Merging upstream version 1.71.1+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 5 insertions, 168 deletions

diff --git a/compiler/rustc_traits/src/implied_outlives_bounds.rs b/compiler/rustc_traits/src/implied_outlives_bounds.rs
index f5bba14d2..959838ab3 100644
--- a/compiler/rustc_traits/src/implied_outlives_bounds.rs
+++ b/compiler/rustc_traits/src/implied_outlives_bounds.rs
@@ -3,18 +3,13 @@
 //! [`rustc_trait_selection::traits::query::type_op::implied_outlives_bounds`].
 
 use rustc_infer::infer::canonical::{self, Canonical};
-use rustc_infer::infer::outlives::components::{push_outlives_components, Component};
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_infer::traits::query::OutlivesBound;
-use rustc_middle::ty::query::Providers;
-use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
-use rustc_span::def_id::CRATE_DEF_ID;
-use rustc_span::source_map::DUMMY_SP;
+use rustc_middle::query::Providers;
+use rustc_middle::ty::TyCtxt;
 use rustc_trait_selection::infer::InferCtxtBuilderExt;
-use rustc_trait_selection::traits::query::{CanonicalTyGoal, Fallible, NoSolution};
-use rustc_trait_selection::traits::wf;
-use rustc_trait_selection::traits::ObligationCtxt;
-use smallvec::{smallvec, SmallVec};
+use rustc_trait_selection::traits::query::type_op::implied_outlives_bounds::compute_implied_outlives_bounds_inner;
+use rustc_trait_selection::traits::query::{CanonicalTyGoal, NoSolution};
 
 pub(crate) fn provide(p: &mut Providers) {
     *p = Providers { implied_outlives_bounds, ..*p };
@@ -29,164 +24,6 @@ fn implied_outlives_bounds<'tcx>(
 > {
     tcx.infer_ctxt().enter_canonical_trait_query(&goal, |ocx, key| {
         let (param_env, ty) = key.into_parts();
-        compute_implied_outlives_bounds(ocx, param_env, ty)
+        compute_implied_outlives_bounds_inner(ocx, param_env, ty)
     })
 }
-
-fn compute_implied_outlives_bounds<'tcx>(
-    ocx: &ObligationCtxt<'_, 'tcx>,
-    param_env: ty::ParamEnv<'tcx>,
-    ty: Ty<'tcx>,
-) -> Fallible<Vec<OutlivesBound<'tcx>>> {
-    let tcx = ocx.infcx.tcx;
-
-    // Sometimes when we ask what it takes for T: WF, we get back that
-    // U: WF is required; in that case, we push U onto this stack and
-    // process it next. Because the resulting predicates aren't always
-    // guaranteed to be a subset of the original type, so we need to store the
-    // WF args we've computed in a set.
-    let mut checked_wf_args = rustc_data_structures::fx::FxHashSet::default();
-    let mut wf_args = vec![ty.into()];
-
-    let mut outlives_bounds: Vec<ty::OutlivesPredicate<ty::GenericArg<'tcx>, ty::Region<'tcx>>> =
-        vec![];
-
-    while let Some(arg) = wf_args.pop() {
-        if !checked_wf_args.insert(arg) {
-            continue;
-        }
-
-        // Compute the obligations for `arg` to be well-formed. If `arg` is
-        // an unresolved inference variable, just substituted an empty set
-        // -- because the return type here is going to be things we *add*
-        // to the environment, it's always ok for this set to be smaller
-        // than the ultimate set. (Note: normally there won't be
-        // unresolved inference variables here anyway, but there might be
-        // during typeck under some circumstances.)
-        //
-        // FIXME(@lcnr): It's not really "always fine", having fewer implied
-        // bounds can be backward incompatible, e.g. #101951 was caused by
-        // us not dealing with inference vars in `TypeOutlives` predicates.
-        let obligations = wf::obligations(ocx.infcx, param_env, CRATE_DEF_ID, 0, arg, DUMMY_SP)
-            .unwrap_or_default();
-
-        for obligation in obligations {
-            debug!(?obligation);
-            assert!(!obligation.has_escaping_bound_vars());
-
-            // While these predicates should all be implied by other parts of
-            // the program, they are still relevant as they may constrain
-            // inference variables, which is necessary to add the correct
-            // implied bounds in some cases, mostly when dealing with projections.
-            //
-            // Another important point here: we only register `Projection`
-            // predicates, since otherwise we might register outlives
-            // predicates containing inference variables, and we don't
-            // learn anything new from those.
-            if obligation.predicate.has_non_region_infer() {
-                match obligation.predicate.kind().skip_binder() {
-                    ty::PredicateKind::Clause(ty::Clause::Projection(..))
-                    | ty::PredicateKind::AliasRelate(..) => {
-                        ocx.register_obligation(obligation.clone());
-                    }
-                    _ => {}
-                }
-            }
-
-            let pred = match obligation.predicate.kind().no_bound_vars() {
-                None => continue,
-                Some(pred) => pred,
-            };
-            match pred {
-                ty::PredicateKind::Clause(ty::Clause::Trait(..))
-                // FIXME(const_generics): Make sure that `<'a, 'b, const N: &'a &'b u32>` is sound
-                // if we ever support that
-                | ty::PredicateKind::Clause(ty::Clause::ConstArgHasType(..))
-                | ty::PredicateKind::Subtype(..)
-                | ty::PredicateKind::Coerce(..)
-                | ty::PredicateKind::Clause(ty::Clause::Projection(..))
-                | ty::PredicateKind::ClosureKind(..)
-                | ty::PredicateKind::ObjectSafe(..)
-                | ty::PredicateKind::ConstEvaluatable(..)
-                | ty::PredicateKind::ConstEquate(..)
-                | ty::PredicateKind::Ambiguous
-                | ty::PredicateKind::AliasRelate(..)
-                | ty::PredicateKind::TypeWellFormedFromEnv(..) => {}
-
-                // We need to search through *all* WellFormed predicates
-                ty::PredicateKind::WellFormed(arg) => {
-                    wf_args.push(arg);
-                }
-
-                // We need to register region relationships
-                ty::PredicateKind::Clause(ty::Clause::RegionOutlives(ty::OutlivesPredicate(
-                    r_a,
-                    r_b,
-                ))) => outlives_bounds.push(ty::OutlivesPredicate(r_a.into(), r_b)),
-
-                ty::PredicateKind::Clause(ty::Clause::TypeOutlives(ty::OutlivesPredicate(
-                    ty_a,
-                    r_b,
-                ))) => outlives_bounds.push(ty::OutlivesPredicate(ty_a.into(), r_b)),
-            }
-        }
-    }
-
-    // This call to `select_all_or_error` is necessary to constrain inference variables, which we
-    // use further down when computing the implied bounds.
-    match ocx.select_all_or_error().as_slice() {
-        [] => (),
-        _ => return Err(NoSolution),
-    }
-
-    // We lazily compute the outlives components as
-    // `select_all_or_error` constrains inference variables.
-    let implied_bounds = outlives_bounds
-        .into_iter()
-        .flat_map(|ty::OutlivesPredicate(a, r_b)| match a.unpack() {
-            ty::GenericArgKind::Lifetime(r_a) => vec![OutlivesBound::RegionSubRegion(r_b, r_a)],
-            ty::GenericArgKind::Type(ty_a) => {
-                let ty_a = ocx.infcx.resolve_vars_if_possible(ty_a);
-                let mut components = smallvec![];
-                push_outlives_components(tcx, ty_a, &mut components);
-                implied_bounds_from_components(r_b, components)
-            }
-            ty::GenericArgKind::Const(_) => unreachable!(),
-        })
-        .collect();
-
-    Ok(implied_bounds)
-}
-
-/// When we have an implied bound that `T: 'a`, we can further break
-/// this down to determine what relationships would have to hold for
-/// `T: 'a` to hold. We get to assume that the caller has validated
-/// those relationships.
-fn implied_bounds_from_components<'tcx>(
-    sub_region: ty::Region<'tcx>,
-    sup_components: SmallVec<[Component<'tcx>; 4]>,
-) -> Vec<OutlivesBound<'tcx>> {
-    sup_components
-        .into_iter()
-        .filter_map(|component| {
-            match component {
-                Component::Region(r) => Some(OutlivesBound::RegionSubRegion(sub_region, r)),
-                Component::Param(p) => Some(OutlivesBound::RegionSubParam(sub_region, p)),
-                Component::Alias(p) => Some(OutlivesBound::RegionSubAlias(sub_region, p)),
-                Component::EscapingAlias(_) =>
-                // If the projection has escaping regions, don't
-                // try to infer any implied bounds even for its
-                // free components. This is conservative, because
-                // the caller will still have to prove that those
-                // free components outlive `sub_region`. But the
-                // idea is that the WAY that the caller proves
-                // that may change in the future and we want to
-                // give ourselves room to get smarter here.
-                {
-                    None
-                }
-                Component::UnresolvedInferenceVariable(..) => None,
-            }
-        })
-        .collect()
-}