1 files changed, 64 insertions, 0 deletions
diff --git a/tests/ui/nll/match-guards-always-borrow.rs b/tests/ui/nll/match-guards-always-borrow.rs
new file mode 100644
index 000000000..ff63cc092
--- /dev/null
+++ b/tests/ui/nll/match-guards-always-borrow.rs
@@ -0,0 +1,64 @@
+#![feature(if_let_guard)]
+
+// Here is arielb1's basic example from rust-lang/rust#27282
+// that AST borrowck is flummoxed by:
+
+fn should_reject_destructive_mutate_in_guard() {
+    match Some(&4) {
+        None => {},
+        ref mut foo if {
+            (|| { let bar = foo; bar.take() })();
+            //~^ ERROR cannot move out of `foo` in pattern guard [E0507]
+            false } => { },
+        Some(s) => std::process::exit(*s),
+    }
+
+    match Some(&4) {
+        None => {},
+        ref mut foo if let Some(()) = {
+            (|| { let bar = foo; bar.take() })();
+            //~^ ERROR cannot move out of `foo` in pattern guard [E0507]
+            None } => { },
+        Some(s) => std::process::exit(*s),
+    }
+}
+
+// Here below is a case that needs to keep working: we only use the
+// binding via immutable-borrow in the guard, and we mutate in the arm
+// body.
+fn allow_mutate_in_arm_body() {
+    match Some(&4) {
+        None => {},
+        ref mut foo if foo.is_some() => { foo.take(); () }
+        Some(s) => std::process::exit(*s),
+    }
+
+    match Some(&4) {
+        None => {},
+        ref mut foo if let Some(_) = foo => { foo.take(); () }
+        Some(s) => std::process::exit(*s),
+    }
+}
+
+// Here below is a case that needs to keep working: we only use the
+// binding via immutable-borrow in the guard, and we move into the arm
+// body.
+fn allow_move_into_arm_body() {
+    match Some(&4) {
+        None => {},
+        mut foo if foo.is_some() => { foo.unwrap(); () }
+        Some(s) => std::process::exit(*s),
+    }
+
+    match Some(&4) {
+        None => {},
+        mut foo if let Some(_) = foo => { foo.unwrap(); () }
+        Some(s) => std::process::exit(*s),
+    }
+}
+
+fn main() {
+    should_reject_destructive_mutate_in_guard();
+    allow_mutate_in_arm_body();
+    allow_move_into_arm_body();
+}