[for errs] perf run sub_relations change

compiler/rustc_hir_typeck/src/fn_ctxt/mod.rs

@@ -19,7 +19,6 @@ use rustc_middle::ty::{self, Const, Ty, TyCtxt, TypeVisitableExt};
 use rustc_session::Session;
 use rustc_span::{self, DUMMY_SP, ErrorGuaranteed, Ident, Span, sym};
 use rustc_trait_selection::error_reporting::TypeErrCtxt;
-use rustc_trait_selection::error_reporting::infer::sub_relations::SubRelations;
 use rustc_trait_selection::traits::{ObligationCause, ObligationCauseCode, ObligationCtxt};
 
 use crate::coercion::DynamicCoerceMany;
@@ -177,14 +176,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ///
     /// [`InferCtxtErrorExt::err_ctxt`]: rustc_trait_selection::error_reporting::InferCtxtErrorExt::err_ctxt
     pub(crate) fn err_ctxt(&'a self) -> TypeErrCtxt<'a, 'tcx> {
-        let mut sub_relations = SubRelations::default();
-        sub_relations.add_constraints(
-            self,
-            self.fulfillment_cx.borrow_mut().pending_obligations().iter().map(|o| o.predicate),
-        );
         TypeErrCtxt {
             infcx: &self.infcx,
-            sub_relations: RefCell::new(sub_relations),
             typeck_results: Some(self.typeck_results.borrow()),
             fallback_has_occurred: self.fallback_has_occurred.get(),
             normalize_fn_sig: Box::new(|fn_sig| {

compiler/rustc_hir_typeck/src/method/probe.rs

@@ -1213,7 +1213,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 debug!("pick_all_method: step={:?}", step);
                 // skip types that are from a type error or that would require dereferencing
                 // a raw pointer
-                !step.self_ty.references_error() && !step.from_unsafe_deref
+                !step.self_ty.value.references_error() && !step.from_unsafe_deref
             })
             .find_map(|step| {
                 let InferOk { value: self_ty, obligations: _ } = self

compiler/rustc_hir_typeck/src/writeback.rs

@@ -9,7 +9,6 @@ use rustc_errors::ErrorGuaranteed;
 use rustc_hir::intravisit::{self, InferKind, Visitor};
 use rustc_hir::{self as hir, AmbigArg, HirId};
 use rustc_infer::traits::solve::Goal;
-use rustc_middle::span_bug;
 use rustc_middle::traits::ObligationCause;
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCoercion};
 use rustc_middle::ty::{
@@ -513,15 +512,6 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
         self.typeck_results.user_provided_types_mut().extend(
             fcx_typeck_results.user_provided_types().items().map(|(local_id, c_ty)| {
                 let hir_id = HirId { owner: common_hir_owner, local_id };
-
-                if cfg!(debug_assertions) && c_ty.has_infer() {
-                    span_bug!(
-                        hir_id.to_span(self.fcx.tcx),
-                        "writeback: `{:?}` has inference variables",
-                        c_ty
-                    );
-                };
-
                 (hir_id, *c_ty)
             }),
         );
@@ -532,17 +522,7 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
         assert_eq!(fcx_typeck_results.hir_owner, self.typeck_results.hir_owner);
 
         self.typeck_results.user_provided_sigs.extend_unord(
-            fcx_typeck_results.user_provided_sigs.items().map(|(&def_id, c_sig)| {
-                if cfg!(debug_assertions) && c_sig.has_infer() {
-                    span_bug!(
-                        self.fcx.tcx.def_span(def_id),
-                        "writeback: `{:?}` has inference variables",
-                        c_sig
-                    );
-                };
-
-                (def_id, *c_sig)
-            }),
+            fcx_typeck_results.user_provided_sigs.items().map(|(def_id, c_sig)| (*def_id, *c_sig)),
         );
     }
 

compiler/rustc_infer/src/infer/canonical/canonicalizer.rs

@@ -17,8 +17,7 @@ use tracing::debug;
 
 use crate::infer::InferCtxt;
 use crate::infer::canonical::{
-    Canonical, CanonicalQueryInput, CanonicalTyVarKind, CanonicalVarInfo, CanonicalVarKind,
-    OriginalQueryValues,
+    Canonical, CanonicalQueryInput, CanonicalVarInfo, CanonicalVarKind, OriginalQueryValues,
 };
 
 impl<'tcx> InferCtxt<'tcx> {
@@ -368,9 +367,7 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
                             ui = ty::UniverseIndex::ROOT;
                         }
                         self.canonicalize_ty_var(
-                            CanonicalVarInfo {
-                                kind: CanonicalVarKind::Ty(CanonicalTyVarKind::General(ui)),
-                            },
+                            CanonicalVarInfo { kind: CanonicalVarKind::Ty(ui) },
                             t,
                         )
                     }
@@ -382,21 +379,15 @@ impl<'cx, 'tcx> TypeFolder<TyCtxt<'tcx>> for Canonicalizer<'cx, 'tcx> {
                 if nt != t {
                     return self.fold_ty(nt);
                 } else {
-                    self.canonicalize_ty_var(
-                        CanonicalVarInfo { kind: CanonicalVarKind::Ty(CanonicalTyVarKind::Int) },
-                        t,
-                    )
+                    self.canonicalize_ty_var(CanonicalVarInfo { kind: CanonicalVarKind::Int }, t)
                 }
             }
             ty::Infer(ty::FloatVar(vid)) => {
                 let nt = self.infcx.unwrap().opportunistic_resolve_float_var(vid);
                 if nt != t {
                     return self.fold_ty(nt);
                 } else {
-                    self.canonicalize_ty_var(
-                        CanonicalVarInfo { kind: CanonicalVarKind::Ty(CanonicalTyVarKind::Float) },
-                        t,
-                    )
+                    self.canonicalize_ty_var(CanonicalVarInfo { kind: CanonicalVarKind::Float }, t)
                 }
             }
 
@@ -690,12 +681,10 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
             .iter()
             .map(|v| CanonicalVarInfo {
                 kind: match v.kind {
-                    CanonicalVarKind::Ty(CanonicalTyVarKind::Int | CanonicalTyVarKind::Float) => {
+                    CanonicalVarKind::Int | CanonicalVarKind::Float => {
                         return *v;
                     }
-                    CanonicalVarKind::Ty(CanonicalTyVarKind::General(u)) => {
-                        CanonicalVarKind::Ty(CanonicalTyVarKind::General(reverse_universe_map[&u]))
-                    }
+                    CanonicalVarKind::Ty(u) => CanonicalVarKind::Ty(reverse_universe_map[&u]),
                     CanonicalVarKind::Region(u) => {
                         CanonicalVarKind::Region(reverse_universe_map[&u])
                     }

compiler/rustc_infer/src/infer/canonical/mod.rs

@@ -108,18 +108,9 @@ impl<'tcx> InferCtxt<'tcx> {
         universe_map: impl Fn(ty::UniverseIndex) -> ty::UniverseIndex,
     ) -> GenericArg<'tcx> {
         match cv_info.kind {
-            CanonicalVarKind::Ty(ty_kind) => {
-                let ty = match ty_kind {
-                    CanonicalTyVarKind::General(ui) => {
-                        self.next_ty_var_in_universe(span, universe_map(ui))
-                    }
-
-                    CanonicalTyVarKind::Int => self.next_int_var(),
-
-                    CanonicalTyVarKind::Float => self.next_float_var(),
-                };
-                ty.into()
-            }
+            CanonicalVarKind::Ty(ui) => self.next_ty_var_in_universe(span, universe_map(ui)).into(),
+            CanonicalVarKind::Int => self.next_int_var().into(),
+            CanonicalVarKind::Float => self.next_float_var().into(),
 
             CanonicalVarKind::PlaceholderTy(ty::PlaceholderType { universe, bound }) => {
                 let universe_mapped = universe_map(universe);

compiler/rustc_infer/src/infer/context.rs

@@ -125,6 +125,10 @@ impl<'tcx> rustc_type_ir::InferCtxtLike for InferCtxt<'tcx> {
         self.inner.borrow_mut().type_variables().equate(a, b);
     }
 
+    fn sub_ty_vids_raw(&self, a: rustc_type_ir::TyVid, b: rustc_type_ir::TyVid) {
+        self.inner.borrow_mut().type_variables().sub(a, b);
+    }
+
     fn equate_int_vids_raw(&self, a: rustc_type_ir::IntVid, b: rustc_type_ir::IntVid) {
         self.inner.borrow_mut().int_unification_table().union(a, b);
     }

compiler/rustc_infer/src/infer/mod.rs

@@ -733,6 +733,7 @@ impl<'tcx> InferCtxt<'tcx> {
         let r_b = self.shallow_resolve(predicate.skip_binder().b);
         match (r_a.kind(), r_b.kind()) {
             (&ty::Infer(ty::TyVar(a_vid)), &ty::Infer(ty::TyVar(b_vid))) => {
+                self.inner.borrow_mut().type_variables().sub(a_vid, b_vid);
                 return Err((a_vid, b_vid));
             }
             _ => {}
@@ -1065,6 +1066,10 @@ impl<'tcx> InferCtxt<'tcx> {
         self.inner.borrow_mut().type_variables().root_var(var)
     }
 
+    pub fn sub_root_var(&self, var: ty::TyVid) -> ty::TyVid {
+        self.inner.borrow_mut().type_variables().sub_root_var(var)
+    }
+
     pub fn root_const_var(&self, var: ty::ConstVid) -> ty::ConstVid {
         self.inner.borrow_mut().const_unification_table().find(var).vid
     }

compiler/rustc_infer/src/infer/relate/generalize.rs

@@ -503,6 +503,10 @@ impl<'tcx> TypeRelation<TyCtxt<'tcx>> for Generalizer<'_, 'tcx> {
                             let origin = inner.type_variables().var_origin(vid);
                             let new_var_id =
                                 inner.type_variables().new_var(self.for_universe, origin);
+                            // Record that `vid` and `new_var_id` have to be subtypes
+                            // of each other. This is currently only used for diagnostics.
+                            // To see why, see the docs in the `type_variables` module.
+                            inner.type_variables().sub(vid, new_var_id);
                             // If we're in the new solver and create a new inference
                             // variable inside of an alias we eagerly constrain that
                             // inference variable to prevent unexpected ambiguity errors.

compiler/rustc_infer/src/infer/snapshot/undo_log.rs

@@ -18,7 +18,7 @@ pub struct Snapshot<'tcx> {
 #[derive(Clone)]
 pub(crate) enum UndoLog<'tcx> {
     OpaqueTypes(OpaqueTypeKey<'tcx>, Option<OpaqueHiddenType<'tcx>>),
-    TypeVariables(sv::UndoLog<ut::Delegate<type_variable::TyVidEqKey<'tcx>>>),
+    TypeVariables(type_variable::UndoLog<'tcx>),
     ConstUnificationTable(sv::UndoLog<ut::Delegate<ConstVidKey<'tcx>>>),
     IntUnificationTable(sv::UndoLog<ut::Delegate<ty::IntVid>>),
     FloatUnificationTable(sv::UndoLog<ut::Delegate<ty::FloatVid>>),
@@ -44,7 +44,9 @@ macro_rules! impl_from {
 impl_from! {
     RegionConstraintCollector(region_constraints::UndoLog<'tcx>),
 
+    TypeVariables(type_variable::UndoLog<'tcx>),
     TypeVariables(sv::UndoLog<ut::Delegate<type_variable::TyVidEqKey<'tcx>>>),
+    TypeVariables(sv::UndoLog<ut::Delegate<ty::TyVid>>),
     IntUnificationTable(sv::UndoLog<ut::Delegate<ty::IntVid>>),
     FloatUnificationTable(sv::UndoLog<ut::Delegate<ty::FloatVid>>),
 

compiler/rustc_infer/src/infer/type_variable.rs

@@ -13,9 +13,33 @@ use tracing::debug;
 
 use crate::infer::InferCtxtUndoLogs;
 
-impl<'tcx> Rollback<sv::UndoLog<ut::Delegate<TyVidEqKey<'tcx>>>> for TypeVariableStorage<'tcx> {
-    fn reverse(&mut self, undo: sv::UndoLog<ut::Delegate<TyVidEqKey<'tcx>>>) {
-        self.eq_relations.reverse(undo)
+/// Represents a single undo-able action that affects a type inference variable.
+#[derive(Clone)]
+pub(crate) enum UndoLog<'tcx> {
+    EqRelation(sv::UndoLog<ut::Delegate<TyVidEqKey<'tcx>>>),
+    SubRelation(sv::UndoLog<ut::Delegate<ty::TyVid>>),
+}
+
+/// Convert from a specific kind of undo to the more general UndoLog
+impl<'tcx> From<sv::UndoLog<ut::Delegate<TyVidEqKey<'tcx>>>> for UndoLog<'tcx> {
+    fn from(l: sv::UndoLog<ut::Delegate<TyVidEqKey<'tcx>>>) -> Self {
+        UndoLog::EqRelation(l)
+    }
+}
+
+/// Convert from a specific kind of undo to the more general UndoLog
+impl<'tcx> From<sv::UndoLog<ut::Delegate<ty::TyVid>>> for UndoLog<'tcx> {
+    fn from(l: sv::UndoLog<ut::Delegate<ty::TyVid>>) -> Self {
+        UndoLog::SubRelation(l)
+    }
+}
+
+impl<'tcx> Rollback<UndoLog<'tcx>> for TypeVariableStorage<'tcx> {
+    fn reverse(&mut self, undo: UndoLog<'tcx>) {
+        match undo {
+            UndoLog::EqRelation(undo) => self.eq_relations.reverse(undo),
+            UndoLog::SubRelation(undo) => self.sub_relations.reverse(undo),
+        }
     }
 }
 
@@ -27,6 +51,24 @@ pub(crate) struct TypeVariableStorage<'tcx> {
     /// constraint `?X == ?Y`. This table also stores, for each key,
     /// the known value.
     eq_relations: ut::UnificationTableStorage<TyVidEqKey<'tcx>>,
+
+    /// Only used by `-Znext-solver` andfor diagnostics.
+    ///
+    /// When reporting ambiguity errors, we sometimes want to
+    /// treat all inference vars which are subtypes of each
+    /// others as if they are equal. For this case we compute
+    /// the transitive closure of our subtype obligations here.
+    ///
+    /// E.g. when encountering ambiguity errors, we want to suggest
+    /// specifying some method argument or to add a type annotation
+    /// to a local variable. Because subtyping cannot change the
+    /// shape of a type, it's fine if the cause of the ambiguity error
+    /// is only related to the suggested variable via subtyping.
+    ///
+    /// Even for something like `let x = returns_arg(); x.method();` the
+    /// type of `x` is only a supertype of the argument of `returns_arg`. We
+    /// still want to suggest specifying the type of the argument.
+    sub_relations: ut::UnificationTableStorage<ty::TyVid>,
 }
 
 pub(crate) struct TypeVariableTable<'a, 'tcx> {
@@ -109,6 +151,16 @@ impl<'tcx> TypeVariableTable<'_, 'tcx> {
         debug_assert!(self.probe(a).is_unknown());
         debug_assert!(self.probe(b).is_unknown());
         self.eq_relations().union(a, b);
+        self.sub_relations().union(a, b);
+    }
+
+    /// Records that `a <: b`, depending on `dir`.
+    ///
+    /// Precondition: neither `a` nor `b` are known.
+    pub(crate) fn sub(&mut self, a: ty::TyVid, b: ty::TyVid) {
+        debug_assert!(self.probe(a).is_unknown());
+        debug_assert!(self.probe(b).is_unknown());
+        self.sub_relations().union(a, b);
     }
 
     /// Instantiates `vid` with the type `ty`.
@@ -142,6 +194,10 @@ impl<'tcx> TypeVariableTable<'_, 'tcx> {
         origin: TypeVariableOrigin,
     ) -> ty::TyVid {
         let eq_key = self.eq_relations().new_key(TypeVariableValue::Unknown { universe });
+
+        let sub_key = self.sub_relations().new_key(());
+        debug_assert_eq!(eq_key.vid, sub_key);
+
         let index = self.storage.values.push(TypeVariableData { origin });
         debug_assert_eq!(eq_key.vid, index);
 
@@ -164,6 +220,18 @@ impl<'tcx> TypeVariableTable<'_, 'tcx> {
         self.eq_relations().find(vid).vid
     }
 
+    /// Returns the "root" variable of `vid` in the `sub_relations`
+    /// equivalence table. All type variables that have been are
+    /// related via equality or subtyping will yield the same root
+    /// variable (per the union-find algorithm), so `sub_root_var(a)
+    /// == sub_root_var(b)` implies that:
+    /// ```text
+    /// exists X. (a <: X || X <: a) && (b <: X || X <: b)
+    /// ```
+    pub(crate) fn sub_root_var(&mut self, vid: ty::TyVid) -> ty::TyVid {
+        self.sub_relations().find(vid)
+    }
+
     /// Retrieves the type to which `vid` has been instantiated, if
     /// any.
     pub(crate) fn probe(&mut self, vid: ty::TyVid) -> TypeVariableValue<'tcx> {
@@ -181,6 +249,11 @@ impl<'tcx> TypeVariableTable<'_, 'tcx> {
         self.storage.eq_relations.with_log(self.undo_log)
     }
 
+    #[inline]
+    fn sub_relations(&mut self) -> super::UnificationTable<'_, 'tcx, ty::TyVid> {
+        self.storage.sub_relations.with_log(self.undo_log)
+    }
+
     /// Returns a range of the type variables created during the snapshot.
     pub(crate) fn vars_since_snapshot(
         &mut self,

compiler/rustc_middle/src/infer/canonical.rs

@@ -27,7 +27,7 @@ use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lock;
 use rustc_macros::{HashStable, TypeFoldable, TypeVisitable};
 pub use rustc_type_ir as ir;
-pub use rustc_type_ir::{CanonicalTyVarKind, CanonicalVarKind};
+pub use rustc_type_ir::CanonicalVarKind;
 use smallvec::SmallVec;
 
 use crate::mir::ConstraintCategory;

compiler/rustc_middle/src/ty/structural_impls.rs

@@ -13,7 +13,6 @@ use rustc_type_ir::{ConstKind, TypeFolder, VisitorResult, try_visit};
 
 use super::print::PrettyPrinter;
 use super::{GenericArg, GenericArgKind, Pattern, Region};
-use crate::infer::canonical::CanonicalVarInfos;
 use crate::mir::PlaceElem;
 use crate::ty::print::{FmtPrinter, Printer, with_no_trimmed_paths};
 use crate::ty::{
@@ -779,5 +778,4 @@ list_fold! {
     ty::Clauses<'tcx> : mk_clauses,
     &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>> : mk_poly_existential_predicates,
     &'tcx ty::List<PlaceElem<'tcx>> : mk_place_elems,
-    CanonicalVarInfos<'tcx> : mk_canonical_var_infos,
 }

compiler/rustc_middle/src/ty/typeck_results.rs

@@ -716,6 +716,8 @@ pub type CanonicalUserTypeAnnotations<'tcx> =
 
 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable, TypeFoldable, TypeVisitable)]
 pub struct CanonicalUserTypeAnnotation<'tcx> {
+    #[type_foldable(identity)]
+    #[type_visitable(ignore)]
     pub user_ty: Box<CanonicalUserType<'tcx>>,
     pub span: Span,
     pub inferred_ty: Ty<'tcx>,