Auto merge of #120798 - compiler-errors:normalize-opaques, r=<try>

Normalize opaques to infer vars eagerly in AssocTypeNormalizer

:forgor:

r? `@ghost`

Author: bors

compiler/rustc_hir_typeck/src/check.rs

@@ -38,15 +38,7 @@ pub(super) fn check_fn<'a, 'tcx>(
     let tcx = fcx.tcx;
     let hir = tcx.hir();
 
-    let declared_ret_ty = fn_sig.output();
-
-    let ret_ty =
-        fcx.register_infer_ok_obligations(fcx.infcx.replace_opaque_types_with_inference_vars(
-            declared_ret_ty,
-            fn_def_id,
-            decl.output.span(),
-            fcx.param_env,
-        ));
+    let ret_ty = fn_sig.output();
 
     fcx.coroutine_types = coroutine_types;
     fcx.ret_coercion = Some(RefCell::new(CoerceMany::new(ret_ty)));
@@ -109,7 +101,7 @@ pub(super) fn check_fn<'a, 'tcx>(
         hir::FnRetTy::DefaultReturn(_) => body.value.span,
         hir::FnRetTy::Return(ty) => ty.span,
     };
-    fcx.require_type_is_sized(declared_ret_ty, return_or_body_span, traits::SizedReturnType);
+    fcx.require_type_is_sized(ret_ty, return_or_body_span, traits::SizedReturnType);
     fcx.is_whole_body.set(true);
     fcx.check_return_expr(body.value, false);
 
@@ -120,7 +112,7 @@ pub(super) fn check_fn<'a, 'tcx>(
     let coercion = fcx.ret_coercion.take().unwrap().into_inner();
     let mut actual_return_ty = coercion.complete(fcx);
     debug!("actual_return_ty = {:?}", actual_return_ty);
-    if let ty::Dynamic(..) = declared_ret_ty.kind() {
+    if let ty::Dynamic(..) = ret_ty.kind() {
         // We have special-cased the case where the function is declared
         // `-> dyn Foo` and we don't actually relate it to the
         // `fcx.ret_coercion`, so just substitute a type variable.

compiler/rustc_hir_typeck/src/closure.rs

@@ -879,17 +879,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let output_ty = self.normalize(closure_span, output_ty);
 
-        // async fn that have opaque types in their return type need to redo the conversion to inference variables
-        // as they fetch the still opaque version from the signature.
-        let InferOk { value: output_ty, obligations } = self
-            .replace_opaque_types_with_inference_vars(
-                output_ty,
-                body_def_id,
-                closure_span,
-                self.param_env,
-            );
-        self.register_predicates(obligations);
-
         Some(output_ty)
     }
 

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -1,4 +1,3 @@
-use super::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use super::{DefineOpaqueTypes, InferResult};
 use crate::errors::OpaqueHiddenTypeDiag;
 use crate::infer::{InferCtxt, InferOk};
@@ -36,60 +35,6 @@ pub struct OpaqueTypeDecl<'tcx> {
 }
 
 impl<'tcx> InferCtxt<'tcx> {
-    /// This is a backwards compatibility hack to prevent breaking changes from
-    /// lazy TAIT around RPIT handling.
-    pub fn replace_opaque_types_with_inference_vars<T: TypeFoldable<TyCtxt<'tcx>>>(
-        &self,
-        value: T,
-        body_id: LocalDefId,
-        span: Span,
-        param_env: ty::ParamEnv<'tcx>,
-    ) -> InferOk<'tcx, T> {
-        // We handle opaque types differently in the new solver.
-        if self.next_trait_solver() {
-            return InferOk { value, obligations: vec![] };
-        }
-
-        if !value.has_opaque_types() {
-            return InferOk { value, obligations: vec![] };
-        }
-
-        let mut obligations = vec![];
-        let replace_opaque_type = |def_id: DefId| {
-            def_id.as_local().is_some_and(|def_id| self.opaque_type_origin(def_id).is_some())
-        };
-        let value = value.fold_with(&mut BottomUpFolder {
-            tcx: self.tcx,
-            lt_op: |lt| lt,
-            ct_op: |ct| ct,
-            ty_op: |ty| match *ty.kind() {
-                ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. })
-                    if replace_opaque_type(def_id) && !ty.has_escaping_bound_vars() =>
-                {
-                    let def_span = self.tcx.def_span(def_id);
-                    let span = if span.contains(def_span) { def_span } else { span };
-                    let code = traits::ObligationCauseCode::OpaqueReturnType(None);
-                    let cause = ObligationCause::new(span, body_id, code);
-                    // FIXME(compiler-errors): We probably should add a new TypeVariableOriginKind
-                    // for opaque types, and then use that kind to fix the spans for type errors
-                    // that we see later on.
-                    let ty_var = self.next_ty_var(TypeVariableOrigin {
-                        kind: TypeVariableOriginKind::OpaqueTypeInference(def_id),
-                        span,
-                    });
-                    obligations.extend(
-                        self.handle_opaque_type(ty, ty_var, true, &cause, param_env)
-                            .unwrap()
-                            .obligations,
-                    );
-                    ty_var
-                }
-                _ => ty,
-            },
-        });
-        InferOk { value, obligations }
-    }
-
     pub fn handle_opaque_type(
         &self,
         a: Ty<'tcx>,
@@ -515,7 +460,7 @@ impl UseKind {
 
 impl<'tcx> InferCtxt<'tcx> {
     #[instrument(skip(self), level = "debug")]
-    fn register_hidden_type(
+    pub fn register_hidden_type(
         &self,
         opaque_type_key: OpaqueTypeKey<'tcx>,
         cause: ObligationCause<'tcx>,

compiler/rustc_middle/src/traits/mod.rs

@@ -1004,14 +1004,14 @@ pub enum CodegenObligationError {
 #[derive(Debug, PartialEq, Eq, Clone, Copy, Hash, HashStable, TypeFoldable, TypeVisitable)]
 pub enum DefiningAnchor {
     /// Define opaques which are in-scope of the `LocalDefId`. Also, eagerly
-    /// replace opaque types in `replace_opaque_types_with_inference_vars`.
+    /// replace opaque types in normalization.
     Bind(LocalDefId),
     /// In contexts where we don't currently know what opaques are allowed to be
     /// defined, such as (old solver) canonical queries, we will simply allow
     /// opaques to be defined, but "bubble" them up in the canonical response or
     /// otherwise treat them to be handled later.
     ///
-    /// We do not eagerly replace opaque types in `replace_opaque_types_with_inference_vars`,
+    /// We do not eagerly replace opaque types in normalization,
     /// which may affect what predicates pass and fail in the old trait solver.
     Bubble,
     /// Do not allow any opaques to be defined. This is used to catch type mismatch

compiler/rustc_trait_selection/src/solve/normalize.rs

@@ -1,6 +1,6 @@
 use crate::traits::error_reporting::TypeErrCtxtExt;
 use crate::traits::query::evaluate_obligation::InferCtxtExt;
-use crate::traits::{needs_normalization, BoundVarReplacer, PlaceholderReplacer};
+use crate::traits::{BoundVarReplacer, PlaceholderReplacer};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_infer::infer::at::At;
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
@@ -205,10 +205,9 @@ impl<'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for NormalizationFolder<'_, 'tcx> {
     }
 
     fn try_fold_const(&mut self, ct: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, Self::Error> {
-        let reveal = self.at.param_env.reveal();
         let infcx = self.at.infcx;
         debug_assert_eq!(ct, infcx.shallow_resolve(ct));
-        if !needs_normalization(&ct, reveal) {
+        if !ct.has_projections() {
             return Ok(ct);
         }
 

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -40,7 +40,7 @@ use rustc_span::Span;
 use std::fmt::Debug;
 use std::ops::ControlFlow;
 
-pub(crate) use self::project::{needs_normalization, BoundVarReplacer, PlaceholderReplacer};
+pub(crate) use self::project::{BoundVarReplacer, PlaceholderReplacer};
 
 pub use self::coherence::{add_placeholder_note, orphan_check, overlapping_impls};
 pub use self::coherence::{OrphanCheckErr, OverlapResult};

compiler/rustc_trait_selection/src/traits/project.rs

@@ -27,6 +27,7 @@ use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_errors::ErrorGuaranteed;
 use rustc_hir::def::DefKind;
 use rustc_hir::lang_items::LangItem;
+use rustc_hir::OpaqueTyOrigin;
 use rustc_infer::infer::at::At;
 use rustc_infer::infer::resolve::OpportunisticRegionResolver;
 use rustc_infer::infer::DefineOpaqueTypes;
@@ -318,17 +319,6 @@ fn project_and_unify_type<'cx, 'tcx>(
     };
     debug!(?normalized, ?obligations, "project_and_unify_type result");
     let actual = obligation.predicate.term;
-    // For an example where this is necessary see tests/ui/impl-trait/nested-return-type2.rs
-    // This allows users to omit re-mentioning all bounds on an associated type and just use an
-    // `impl Trait` for the assoc type to add more bounds.
-    let InferOk { value: actual, obligations: new } =
-        selcx.infcx.replace_opaque_types_with_inference_vars(
-            actual,
-            obligation.cause.body_id,
-            obligation.cause.span,
-            obligation.param_env,
-        );
-    obligations.extend(new);
 
     // Need to define opaque types to support nested opaque types like `impl Fn() -> impl Trait`
     match infcx.at(&obligation.cause, obligation.param_env).eq(
@@ -409,25 +399,6 @@ where
     result
 }
 
-pub(crate) fn needs_normalization<'tcx, T: TypeVisitable<TyCtxt<'tcx>>>(
-    value: &T,
-    reveal: Reveal,
-) -> bool {
-    match reveal {
-        Reveal::UserFacing => value.has_type_flags(
-            ty::TypeFlags::HAS_TY_PROJECTION
-                | ty::TypeFlags::HAS_TY_INHERENT
-                | ty::TypeFlags::HAS_CT_PROJECTION,
-        ),
-        Reveal::All => value.has_type_flags(
-            ty::TypeFlags::HAS_TY_PROJECTION
-                | ty::TypeFlags::HAS_TY_INHERENT
-                | ty::TypeFlags::HAS_TY_OPAQUE
-                | ty::TypeFlags::HAS_CT_PROJECTION,
-        ),
-    }
-}
-
 struct AssocTypeNormalizer<'a, 'b, 'tcx> {
     selcx: &'a mut SelectionContext<'b, 'tcx>,
     param_env: ty::ParamEnv<'tcx>,
@@ -488,11 +459,7 @@ impl<'a, 'b, 'tcx> AssocTypeNormalizer<'a, 'b, 'tcx> {
             "Normalizing {value:?} without wrapping in a `Binder`"
         );
 
-        if !needs_normalization(&value, self.param_env.reveal()) {
-            value
-        } else {
-            value.fold_with(self)
-        }
+        if !value.has_projections() { value } else { value.fold_with(self) }
     }
 }
 
@@ -512,7 +479,7 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
     }
 
     fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        if !needs_normalization(&ty, self.param_env.reveal()) {
+        if !ty.has_projections() {
             return ty;
         }
 
@@ -548,7 +515,36 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
             ty::Opaque => {
                 // Only normalize `impl Trait` outside of type inference, usually in codegen.
                 match self.param_env.reveal() {
-                    Reveal::UserFacing => ty.super_fold_with(self),
+                    Reveal::UserFacing => {
+                        if !data.has_escaping_bound_vars()
+                            && let Some(def_id) = data.def_id.as_local()
+                            && let Some(
+                                OpaqueTyOrigin::TyAlias { in_assoc_ty: true }
+                                | OpaqueTyOrigin::AsyncFn(_)
+                                | OpaqueTyOrigin::FnReturn(_),
+                            ) = self.selcx.infcx.opaque_type_origin(def_id)
+                        {
+                            let infer = self.selcx.infcx.next_ty_var(TypeVariableOrigin {
+                                kind: TypeVariableOriginKind::OpaqueTypeInference(data.def_id),
+                                span: self.cause.span,
+                            });
+                            let InferOk { value: (), obligations } = self
+                                .selcx
+                                .infcx
+                                .register_hidden_type(
+                                    ty::OpaqueTypeKey { def_id, args: data.args },
+                                    self.cause.clone(),
+                                    self.param_env,
+                                    infer,
+                                    true,
+                                )
+                                .expect("uwu");
+                            self.obligations.extend(obligations);
+                            self.selcx.infcx.resolve_vars_if_possible(infer)
+                        } else {
+                            ty.super_fold_with(self)
+                        }
+                    }
 
                     Reveal::All => {
                         let recursion_limit = self.interner().recursion_limit();
@@ -752,9 +748,7 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
     #[instrument(skip(self), level = "debug")]
     fn fold_const(&mut self, constant: ty::Const<'tcx>) -> ty::Const<'tcx> {
         let tcx = self.selcx.tcx();
-        if tcx.features().generic_const_exprs
-            || !needs_normalization(&constant, self.param_env.reveal())
-        {
+        if tcx.features().generic_const_exprs || !constant.has_projections() {
             constant
         } else {
             let constant = constant.super_fold_with(self);
@@ -770,11 +764,7 @@ impl<'a, 'b, 'tcx> TypeFolder<TyCtxt<'tcx>> for AssocTypeNormalizer<'a, 'b, 'tcx
 
     #[inline]
     fn fold_predicate(&mut self, p: ty::Predicate<'tcx>) -> ty::Predicate<'tcx> {
-        if p.allow_normalization() && needs_normalization(&p, self.param_env.reveal()) {
-            p.super_fold_with(self)
-        } else {
-            p
-        }
+        if p.allow_normalization() && p.has_projections() { p.super_fold_with(self) } else { p }
     }
 }
 

compiler/rustc_trait_selection/src/traits/query/normalize.rs

@@ -6,7 +6,7 @@ use crate::infer::at::At;
 use crate::infer::canonical::OriginalQueryValues;
 use crate::infer::{InferCtxt, InferOk};
 use crate::traits::error_reporting::TypeErrCtxtExt;
-use crate::traits::project::{needs_normalization, BoundVarReplacer, PlaceholderReplacer};
+use crate::traits::project::{BoundVarReplacer, PlaceholderReplacer};
 use crate::traits::{ObligationCause, PredicateObligation, Reveal};
 use rustc_data_structures::sso::SsoHashMap;
 use rustc_data_structures::stack::ensure_sufficient_stack;
@@ -89,7 +89,7 @@ impl<'cx, 'tcx> QueryNormalizeExt<'tcx> for At<'cx, 'tcx> {
             }
         }
 
-        if !needs_normalization(&value, self.param_env.reveal()) {
+        if !value.has_projections() {
             return Ok(Normalized { value, obligations: vec![] });
         }
 
@@ -198,7 +198,7 @@ impl<'cx, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for QueryNormalizer<'cx, 'tcx>
 
     #[instrument(level = "debug", skip(self))]
     fn try_fold_ty(&mut self, ty: Ty<'tcx>) -> Result<Ty<'tcx>, Self::Error> {
-        if !needs_normalization(&ty, self.param_env.reveal()) {
+        if !ty.has_projections() {
             return Ok(ty);
         }
 
@@ -335,7 +335,7 @@ impl<'cx, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for QueryNormalizer<'cx, 'tcx>
         &mut self,
         constant: ty::Const<'tcx>,
     ) -> Result<ty::Const<'tcx>, Self::Error> {
-        if !needs_normalization(&constant, self.param_env.reveal()) {
+        if !constant.has_projections() {
             return Ok(constant);
         }
 
@@ -354,7 +354,7 @@ impl<'cx, 'tcx> FallibleTypeFolder<TyCtxt<'tcx>> for QueryNormalizer<'cx, 'tcx>
         &mut self,
         p: ty::Predicate<'tcx>,
     ) -> Result<ty::Predicate<'tcx>, Self::Error> {
-        if p.allow_normalization() && needs_normalization(&p, self.param_env.reveal()) {
+        if p.allow_normalization() && p.has_projections() {
             p.try_super_fold_with(self)
         } else {
             Ok(p)