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+A borrowed variable was used by a closure.
+
+Erroneous code example:
+
+```compile_fail,E0500
+fn you_know_nothing(jon_snow: &mut i32) {
+    let nights_watch = &jon_snow;
+    let starks = || {
+        *jon_snow = 3; // error: closure requires unique access to `jon_snow`
+                       //        but it is already borrowed
+    };
+    println!("{}", nights_watch);
+}
+```
+
+In here, `jon_snow` is already borrowed by the `nights_watch` reference, so it
+cannot be borrowed by the `starks` closure at the same time. To fix this issue,
+you can create the closure after the borrow has ended:
+
+```
+fn you_know_nothing(jon_snow: &mut i32) {
+    let nights_watch = &jon_snow;
+    println!("{}", nights_watch);
+    let starks = || {
+        *jon_snow = 3;
+    };
+}
+```
+
+Or, if the type implements the `Clone` trait, you can clone it between
+closures:
+
+```
+fn you_know_nothing(jon_snow: &mut i32) {
+    let mut jon_copy = jon_snow.clone();
+    let starks = || {
+        *jon_snow = 3;
+    };
+    println!("{}", jon_copy);
+}
+```