Auto merge of #136038 - compiler-errors:outlives, r=lcnr

Simplify and consolidate the way we handle construct `OutlivesEnvironment` for lexical region resolution

This is best reviewed commit-by-commit. I tried to consolidate the API for lexical region resolution *first*, then change the API when it was finally behind a single surface.

r? lcnr or reassign

7 files changed, 107 insertions, 70 deletions

diff --git a/compiler/rustc_trait_selection/src/regions.rs b/compiler/rustc_trait_selection/src/regions.rs
index 863b6e293ff..55171754618 100644
--- a/compiler/rustc_trait_selection/src/regions.rs
+++ b/compiler/rustc_trait_selection/src/regions.rs
@@ -1,10 +1,73 @@
+use rustc_hir::def_id::LocalDefId;
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
 use rustc_infer::infer::{InferCtxt, RegionResolutionError};
 use rustc_macros::extension;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::traits::query::NoSolution;
+use rustc_middle::ty::{self, Ty};
 
 use crate::traits::ScrubbedTraitError;
+use crate::traits::outlives_bounds::InferCtxtExt;
+
+#[extension(pub trait OutlivesEnvironmentBuildExt<'tcx>)]
+impl<'tcx> OutlivesEnvironment<'tcx> {
+    fn new(
+        infcx: &InferCtxt<'tcx>,
+        body_id: LocalDefId,
+        param_env: ty::ParamEnv<'tcx>,
+        assumed_wf_tys: impl IntoIterator<Item = Ty<'tcx>>,
+    ) -> Self {
+        Self::new_with_implied_bounds_compat(
+            infcx,
+            body_id,
+            param_env,
+            assumed_wf_tys,
+            !infcx.tcx.sess.opts.unstable_opts.no_implied_bounds_compat,
+        )
+    }
+
+    fn new_with_implied_bounds_compat(
+        infcx: &InferCtxt<'tcx>,
+        body_id: LocalDefId,
+        param_env: ty::ParamEnv<'tcx>,
+        assumed_wf_tys: impl IntoIterator<Item = Ty<'tcx>>,
+        implied_bounds_compat: bool,
+    ) -> Self {
+        let mut bounds = vec![];
+
+        for bound in param_env.caller_bounds() {
+            if let Some(mut type_outlives) = bound.as_type_outlives_clause() {
+                if infcx.next_trait_solver() {
+                    match crate::solve::deeply_normalize::<_, ScrubbedTraitError<'tcx>>(
+                        infcx.at(&ObligationCause::dummy(), param_env),
+                        type_outlives,
+                    ) {
+                        Ok(new) => type_outlives = new,
+                        Err(_) => {
+                            infcx.dcx().delayed_bug(format!("could not normalize `{bound}`"));
+                        }
+                    }
+                }
+                bounds.push(type_outlives);
+            }
+        }
+
+        // FIXME: This needs to be modified so that we normalize the known type
+        // outlives obligations then elaborate them into their region/type components.
+        // Otherwise, `<W<'a> as Mirror>::Assoc: 'b` will not imply `'a: 'b` even
+        // if we can normalize `'a`.
+        OutlivesEnvironment::from_normalized_bounds(
+            param_env,
+            bounds,
+            infcx.implied_bounds_tys_with_compat(
+                body_id,
+                param_env,
+                assumed_wf_tys,
+                implied_bounds_compat,
+            ),
+        )
+    }
+}
 
 #[extension(pub trait InferCtxtRegionExt<'tcx>)]
 impl<'tcx> InferCtxt<'tcx> {
@@ -16,9 +79,24 @@ impl<'tcx> InferCtxt<'tcx> {
     /// doing something specific for normalization.
     fn resolve_regions(
         &self,
+        body_id: LocalDefId,
+        param_env: ty::ParamEnv<'tcx>,
+        assumed_wf_tys: impl IntoIterator<Item = Ty<'tcx>>,
+    ) -> Vec<RegionResolutionError<'tcx>> {
+        self.resolve_regions_with_outlives_env(&OutlivesEnvironment::new(
+            self,
+            body_id,
+            param_env,
+            assumed_wf_tys,
+        ))
+    }
+
+    /// Don't call this directly unless you know what you're doing.
+    fn resolve_regions_with_outlives_env(
+        &self,
         outlives_env: &OutlivesEnvironment<'tcx>,
     ) -> Vec<RegionResolutionError<'tcx>> {
-        self.resolve_regions_with_normalize(outlives_env, |ty, origin| {
+        self.resolve_regions_with_normalize(&outlives_env, |ty, origin| {
             let ty = self.resolve_vars_if_possible(ty);
 
             if self.next_trait_solver() {
diff --git a/compiler/rustc_trait_selection/src/traits/auto_trait.rs b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
index 9a53e8a5d51..1fca2f4da7e 100644
--- a/compiler/rustc_trait_selection/src/traits/auto_trait.rs
+++ b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
@@ -6,6 +6,7 @@ use std::iter;
 
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet, IndexEntry};
 use rustc_data_structures::unord::UnordSet;
+use rustc_hir::def_id::CRATE_DEF_ID;
 use rustc_infer::infer::DefineOpaqueTypes;
 use rustc_middle::ty::{Region, RegionVid};
 use tracing::debug;
@@ -13,6 +14,7 @@ use tracing::debug;
 use super::*;
 use crate::errors::UnableToConstructConstantValue;
 use crate::infer::region_constraints::{Constraint, RegionConstraintData};
+use crate::regions::OutlivesEnvironmentBuildExt;
 use crate::traits::project::ProjectAndUnifyResult;
 
 // FIXME(twk): this is obviously not nice to duplicate like that
@@ -158,7 +160,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
             panic!("Unable to fulfill trait {trait_did:?} for '{ty:?}': {errors:?}");
         }
 
-        let outlives_env = OutlivesEnvironment::new(full_env);
+        let outlives_env = OutlivesEnvironment::new(&infcx, CRATE_DEF_ID, full_env, []);
         let _ = infcx.process_registered_region_obligations(&outlives_env, |ty, _| Ok(ty));
 
         let region_data = infcx.inner.borrow_mut().unwrap_region_constraints().data().clone();
diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs
index 50d47d20e1a..7ee9eb45309 100644
--- a/compiler/rustc_trait_selection/src/traits/coherence.rs
+++ b/compiler/rustc_trait_selection/src/traits/coherence.rs
@@ -9,7 +9,7 @@ use std::fmt::Debug;
 use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
 use rustc_errors::{Diag, EmissionGuarantee};
 use rustc_hir::def::DefKind;
-use rustc_hir::def_id::DefId;
+use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
 use rustc_infer::infer::{DefineOpaqueTypes, InferCtxt, TyCtxtInferExt};
 use rustc_infer::traits::PredicateObligations;
 use rustc_middle::bug;
@@ -27,7 +27,6 @@ use tracing::{debug, instrument, warn};
 use super::ObligationCtxt;
 use crate::error_reporting::traits::suggest_new_overflow_limit;
 use crate::infer::InferOk;
-use crate::infer::outlives::env::OutlivesEnvironment;
 use crate::solve::inspect::{InspectGoal, ProofTreeInferCtxtExt, ProofTreeVisitor};
 use crate::solve::{SolverDelegate, deeply_normalize_for_diagnostics, inspect};
 use crate::traits::query::evaluate_obligation::InferCtxtExt;
@@ -596,8 +595,7 @@ fn try_prove_negated_where_clause<'tcx>(
     // FIXME: We could use the assumed_wf_types from both impls, I think,
     // if that wasn't implemented just for LocalDefId, and we'd need to do
     // the normalization ourselves since this is totally fallible...
-    let outlives_env = OutlivesEnvironment::new(param_env);
-    let errors = ocx.resolve_regions(&outlives_env);
+    let errors = ocx.resolve_regions(CRATE_DEF_ID, param_env, []);
     if !errors.is_empty() {
         return false;
     }
diff --git a/compiler/rustc_trait_selection/src/traits/engine.rs b/compiler/rustc_trait_selection/src/traits/engine.rs
index 4a3983fca31..9f3178f8879 100644
--- a/compiler/rustc_trait_selection/src/traits/engine.rs
+++ b/compiler/rustc_trait_selection/src/traits/engine.rs
@@ -8,7 +8,6 @@ use rustc_infer::infer::at::ToTrace;
 use rustc_infer::infer::canonical::{
     Canonical, CanonicalQueryResponse, CanonicalVarValues, QueryResponse,
 };
-use rustc_infer::infer::outlives::env::OutlivesEnvironment;
 use rustc_infer::infer::{DefineOpaqueTypes, InferCtxt, InferOk, RegionResolutionError, TypeTrace};
 use rustc_infer::traits::PredicateObligations;
 use rustc_macros::extension;
@@ -217,14 +216,15 @@ where
     /// will result in region constraints getting ignored.
     pub fn resolve_regions_and_report_errors(
         self,
-        generic_param_scope: LocalDefId,
-        outlives_env: &OutlivesEnvironment<'tcx>,
+        body_id: LocalDefId,
+        param_env: ty::ParamEnv<'tcx>,
+        assumed_wf_tys: impl IntoIterator<Item = Ty<'tcx>>,
     ) -> Result<(), ErrorGuaranteed> {
-        let errors = self.infcx.resolve_regions(outlives_env);
+        let errors = self.infcx.resolve_regions(body_id, param_env, assumed_wf_tys);
         if errors.is_empty() {
             Ok(())
         } else {
-            Err(self.infcx.err_ctxt().report_region_errors(generic_param_scope, &errors))
+            Err(self.infcx.err_ctxt().report_region_errors(body_id, &errors))
         }
     }
 
@@ -235,9 +235,11 @@ where
     #[must_use]
     pub fn resolve_regions(
         self,
-        outlives_env: &OutlivesEnvironment<'tcx>,
+        body_id: LocalDefId,
+        param_env: ty::ParamEnv<'tcx>,
+        assumed_wf_tys: impl IntoIterator<Item = Ty<'tcx>>,
     ) -> Vec<RegionResolutionError<'tcx>> {
-        self.infcx.resolve_regions(outlives_env)
+        self.infcx.resolve_regions(body_id, param_env, assumed_wf_tys)
     }
 }
 
diff --git a/compiler/rustc_trait_selection/src/traits/misc.rs b/compiler/rustc_trait_selection/src/traits/misc.rs
index 7a67b943e94..79e178150de 100644
--- a/compiler/rustc_trait_selection/src/traits/misc.rs
+++ b/compiler/rustc_trait_selection/src/traits/misc.rs
@@ -4,13 +4,10 @@ use std::assert_matches::assert_matches;
 
 use hir::LangItem;
 use rustc_ast::Mutability;
-use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir as hir;
-use rustc_infer::infer::outlives::env::OutlivesEnvironment;
 use rustc_infer::infer::{RegionResolutionError, TyCtxtInferExt};
 use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt, TypeVisitableExt, TypingMode};
 
-use super::outlives_bounds::InferCtxtExt;
 use crate::regions::InferCtxtRegionExt;
 use crate::traits::{self, FulfillmentError, ObligationCause};
 
@@ -170,15 +167,7 @@ pub fn type_allowed_to_implement_const_param_ty<'tcx>(
         }
 
         // Check regions assuming the self type of the impl is WF
-        let outlives_env = OutlivesEnvironment::with_bounds(
-            param_env,
-            infcx.implied_bounds_tys(
-                param_env,
-                parent_cause.body_id,
-                &FxIndexSet::from_iter([self_type]),
-            ),
-        );
-        let errors = infcx.resolve_regions(&outlives_env);
+        let errors = infcx.resolve_regions(parent_cause.body_id, param_env, [self_type]);
         if !errors.is_empty() {
             infringing_inner_tys.push((inner_ty, InfringingFieldsReason::Regions(errors)));
             continue;
@@ -261,15 +250,7 @@ pub fn all_fields_implement_trait<'tcx>(
             }
 
             // Check regions assuming the self type of the impl is WF
-            let outlives_env = OutlivesEnvironment::with_bounds(
-                param_env,
-                infcx.implied_bounds_tys(
-                    param_env,
-                    parent_cause.body_id,
-                    &FxIndexSet::from_iter([self_type]),
-                ),
-            );
-            let errors = infcx.resolve_regions(&outlives_env);
+            let errors = infcx.resolve_regions(parent_cause.body_id, param_env, [self_type]);
             if !errors.is_empty() {
                 infringing.push((field, ty, InfringingFieldsReason::Regions(errors)));
             }
diff --git a/compiler/rustc_trait_selection/src/traits/mod.rs b/compiler/rustc_trait_selection/src/traits/mod.rs
index fe5ad003a7e..6b5ebade6ae 100644
--- a/compiler/rustc_trait_selection/src/traits/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/mod.rs
@@ -290,12 +290,10 @@ fn do_normalize_predicates<'tcx>(
 
     // We can use the `elaborated_env` here; the region code only
     // cares about declarations like `'a: 'b`.
-    let outlives_env = OutlivesEnvironment::new(elaborated_env);
-
     // FIXME: It's very weird that we ignore region obligations but apparently
     // still need to use `resolve_regions` as we need the resolved regions in
     // the normalized predicates.
-    let errors = infcx.resolve_regions(&outlives_env);
+    let errors = infcx.resolve_regions(cause.body_id, elaborated_env, []);
     if !errors.is_empty() {
         tcx.dcx().span_delayed_bug(
             span,
diff --git a/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs b/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
index 23dabe32ff2..18932695807 100644
--- a/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
+++ b/compiler/rustc_trait_selection/src/traits/outlives_bounds.rs
@@ -1,4 +1,3 @@
-use rustc_data_structures::fx::FxIndexSet;
 use rustc_infer::infer::InferOk;
 use rustc_infer::infer::resolve::OpportunisticRegionResolver;
 use rustc_infer::traits::query::type_op::ImpliedOutlivesBounds;
@@ -12,9 +11,6 @@ use tracing::instrument;
 use crate::infer::InferCtxt;
 use crate::traits::{ObligationCause, ObligationCtxt};
 
-pub type BoundsCompat<'a, 'tcx: 'a> = impl Iterator<Item = OutlivesBound<'tcx>> + 'a;
-pub type Bounds<'a, 'tcx: 'a> = impl Iterator<Item = OutlivesBound<'tcx>> + 'a;
-
 /// Implied bounds are region relationships that we deduce
 /// automatically. The idea is that (e.g.) a caller must check that a
 /// function's argument types are well-formed immediately before
@@ -110,36 +106,18 @@ fn implied_outlives_bounds<'a, 'tcx>(
     bounds
 }
 
-#[extension(pub trait InferCtxtExt<'a, 'tcx>)]
-impl<'a, 'tcx: 'a> InferCtxt<'tcx> {
-    /// Do *NOT* call this directly.
-    fn implied_bounds_tys_compat(
-        &'a self,
-        param_env: ParamEnv<'tcx>,
+#[extension(pub trait InferCtxtExt<'tcx>)]
+impl<'tcx> InferCtxt<'tcx> {
+    /// Do *NOT* call this directly. You probably want to construct a `OutlivesEnvironment`
+    /// instead if you're interested in the implied bounds for a given signature.
+    fn implied_bounds_tys_with_compat<Tys: IntoIterator<Item = Ty<'tcx>>>(
+        &self,
         body_id: LocalDefId,
-        tys: &'a FxIndexSet<Ty<'tcx>>,
-        compat: bool,
-    ) -> BoundsCompat<'a, 'tcx> {
-        tys.iter()
-            .flat_map(move |ty| implied_outlives_bounds(self, param_env, body_id, *ty, compat))
-    }
-
-    /// If `-Z no-implied-bounds-compat` is set, calls `implied_bounds_tys_compat`
-    /// with `compat` set to `true`, otherwise `false`.
-    fn implied_bounds_tys(
-        &'a self,
         param_env: ParamEnv<'tcx>,
-        body_id: LocalDefId,
-        tys: &'a FxIndexSet<Ty<'tcx>>,
-    ) -> Bounds<'a, 'tcx> {
-        tys.iter().flat_map(move |ty| {
-            implied_outlives_bounds(
-                self,
-                param_env,
-                body_id,
-                *ty,
-                !self.tcx.sess.opts.unstable_opts.no_implied_bounds_compat,
-            )
-        })
+        tys: Tys,
+        compat: bool,
+    ) -> impl Iterator<Item = OutlivesBound<'tcx>> {
+        tys.into_iter()
+            .flat_map(move |ty| implied_outlives_bounds(self, param_env, body_id, ty, compat))
     }
 }