Rewrite normalize_erasing_regions to not use QueryNormalizer

Author: compiler-errors

compiler/rustc_traits/src/normalize_erasing_regions.rs

@@ -1,9 +1,16 @@
 use rustc_infer::infer::TyCtxtInferExt;
+use rustc_infer::traits::ScrubbedTraitError;
+use rustc_middle::bug;
 use rustc_middle::query::Providers;
 use rustc_middle::traits::query::NoSolution;
-use rustc_middle::ty::{self, PseudoCanonicalInput, TyCtxt, TypeFoldable, TypeVisitableExt};
-use rustc_trait_selection::traits::query::normalize::QueryNormalizeExt;
-use rustc_trait_selection::traits::{Normalized, ObligationCause};
+use rustc_middle::ty::{
+    self, PseudoCanonicalInput, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable,
+    TypeVisitableExt, TypingMode,
+};
+use rustc_span::DUMMY_SP;
+use rustc_trait_selection::error_reporting::InferCtxtErrorExt;
+use rustc_trait_selection::error_reporting::traits::OverflowCause;
+use rustc_trait_selection::traits::{self, ObligationCause, ObligationCtxt};
 use tracing::debug;
 
 pub(crate) fn provide(p: &mut Providers) {
@@ -17,54 +24,83 @@ pub(crate) fn provide(p: &mut Providers) {
     };
 }
 
+// FIXME(-Znext-solver): This can be simplified further to just a `deeply_normalize` call.
 fn try_normalize_after_erasing_regions<'tcx, T: TypeFoldable<TyCtxt<'tcx>> + PartialEq + Copy>(
     tcx: TyCtxt<'tcx>,
     goal: PseudoCanonicalInput<'tcx, T>,
 ) -> Result<T, NoSolution> {
     let PseudoCanonicalInput { typing_env, value } = goal;
     let (infcx, param_env) = tcx.infer_ctxt().build_with_typing_env(typing_env);
-    let cause = ObligationCause::dummy();
-    match infcx.at(&cause, param_env).query_normalize(value) {
-        Ok(Normalized { value: normalized_value, obligations: normalized_obligations }) => {
-            // We don't care about the `obligations`; they are
-            // always only region relations, and we are about to
-            // erase those anyway:
-            // This has been seen to fail in RL, so making it a non-debug assertion to better catch
-            // those cases.
-            assert_eq!(
-                normalized_obligations.iter().find(|p| not_outlives_predicate(p.predicate)),
-                None,
-            );
+    let ocx = ObligationCtxt::new(&infcx);
+    let mut normalized =
+        ocx.deeply_normalize(&ObligationCause::dummy(), param_env, value).map_err(|errors| {
+            match infcx.typing_mode() {
+                TypingMode::PostAnalysis => {
+                    for error in errors {
+                        match error {
+                            ScrubbedTraitError::Cycle(pred) => {
+                                infcx.err_ctxt().report_overflow_error(
+                                    OverflowCause::TraitSolver(pred.first().unwrap().predicate),
+                                    DUMMY_SP,
+                                    false,
+                                    |_| {},
+                                );
+                            }
+                            _ => {}
+                        }
+                    }
+                }
+                _ => {}
+            }
 
-            let resolved_value = infcx.resolve_vars_if_possible(normalized_value);
-            // It's unclear when `resolve_vars` would have an effect in a
-            // fresh `InferCtxt`. If this assert does trigger, it will give
-            // us a test case.
-            debug_assert_eq!(normalized_value, resolved_value);
-            let erased = infcx.tcx.erase_regions(resolved_value);
-            debug_assert!(!erased.has_infer(), "{erased:?}");
-            Ok(erased)
-        }
-        Err(NoSolution) => Err(NoSolution),
+            // Otherwise, bail with `NoSolution`
+            NoSolution
+        })?;
+
+    if tcx.features().generic_const_exprs() {
+        normalized =
+            normalized.fold_with(&mut FoldConsts { ocx: &ocx, param_env, universes: vec![] });
+    }
+
+    let resolved = infcx.resolve_vars_if_possible(normalized);
+    let erased = tcx.erase_regions(resolved);
+
+    if erased.has_non_region_infer() {
+        bug!("encountered infer when normalizing {value:?} to {erased:?}");
     }
+
+    Ok(erased)
 }
 
-fn not_outlives_predicate(p: ty::Predicate<'_>) -> bool {
-    match p.kind().skip_binder() {
-        ty::PredicateKind::Clause(ty::ClauseKind::RegionOutlives(..))
-        | ty::PredicateKind::Clause(ty::ClauseKind::TypeOutlives(..)) => false,
-        ty::PredicateKind::Clause(ty::ClauseKind::Trait(..))
-        | ty::PredicateKind::Clause(ty::ClauseKind::Projection(..))
-        | ty::PredicateKind::Clause(ty::ClauseKind::HostEffect(..))
-        | ty::PredicateKind::Clause(ty::ClauseKind::ConstArgHasType(..))
-        | ty::PredicateKind::NormalizesTo(..)
-        | ty::PredicateKind::AliasRelate(..)
-        | ty::PredicateKind::Clause(ty::ClauseKind::WellFormed(..))
-        | ty::PredicateKind::DynCompatible(..)
-        | ty::PredicateKind::Subtype(..)
-        | ty::PredicateKind::Coerce(..)
-        | ty::PredicateKind::Clause(ty::ClauseKind::ConstEvaluatable(..))
-        | ty::PredicateKind::ConstEquate(..)
-        | ty::PredicateKind::Ambiguous => true,
+struct FoldConsts<'a, 'tcx> {
+    ocx: &'a ObligationCtxt<'a, 'tcx>,
+    param_env: ty::ParamEnv<'tcx>,
+    universes: Vec<Option<ty::UniverseIndex>>,
+}
+
+impl<'tcx> TypeFolder<TyCtxt<'tcx>> for FoldConsts<'_, 'tcx> {
+    fn cx(&self) -> TyCtxt<'tcx> {
+        self.ocx.infcx.tcx
+    }
+
+    fn fold_binder<T>(&mut self, binder: ty::Binder<'tcx, T>) -> ty::Binder<'tcx, T>
+    where
+        T: TypeFoldable<TyCtxt<'tcx>>,
+    {
+        self.universes.push(None);
+        let binder = binder.super_fold_with(self);
+        self.universes.pop();
+        binder
+    }
+
+    fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
+        let ct = traits::with_replaced_escaping_bound_vars(
+            self.ocx.infcx,
+            &mut self.universes,
+            ct,
+            |constant| traits::evaluate_const(self.ocx.infcx, constant, self.param_env),
+        );
+        debug!(?ct, ?self.param_env);
+        ct.super_fold_with(self)
     }
 }

tests/crashes/125801.rs

@@ -1,7 +1,7 @@
+//~ ERROR overflow normalizing the opaque type
 #![feature(type_alias_impl_trait)]
 
 type T = impl Copy;
-//~^ ERROR cannot resolve opaque type
 
 static STATIC: T = None::<&'static T>;
 

tests/ui/type-alias-impl-trait/infinite-cycle-involving-weak.rs

@@ -1,9 +1,7 @@
-error[E0720]: cannot resolve opaque type
-  --> $DIR/infinite-cycle-involving-weak.rs:3:10
+error[E0275]: overflow normalizing the opaque type `T::{opaque#0}`
    |
-LL | type T = impl Copy;
-   |          ^^^^^^^^^ cannot resolve opaque type
+   = help: consider increasing the recursion limit by adding a `#![recursion_limit = "256"]` attribute to your crate (`infinite_cycle_involving_weak`)
 
 error: aborting due to 1 previous error
 
-For more information about this error, try `rustc --explain E0720`.
+For more information about this error, try `rustc --explain E0275`.