error[E0600]: cannot apply unary operator `!` to type `&'static str`
  --> $DIR/issue-28308.rs:12:5
   |
LL |     assert!("foo");
   |     ^^^^^^^^^^^^^^^
   |
   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

error: aborting due to previous error

If you want more information on this error, try using "rustc --explain E0600"