clarify bind-by-move-neither-can-livee..

Author: Centril

src/test/ui/pattern/bindings-after-at/bind-by-move-neither-can-live-while-the-other-survives-1.rs

@@ -1,3 +1,7 @@
+// This test is taken directly from #16053.
+// It checks that you cannot use an AND-pattern (`binding @ pat`)
+// where one side is by-ref and the other is by-move.
+
 #![feature(bindings_after_at)]
 //~^ WARN the feature `bindings_after_at` is incomplete and may cause the compiler to crash
 
@@ -9,4 +13,24 @@ fn main() {
         Some(ref _y @ _z) => { }, //~ ERROR cannot bind by-move and by-ref in the same pattern
         None => panic!()
     }
+
+    let x = Some(X { x: () });
+    match x {
+        Some(_z @ ref _y) => { }, //~ ERROR cannot bind by-move with sub-bindings
+        //~^ ERROR borrow of moved value
+        None => panic!()
+    }
+
+    let mut x = Some(X { x: () });
+    match x {
+        Some(ref mut _y @ _z) => { }, //~ ERROR cannot bind by-move and by-ref in the same pattern
+        None => panic!()
+    }
+
+    let mut x = Some(X { x: () });
+    match x {
+        Some(_z @ ref mut _y) => { }, //~ ERROR cannot bind by-move with sub-bindings
+        //~^ ERROR borrow of moved value
+        None => panic!()
+    }
 }

src/test/ui/pattern/bindings-after-at/bind-by-move-neither-can-live-while-the-other-survives-1.stderr

@@ -1,20 +1,64 @@
 warning: the feature `bindings_after_at` is incomplete and may cause the compiler to crash
-  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:1:12
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:5:12
    |
 LL | #![feature(bindings_after_at)]
    |            ^^^^^^^^^^^^^^^^^
    |
    = note: `#[warn(incomplete_features)]` on by default
 
 error[E0009]: cannot bind by-move and by-ref in the same pattern
-  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:9:23
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:13:23
    |
 LL |         Some(ref _y @ _z) => { },
    |              ---------^^
    |              |        |
    |              |        by-move pattern here
    |              by-ref pattern here
 
-error: aborting due to previous error
+error[E0007]: cannot bind by-move with sub-bindings
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:19:14
+   |
+LL |         Some(_z @ ref _y) => { },
+   |              ^^^^^^^^^^^ binds an already bound by-move value by moving it
+
+error[E0009]: cannot bind by-move and by-ref in the same pattern
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:26:27
+   |
+LL |         Some(ref mut _y @ _z) => { },
+   |              -------------^^
+   |              |            |
+   |              |            by-move pattern here
+   |              by-ref pattern here
+
+error[E0007]: cannot bind by-move with sub-bindings
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:32:14
+   |
+LL |         Some(_z @ ref mut _y) => { },
+   |              ^^^^^^^^^^^^^^^ binds an already bound by-move value by moving it
+
+error[E0382]: borrow of moved value
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:19:19
+   |
+LL |         Some(_z @ ref _y) => { },
+   |              -----^^^^^^
+   |              |    |
+   |              |    value borrowed here after move
+   |              value moved here
+   |
+   = note: move occurs because value has type `X`, which does not implement the `Copy` trait
+
+error[E0382]: borrow of moved value
+  --> $DIR/bind-by-move-neither-can-live-while-the-other-survives-1.rs:32:19
+   |
+LL |         Some(_z @ ref mut _y) => { },
+   |              -----^^^^^^^^^^
+   |              |    |
+   |              |    value borrowed here after move
+   |              value moved here
+   |
+   = note: move occurs because value has type `X`, which does not implement the `Copy` trait
+
+error: aborting due to 6 previous errors
 
-For more information about this error, try `rustc --explain E0009`.
+Some errors have detailed explanations: E0007, E0009, E0382.
+For more information about an error, try `rustc --explain E0007`.