --------- value is mutably borrowed by `b` here
@@ -162,7 +162,7 @@ LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { drop(b); false
    |         value is borrowed by `a` here
 
 error: cannot borrow value as mutable because it is also borrowed as immutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:101:33
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:103:33
    |
 LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { drop(b); false } => {}
    |                                 ^^^^^       --------- value is mutably borrowed by `b` here
@@ -170,7 +170,7 @@ LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { drop(b); false
    |                                 value is borrowed by `a` here
 
 error: cannot borrow value as immutable because it is also borrowed as mutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:109:9
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:113:9
    |
 LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { drop(a); false } => {}
    |         ^^^^^^^^^      ----- value is borrowed by `b` here
@@ -178,7 +178,7 @@ LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { drop(a); false
    |         value is mutably borrowed by `a` here
 
 error: cannot borrow value as immutable because it is also borrowed as mutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:109:33
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:113:33
    |
 LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { drop(a); false } => {}
    |                                 ^^^^^^^^^       ----- value is borrowed by `b` here
@@ -186,7 +186,7 @@ LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { drop(a); false
    |                                 value is mutably borrowed by `a` here
 
 error: cannot borrow value as mutable because it is also borrowed as immutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:117:9
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:121:9
    |
 LL |     let ref a @ (ref mut b, ref mut c) = (U, U);
    |         ^^^^^    ---------  --------- value is mutably borrowed by `c` here
@@ -195,7 +195,7 @@ LL |     let ref a @ (ref mut b, ref mut c) = (U, U);
    |         value is borrowed by `a` here
 
 error: cannot borrow value as mutable because it is also borrowed as immutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:123:9
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:127:9
    |
 LL |     let ref a @ (ref mut b, ref mut c) = (U, U);
    |         ^^^^^    ---------  --------- value is mutably borrowed by `c` here
@@ -204,7 +204,7 @@ LL |     let ref a @ (ref mut b, ref mut c) = (U, U);
    |         value is borrowed by `a` here
 
 error: cannot borrow value as mutable because it is also borrowed as immutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:129:9
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:133:9
    |
 LL |     let ref a @ (ref mut b, ref mut c) = (U, U);
    |         ^^^^^    ---------  --------- value is mutably borrowed by `c` here
@@ -213,7 +213,7 @@ LL |     let ref a @ (ref mut b, ref mut c) = (U, U);
    |         value is borrowed by `a` here
 
 error: cannot borrow value as immutable because it is also borrowed as mutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:134:9
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:138:9
    |
 LL |     let ref mut a @ (ref b, ref c) = (U, U);
    |         ^^^^^^^^^    -----  ----- value is borrowed by `c` here
@@ -221,16 +221,16 @@ LL |     let ref mut a @ (ref b, ref c) = (U, U);
    |         |            value is borrowed by `b` here
    |         value is mutably borrowed by `a` here
 
-error[E0502]: cannot borrow value as immutable because it is also borrowed as mutable
+error[E0502]: cannot borrow value as mutable because it is also borrowed as immutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:8:31
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:8:9
    |
 LL |         ref mut z @ &mut Some(ref a) => {
-   |         ---------             ^^^^^ immutable borrow occurs here
+   |         ^^^^^^^^^             ----- immutable borrow occurs here
    |         |
    |         mutable borrow occurs here
 ...
-LL |             **z = None;
+LL |             println!("{}", *a);
-   |             ---------- mutable borrow later used here
+   |                            -- immutable borrow later used here
 
 error[E0502]: cannot borrow value as mutable because it is also borrowed as immutable
   --> $DIR/borrowck-pat-ref-mut-and-ref.rs:46:9
@@ -254,27 +254,44 @@ LL |     let ref a @ ref mut b = u();
 LL |     *b = u();
    |     -------- mutable borrow later used here
 
-error[E0502]: cannot borrow value as mutable because it is also borrowed as immutable
+error[E0502]: cannot borrow value as immutable because it is also borrowed as mutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:76:20
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:76:9
    |
 LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) => {
-   |         -----      ^^^^^^^^^ mutable borrow occurs here
+   |         ^^^^^      --------- mutable borrow occurs here
    |         |
    |         immutable borrow occurs here
 ...
-LL |             drop(a);
+LL |             *b = U;
-   |                  - immutable borrow later used here
+   |             ------ mutable borrow later used here
 
-error[E0502]: cannot borrow value as mutable because it is also borrowed as immutable
+error[E0502]: cannot borrow value as immutable because it is also borrowed as mutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:76:45
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:76:33
    |
 LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) => {
-   |                                 -----       ^^^^^^^^^ mutable borrow occurs here
+   |                                 ^^^^^       --------- mutable borrow occurs here
    |                                 |
    |                                 immutable borrow occurs here
 ...
-LL |             drop(a);
+LL |             *b = U;
-   |                  - immutable borrow later used here
+   |             ------ mutable borrow later used here
+
+error[E0502]: cannot borrow value as immutable because it is also borrowed as mutable
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:87:9
+   |
+LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { *b = U; false } => {}
+   |         ^^^^^      --------- mutable borrow occurs here     ------ mutable borrow later used here
+   |         |
+   |         immutable borrow occurs here
+
+error[E0502]: cannot borrow value as immutable because it is also borrowed as mutable
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:87:33
+   |
+LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { *b = U; false } => {}
+   |                                 ^^^^^       ---------       ------ mutable borrow later used here
+   |                                 |           |
+   |                                 |           mutable borrow occurs here
+   |                                 immutable borrow occurs here
 
 error[E0594]: cannot assign to `*b`, as it is immutable for the pattern guard
   --> $DIR/borrowck-pat-ref-mut-and-ref.rs:87:61
@@ -285,15 +302,32 @@ LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { *b = U; false }
    = note: variables bound in patterns are immutable until the end of the pattern guard
 
 error[E0594]: cannot assign to `*a`, as it is immutable for the pattern guard
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:94:61
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:96:61
    |
 LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { *a = Err(U); false } => {}
    |                                                             ^^^^^^^^^^^ cannot assign
    |
    = note: variables bound in patterns are immutable until the end of the pattern guard
 
+error[E0502]: cannot borrow value as immutable because it is also borrowed as mutable
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:103:9
+   |
+LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { drop(b); false } => {}
+   |         ^^^^^      --------- mutable borrow occurs here          - mutable borrow later used here
+   |         |
+   |         immutable borrow occurs here
+
+error[E0502]: cannot borrow value as immutable because it is also borrowed as mutable
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:103:33
+   |
+LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { drop(b); false } => {}
+   |                                 ^^^^^       ---------            - mutable borrow later used here
+   |                                 |           |
+   |                                 |           mutable borrow occurs here
+   |                                 immutable borrow occurs here
+
 error[E0507]: cannot move out of `b` in pattern guard
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:101:66
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:103:66
    |
 LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { drop(b); false } => {}
    |                                                                  ^ move occurs because `b` has type `&mut U`, which does not implement the `Copy` trait
@@ -301,7 +335,7 @@ LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { drop(b); false
    = note: variables bound in patterns cannot be moved from until after the end of the pattern guard
 
 error[E0507]: cannot move out of `b` in pattern guard
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:101:66
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:103:66
    |
 LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { drop(b); false } => {}
    |                                                                  ^ move occurs because `b` has type `&mut U`, which does not implement the `Copy` trait
@@ -310,7 +344,7 @@ LL |         ref a @ Ok(ref mut b) | ref a @ Err(ref mut b) if { drop(b); false
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0507]: cannot move out of `a` in pattern guard
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:109:66
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:113:66
    |
 LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { drop(a); false } => {}
    |                                                                  ^ move occurs because `a` has type `&mut Result<U, U>`, which does not implement the `Copy` trait
@@ -318,7 +352,7 @@ LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { drop(a); false
    = note: variables bound in patterns cannot be moved from until after the end of the pattern guard
 
 error[E0507]: cannot move out of `a` in pattern guard
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:109:66
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:113:66
    |
 LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { drop(a); false } => {}
    |                                                                  ^ move occurs because `a` has type `&mut Result<U, U>`, which does not implement the `Copy` trait
@@ -327,7 +361,7 @@ LL |         ref mut a @ Ok(ref b) | ref mut a @ Err(ref b) if { drop(a); false
    = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
 
 error[E0502]: cannot borrow value as immutable because it is also borrowed as mutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:117:9
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:121:9
    |
 LL |     let ref a @ (ref mut b, ref mut c) = (U, U);
    |         ^^^^^    --------- mutable borrow occurs here
@@ -338,7 +372,7 @@ LL |     *b = U;
    |     ------ mutable borrow later used here
 
 error[E0502]: cannot borrow value as immutable because it is also borrowed as mutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:123:9
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:127:9
    |
 LL |     let ref a @ (ref mut b, ref mut c) = (U, U);
    |         ^^^^^    --------- mutable borrow occurs here
@@ -349,7 +383,7 @@ LL |     *b = U;
    |     ------ mutable borrow later used here
 
 error[E0502]: cannot borrow value as immutable because it is also borrowed as mutable
-  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:129:9
+  --> $DIR/borrowck-pat-ref-mut-and-ref.rs:133:9
    |
 LL |     let ref a @ (ref mut b, ref mut c) = (U, U);
    |         ^^^^^    --------- mutable borrow occurs here
@@ -409,7 +443,7 @@ LL |     fn f4_also_moved(ref a @ ref mut b @ c: U) {}
    |                      |       value borrowed here after move
    |                      move occurs because value has type `U`, which does not implement the `Copy` trait
 
-error: aborting due to 47 previous errors
+error: aborting due to 51 previous errors
 
 Some errors have detailed explanations: E0382, E0502, E0507, E0594.
 For more information about an error, try `rustc --explain E0382`.

tests/ui/pattern/bindings-after-at/borrowck-pat-ref-mut-twice.rs

@@ -82,6 +82,8 @@ fn main() {
         ref mut a @ Ok(ref mut b) | ref mut a @ Err(ref mut b) => {
             //~^ ERROR cannot borrow value as mutable more than once at a time
             //~| ERROR cannot borrow value as mutable more than once at a time
+            //~| ERROR cannot borrow value as mutable more than once at a time
+            //~| ERROR cannot borrow value as mutable more than once at a time
             *b = U;
         }
     }
@@ -89,8 +91,6 @@ fn main() {
         ref mut a @ Ok(ref mut b) | ref mut a @ Err(ref mut b) => {
             //~^ ERROR cannot borrow value as mutable more than once at a time
             //~| ERROR cannot borrow value as mutable more than once at a time
-            //~| ERROR cannot borrow value as mutable more than once at a time
-            //~| ERROR cannot borrow value as mutable more than once at a time
             *a = Err(U);
 
             // FIXME: The binding name value used above makes for problematic diagnostics.
@@ -101,8 +101,6 @@ fn main() {
         ref mut a @ Ok(ref mut b) | ref mut a @ Err(ref mut b) => {
             //~^ ERROR cannot borrow value as mutable more than once at a time
             //~| ERROR cannot borrow value as mutable more than once at a time
-            //~| ERROR cannot borrow value as mutable more than once at a time
-            //~| ERROR cannot borrow value as mutable more than once at a time
             drop(a);
         }
     }

tests/ui/pattern/bindings-after-at/borrowck-pat-ref-mut-twice.stderr

@@ -163,7 +163,7 @@ LL |         ref mut a @ Ok(ref mut b) | ref mut a @ Err(ref mut b) => {
    |                                     value is mutably borrowed by `a` here
 
 error: cannot borrow value as mutable more than once at a time
-  --> $DIR/borrowck-pat-ref-mut-twice.rs:89:9
+  --> $DIR/borrowck-pat-ref-mut-twice.rs:91:9
    |
 LL |         ref mut a @ Ok(ref mut b) | ref mut a @ Err(ref mut b) => {
    |         ^^^^^^^^^      --------- value is mutably borrowed by `b` here
@@ -171,7 +171,7 @@ LL |         ref mut a @ Ok(ref mut b) | ref mut a @ Err(ref mut b) => {
    |         value is mutably borrowed by `a` here
 
 error: cannot borrow value as mutable more than once at a time
-  --> $DIR/borrowck-pat-ref-mut-twice.rs:89:37
+  --> $DIR/borrowck-pat-ref-mut-twice.rs:91:37
    |
 LL |         ref mut a @ Ok(ref mut b) | ref mut a @ Err(ref mut b) => {
    |                                     ^^^^^^^^^       --------- value is mutably borrowed by `b` here
@@ -217,48 +217,26 @@ LL |     *b = U;
    |     ------ first borrow later used here
 
 error[E0499]: cannot borrow value as mutable more than once at a time
-  --> $DIR/borrowck-pat-ref-mut-twice.rs:89:24
+  --> $DIR/borrowck-pat-ref-mut-twice.rs:82:9
    |
 LL |         ref mut a @ Ok(ref mut b) | ref mut a @ Err(ref mut b) => {
-   |         ---------      ^^^^^^^^^ second mutable borrow occurs here
+   |         ^^^^^^^^^      --------- first mutable borrow occurs here
    |         |
-   |         first mutable borrow occurs here
+   |         second mutable borrow occurs here
 ...
-LL |             *a = Err(U);
+LL |             *b = U;
-   |             ----------- first borrow later used here
+   |             ------ first borrow later used here
 
 error[E0499]: cannot borrow value as mutable more than once at a time
-  --> $DIR/borrowck-pat-ref-mut-twice.rs:89:53
+  --> $DIR/borrowck-pat-ref-mut-twice.rs:82:37
    |
 LL |         ref mut a @ Ok(ref mut b) | ref mut a @ Err(ref mut b) => {
-   |                                     ---------       ^^^^^^^^^ second mutable borrow occurs here
+   |                                     ^^^^^^^^^       --------- first mutable borrow occurs here
    |                                     |
-   |                                     first mutable borrow occurs here
+   |                                     second mutable borrow occurs here
 ...
-LL |             *a = Err(U);
+LL |             *b = U;
-   |             ----------- first borrow later used here
+   |             ------ first borrow later used here
-
-error[E0499]: cannot borrow value as mutable more than once at a time
-  --> $DIR/borrowck-pat-ref-mut-twice.rs:101:24
-   |
-LL |         ref mut a @ Ok(ref mut b) | ref mut a @ Err(ref mut b) => {
-   |         ---------      ^^^^^^^^^ second mutable borrow occurs here
-   |         |
-   |         first mutable borrow occurs here
-...
-LL |             drop(a);
-   |                  - first borrow later used here
-
-error[E0499]: cannot borrow value as mutable more than once at a time
-  --> $DIR/borrowck-pat-ref-mut-twice.rs:101:53
-   |
-LL |         ref mut a @ Ok(ref mut b) | ref mut a @ Err(ref mut b) => {
-   |                                     ---------       ^^^^^^^^^ second mutable borrow occurs here
-   |                                     |
-   |                                     first mutable borrow occurs here
-...
-LL |             drop(a);
-   |                  - first borrow later used here
 
 error: cannot borrow value as mutable more than once at a time
   --> $DIR/borrowck-pat-ref-mut-twice.rs:8:11
@@ -313,7 +291,7 @@ LL |     fn f4_also_moved(ref mut a @ ref mut b @ c: U) {}
    |                      |           value borrowed here after move
    |                      move occurs because value has type `U`, which does not implement the `Copy` trait
 
-error: aborting due to 31 previous errors
+error: aborting due to 29 previous errors
 
 Some errors have detailed explanations: E0382, E0499.
 For more information about an error, try `rustc --explain E0382`.