1 files changed, 55 insertions, 0 deletions
diff --git a/src/test/ui/borrowck/borrowck-closures-two-mut.rs b/src/test/ui/borrowck/borrowck-closures-two-mut.rs
new file mode 100644
index 000000000..cdff8f9e8
--- /dev/null
+++ b/src/test/ui/borrowck/borrowck-closures-two-mut.rs
@@ -0,0 +1,55 @@
+// Tests that two closures cannot simultaneously have mutable
+// access to the variable, whether that mutable access be used
+// for direct assignment or for taking mutable ref. Issue #6801.
+
+
+
+fn to_fn_mut<F: FnMut()>(f: F) -> F { f }
+
+fn a() {
+    let mut x = 3;
+    let c1 = to_fn_mut(|| x = 4);
+    let c2 = to_fn_mut(|| x = 5); //~ ERROR cannot borrow `x` as mutable more than once
+    drop((c1, c2));
+}
+
+fn set(x: &mut isize) {
+    *x = 4;
+}
+
+fn b() {
+    let mut x = 3;
+    let c1 = to_fn_mut(|| set(&mut x));
+    let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
+    drop((c1, c2));
+}
+
+fn c() {
+    let mut x = 3;
+    let c1 = to_fn_mut(|| x = 5);
+    let c2 = to_fn_mut(|| set(&mut x)); //~ ERROR cannot borrow `x` as mutable more than once
+    drop((c1, c2));
+}
+
+fn d() {
+    let mut x = 3;
+    let c1 = to_fn_mut(|| x = 5);
+    let c2 = to_fn_mut(|| { let _y = to_fn_mut(|| set(&mut x)); }); // (nested closure)
+    //~^ ERROR cannot borrow `x` as mutable more than once
+    drop((c1, c2));
+}
+
+fn g() {
+    struct Foo {
+        f: Box<isize>
+    }
+
+    let mut x: Box<_> = Box::new(Foo { f: Box::new(3) });
+    let c1 = to_fn_mut(|| set(&mut *x.f));
+    let c2 = to_fn_mut(|| set(&mut *x.f));
+    //~^ ERROR cannot borrow `x` as mutable more than once
+    drop((c1, c2));
+}
+
+fn main() {
+}