src/librustc_plugin/build.rs

   1 //! Used by `rustc` when compiling a plugin crate.
   2
   3 use syntax::attr;
   4 use syntax::symbol::sym;
   5 use syntax_pos::Span;
   6 use rustc::hir::itemlikevisit::ItemLikeVisitor;
   7 use rustc::hir;
   8 use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
   9 use rustc::ty::TyCtxt;
  10 use rustc::ty::query::Providers;
  11
  12 struct RegistrarFinder {
  13     registrars: Vec<(hir::HirId, Span)> ,
  14 }
  15
  16 impl<'v> ItemLikeVisitor<'v> for RegistrarFinder {
  17     fn visit_item(&mut self, item: &hir::Item) {
  18         if let hir::ItemKind::Fn(..) = item.kind {
  19             if attr::contains_name(&item.attrs, sym::plugin_registrar) {
  20                 self.registrars.push((item.hir_id, item.span));
  21             }
  22         }
  23     }
  24
  25     fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
  26     }
  27
  28     fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
  29     }
  30 }
  31
  32 /// Finds the function marked with `#[plugin_registrar]`, if any.
  33 pub fn find_plugin_registrar(tcx: TyCtxt<'_>) -> Option<DefId> {
  34     tcx.plugin_registrar_fn(LOCAL_CRATE)
  35 }
  36
  37 fn plugin_registrar_fn(tcx: TyCtxt<'_>, cnum: CrateNum) -> Option<DefId> {
  38     assert_eq!(cnum, LOCAL_CRATE);
  39
  40     let mut finder = RegistrarFinder { registrars: Vec::new() };
  41     tcx.hir().krate().visit_all_item_likes(&mut finder);
  42
  43     match finder.registrars.len() {
  44         0 => None,
  45         1 => {
  46             let (hir_id, _) = finder.registrars.pop().unwrap();
  47             Some(tcx.hir().local_def_id(hir_id))
  48         },
  49         _ => {
  50             let diagnostic = tcx.sess.diagnostic();
  51             let mut e = diagnostic.struct_err("multiple plugin registration functions found");
  52             for &(_, span) in &finder.registrars {
  53                 e.span_note(span, "one is here");
  54             }
  55             e.emit();
  56             diagnostic.abort_if_errors();
  57             unreachable!();
  58         }
  59     }
  60 }
  61
  62
  63 pub fn provide(providers: &mut Providers<'_>) {
  64     *providers = Providers {
  65         plugin_registrar_fn,
  66         ..*providers
  67     };
  68 }