compiler/rustc_plugin_impl/src/build.rs

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