Add diverging match guard test.

Author: cjgillot

tests/ui/binding/issue-53114-borrow-checks.rs

@@ -20,7 +20,7 @@ fn let_wild_gets_moved_expr() {
 fn match_moved_expr_to_wild() {
     let m = M;
     drop(m);
-    match m { _ => { } } // #53114: should eventually be accepted too
+    match m { _ => { } } // #53114: accepted too
 
     let mm = (M, M); // variation on above with `_` in substructure
     match mm { (_x, _) => { } }
@@ -31,7 +31,7 @@ fn match_moved_expr_to_wild() {
 fn if_let_moved_expr_to_wild() {
     let m = M;
     drop(m);
-    if let _ = m { } // #53114: should eventually be accepted too
+    if let _ = m { } // #53114: accepted too
 
     let mm = (M, M); // variation on above with `_` in substructure
     if let (_x, _) = mm { }

tests/ui/uninhabited/diverging-guard.rs

@@ -0,0 +1,10 @@
+// check-pass
+
+enum Void {}
+
+fn main() {
+    let x: Void;
+    match x {
+        _ if { loop {} } => (),
+    }
+}