collect explicit-mut passing tests in one file

Author: cormacrelf

src/test/ui/let-else/let-else-binding-explicit-mut-annotated.rs

@@ -13,8 +13,4 @@ fn main() {
     let Some(n): &mut Option<i32> = &&mut Some(5i32) else { return }; //~ ERROR mismatched types
     *n += 1;
     let _ = n;
-
-    let Some(n): &mut Option<i32> = &mut &mut Some(5i32) else { return }; // OK
-    *n += 1;
-    let _ = n;
 }

src/test/ui/let-else/let-else-binding-explicit-mut-borrow.rs

@@ -4,7 +4,8 @@
 // Should it show a type error instead?
 
 fn main() {
-    let Some(n): &mut Option<i32> = &mut &Some(5i32) else { //~ ERROR cannot borrow data in a `&` reference as mutable
+    let Some(n): &mut Option<i32> = &mut &Some(5i32) else {
+        //~^ ERROR cannot borrow data in a `&` reference as mutable
         return
     };
     *n += 1;

src/test/ui/let-else/let-else-binding-explicit-mut-pass.rs

@@ -0,0 +1,13 @@
+// check-pass
+
+#![feature(let_else)]
+
+fn main() {
+    let Some(n) = &mut &mut Some(5i32) else { return; };
+    *n += 1; // OK
+    let _ = n;
+
+    let Some(n): &mut Option<i32> = &mut &mut Some(5i32) else { return; };
+    *n += 1; // OK
+    let _ = n;
+}

src/test/ui/let-else/let-else-binding-explicit-mut.rs

@@ -17,8 +17,4 @@ fn main() {
     let Some(n) = &&mut Some(5i32) else { return };
     *n += 1; //~ ERROR cannot assign to `*n`, which is behind a `&` reference
     let _ = n;
-
-    let Some(n) = &mut &mut Some(5i32) else { return };
-    *n += 1; // OK
-    let _ = n;
 }