Auto merge of #126614 - compiler-errors:uplift-next-trait-solver, r=lcnr

Uplift next trait solver to `rustc_next_trait_solver`

🎉

There's so many FIXMEs! Sorry! Ideally this merges with the FIXMEs and we track and squash them over the near future.

Also, this still doesn't build on anything other than rustc. I still need to fix `feature = "nightly"` in `rustc_type_ir`, and remove and fix all the nightly feature usage in the new trait solver (notably: let-chains).

Also, sorry `@lcnr` I know you asked for me to separate the commit where we `mv rustc_trait_selection/solve/... rustc_next_trait_solver/solve/...`, but I had already done all the work by that point. Luckily, `git` understands the file moves so it should still be relatively reviewable.

If this is still very difficult to review, then I can do some rebasing magic to try to separate this out. Please let me know!

r? lcnr

Cargo.lock

@@ -4520,7 +4520,16 @@ dependencies = [
 name = "rustc_next_trait_solver"
 version = "0.0.0"
 dependencies = [
+ "bitflags 2.5.0",
+ "derivative",
+ "rustc_ast_ir",
+ "rustc_data_structures",
+ "rustc_index",
+ "rustc_macros",
+ "rustc_serialize",
  "rustc_type_ir",
+ "rustc_type_ir_macros",
+ "tracing",
 ]
 
 [[package]]

compiler/rustc_infer/src/infer/mod.rs

@@ -11,7 +11,7 @@ pub use BoundRegionConversionTime::*;
 pub use RegionVariableOrigin::*;
 pub use SubregionOrigin::*;
 
-use crate::infer::relate::{Relate, RelateResult};
+use crate::infer::relate::RelateResult;
 use crate::traits::{self, ObligationCause, ObligationInspector, PredicateObligation, TraitEngine};
 use error_reporting::TypeErrCtxt;
 use free_regions::RegionRelations;
@@ -45,7 +45,7 @@ use rustc_middle::ty::{ConstVid, EffectVid, FloatVid, IntVid, TyVid};
 use rustc_middle::ty::{GenericArg, GenericArgKind, GenericArgs, GenericArgsRef};
 use rustc_middle::{bug, span_bug};
 use rustc_span::symbol::Symbol;
-use rustc_span::{Span, DUMMY_SP};
+use rustc_span::Span;
 use snapshot::undo_log::InferCtxtUndoLogs;
 use std::cell::{Cell, RefCell};
 use std::fmt;
@@ -335,149 +335,6 @@ pub struct InferCtxt<'tcx> {
     pub obligation_inspector: Cell<Option<ObligationInspector<'tcx>>>,
 }
 
-impl<'tcx> ty::InferCtxtLike for InferCtxt<'tcx> {
-    type Interner = TyCtxt<'tcx>;
-
-    fn interner(&self) -> TyCtxt<'tcx> {
-        self.tcx
-    }
-
-    fn universe_of_ty(&self, vid: TyVid) -> Option<ty::UniverseIndex> {
-        // FIXME(BoxyUwU): this is kind of jank and means that printing unresolved
-        // ty infers will give you the universe of the var it resolved to not the universe
-        // it actually had. It also means that if you have a `?0.1` and infer it to `u8` then
-        // try to print out `?0.1` it will just print `?0`.
-        match self.probe_ty_var(vid) {
-            Err(universe) => Some(universe),
-            Ok(_) => None,
-        }
-    }
-
-    fn universe_of_lt(&self, lt: ty::RegionVid) -> Option<ty::UniverseIndex> {
-        match self.inner.borrow_mut().unwrap_region_constraints().probe_value(lt) {
-            Err(universe) => Some(universe),
-            Ok(_) => None,
-        }
-    }
-
-    fn universe_of_ct(&self, ct: ConstVid) -> Option<ty::UniverseIndex> {
-        // Same issue as with `universe_of_ty`
-        match self.probe_const_var(ct) {
-            Err(universe) => Some(universe),
-            Ok(_) => None,
-        }
-    }
-
-    fn root_ty_var(&self, var: TyVid) -> TyVid {
-        self.root_var(var)
-    }
-
-    fn root_const_var(&self, var: ConstVid) -> ConstVid {
-        self.root_const_var(var)
-    }
-
-    fn opportunistic_resolve_ty_var(&self, vid: TyVid) -> Ty<'tcx> {
-        match self.probe_ty_var(vid) {
-            Ok(ty) => ty,
-            Err(_) => Ty::new_var(self.tcx, self.root_var(vid)),
-        }
-    }
-
-    fn opportunistic_resolve_int_var(&self, vid: IntVid) -> Ty<'tcx> {
-        self.opportunistic_resolve_int_var(vid)
-    }
-
-    fn opportunistic_resolve_float_var(&self, vid: FloatVid) -> Ty<'tcx> {
-        self.opportunistic_resolve_float_var(vid)
-    }
-
-    fn opportunistic_resolve_ct_var(&self, vid: ConstVid) -> ty::Const<'tcx> {
-        match self.probe_const_var(vid) {
-            Ok(ct) => ct,
-            Err(_) => ty::Const::new_var(self.tcx, self.root_const_var(vid)),
-        }
-    }
-
-    fn opportunistic_resolve_effect_var(&self, vid: EffectVid) -> ty::Const<'tcx> {
-        match self.probe_effect_var(vid) {
-            Some(ct) => ct,
-            None => {
-                ty::Const::new_infer(self.tcx, InferConst::EffectVar(self.root_effect_var(vid)))
-            }
-        }
-    }
-
-    fn opportunistic_resolve_lt_var(&self, vid: ty::RegionVid) -> ty::Region<'tcx> {
-        self.inner.borrow_mut().unwrap_region_constraints().opportunistic_resolve_var(self.tcx, vid)
-    }
-
-    fn defining_opaque_types(&self) -> &'tcx ty::List<LocalDefId> {
-        self.defining_opaque_types
-    }
-
-    fn next_ty_infer(&self) -> Ty<'tcx> {
-        self.next_ty_var(DUMMY_SP)
-    }
-
-    fn next_const_infer(&self) -> ty::Const<'tcx> {
-        self.next_const_var(DUMMY_SP)
-    }
-
-    fn fresh_args_for_item(&self, def_id: DefId) -> ty::GenericArgsRef<'tcx> {
-        self.fresh_args_for_item(DUMMY_SP, def_id)
-    }
-
-    fn instantiate_binder_with_infer<T: TypeFoldable<Self::Interner> + Copy>(
-        &self,
-        value: ty::Binder<'tcx, T>,
-    ) -> T {
-        self.instantiate_binder_with_fresh_vars(
-            DUMMY_SP,
-            BoundRegionConversionTime::HigherRankedType,
-            value,
-        )
-    }
-
-    fn enter_forall<T: TypeFoldable<TyCtxt<'tcx>> + Copy, U>(
-        &self,
-        value: ty::Binder<'tcx, T>,
-        f: impl FnOnce(T) -> U,
-    ) -> U {
-        self.enter_forall(value, f)
-    }
-
-    fn relate<T: Relate<TyCtxt<'tcx>>>(
-        &self,
-        param_env: ty::ParamEnv<'tcx>,
-        lhs: T,
-        variance: ty::Variance,
-        rhs: T,
-    ) -> Result<Vec<Goal<'tcx, ty::Predicate<'tcx>>>, NoSolution> {
-        self.at(&ObligationCause::dummy(), param_env).relate_no_trace(lhs, variance, rhs)
-    }
-
-    fn eq_structurally_relating_aliases<T: Relate<TyCtxt<'tcx>>>(
-        &self,
-        param_env: ty::ParamEnv<'tcx>,
-        lhs: T,
-        rhs: T,
-    ) -> Result<Vec<Goal<'tcx, ty::Predicate<'tcx>>>, NoSolution> {
-        self.at(&ObligationCause::dummy(), param_env)
-            .eq_structurally_relating_aliases_no_trace(lhs, rhs)
-    }
-
-    fn resolve_vars_if_possible<T>(&self, value: T) -> T
-    where
-        T: TypeFoldable<TyCtxt<'tcx>>,
-    {
-        self.resolve_vars_if_possible(value)
-    }
-
-    fn probe<T>(&self, probe: impl FnOnce() -> T) -> T {
-        self.probe(|_| probe())
-    }
-}
-
 /// See the `error_reporting` module for more details.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable)]
 pub enum ValuePairs<'tcx> {
@@ -831,6 +688,10 @@ impl<'tcx> InferCtxt<'tcx> {
         self.tcx.dcx()
     }
 
+    pub fn defining_opaque_types(&self) -> &'tcx ty::List<LocalDefId> {
+        self.defining_opaque_types
+    }
+
     pub fn next_trait_solver(&self) -> bool {
         self.next_trait_solver
     }

compiler/rustc_middle/src/arena.rs

@@ -111,7 +111,7 @@ macro_rules! arena_types {
                     rustc_middle::ty::EarlyBinder<'tcx, rustc_middle::ty::Ty<'tcx>>
                 >,
             [] external_constraints: rustc_middle::traits::solve::ExternalConstraintsData<rustc_middle::ty::TyCtxt<'tcx>>,
-            [] predefined_opaques_in_body: rustc_middle::traits::solve::PredefinedOpaquesData<'tcx>,
+            [] predefined_opaques_in_body: rustc_middle::traits::solve::PredefinedOpaquesData<rustc_middle::ty::TyCtxt<'tcx>>,
             [decode] doc_link_resolutions: rustc_hir::def::DocLinkResMap,
             [] stripped_cfg_items: rustc_ast::expand::StrippedCfgItem,
             [] mod_child: rustc_middle::metadata::ModChild,

compiler/rustc_middle/src/traits/solve.rs

@@ -5,12 +5,12 @@ use rustc_type_ir as ir;
 pub use rustc_type_ir::solve::*;
 
 use crate::ty::{
-    self, FallibleTypeFolder, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeVisitable, TypeVisitor,
+    self, FallibleTypeFolder, TyCtxt, TypeFoldable, TypeFolder, TypeVisitable, TypeVisitor,
 };
 
 mod cache;
 
-pub use cache::{CacheData, EvaluationCache};
+pub use cache::EvaluationCache;
 
 pub type Goal<'tcx, P> = ir::solve::Goal<TyCtxt<'tcx>, P>;
 pub type QueryInput<'tcx, P> = ir::solve::QueryInput<TyCtxt<'tcx>, P>;
@@ -19,17 +19,11 @@ pub type CandidateSource<'tcx> = ir::solve::CandidateSource<TyCtxt<'tcx>>;
 pub type CanonicalInput<'tcx, P = ty::Predicate<'tcx>> = ir::solve::CanonicalInput<TyCtxt<'tcx>, P>;
 pub type CanonicalResponse<'tcx> = ir::solve::CanonicalResponse<TyCtxt<'tcx>>;
 
-/// Additional constraints returned on success.
-#[derive(Debug, PartialEq, Eq, Clone, Hash, HashStable, Default)]
-pub struct PredefinedOpaquesData<'tcx> {
-    pub opaque_types: Vec<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)>,
-}
-
 #[derive(Debug, PartialEq, Eq, Copy, Clone, Hash, HashStable)]
-pub struct PredefinedOpaques<'tcx>(pub(crate) Interned<'tcx, PredefinedOpaquesData<'tcx>>);
+pub struct PredefinedOpaques<'tcx>(pub(crate) Interned<'tcx, PredefinedOpaquesData<TyCtxt<'tcx>>>);
 
 impl<'tcx> std::ops::Deref for PredefinedOpaques<'tcx> {
-    type Target = PredefinedOpaquesData<'tcx>;
+    type Target = PredefinedOpaquesData<TyCtxt<'tcx>>;
 
     fn deref(&self) -> &Self::Target {
         &self.0

compiler/rustc_middle/src/traits/solve/cache.rs

@@ -5,6 +5,8 @@ use rustc_data_structures::sync::Lock;
 use rustc_query_system::cache::WithDepNode;
 use rustc_query_system::dep_graph::DepNodeIndex;
 use rustc_session::Limit;
+use rustc_type_ir::solve::CacheData;
+
 /// The trait solver cache used by `-Znext-solver`.
 ///
 /// FIXME(@lcnr): link to some official documentation of how
@@ -14,17 +16,9 @@ pub struct EvaluationCache<'tcx> {
     map: Lock<FxHashMap<CanonicalInput<'tcx>, CacheEntry<'tcx>>>,
 }
 
-#[derive(Debug, PartialEq, Eq)]
-pub struct CacheData<'tcx> {
-    pub result: QueryResult<'tcx>,
-    pub proof_tree: Option<&'tcx inspect::CanonicalGoalEvaluationStep<TyCtxt<'tcx>>>,
-    pub additional_depth: usize,
-    pub encountered_overflow: bool,
-}
-
-impl<'tcx> EvaluationCache<'tcx> {
+impl<'tcx> rustc_type_ir::inherent::EvaluationCache<TyCtxt<'tcx>> for &'tcx EvaluationCache<'tcx> {
     /// Insert a final result into the global cache.
-    pub fn insert(
+    fn insert(
         &self,
         tcx: TyCtxt<'tcx>,
         key: CanonicalInput<'tcx>,
@@ -48,7 +42,7 @@ impl<'tcx> EvaluationCache<'tcx> {
         if cfg!(debug_assertions) {
             drop(map);
             let expected = CacheData { result, proof_tree, additional_depth, encountered_overflow };
-            let actual = self.get(tcx, key, [], Limit(additional_depth));
+            let actual = self.get(tcx, key, [], additional_depth);
             if !actual.as_ref().is_some_and(|actual| expected == *actual) {
                 bug!("failed to lookup inserted element for {key:?}: {expected:?} != {actual:?}");
             }
@@ -59,13 +53,13 @@ impl<'tcx> EvaluationCache<'tcx> {
     /// and handling root goals of coinductive cycles.
     ///
     /// If this returns `Some` the cache result can be used.
-    pub fn get(
+    fn get(
         &self,
         tcx: TyCtxt<'tcx>,
         key: CanonicalInput<'tcx>,
         stack_entries: impl IntoIterator<Item = CanonicalInput<'tcx>>,
-        available_depth: Limit,
-    ) -> Option<CacheData<'tcx>> {
+        available_depth: usize,
+    ) -> Option<CacheData<TyCtxt<'tcx>>> {
         let map = self.map.borrow();
         let entry = map.get(&key)?;
 
@@ -76,7 +70,7 @@ impl<'tcx> EvaluationCache<'tcx> {
         }
 
         if let Some(ref success) = entry.success {
-            if available_depth.value_within_limit(success.additional_depth) {
+            if Limit(available_depth).value_within_limit(success.additional_depth) {
                 let QueryData { result, proof_tree } = success.data.get(tcx);
                 return Some(CacheData {
                     result,
@@ -87,12 +81,12 @@ impl<'tcx> EvaluationCache<'tcx> {
             }
         }
 
-        entry.with_overflow.get(&available_depth.0).map(|e| {
+        entry.with_overflow.get(&available_depth).map(|e| {
             let QueryData { result, proof_tree } = e.get(tcx);
             CacheData {
                 result,
                 proof_tree,
-                additional_depth: available_depth.0,
+                additional_depth: available_depth,
                 encountered_overflow: true,
             }
         })

compiler/rustc_middle/src/ty/adt.rs

@@ -205,14 +205,22 @@ impl<'tcx> rustc_type_ir::inherent::AdtDef<TyCtxt<'tcx>> for AdtDef<'tcx> {
         self.did()
     }
 
+    fn is_struct(self) -> bool {
+        self.is_struct()
+    }
+
+    fn struct_tail_ty(self, interner: TyCtxt<'tcx>) -> Option<ty::EarlyBinder<'tcx, Ty<'tcx>>> {
+        Some(interner.type_of(self.non_enum_variant().tail_opt()?.did))
+    }
+
     fn is_phantom_data(self) -> bool {
         self.is_phantom_data()
     }
 
     fn all_field_tys(
         self,
         tcx: TyCtxt<'tcx>,
-    ) -> ty::EarlyBinder<'tcx, impl Iterator<Item = Ty<'tcx>>> {
+    ) -> ty::EarlyBinder<'tcx, impl IntoIterator<Item = Ty<'tcx>>> {
         ty::EarlyBinder::bind(
             self.all_fields().map(move |field| tcx.type_of(field.did).skip_binder()),
         )

compiler/rustc_middle/src/ty/consts.rs

@@ -16,8 +16,8 @@ mod valtree;
 
 pub use int::*;
 pub use kind::*;
-use rustc_span::Span;
 use rustc_span::DUMMY_SP;
+use rustc_span::{ErrorGuaranteed, Span};
 pub use valtree::*;
 
 pub type ConstKind<'tcx> = ir::ConstKind<TyCtxt<'tcx>>;
@@ -176,6 +176,10 @@ impl<'tcx> rustc_type_ir::inherent::Const<TyCtxt<'tcx>> for Const<'tcx> {
     fn new_expr(interner: TyCtxt<'tcx>, expr: ty::Expr<'tcx>) -> Self {
         Const::new_expr(interner, expr)
     }
+
+    fn new_error(interner: TyCtxt<'tcx>, guar: ErrorGuaranteed) -> Self {
+        Const::new_error(interner, guar)
+    }
 }
 
 impl<'tcx> Const<'tcx> {