-use crate::hir;
-use crate::hir::def_id::{DefId, DefIdMap};
-use crate::hir::Node;
-use crate::infer::outlives::free_region_map::FreeRegionRelations;
+use crate::infer::error_reporting::{note_and_explain_free_region, note_and_explain_region};
use crate::infer::{self, InferCtxt, InferOk, TypeVariableOrigin, TypeVariableOriginKind};
use crate::middle::region;
use crate::traits::{self, PredicateObligation};
use crate::ty::fold::{BottomUpFolder, TypeFoldable, TypeFolder, TypeVisitor};
+use crate::ty::free_region_map::FreeRegionRelations;
use crate::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, SubstsRef};
use crate::ty::{self, GenericParamDefKind, Ty, TyCtxt};
-use errors::DiagnosticBuilder;
use rustc::session::config::nightly_options;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::sync::Lrc;
+use rustc_errors::{struct_span_err, DiagnosticBuilder};
+use rustc_hir as hir;
+use rustc_hir::def_id::{DefId, DefIdMap};
+use rustc_hir::Node;
use rustc_span::Span;
use rustc_error_codes::*;
debug!("constrain_opaque_type: bounds={:#?}", bounds);
let opaque_type = tcx.mk_opaque(def_id, opaque_defn.substs);
- let required_region_bounds = tcx.required_region_bounds(opaque_type, bounds.predicates);
+ let required_region_bounds =
+ required_region_bounds(tcx, opaque_type, bounds.predicates);
debug_assert!(!required_region_bounds.is_empty());
for required_region in required_region_bounds {
err.span_label(span, label);
if nightly_options::is_nightly_build() {
- help!(
- err,
- "add #![feature(member_constraints)] to the crate attributes \
- to enable"
- );
+ err.help("add #![feature(member_constraints)] to the crate attributes to enable");
}
err.emit();
//
// (*) if not, the `tainted_by_errors` flag would be set to
// true in any case, so we wouldn't be here at all.
- tcx.note_and_explain_free_region(
+ note_and_explain_free_region(
+ tcx,
&mut err,
&format!("hidden type `{}` captures ", hidden_ty),
hidden_region,
// If the `region_scope_tree` is available, this is being
// invoked from the "region inferencer error". We can at
// least report a really cryptic error for now.
- tcx.note_and_explain_region(
+ note_and_explain_region(
+ tcx,
region_scope_tree,
&mut err,
&format!("hidden type `{}` captures ", hidden_ty),
debug!("instantiate_opaque_types: bounds={:?}", bounds);
- let required_region_bounds = tcx.required_region_bounds(ty, bounds.predicates.clone());
+ let required_region_bounds = required_region_bounds(tcx, ty, bounds.predicates.clone());
debug!("instantiate_opaque_types: required_region_bounds={:?}", required_region_bounds);
// Make sure that we are in fact defining the *entire* type
);
res
}
+
+/// Given a set of predicates that apply to an object type, returns
+/// the region bounds that the (erased) `Self` type must
+/// outlive. Precisely *because* the `Self` type is erased, the
+/// parameter `erased_self_ty` must be supplied to indicate what type
+/// has been used to represent `Self` in the predicates
+/// themselves. This should really be a unique type; `FreshTy(0)` is a
+/// popular choice.
+///
+/// N.B., in some cases, particularly around higher-ranked bounds,
+/// this function returns a kind of conservative approximation.
+/// That is, all regions returned by this function are definitely
+/// required, but there may be other region bounds that are not
+/// returned, as well as requirements like `for<'a> T: 'a`.
+///
+/// Requires that trait definitions have been processed so that we can
+/// elaborate predicates and walk supertraits.
+//
+// FIXME: callers may only have a `&[Predicate]`, not a `Vec`, so that's
+// what this code should accept.
+crate fn required_region_bounds(
+ tcx: TyCtxt<'tcx>,
+ erased_self_ty: Ty<'tcx>,
+ predicates: Vec<ty::Predicate<'tcx>>,
+) -> Vec<ty::Region<'tcx>> {
+ debug!(
+ "required_region_bounds(erased_self_ty={:?}, predicates={:?})",
+ erased_self_ty, predicates
+ );
+
+ assert!(!erased_self_ty.has_escaping_bound_vars());
+
+ traits::elaborate_predicates(tcx, predicates)
+ .filter_map(|predicate| {
+ match predicate {
+ ty::Predicate::Projection(..)
+ | ty::Predicate::Trait(..)
+ | ty::Predicate::Subtype(..)
+ | ty::Predicate::WellFormed(..)
+ | ty::Predicate::ObjectSafe(..)
+ | ty::Predicate::ClosureKind(..)
+ | ty::Predicate::RegionOutlives(..)
+ | ty::Predicate::ConstEvaluatable(..) => None,
+ ty::Predicate::TypeOutlives(predicate) => {
+ // Search for a bound of the form `erased_self_ty
+ // : 'a`, but be wary of something like `for<'a>
+ // erased_self_ty : 'a` (we interpret a
+ // higher-ranked bound like that as 'static,
+ // though at present the code in `fulfill.rs`
+ // considers such bounds to be unsatisfiable, so
+ // it's kind of a moot point since you could never
+ // construct such an object, but this seems
+ // correct even if that code changes).
+ let ty::OutlivesPredicate(ref t, ref r) = predicate.skip_binder();
+ if t == &erased_self_ty && !r.has_escaping_bound_vars() {
+ Some(*r)
+ } else {
+ None
+ }
+ }
+ }
+ })
+ .collect()
+}
projects / rust.git / blobdiff