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

error[E0412]: cannot find type `FooBar` in this scope
  --> $DIR/issue-32950.rs:5:5
   |
LL |     concat_idents!(Foo, Bar) //~ ERROR `derive` cannot be used on items with type macros
   |     ^^^^^^^^^^^^^^^^^^^^^^^^ not found in this scope

error: aborting due to 2 previous errors

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