Adjust UI tests for unit_bindings

- Either explicitly annotate `let x: () = expr;` where `x` has unit
  type, or remove the unit binding to leave only `expr;` instead.
- Fix disjoint-capture-in-same-closure test

Author: jieyouxu

tests/ui/assign-assign.rs

@@ -6,7 +6,7 @@ fn test_assign() {
     let y: () = x = 10;
     assert_eq!(x, 10);
     assert_eq!(y, ());
-    let mut z = x = 11;
+    let mut z: () = x = 11;
     assert_eq!(x, 11);
     assert_eq!(z, ());
     z = x = 12;
@@ -19,7 +19,7 @@ fn test_assign_op() {
     let y: () = x += 10;
     assert_eq!(x, 10);
     assert_eq!(y, ());
-    let mut z = x += 11;
+    let mut z: () = x += 11;
     assert_eq!(x, 21);
     assert_eq!(z, ());
     z = x += 12;

tests/ui/associated-type-bounds/dyn-impl-trait-type.rs

@@ -59,8 +59,8 @@ fn def_et4() -> Et4 {
 pub fn use_et4() { assert_forall_tr2(def_et4().mk()); }
 
 fn main() {
-    let _ = use_et1();
-    let _ = use_et2();
-    let _ = use_et3();
-    let _ = use_et4();
+    use_et1();
+    use_et2();
+    use_et3();
+    use_et4();
 }