Auto merge of rust-lang#135969 - compiler-errors:normalize-erasing-regions, r=<try>

Rewrite `normalize_erasing_regions` to not use `QueryNormalizer`

r? `@ghost`

Author: bors

compiler/rustc_middle/src/ty/normalize_erasing_regions.rs

@@ -11,7 +11,7 @@ use rustc_macros::{HashStable, TyDecodable, TyEncodable};
 use tracing::{debug, instrument};
 
 use crate::traits::query::NoSolution;
-use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder};
+use crate::ty::fold::{FallibleTypeFolder, TypeFoldable, TypeFolder, TypeSuperFoldable};
 use crate::ty::{self, EarlyBinder, GenericArgsRef, Ty, TyCtxt, TypeVisitableExt};
 
 #[derive(Debug, Copy, Clone, HashStable, TyEncodable, TyDecodable)]
@@ -46,6 +46,10 @@ impl<'tcx> TyCtxt<'tcx> {
             value,
             typing_env,
         );
+        debug_assert!(
+            !value.has_escaping_bound_vars(),
+            "{value:?} cannot be normalized with escaping bound vars"
+        );
 
         // Erase first before we do the real query -- this keeps the
         // cache from being too polluted.
@@ -218,16 +222,27 @@ impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for TryNormalizeAfterErasingRegionsF
     }
 
     fn try_fold_ty(&mut self, ty: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
-        match self.try_normalize_generic_arg_after_erasing_regions(ty.into()) {
-            Ok(t) => Ok(t.expect_ty()),
-            Err(_) => Err(NormalizationError::Type(ty)),
+        // HACKY HACK: dont walk into binders
+        if let ty::Alias(..) | ty::Dynamic(..) | ty::FnPtr(..) = ty.kind() {
+            self.try_normalize_generic_arg_after_erasing_regions(ty.into())
+                .map(|arg| arg.expect_ty())
+                .map_err(|_| NormalizationError::Type(ty))
+        } else if ty.has_aliases() {
+            ty.try_super_fold_with(self)
+        } else {
+            Ok(ty)
         }
     }
 
-    fn try_fold_const(&mut self, c: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, Self::Error> {
-        match self.try_normalize_generic_arg_after_erasing_regions(c.into()) {
-            Ok(t) => Ok(t.expect_const()),
-            Err(_) => Err(NormalizationError::Const(c)),
+    fn try_fold_const(&mut self, ct: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, Self::Error> {
+        if let ty::ConstKind::Unevaluated(..) = ct.kind() {
+            self.try_normalize_generic_arg_after_erasing_regions(ct.into())
+                .map(|arg| arg.expect_const())
+                .map_err(|_| NormalizationError::Const(ct))
+        } else if ct.has_aliases() {
+            ct.try_super_fold_with(self)
+        } else {
+            Ok(ct)
         }
     }
 }

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

@@ -11,7 +11,7 @@ LL |     bytes: [u8; std::mem::size_of::<Foo>()]
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: ...which requires computing layout of `Foo`...
    = note: ...which requires computing layout of `[u8; std::mem::size_of::<Foo>()]`...
-   = note: ...which requires normalizing `[u8; std::mem::size_of::<Foo>()]`...
+   = note: ...which requires normalizing `std::mem::size_of::<Foo>()`...
    = note: ...which again requires evaluating type-level constant, completing the cycle
 note: cycle used when checking that `Foo` is well-formed
   --> $DIR/const-size_of-cycle.rs:3:1

tests/ui/consts/const-size_of-cycle.stderr

@@ -11,7 +11,7 @@ LL |     bytes: [u8; unsafe { intrinsics::size_of::<Foo>() }],
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = note: ...which requires computing layout of `Foo`...
    = note: ...which requires computing layout of `[u8; unsafe { intrinsics::size_of::<Foo>() }]`...
-   = note: ...which requires normalizing `[u8; unsafe { intrinsics::size_of::<Foo>() }]`...
+   = note: ...which requires normalizing `unsafe { intrinsics::size_of::<Foo>() }`...
    = note: ...which again requires evaluating type-level constant, completing the cycle
 note: cycle used when checking that `Foo` is well-formed
   --> $DIR/issue-44415.rs:5:1

tests/ui/consts/issue-44415.stderr

@@ -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`.