error: `proc-macro` crate types currently cannot export any items other than functions tagged with `#[proc_macro]`, `#[proc_macro_derive]`, or `#[proc_macro_attribute]`
  --> $DIR/pub-at-crate-root.rs:8:1
   |
LL | pub mod a {
   | ^^^^^^^^^

error: functions tagged with `#[proc_macro_derive]` must currently reside in the root of the crate
  --> $DIR/pub-at-crate-root.rs:12:5
   |
LL |     pub fn bar(a: TokenStream) -> TokenStream {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: functions tagged with `#[proc_macro_derive]` must be `pub`
  --> $DIR/pub-at-crate-root.rs:19:1
   |
LL | fn bar(a: proc_macro::TokenStream) -> proc_macro::TokenStream {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 3 previous errors