cut scope for more complicated cases of flow-sensitivity

Author: lqd

tests/ui/nll/issue-46589.polonius_next.stderr

@@ -0,0 +1,15 @@
+error[E0499]: cannot borrow `**other` as mutable more than once at a time
+  --> $DIR/issue-46589.rs:24:21
+   |
+LL |         *other = match (*other).get_self() {
+   |                        -------- first mutable borrow occurs here
+LL |             Some(s) => s,
+LL |             None => (*other).new_self()
+   |                     ^^^^^^^^
+   |                     |
+   |                     second mutable borrow occurs here
+   |                     first borrow later used here
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0499`.

tests/ui/nll/issue-46589.rs

@@ -1,6 +1,6 @@
 //@ ignore-compare-mode-polonius (explicit revisions)
 //@ revisions: nll polonius_next polonius
-//@ [polonius_next] check-pass
+//@ [polonius_next] check-fail
 //@ [polonius_next] compile-flags: -Zpolonius=next
 //@ [polonius] check-pass
 //@ [polonius] compile-flags: -Zpolonius
@@ -23,6 +23,7 @@ impl Foo {
             Some(s) => s,
             None => (*other).new_self()
             //[nll]~^ ERROR cannot borrow `**other` as mutable more than once at a time [E0499]
+            //[polonius_next]~^^ ERROR cannot borrow `**other` as mutable more than once at a time [E0499]
         };
 
         let c = other;