Add additional tests for trailing ..

Author: varkor

src/test/ui/destructuring-assignment/slice_destructure.rs

@@ -6,10 +6,12 @@ fn main() {
   let (mut a, mut b);
   [a, b] = [0, 1];
   assert_eq!((a, b), (0, 1));
-  let c;
+  let mut c;
   [a, .., b, c] = [1, 2, 3, 4, 5];
   assert_eq!((a, b, c), (1, 4, 5));
   [_, a, _] = [1, 2, 3];
   assert_eq!((a, b), (2, 4));
   [..] = [1, 2, 3];
+  [c, ..] = [5, 6, 6];
+  assert_eq!(c, 5);
 }

src/test/ui/destructuring-assignment/tuple_destructure.rs

@@ -14,4 +14,6 @@ fn main() {
     assert_eq!((a, b), (2, 2));
     (..) = (3, 4);
     assert_eq!((a, b), (2, 2));
+    (b, ..) = (5, 6, 7);
+    assert_eq!(b, 5);
 }