error: `derive` cannot be used on items with type macros
  --> $DIR/issue-32950.rs:5:5
   |
LL |     concat_idents!(Foo, Bar)
   |     ^^^^^^^^^^^^^^^^^^^^^^^^

error[E0412]: cannot find type `FooBar` in this scope
  --> $DIR/issue-32950.rs:5:5
   |
LL |     concat_idents!(Foo, Bar)
   |     ^^^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
   |
   = note: this error originates in the macro `concat_idents` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0412`.
