Attribute Macro proc_macro_error::proc_macro_error

#[proc_macro_error]

This attribute MUST be present on the top level of your macro.

This attribute performs the setup and cleanup necessary to make things work.

Syntax

#[proc_macro_error] or #[proc_macro_error(settings...)], where settings... is a comma-separated list of:

• proc_macro_hack:

  To correctly cooperate with #[proc_macro_hack] #[proc_macro_error] attribute must be placed before (above) it, like this:

  #[proc_macro_error]
  #[proc_macro_hack]
  #[proc_macro]
  fn my_macro(input: TokenStream) -> TokenStream {
      unimplemented!()
  }

  If, for some reason, you can't place it like that you can use #[proc_macro_error(proc_macro_hack)] instead.

• allow_not_macro:

  By default, the attribute checks that it's applied to a proc-macro. If none of #[proc_macro], #[proc_macro_derive] nor #[proc_macro_attribute] are present it will panic. It's the intention - this crate is supposed to be used only with proc-macros. This setting is made to bypass the check, useful in certain circumstances.

• assert_unwind_safe:

  By default, your code must be unwind safe. If your code is not unwind safe but you believe it's correct you can use this setting to bypass the check. This is typically needed for code that uses lazy_static or thread_local with Call/RefCell inside.

  This setting is implied if #[proc_macro_error] is placed on top of a function marked as #[proc_macro], #[proc_macro_derive] or #[proc_macro_attribute].