reserve variable for empty root region

src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-no-fg.stderr

@@ -34,7 +34,7 @@ LL | |     (a, b)
 LL | | }
    | |_^
    |
-   = note: hidden type `(&u8, &u8)` captures lifetime '_#4r
+   = note: hidden type `(&u8, &u8)` captures lifetime '_#5r
 
 error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
   --> $DIR/ret-impl-trait-no-fg.rs:9:1
@@ -48,7 +48,7 @@ LL | |     (a, b)
 LL | | }
    | |_^
    |
-   = note: hidden type `(&u8, &u8)` captures lifetime '_#5r
+   = note: hidden type `(&u8, &u8)` captures lifetime '_#6r
 
 error: aborting due to 5 previous errors
 

src/test/ui/hrtb/due-to-where-clause.nll.stderr

@@ -2,7 +2,7 @@ error: higher-ranked subtype error
   --> $DIR/due-to-where-clause.rs:2:5
    |
 LL |     test::<FooS>(&mut 42);
-   |     ^^^^^^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/impl-trait/multiple-lifetimes/ordinary-bounds-unrelated.nll.stderr

@@ -4,7 +4,7 @@ error[E0700]: hidden type for `impl Trait` captures lifetime that does not appea
 LL | fn upper_bounds<'a, 'b, 'c, 'd, 'e>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'d, 'e>
    |                                                                          ^^^^^^^^^^^^^^^^^^
    |
-   = note: hidden type `Ordinary<'_>` captures lifetime '_#8r
+   = note: hidden type `Ordinary<'_>` captures lifetime '_#9r
 
 error: aborting due to previous error
 

src/test/ui/impl-trait/multiple-lifetimes/ordinary-bounds-unsuited.nll.stderr

@@ -4,7 +4,7 @@ error[E0700]: hidden type for `impl Trait` captures lifetime that does not appea
 LL | fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b>
    |                                                              ^^^^^^^^^^^^^^^^^^
    |
-   = note: hidden type `Ordinary<'_>` captures lifetime '_#5r
+   = note: hidden type `Ordinary<'_>` captures lifetime '_#6r
 
 error: aborting due to previous error
 

src/test/ui/nll/issue-68550.rs

@@ -0,0 +1,15 @@
+// Regression test for issue #68550.
+//
+// The `&'static A:` where clause was triggering
+// ICEs because it wound up being compiled to reference
+// the `'empty(U0)` region.
+
+fn run<'a, A>(x: A)
+where
+    A: 'static,
+    &'static A: ,
+{
+    let _: &'a A = &x; //~ ERROR `x` does not live long enough
+}
+
+fn main() {}

src/test/ui/nll/issue-68550.stderr

@@ -0,0 +1,16 @@
+error[E0597]: `x` does not live long enough
+  --> $DIR/issue-68550.rs:12:20
+   |
+LL | fn run<'a, A>(x: A)
+   |        -- lifetime `'a` defined here
+...
+LL |     let _: &'a A = &x;
+   |            -----   ^^ borrowed value does not live long enough
+   |            |
+   |            type annotation requires that `x` is borrowed for `'a`
+LL | }
+   | - `x` dropped here while still borrowed
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0597`.