error: expected `{`, found `foo`
  --> $DIR/issue-39848.rs:3:21
   |
LL |         if $tgt.has_$field() {}
   |         --          ^^^^^^--
   |         |           |
   |         |           expected `{`
   |         |           help: try placing this code inside a block: `{ $field() }`
   |         this `if` expression has a condition, but no block
...
LL |     get_opt!(bar, foo);
   |     ------------------ in this macro invocation
   |
   = note: this error originates in the macro `get_opt` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to previous error