Rollup merge of rust-lang#24482 - GuillaumeGomez:error-explanation, r…

…=alexcrichton

 Part of rust-lang#24407.

src/librustc/diagnostics.rs

@@ -112,6 +112,53 @@ reference when using guards or refactor the entire expression, perhaps by
 putting the condition inside the body of the arm.
 "##,
 
+E0009: r##"
+In a pattern, all values that don't implement the `Copy` trait have to be bound
+the same way. The goal here is to avoid binding simultaneous by-move and by-ref.
+
+This limitation may be removed in a future version of Rust.
+
+Wrong example:
+
+```
+struct X { x: (), }
+
+let x = Some((X { x: () }, X { x: () }));
+match x {
+    Some((y, ref z)) => {},
+    None => panic!()
+}
+```
+
+You have two solutions:
+1. Bind the pattern's values the same way:
+
+```
+struct X { x: (), }
+
+let x = Some((X { x: () }, X { x: () }));
+match x {
+    Some((ref y, ref z)) => {},
+    // or Some((y, z)) => {}
+    None => panic!()
+}
+```
+
+2. Implement the `Copy` trait for the X structure (however, please
+keep in mind that the first solution should be preferred!):
+
+```
+#[derive(Clone, Copy)]
+struct X { x: (), }
+
+let x = Some((X { x: () }, X { x: () }));
+match x {
+    Some((y, ref z)) => {},
+    None => panic!()
+}
+```
+"##,
+
 E0162: r##"
 An if-let pattern attempts to match the pattern, and enters the body if the
 match was succesful. If the match is irrefutable (when it cannot fail to match),
@@ -278,7 +325,6 @@ See also https://github.com/rust-lang/rust/issues/14587
 }
 
 register_diagnostics! {
-    E0009,
     E0010,
     E0011,
     E0012,