Auto merge of #93893 - oli-obk:sad_revert, r=oli-obk

Revert lazy TAIT PR

Revert #92306 (sorry `@Aaron1011,` will include your changes in the fix PR)
Revert #93783
Revert #92007

fixes #93788
fixes #93794
fixes #93821
fixes #93831
fixes #93841

compiler/rustc_borrowck/src/diagnostics/bound_region_errors.rs

@@ -2,13 +2,9 @@ use rustc_errors::DiagnosticBuilder;
 use rustc_infer::infer::canonical::Canonical;
 use rustc_infer::infer::error_reporting::nice_region_error::NiceRegionError;
 use rustc_infer::infer::region_constraints::Constraint;
-use rustc_infer::infer::region_constraints::RegionConstraintData;
-use rustc_infer::infer::RegionVariableOrigin;
 use rustc_infer::infer::{InferCtxt, RegionResolutionError, SubregionOrigin, TyCtxtInferExt as _};
 use rustc_infer::traits::{Normalized, ObligationCause, TraitEngine, TraitEngineExt};
 use rustc_middle::ty::error::TypeError;
-use rustc_middle::ty::RegionVid;
-use rustc_middle::ty::UniverseIndex;
 use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
 use rustc_span::Span;
 use rustc_trait_selection::traits::query::type_op;
@@ -82,15 +78,6 @@ crate trait ToUniverseInfo<'tcx> {
     fn to_universe_info(self, base_universe: ty::UniverseIndex) -> UniverseInfo<'tcx>;
 }
 
-impl<'tcx> ToUniverseInfo<'tcx> for crate::type_check::InstantiateOpaqueType<'tcx> {
-    fn to_universe_info(self, base_universe: ty::UniverseIndex) -> UniverseInfo<'tcx> {
-        UniverseInfo(UniverseInfoInner::TypeOp(Rc::new(crate::type_check::InstantiateOpaqueType {
-            base_universe: Some(base_universe),
-            ..self
-        })))
-    }
-}
-
 impl<'tcx> ToUniverseInfo<'tcx>
     for Canonical<'tcx, ty::ParamEnvAnd<'tcx, type_op::prove_predicate::ProvePredicate<'tcx>>>
 {
@@ -131,12 +118,6 @@ impl<'tcx, F, G> ToUniverseInfo<'tcx> for Canonical<'tcx, type_op::custom::Custo
     }
 }
 
-impl<'tcx> ToUniverseInfo<'tcx> for ! {
-    fn to_universe_info(self, _base_universe: ty::UniverseIndex) -> UniverseInfo<'tcx> {
-        self
-    }
-}
-
 #[allow(unused_lifetimes)]
 trait TypeOpInfo<'tcx> {
     /// Returns an error to be reported if rerunning the type op fails to
@@ -147,7 +128,7 @@ trait TypeOpInfo<'tcx> {
 
     fn nice_error(
         &self,
-        mbcx: &mut MirBorrowckCtxt<'_, 'tcx>,
+        tcx: TyCtxt<'tcx>,
         cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
@@ -194,7 +175,7 @@ trait TypeOpInfo<'tcx> {
         debug!(?placeholder_region);
 
         let span = cause.span;
-        let nice_error = self.nice_error(mbcx, cause, placeholder_region, error_region);
+        let nice_error = self.nice_error(tcx, cause, placeholder_region, error_region);
 
         if let Some(nice_error) = nice_error {
             nice_error.buffer(&mut mbcx.errors_buffer);
@@ -223,16 +204,16 @@ impl<'tcx> TypeOpInfo<'tcx> for PredicateQuery<'tcx> {
 
     fn nice_error(
         &self,
-        mbcx: &mut MirBorrowckCtxt<'_, 'tcx>,
+        tcx: TyCtxt<'tcx>,
         cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
     ) -> Option<DiagnosticBuilder<'tcx>> {
-        mbcx.infcx.tcx.infer_ctxt().enter_with_canonical(
+        tcx.infer_ctxt().enter_with_canonical(
             cause.span,
             &self.canonical_query,
             |ref infcx, key, _| {
-                let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
+                let mut fulfill_cx = <dyn TraitEngine<'_>>::new(tcx);
                 type_op_prove_predicate_with_cause(infcx, &mut *fulfill_cx, key, cause);
                 try_extract_error_from_fulfill_cx(
                     fulfill_cx,
@@ -266,16 +247,16 @@ where
 
     fn nice_error(
         &self,
-        mbcx: &mut MirBorrowckCtxt<'_, 'tcx>,
+        tcx: TyCtxt<'tcx>,
         cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
     ) -> Option<DiagnosticBuilder<'tcx>> {
-        mbcx.infcx.tcx.infer_ctxt().enter_with_canonical(
+        tcx.infer_ctxt().enter_with_canonical(
             cause.span,
             &self.canonical_query,
             |ref infcx, key, _| {
-                let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
+                let mut fulfill_cx = <dyn TraitEngine<'_>>::new(tcx);
 
                 let mut selcx = SelectionContext::new(infcx);
 
@@ -323,16 +304,16 @@ impl<'tcx> TypeOpInfo<'tcx> for AscribeUserTypeQuery<'tcx> {
 
     fn nice_error(
         &self,
-        mbcx: &mut MirBorrowckCtxt<'_, 'tcx>,
+        tcx: TyCtxt<'tcx>,
         cause: ObligationCause<'tcx>,
         placeholder_region: ty::Region<'tcx>,
         error_region: Option<ty::Region<'tcx>>,
     ) -> Option<DiagnosticBuilder<'tcx>> {
-        mbcx.infcx.tcx.infer_ctxt().enter_with_canonical(
+        tcx.infer_ctxt().enter_with_canonical(
             cause.span,
             &self.canonical_query,
             |ref infcx, key, _| {
-                let mut fulfill_cx = <dyn TraitEngine<'_>>::new(infcx.tcx);
+                let mut fulfill_cx = <dyn TraitEngine<'_>>::new(tcx);
                 type_op_ascribe_user_type_with_span(infcx, &mut *fulfill_cx, key, Some(cause.span))
                     .ok()?;
                 try_extract_error_from_fulfill_cx(
@@ -346,90 +327,43 @@ impl<'tcx> TypeOpInfo<'tcx> for AscribeUserTypeQuery<'tcx> {
     }
 }
 
-impl<'tcx> TypeOpInfo<'tcx> for crate::type_check::InstantiateOpaqueType<'tcx> {
-    fn fallback_error(&self, tcx: TyCtxt<'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
-        // FIXME: This error message isn't great, but it doesn't show up in the existing UI tests,
-        // and is only the fallback when the nice error fails. Consider improving this some more.
-        tcx.sess.struct_span_err(span, "higher-ranked lifetime error for opaque type!")
-    }
-
-    fn base_universe(&self) -> ty::UniverseIndex {
-        self.base_universe.unwrap()
-    }
-
-    fn nice_error(
-        &self,
-        mbcx: &mut MirBorrowckCtxt<'_, 'tcx>,
-        _cause: ObligationCause<'tcx>,
-        placeholder_region: ty::Region<'tcx>,
-        error_region: Option<ty::Region<'tcx>>,
-    ) -> Option<DiagnosticBuilder<'tcx>> {
-        try_extract_error_from_region_constraints(
-            mbcx.infcx,
-            placeholder_region,
-            error_region,
-            self.region_constraints.as_ref().unwrap(),
-            // We're using the original `InferCtxt` that we
-            // started MIR borrowchecking with, so the region
-            // constraints have already been taken. Use the data from
-            // our `mbcx` instead.
-            |vid| mbcx.regioncx.var_infos[vid].origin,
-            |vid| mbcx.regioncx.var_infos[vid].universe,
-        )
-    }
-}
-
 #[instrument(skip(fulfill_cx, infcx), level = "debug")]
 fn try_extract_error_from_fulfill_cx<'tcx>(
     mut fulfill_cx: Box<dyn TraitEngine<'tcx> + 'tcx>,
     infcx: &InferCtxt<'_, 'tcx>,
     placeholder_region: ty::Region<'tcx>,
     error_region: Option<ty::Region<'tcx>>,
 ) -> Option<DiagnosticBuilder<'tcx>> {
+    let tcx = infcx.tcx;
+
     // We generally shouldn't have errors here because the query was
     // already run, but there's no point using `delay_span_bug`
     // when we're going to emit an error here anyway.
     let _errors = fulfill_cx.select_all_or_error(infcx);
-    let region_constraints = infcx.with_region_constraints(|r| r.clone());
-    try_extract_error_from_region_constraints(
-        infcx,
-        placeholder_region,
-        error_region,
-        &region_constraints,
-        |vid| infcx.region_var_origin(vid),
-        |vid| infcx.universe_of_region(infcx.tcx.mk_region(ty::ReVar(vid))),
-    )
-}
 
-fn try_extract_error_from_region_constraints<'tcx>(
-    infcx: &InferCtxt<'_, 'tcx>,
-    placeholder_region: ty::Region<'tcx>,
-    error_region: Option<ty::Region<'tcx>>,
-    region_constraints: &RegionConstraintData<'tcx>,
-    mut region_var_origin: impl FnMut(RegionVid) -> RegionVariableOrigin,
-    mut universe_of_region: impl FnMut(RegionVid) -> UniverseIndex,
-) -> Option<DiagnosticBuilder<'tcx>> {
-    let (sub_region, cause) =
+    let (sub_region, cause) = infcx.with_region_constraints(|region_constraints| {
+        debug!("{:#?}", region_constraints);
         region_constraints.constraints.iter().find_map(|(constraint, cause)| {
             match *constraint {
                 Constraint::RegSubReg(sub, sup) if sup == placeholder_region && sup != sub => {
                     Some((sub, cause.clone()))
                 }
                 // FIXME: Should this check the universe of the var?
                 Constraint::VarSubReg(vid, sup) if sup == placeholder_region => {
-                    Some((infcx.tcx.mk_region(ty::ReVar(vid)), cause.clone()))
+                    Some((tcx.mk_region(ty::ReVar(vid)), cause.clone()))
                 }
                 _ => None,
             }
-        })?;
+        })
+    })?;
 
     debug!(?sub_region, "cause = {:#?}", cause);
     let nice_error = match (error_region, sub_region) {
         (Some(error_region), &ty::ReVar(vid)) => NiceRegionError::new(
             infcx,
             RegionResolutionError::SubSupConflict(
                 vid,
-                region_var_origin(vid),
+                infcx.region_var_origin(vid),
                 cause.clone(),
                 error_region,
                 cause.clone(),
@@ -446,8 +380,8 @@ fn try_extract_error_from_region_constraints<'tcx>(
             infcx,
             RegionResolutionError::UpperBoundUniverseConflict(
                 vid,
-                region_var_origin(vid),
-                universe_of_region(vid),
+                infcx.region_var_origin(vid),
+                infcx.universe_of_region(sub_region),
                 cause.clone(),
                 placeholder_region,
             ),

compiler/rustc_borrowck/src/lib.rs

@@ -5,7 +5,6 @@
 #![feature(crate_visibility_modifier)]
 #![feature(let_else)]
 #![feature(min_specialization)]
-#![feature(never_type)]
 #![feature(stmt_expr_attributes)]
 #![feature(trusted_step)]
 #![feature(try_blocks)]
@@ -125,9 +124,8 @@ fn mir_borrowck<'tcx>(
 ) -> &'tcx BorrowCheckResult<'tcx> {
     let (input_body, promoted) = tcx.mir_promoted(def);
     debug!("run query mir_borrowck: {}", tcx.def_path_str(def.did.to_def_id()));
-    let hir_owner = tcx.hir().local_def_id_to_hir_id(def.did).owner;
 
-    let opt_closure_req = tcx.infer_ctxt().with_opaque_type_inference(hir_owner).enter(|infcx| {
+    let opt_closure_req = tcx.infer_ctxt().with_opaque_type_inference(def.did).enter(|infcx| {
         let input_body: &Body<'_> = &input_body.borrow();
         let promoted: &IndexVec<_, _> = &promoted.borrow();
         do_mir_borrowck(&infcx, input_body, promoted, false).0
@@ -142,7 +140,7 @@ fn mir_borrowck<'tcx>(
 /// If `return_body_with_facts` is true, then return the body with non-erased
 /// region ids on which the borrow checking was performed together with Polonius
 /// facts.
-#[instrument(skip(infcx, input_body, input_promoted), fields(id=?input_body.source.with_opt_param().as_local().unwrap()), level = "debug")]
+#[instrument(skip(infcx, input_body, input_promoted), level = "debug")]
 fn do_mir_borrowck<'a, 'tcx>(
     infcx: &InferCtxt<'a, 'tcx>,
     input_body: &Body<'tcx>,

compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -44,7 +44,6 @@ mod reverse_sccs;
 pub mod values;
 
 pub struct RegionInferenceContext<'tcx> {
-    pub var_infos: VarInfos,
     /// Contains the definition for every region variable. Region
     /// variables are identified by their index (`RegionVid`). The
     /// definition contains information about where the region came
@@ -267,7 +266,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     ) -> Self {
         // Create a RegionDefinition for each inference variable.
         let definitions: IndexVec<_, _> = var_infos
-            .iter()
+            .into_iter()
             .map(|info| RegionDefinition::new(info.universe, info.origin))
             .collect();
 
@@ -292,7 +291,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             Rc::new(member_constraints_in.into_mapped(|r| constraint_sccs.scc(r)));
 
         let mut result = Self {
-            var_infos,
             definitions,
             liveness_constraints,
             constraints,

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -1,6 +1,7 @@
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::vec_map::VecMap;
 use rustc_hir::OpaqueTyOrigin;
+use rustc_infer::infer::opaque_types::OpaqueTypeDecl;
 use rustc_infer::infer::InferCtxt;
 use rustc_middle::ty::subst::GenericArgKind;
 use rustc_middle::ty::{self, OpaqueTypeKey, Ty, TyCtxt, TypeFoldable};
@@ -53,44 +54,27 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     pub(crate) fn infer_opaque_types(
         &self,
         infcx: &InferCtxt<'_, 'tcx>,
-        opaque_ty_decls: VecMap<OpaqueTypeKey<'tcx>, (Ty<'tcx>, Span, OpaqueTyOrigin)>,
+        opaque_ty_decls: VecMap<OpaqueTypeKey<'tcx>, OpaqueTypeDecl<'tcx>>,
         span: Span,
     ) -> VecMap<OpaqueTypeKey<'tcx>, Ty<'tcx>> {
         opaque_ty_decls
             .into_iter()
-            .map(|(opaque_type_key, (concrete_type, decl_span, origin))| {
+            .filter_map(|(opaque_type_key, decl)| {
                 let substs = opaque_type_key.substs;
-                // FIXME: why are the spans in decl_span often DUMMY_SP?
-                let span = decl_span.substitute_dummy(span);
+                let concrete_type = decl.concrete_ty;
                 debug!(?concrete_type, ?substs);
 
                 let mut subst_regions = vec![self.universal_regions.fr_static];
                 let universal_substs = infcx.tcx.fold_regions(substs, &mut false, |region, _| {
-                    if let ty::RePlaceholder(..) = region {
-                        // Higher kinded regions don't need remapping, they don't refer to anything outside of this the substs.
-                        return region;
-                    }
-                    let vid = self.to_region_vid(region);
-                    trace!(?vid);
-                    let scc = self.constraint_sccs.scc(vid);
-                    trace!(?scc);
-                    match self.scc_values.universal_regions_outlived_by(scc).find_map(|lb| {
-                        self.eval_equal(vid, lb).then_some(self.definitions[lb].external_name?)
-                    }) {
-                        Some(region) => {
-                            let vid = self.universal_regions.to_region_vid(region);
-                            subst_regions.push(vid);
-                            region
-                        }
-                        None => {
-                            subst_regions.push(vid);
-                            infcx.tcx.sess.delay_span_bug(
-                                span,
-                                "opaque type with non-universal region substs",
-                            );
-                            infcx.tcx.lifetimes.re_static
-                        }
-                    }
+                    let vid = self.universal_regions.to_region_vid(region);
+                    subst_regions.push(vid);
+                    self.definitions[vid].external_name.unwrap_or_else(|| {
+                        infcx
+                            .tcx
+                            .sess
+                            .delay_span_bug(span, "opaque type with non-universal region substs");
+                        infcx.tcx.lifetimes.re_static
+                    })
                 });
 
                 subst_regions.sort();
@@ -116,14 +100,12 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                     span,
                 );
 
-                (
+                check_opaque_type_parameter_valid(
+                    infcx.tcx,
                     opaque_type_key,
-                    if check_opaque_type_parameter_valid(infcx.tcx, opaque_type_key, origin, span) {
-                        remapped_type
-                    } else {
-                        infcx.tcx.ty_error()
-                    },
+                    OpaqueTypeDecl { concrete_ty: remapped_type, ..decl },
                 )
+                .then_some((opaque_type_key, remapped_type))
             })
             .collect()
     }
@@ -167,10 +149,9 @@ impl<'tcx> RegionInferenceContext<'tcx> {
 fn check_opaque_type_parameter_valid(
     tcx: TyCtxt<'_>,
     opaque_type_key: OpaqueTypeKey<'_>,
-    origin: OpaqueTyOrigin,
-    span: Span,
+    decl: OpaqueTypeDecl<'_>,
 ) -> bool {
-    match origin {
+    match decl.origin {
         // No need to check return position impl trait (RPIT)
         // because for type and const parameters they are correct
         // by construction: we convert
@@ -196,6 +177,7 @@ fn check_opaque_type_parameter_valid(
         // Check these
         OpaqueTyOrigin::TyAlias => {}
     }
+    let span = decl.definition_span;
     let opaque_generics = tcx.generics_of(opaque_type_key.def_id);
     let mut seen_params: FxHashMap<_, Vec<_>> = FxHashMap::default();
     for (i, arg) in opaque_type_key.substs.iter().enumerate() {