proc-macro-error-attr

• proc-macro-hack is now well tested and supported. Not sure about proc-macro-nested, please fill a request if you need it.
• Fixed emit_call_site_error.
• Documentation improvements.

I believe the API can be considered stable because it's been a few months without breaking changes, and I also don't think this crate will receive much further evolution. It's perfect, admit it.

Hence, meet the new, stable release!

Improvements

• Supported nested #[proc_macro_error] attributes. Well, you aren't supposed to do that, but I caught myself doing it by accident on one occasion and the behavior was... surprising. Better to handle this smooth.

• Error message on macros' misuse is now a bit more understandable.

• build.rs no longer fails when rustc date could not be determined, (thanks to Fabian Möller for noticing and to Igor Gnatenko for fixing).

• proc-macro-error doesn't depend on syn[full] anymore, the compilation is ~30secs faster.

• New function: append_dummy.

• Support for children messages

• Now any type that implements quote::ToTokens can be used instead of spans. This allows for high quality error messages.

• From<syn::Error> implementation doesn't lose span info anymore, see #6.

Just a small intermediate release.

• Fix some bugs.
• Populate license files into subfolders.

• Fixed __pme__suggestions not found bug
• Documentation improvements, links checked

New features

• "help" messages that can have their own span on nightly, they inherit parent span on stable.

  let cond_help = if condition { Some("some help message") else { None } };
  abort!(
      span, // parent span
      "something's wrong, {} wrongs in total", 10; // main message
      help = "here's a help for you, {}", "take it"; // unconditional help message
      help =? cond_help; // conditional help message, must be Option
      note = note_span => "don't forget the note, {}", "would you?" // notes can have their own span but it's effective only on nightly
  )
  

• Warnings via emit_warning and emit_warning_call_site. Nightly only, they're ignored on stable.
• Now proc-macro-error delegates to proc_macro::Diagnostic on nightly.

Breaking changes

• MacroError is now replaced by Diagnostic. Its API resembles proc_macro::Diagnostic.
• Diagnostic does not implement From<&str/String> so Result<T, &str/String>::abort_or_exit() won't work anymore (nobody used it anyway).
• macro_error! macro is replaced with diagnostic!.

Improvements

• Now proc-macro-error renders notes exactly just like rustc does.
• We don't parse a body of a function annotated with #[proc_macro_error] anymore, only looking at the signature. This should somewhat decrease expansion time for large functions.

• Now you can use any word instead of "help", undocumented.

• Introduced support for "help" messages, undocumented.

The crate has been completely rewritten from scratch!

Changes (most are breaking):

• Renamed macros:
  • span_error => abort
  • call_site_error => abort_call_site
• filter_macro_errors was replaced by #[proc_macro_error] attribute.
• set_dummy now takes TokenStream instead of Option<TokenStream>
• Support for multiple errors via emit_error and emit_call_site_error
• New macro_error macro for building errors in format=like style.
• MacroError API had been reconsidered. It also now implements quote::ToTokens.