compiler/rustc_typeck/src/outlives/mod.rs

   1 use hir::Node;
   2 use rustc_hir as hir;
   3 use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
   4 use rustc_middle::ty::query::Providers;
   5 use rustc_middle::ty::subst::GenericArgKind;
   6 use rustc_middle::ty::{self, CratePredicatesMap, ToPredicate, TyCtxt};
   7 use rustc_span::symbol::sym;
   8 use rustc_span::Span;
   9
  10 mod explicit;
  11 mod implicit_infer;
  12 /// Code to write unit test for outlives.
  13 pub mod test;
  14 mod utils;
  15
  16 pub fn provide(providers: &mut Providers) {
  17     *providers = Providers { inferred_outlives_of, inferred_outlives_crate, ..*providers };
  18 }
  19
  20 fn inferred_outlives_of(tcx: TyCtxt<'_>, item_def_id: DefId) -> &[(ty::Predicate<'_>, Span)] {
  21     let id = tcx.hir().local_def_id_to_hir_id(item_def_id.expect_local());
  22
  23     match tcx.hir().get(id) {
  24         Node::Item(item) => match item.kind {
  25             hir::ItemKind::Struct(..) | hir::ItemKind::Enum(..) | hir::ItemKind::Union(..) => {
  26                 let crate_map = tcx.inferred_outlives_crate(LOCAL_CRATE);
  27
  28                 let predicates = crate_map.predicates.get(&item_def_id).copied().unwrap_or(&[]);
  29
  30                 if tcx.has_attr(item_def_id, sym::rustc_outlives) {
  31                     let mut pred: Vec<String> = predicates
  32                         .iter()
  33                         .map(|(out_pred, _)| {
  34                             let binder = out_pred.kind();
  35                             match binder.skip_binder() {
  36                                 ty::PredicateAtom::RegionOutlives(p) => p.to_string(),
  37                                 ty::PredicateAtom::TypeOutlives(p) => p.to_string(),
  38                                 err => bug!("unexpected predicate {:?}", err),
  39                             }
  40                         })
  41                         .collect();
  42                     pred.sort();
  43
  44                     let span = tcx.def_span(item_def_id);
  45                     let mut err = tcx.sess.struct_span_err(span, "rustc_outlives");
  46                     for p in &pred {
  47                         err.note(p);
  48                     }
  49                     err.emit();
  50                 }
  51
  52                 debug!("inferred_outlives_of({:?}) = {:?}", item_def_id, predicates);
  53
  54                 predicates
  55             }
  56
  57             _ => &[],
  58         },
  59
  60         _ => &[],
  61     }
  62 }
  63
  64 fn inferred_outlives_crate(tcx: TyCtxt<'_>, crate_num: CrateNum) -> CratePredicatesMap<'_> {
  65     assert_eq!(crate_num, LOCAL_CRATE);
  66
  67     // Compute a map from each struct/enum/union S to the **explicit**
  68     // outlives predicates (`T: 'a`, `'a: 'b`) that the user wrote.
  69     // Typically there won't be many of these, except in older code where
  70     // they were mandatory. Nonetheless, we have to ensure that every such
  71     // predicate is satisfied, so they form a kind of base set of requirements
  72     // for the type.
  73
  74     // Compute the inferred predicates
  75     let mut exp_map = explicit::ExplicitPredicatesMap::new();
  76
  77     let global_inferred_outlives = implicit_infer::infer_predicates(tcx, &mut exp_map);
  78
  79     // Convert the inferred predicates into the "collected" form the
  80     // global data structure expects.
  81     //
  82     // FIXME -- consider correcting impedance mismatch in some way,
  83     // probably by updating the global data structure.
  84     let predicates = global_inferred_outlives
  85         .iter()
  86         .map(|(&def_id, set)| {
  87             let predicates = &*tcx.arena.alloc_from_iter(set.iter().filter_map(
  88                 |(ty::OutlivesPredicate(kind1, region2), &span)| {
  89                     match kind1.unpack() {
  90                         GenericArgKind::Type(ty1) => Some((
  91                             ty::PredicateAtom::TypeOutlives(ty::OutlivesPredicate(ty1, region2))
  92                                 .to_predicate(tcx),
  93                             span,
  94                         )),
  95                         GenericArgKind::Lifetime(region1) => Some((
  96                             ty::PredicateAtom::RegionOutlives(ty::OutlivesPredicate(
  97                                 region1, region2,
  98                             ))
  99                             .to_predicate(tcx),
 100                             span,
 101                         )),
 102                         GenericArgKind::Const(_) => {
 103                             // Generic consts don't impose any constraints.
 104                             None
 105                         }
 106                     }
 107                 },
 108             ));
 109             (def_id, predicates)
 110         })
 111         .collect();
 112
 113     ty::CratePredicatesMap { predicates }
 114 }