error: the `#[proc_macro_derive]` attribute may only be used on bare functions
  --> $DIR/issue-43106-gating-of-proc_macro_derive.rs:20:1
   |
LL | #[proc_macro_derive = "2500"]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: the `#[proc_macro_derive]` attribute may only be used on bare functions
  --> $DIR/issue-43106-gating-of-proc_macro_derive.rs:28:17
   |
LL |     mod inner { #![proc_macro_derive="2500"] }
   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: the `#[proc_macro_derive]` attribute is only usable with crates of the `proc-macro` crate type
  --> $DIR/issue-43106-gating-of-proc_macro_derive.rs:31:5
   |
LL |     #[proc_macro_derive = "2500"] fn f() { }
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: the `#[proc_macro_derive]` attribute may only be used on bare functions
  --> $DIR/issue-43106-gating-of-proc_macro_derive.rs:34:5
   |
LL |     #[proc_macro_derive = "2500"] struct S;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: the `#[proc_macro_derive]` attribute may only be used on bare functions
  --> $DIR/issue-43106-gating-of-proc_macro_derive.rs:37:5
   |
LL |     #[proc_macro_derive = "2500"] type T = S;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: the `#[proc_macro_derive]` attribute may only be used on bare functions
  --> $DIR/issue-43106-gating-of-proc_macro_derive.rs:40:5
   |
LL |     #[proc_macro_derive = "2500"] impl S { }
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 6 previous errors