1 files changed, 95 insertions, 0 deletions
diff --git a/src/test/ui/overloaded/overloaded_deref_with_ref_pattern.rs b/src/test/ui/overloaded/overloaded_deref_with_ref_pattern.rs
new file mode 100644
index 000000000..c87ba6a02
--- /dev/null
+++ b/src/test/ui/overloaded/overloaded_deref_with_ref_pattern.rs
@@ -0,0 +1,95 @@
+// run-pass
+#![allow(unused_mut)]
+#![allow(unused_variables)]
+// Test that we choose Deref or DerefMut appropriately based on mutability of ref bindings (#15609).
+
+use std::ops::{Deref, DerefMut};
+
+struct DerefOk<T>(T);
+struct DerefMutOk<T>(T);
+
+impl<T> Deref for DerefOk<T> {
+    type Target = T;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<T> DerefMut for DerefOk<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        panic!()
+    }
+}
+
+impl<T> Deref for DerefMutOk<T> {
+    type Target = T;
+    fn deref(&self) -> &Self::Target {
+        panic!()
+    }
+}
+
+impl<T> DerefMut for DerefMutOk<T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+fn main() {
+    // Check that mutable ref binding in match picks DerefMut
+    let mut b = DerefMutOk(0);
+    match *b {
+        ref mut n => n,
+    };
+
+    // Check that mutable ref binding in let picks DerefMut
+    let mut y = DerefMutOk(1);
+    let ref mut z = *y;
+
+    // Check that immutable ref binding in match picks Deref
+    let mut b = DerefOk(2);
+    match *b {
+        ref n => n,
+    };
+
+    // Check that immutable ref binding in let picks Deref
+    let mut y = DerefOk(3);
+    let ref z = *y;
+
+    // Check that mixed mutable/immutable ref binding in match picks DerefMut
+    let mut b = DerefMutOk((0, 9));
+    match *b {
+        (ref mut n, ref m) => (n, m),
+    };
+
+    let mut b = DerefMutOk((0, 9));
+    match *b {
+        (ref n, ref mut m) => (n, m),
+    };
+
+    // Check that mixed mutable/immutable ref binding in let picks DerefMut
+    let mut y = DerefMutOk((1, 8));
+    let (ref mut z, ref a) = *y;
+
+    let mut y = DerefMutOk((1, 8));
+    let (ref z, ref mut a) = *y;
+
+    // Check that multiple immutable ref bindings in match picks Deref
+    let mut b = DerefOk((2, 7));
+    match *b {
+        (ref n, ref m) => (n, m),
+    };
+
+    // Check that multiple immutable ref bindings in let picks Deref
+    let mut y = DerefOk((3, 6));
+    let (ref z, ref a) = *y;
+
+    // Check that multiple mutable ref bindings in match picks DerefMut
+    let mut b = DerefMutOk((4, 5));
+    match *b {
+        (ref mut n, ref mut m) => (n, m),
+    };
+
+    // Check that multiple mutable ref bindings in let picks DerefMut
+    let mut y = DerefMutOk((5, 4));
+    let (ref mut z, ref mut a) = *y;
+}