error: expected expression, found `$`
  --> $DIR/issue-6596-1.rs:3:9
   |
LL |         $nonexistent
   |         ^^^^^^^^^^^^ expected expression
...
LL |     e!(foo);
   |     ------- in this macro invocation
   |
   = note: this error originates in the macro `e` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 1 previous error