@@ -586,6 +586,7 @@ There are multiple [directives](directives.md) to assist with that:
586586- ` aux-crate `
587587- ` aux-bin `
588588- ` aux-codegen-backend `
589+ - ` proc-macro `
589590
590591` aux-build ` will build a separate crate from the named source file. The source
591592file should be in a directory called ` auxiliary ` beside the test file.
@@ -618,45 +619,55 @@ for tests in `tests/ui-fulldeps`, since it requires the use of compiler crates.
618619
619620### Auxiliary proc-macro
620621
621- If you want a proc-macro dependency, then there currently is some ceremony
622- needed.
622+ If you want a proc-macro dependency, then you can use the ` proc-macro `
623+ directive. This directive behaves just like ` aux-build ` , i.e. that you should
624+ place the proc-macro test auxiliary file under a ` auxiliary ` folder under the
625+ same parent folder as the main test file. However, it also has four additional
626+ preset behavior compared to ` aux-build ` for the proc-macro test auxiliary:
627+ 628+ 1 . The aux test file is built with ` --crate-type=proc-macro ` .
629+ 2 . The aux test file is built without ` -C prefer-dynamic ` , i.e. it will not try
630+ to produce a dylib for the aux crate.
631+ 3 . The aux crate is made available to the test file via extern prelude with
632+ ` --extern <aux_crate_name> ` . Note that since UI tests default to edition
633+ 2015, you still need to specify ` extern <aux_crate_name> ` unless the main
634+ test file is using an edition that is 2018 or newer.
635+ 4 . The ` proc_macro ` crate is made available as an extern prelude module. Same
636+ edition 2015 vs newer edition distinction for ` extern proc_macro; ` applies.
637+ 638+ For example, you might have a test ` tests/ui/cat/meow.rs ` and proc-macro
639+ auxiliary ` tests/ui/cat/auxiliary/whiskers.rs ` :
623640
624- Place the proc-macro itself in a file like ` auxiliary/my-proc-macro.rs ` with the
625- following structure:
641+ ``` text
642+ tests/ui/cat/
643+ meow.rs # main test file
644+ auxiliary/whiskers.rs # auxiliary
645+ ```
626646
627- ``` rust,ignore
628- //@ force-host
629- //@ no-prefer-dynamic
647+ ``` rs
648+ // tests/ui/cat/meow.rs
630649
631- #![crate_type = " proc-macro"]
650+ // @ proc-macro: whiskers.rs
632651
633- extern crate proc_macro;
634- use proc_macro::TokenStream;
652+ extern crate whiskers; // needed as ui test defaults to edition 2015
635653
636- #[proc_macro]
637- pub fn foo(input: TokenStream) -> TokenStream {
638- "".parse().unwrap()
654+ fn main () {
655+ whiskers :: identity! ();
639656}
640657```
641658
642- The ` force-host ` is needed because proc-macros are loaded in the host compiler,
643- and ` no-prefer-dynamic ` is needed to tell compiletest to not use
644- ` prefer-dynamic ` which is not compatible with proc-macros. The ` #![crate_type] `
645- attribute is needed to specify the correct crate-type.
646- 647- Then in your test, you can build with ` aux-build ` :
659+ ``` rs
660+ // tests/ui/cat/auxiliary/whiskers.rs
648661
649- ``` rust,ignore
650- //@ aux-build: my-proc-macro.rs
651-
652- extern crate my_proc_macro;
662+ extern crate proc_macro;
663+ use proc_macro :: * ;
653664
654- fn main() {
655- my_proc_macro::foo!();
665+ #[proc_macro]
666+ pub fn identity (ts : TokenStream ) -> TokenStream {
667+ ts
656668}
657669```
658670
659- 660671## Revisions
661672
662673Revisions allow a single test file to be used for multiple tests. This is done
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