Addressed minor issues brought up in review.

src/test/ui/consts/const-eval/promoted_const_fn_fail_deny_const_err.rs

@@ -19,17 +19,15 @@ union Bar {
 
 const fn bar() -> u8 {
     unsafe {
-        // this will error as long as this test
-        // is run on a system whose pointers need more
-        // than 8 bits
+        // This will error as long as this test is run on a system whose
+        // pointers need more than 8 bits.
         Bar { a: &42 }.b as u8
     }
 }
 
 fn main() {
-    // FIXME(oli-obk): this should panic at runtime
-    // this will actually compile, but then
-    // abort at runtime (not panic, hard abort).
+    // This will compile, but then hard-abort at runtime.
+    // FIXME(oli-obk): this should instead panic (not hard-abort) at runtime.
     let x: &'static u8 = &(bar() + 1);
     let y = *x;
     unreachable!();

src/test/ui/consts/const-eval/promoted_const_fn_fail_deny_const_err.stderr

@@ -1,5 +1,5 @@
 error: reaching this expression at runtime will panic or abort
-  --> $DIR/promoted_const_fn_fail_deny_const_err.rs:33:26
+  --> $DIR/promoted_const_fn_fail_deny_const_err.rs:31:26
    |
 LL |         Bar { a: &42 }.b as u8
    |         ---------------------- a raw memory access tried to access part of a pointer value as raw bytes
@@ -16,4 +16,3 @@ LL | #![deny(const_err)]
    |         ^^^^^^^^^
 
 error: aborting due to previous error
-