Rollup merge of #107981 - lcnr:canonicalization-uwu, r=compiler-errors

new solver: implement canonicalization and region constraints

see the corresponding rustc-dev-guide chapter: https://rustc-dev-guide.rust-lang.org/solve/canonicalization.html

r? ``@compiler-errors``

compiler/rustc_infer/src/infer/at.rs

@@ -369,6 +369,34 @@ impl<'tcx> ToTrace<'tcx> for Const<'tcx> {
  }
 }
 
+impl<'tcx> ToTrace<'tcx> for ty::GenericArg<'tcx> {
+ fn to_trace(
+ _: TyCtxt<'tcx>,
+ cause: &ObligationCause<'tcx>,
+ a_is_expected: bool,
+ a: Self,
+ b: Self,
+ ) -> TypeTrace<'tcx> {
+ use GenericArgKind::*;
+ TypeTrace {
+ cause: cause.clone(),
+ values: match (a.unpack(), b.unpack()) {
+ (Lifetime(a), Lifetime(b)) => Regions(ExpectedFound::new(a_is_expected, a, b)),
+ (Type(a), Type(b)) => Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
+ (Const(a), Const(b)) => {
+ Terms(ExpectedFound::new(a_is_expected, a.into(), b.into()))
+ }
+
+ (Lifetime(_), Type(_) | Const(_))
+ | (Type(_), Lifetime(_) | Const(_))
+ | (Const(_), Lifetime(_) | Type(_)) => {
+ bug!("relating different kinds: {a:?} {b:?}")
+ }
+ },
+ }
+ }
+}
+
 impl<'tcx> ToTrace<'tcx> for ty::Term<'tcx> {
  fn to_trace(
  _: TyCtxt<'tcx>,

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

@@ -30,7 +30,7 @@ use rustc_middle::ty::{self, List, TyCtxt};
 use rustc_span::source_map::Span;
 
 pub use rustc_middle::infer::canonical::*;
-use substitute::CanonicalExt;
+pub use substitute::CanonicalExt;
 
 mod canonicalizer;
 pub mod query_response;
@@ -100,7 +100,11 @@ impl<'tcx> InferCtxt<'tcx> {
  /// variable for it. If this is an existentially quantified
  /// variable, then you'll get a new inference variable; if it is a
  /// universally quantified variable, you get a placeholder.
- fn instantiate_canonical_var(
+ ///
+ /// FIXME(-Ztrait-solver=next): This is public because it's used by the
+ /// new trait solver which has a different canonicalization routine.
+ /// We should somehow deduplicate all of this.
+ pub fn instantiate_canonical_var(
  &self,
  span: Span,
  cv_info: CanonicalVarInfo<'tcx>,

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

@@ -151,11 +151,21 @@ impl<'tcx> InferCtxt<'tcx> {
  })
  }
 
- /// FIXME: This method should only be used for canonical queries and therefore be private.
- ///
- /// As the new solver does canonicalization slightly differently, this is also used there
- /// for now. This should hopefully change fairly soon.
- pub fn take_opaque_types_for_query_response(&self) -> Vec<(Ty<'tcx>, Ty<'tcx>)> {
+ /// Used by the new solver as that one takes the opaque types at the end of a probe
+ /// to deal with multiple candidates without having to recompute them.
+ pub fn clone_opaque_types_for_query_response(&self) -> Vec<(Ty<'tcx>, Ty<'tcx>)> {
+ self.inner
+ .borrow()
+ .opaque_type_storage
+ .opaque_types
+ .iter()
+ .map(|&(k, ref v)| {
+ (self.tcx.mk_opaque(k.def_id.to_def_id(), k.substs), v.hidden_type.ty)
+ })
+ .collect()
+ }
+
+ fn take_opaque_types_for_query_response(&self) -> Vec<(Ty<'tcx>, Ty<'tcx>)> {
  std::mem::take(&mut self.inner.borrow_mut().opaque_type_storage.opaque_types)
  .into_iter()
  .map(|(k, v)| (self.tcx.mk_opaque(k.def_id.to_def_id(), k.substs), v.hidden_type.ty))

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

@@ -11,7 +11,9 @@ use rustc_middle::ty::fold::{FnMutDelegate, TypeFoldable};
 use rustc_middle::ty::subst::GenericArgKind;
 use rustc_middle::ty::{self, TyCtxt};
 
-pub(super) trait CanonicalExt<'tcx, V> {
+/// FIXME(-Ztrait-solver=next): This or public because it is shared with the
+/// new trait solver implementation. We should deduplicate canonicalization.
+pub trait CanonicalExt<'tcx, V> {
  /// Instantiate the wrapped value, replacing each canonical value
  /// with the value given in `var_values`.
  fn substitute(&self, tcx: TyCtxt<'tcx>, var_values: &CanonicalVarValues<'tcx>) -> V

compiler/rustc_middle/src/infer/canonical.rs

@@ -123,6 +123,11 @@ impl<'tcx> CanonicalVarInfo<'tcx> {
  self.kind.universe()
  }
 
+ #[must_use]
+ pub fn with_updated_universe(self, ui: ty::UniverseIndex) -> CanonicalVarInfo<'tcx> {
+ CanonicalVarInfo { kind: self.kind.with_updated_universe(ui) }
+ }
+
  pub fn is_existential(&self) -> bool {
  match self.kind {
  CanonicalVarKind::Ty(_) => true,
@@ -133,6 +138,28 @@ impl<'tcx> CanonicalVarInfo<'tcx> {
  CanonicalVarKind::PlaceholderConst(_, _) => false,
  }
  }
+
+ pub fn is_region(&self) -> bool {
+ match self.kind {
+ CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => true,
+ CanonicalVarKind::Ty(_)
+ | CanonicalVarKind::PlaceholderTy(_)
+ | CanonicalVarKind::Const(_, _)
+ | CanonicalVarKind::PlaceholderConst(_, _) => false,
+ }
+ }
+
+ pub fn expect_anon_placeholder(self) -> u32 {
+ match self.kind {
+ CanonicalVarKind::Ty(_)
+ | CanonicalVarKind::Region(_)
+ | CanonicalVarKind::Const(_, _) => bug!("expected placeholder: {self:?}"),
+
+ CanonicalVarKind::PlaceholderRegion(placeholder) => placeholder.name.expect_anon(),
+ CanonicalVarKind::PlaceholderTy(placeholder) => placeholder.name.expect_anon(),
+ CanonicalVarKind::PlaceholderConst(placeholder, _) => placeholder.name.as_u32(),
+ }
+ }
 }
 
 /// Describes the "kind" of the canonical variable. This is a "kind"
@@ -177,6 +204,38 @@ impl<'tcx> CanonicalVarKind<'tcx> {
  CanonicalVarKind::PlaceholderConst(placeholder, _) => placeholder.universe,
  }
  }
+
+ /// Replaces the universe of this canonical variable with `ui`.
+ ///
+ /// In case this is a float or int variable, this causes an ICE if
+ /// the updated universe is not the root.
+ pub fn with_updated_universe(self, ui: ty::UniverseIndex) -> CanonicalVarKind<'tcx> {
+ match self {
+ CanonicalVarKind::Ty(kind) => match kind {
+ CanonicalTyVarKind::General(_) => {
+ CanonicalVarKind::Ty(CanonicalTyVarKind::General(ui))
+ }
+ CanonicalTyVarKind::Int | CanonicalTyVarKind::Float => {
+ assert_eq!(ui, ty::UniverseIndex::ROOT);
+ CanonicalVarKind::Ty(kind)
+ }
+ },
+ CanonicalVarKind::PlaceholderTy(placeholder) => {
+ CanonicalVarKind::PlaceholderTy(ty::Placeholder { universe: ui, ..placeholder })
+ }
+ CanonicalVarKind::Region(_) => CanonicalVarKind::Region(ui),
+ CanonicalVarKind::PlaceholderRegion(placeholder) => {
+ CanonicalVarKind::PlaceholderRegion(ty::Placeholder { universe: ui, ..placeholder })
+ }
+ CanonicalVarKind::Const(_, ty) => CanonicalVarKind::Const(ui, ty),
+ CanonicalVarKind::PlaceholderConst(placeholder, ty) => {
+ CanonicalVarKind::PlaceholderConst(
+ ty::Placeholder { universe: ui, ..placeholder },
+ ty,
+ )
+ }
+ }
+ }
 }
 
 /// Rust actually has more than one category of type variables;
@@ -213,7 +272,8 @@ pub struct QueryResponse<'tcx, R> {
  pub value: R,
 }
 
-#[derive(Clone, Debug, Default, HashStable, TypeFoldable, TypeVisitable, Lift)]
+#[derive(Clone, Debug, Default, PartialEq, Eq, Hash)]
+#[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct QueryRegionConstraints<'tcx> {
  pub outlives: Vec<QueryOutlivesConstraint<'tcx>>,
  pub member_constraints: Vec<MemberConstraint<'tcx>>,

compiler/rustc_middle/src/infer/mod.rs

@@ -12,7 +12,8 @@ use rustc_span::Span;
 /// ```text
 /// R0 member of [O1..On]
 /// ```
-#[derive(Debug, Clone, HashStable, TypeFoldable, TypeVisitable, Lift)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+#[derive(HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct MemberConstraint<'tcx> {
  /// The `DefId` and substs of the opaque type causing this constraint.
  /// Used for error reporting.

compiler/rustc_middle/src/traits/solve.rs

@@ -2,6 +2,7 @@ use std::ops::ControlFlow;
 
 use rustc_data_structures::intern::Interned;
 
+use crate::infer::canonical::QueryRegionConstraints;
 use crate::ty::{
  FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeVisitable, TypeVisitor,
 };
@@ -18,20 +19,25 @@ impl<'tcx> std::ops::Deref for ExternalConstraints<'tcx> {
 }
 
 /// Additional constraints returned on success.
-#[derive(Debug, PartialEq, Eq, Clone, Hash, Default)]
+#[derive(Debug, PartialEq, Eq, Clone, Hash, Default, TypeFoldable, TypeVisitable)]
 pub struct ExternalConstraintsData<'tcx> {
  // FIXME: implement this.
- pub regions: (),
+ pub region_constraints: QueryRegionConstraints<'tcx>,
  pub opaque_types: Vec<(Ty<'tcx>, Ty<'tcx>)>,
 }
 
+// FIXME: Having to clone `region_constraints` for folding feels bad and
+// probably isn't great wrt performance.
+//
+// Not sure how to fix this, maybe we should also intern `opaque_types` and
+// `region_constraints` here or something.
 impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ExternalConstraints<'tcx> {
  fn try_fold_with<F: FallibleTypeFolder<TyCtxt<'tcx>>>(
  self,
  folder: &mut F,
  ) -> Result<Self, F::Error> {
  Ok(FallibleTypeFolder::interner(folder).mk_external_constraints(ExternalConstraintsData {
- regions: (),
+ region_constraints: self.region_constraints.clone().try_fold_with(folder)?,
  opaque_types: self
  .opaque_types
  .iter()
@@ -42,7 +48,7 @@ impl<'tcx> TypeFoldable<TyCtxt<'tcx>> for ExternalConstraints<'tcx> {
 
  fn fold_with<F: TypeFolder<TyCtxt<'tcx>>>(self, folder: &mut F) -> Self {
  TypeFolder::interner(folder).mk_external_constraints(ExternalConstraintsData {
- regions: (),
+ region_constraints: self.region_constraints.clone().fold_with(folder),
  opaque_types: self.opaque_types.iter().map(|opaque| opaque.fold_with(folder)).collect(),
  })
  }
@@ -53,7 +59,7 @@ impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for ExternalConstraints<'tcx> {
  &self,
  visitor: &mut V,
  ) -> std::ops::ControlFlow<V::BreakTy> {
- self.regions.visit_with(visitor)?;
+ self.region_constraints.visit_with(visitor)?;
  self.opaque_types.visit_with(visitor)?;
  ControlFlow::Continue(())
  }

compiler/rustc_middle/src/ty/sty.rs

@@ -107,6 +107,15 @@ impl BoundRegionKind {
  _ => None,
  }
  }
+
+ pub fn expect_anon(&self) -> u32 {
+ match *self {
+ BoundRegionKind::BrNamed(_, _) | BoundRegionKind::BrEnv => {
+ bug!("expected anon region: {self:?}")
+ }
+ BoundRegionKind::BrAnon(idx, _) => idx,
+ }
+ }
 }
 
 pub trait Article {