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Use Binder<Vec<Ty>> instead of Vec<Binder<Ty>> in both solvers for sized/auto traits/etc. #137689

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Mar 1, 2025
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Use Binder<Vec<Ty>> instead of Vec<Binder<Ty>> in both solvers for sized/auto traits/etc. #137689

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8282181
Use Binder<Vec<T>> instead of Vec<Binder<T>> in new solver
compiler-errors Feb 26, 2025
ad74788
Use bound_coroutine_witnesses in old solver
compiler-errors Feb 26, 2025
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6 changes: 4 additions & 2 deletions compiler/rustc_infer/src/infer/relate/higher_ranked.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
//! the end of the file for details.

use rustc_middle::ty::fold::FnMutDelegate;
use rustc_middle::ty::visit::TypeVisitableExt;
use rustc_middle::ty::{self, Ty, TyCtxt, TypeFoldable};
use tracing::{debug, instrument};

Expand All @@ -26,8 +27,9 @@ impl<'tcx> InferCtxt<'tcx> {
where
T: TypeFoldable<TyCtxt<'tcx>>,
{
if let Some(inner) = binder.clone().no_bound_vars() {
return inner;
// Inlined `no_bound_vars`.
if !binder.as_ref().skip_binder().has_escaping_bound_vars() {
return binder.skip_binder();
Comment on lines +31 to +32
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to avoid clone?

do we do this more often, I've encountered this myself and have considered try_no_bound_vars() -> Result<T, Binder<T>> or maybe just changing no_bound_vars to that

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well now in this pr we're entering whole binders of vecs rather than iterating over a vec of binder of ty which we then enter, so we do this more often i think

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"do we do this more often"

as in: the pattern of no_bound_vars() and doing something with the binder if it returns None.

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ohhh, as far as i can tell, no this seems like the only place where we were previously repeatedly fighting the Copy bound bc no_bound_vars consumes its valur

}

let next_universe = self.create_next_universe();
Expand Down
6 changes: 3 additions & 3 deletions compiler/rustc_middle/src/ty/context.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -324,11 +324,11 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
self.features()
}

fn bound_coroutine_hidden_types(
fn coroutine_hidden_types(
self,
def_id: DefId,
) -> impl IntoIterator<Item = ty::EarlyBinder<'tcx, ty::Binder<'tcx, Ty<'tcx>>>> {
self.bound_coroutine_hidden_types(def_id)
) -> ty::EarlyBinder<'tcx, ty::Binder<'tcx, &'tcx ty::List<Ty<'tcx>>>> {
self.coroutine_hidden_types(def_id)
}

fn fn_sig(self, def_id: DefId) -> ty::EarlyBinder<'tcx, ty::PolyFnSig<'tcx>> {
Expand Down
66 changes: 26 additions & 40 deletions compiler/rustc_middle/src/ty/util.rs
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Expand Up @@ -725,52 +725,38 @@ impl<'tcx> TyCtxt<'tcx> {
}
}

/// Return the set of types that should be taken into account when checking
/// trait bounds on a coroutine's internal state.
// FIXME(compiler-errors): We should remove this when the old solver goes away;
// and all other usages of this function should go through `bound_coroutine_hidden_types`
// instead.
pub fn coroutine_hidden_types(
self,
def_id: DefId,
) -> impl Iterator<Item = ty::EarlyBinder<'tcx, Ty<'tcx>>> {
let coroutine_layout = self.mir_coroutine_witnesses(def_id);
coroutine_layout
.as_ref()
.map_or_else(|| [].iter(), |l| l.field_tys.iter())
.filter(|decl| !decl.ignore_for_traits)
.map(|decl| ty::EarlyBinder::bind(decl.ty))
}

/// Return the set of types that should be taken into account when checking
/// trait bounds on a coroutine's internal state. This properly replaces
/// `ReErased` with new existential bound lifetimes.
pub fn bound_coroutine_hidden_types(
pub fn coroutine_hidden_types(
self,
def_id: DefId,
) -> impl Iterator<Item = ty::EarlyBinder<'tcx, ty::Binder<'tcx, Ty<'tcx>>>> {
) -> ty::EarlyBinder<'tcx, ty::Binder<'tcx, &'tcx ty::List<Ty<'tcx>>>> {
let coroutine_layout = self.mir_coroutine_witnesses(def_id);
coroutine_layout
.as_ref()
.map_or_else(|| [].iter(), |l| l.field_tys.iter())
.filter(|decl| !decl.ignore_for_traits)
.map(move |decl| {
let mut vars = vec![];
let ty = fold_regions(self, decl.ty, |re, debruijn| {
assert_eq!(re, self.lifetimes.re_erased);
let var = ty::BoundVar::from_usize(vars.len());
vars.push(ty::BoundVariableKind::Region(ty::BoundRegionKind::Anon));
ty::Region::new_bound(
self,
debruijn,
ty::BoundRegion { var, kind: ty::BoundRegionKind::Anon },
)
});
ty::EarlyBinder::bind(ty::Binder::bind_with_vars(
ty,
self.mk_bound_variable_kinds(&vars),
))
})
let mut vars = vec![];
let bound_tys = self.mk_type_list_from_iter(
coroutine_layout
.as_ref()
.map_or_else(|| [].iter(), |l| l.field_tys.iter())
.filter(|decl| !decl.ignore_for_traits)
.map(|decl| {
let ty = fold_regions(self, decl.ty, |re, debruijn| {
assert_eq!(re, self.lifetimes.re_erased);
let var = ty::BoundVar::from_usize(vars.len());
vars.push(ty::BoundVariableKind::Region(ty::BoundRegionKind::Anon));
ty::Region::new_bound(
self,
debruijn,
ty::BoundRegion { var, kind: ty::BoundRegionKind::Anon },
)
});
ty
}),
);
ty::EarlyBinder::bind(ty::Binder::bind_with_vars(
bound_tys,
self.mk_bound_variable_kinds(&vars),
))
}

/// Expands the given impl trait type, stopping if the type is recursive.
Expand Down
72 changes: 32 additions & 40 deletions compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs
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Expand Up @@ -18,7 +18,7 @@ use crate::solve::{AdtDestructorKind, EvalCtxt, Goal, NoSolution};
pub(in crate::solve) fn instantiate_constituent_tys_for_auto_trait<D, I>(
ecx: &EvalCtxt<'_, D>,
ty: I::Ty,
) -> Result<Vec<ty::Binder<I, I::Ty>>, NoSolution>
) -> Result<ty::Binder<I, Vec<I::Ty>>, NoSolution>
where
D: SolverDelegate<Interner = I>,
I: Interner,
Expand All @@ -33,10 +33,10 @@ where
| ty::FnPtr(..)
| ty::Error(_)
| ty::Never
| ty::Char => Ok(vec![]),
| ty::Char => Ok(ty::Binder::dummy(vec![])),

// Treat `str` like it's defined as `struct str([u8]);`
ty::Str => Ok(vec![ty::Binder::dummy(Ty::new_slice(cx, Ty::new_u8(cx)))]),
ty::Str => Ok(ty::Binder::dummy(vec![Ty::new_slice(cx, Ty::new_u8(cx))])),

ty::Dynamic(..)
| ty::Param(..)
Expand All @@ -49,53 +49,49 @@ where
}

ty::RawPtr(element_ty, _) | ty::Ref(_, element_ty, _) => {
Ok(vec![ty::Binder::dummy(element_ty)])
Ok(ty::Binder::dummy(vec![element_ty]))
}

ty::Pat(element_ty, _) | ty::Array(element_ty, _) | ty::Slice(element_ty) => {
Ok(vec![ty::Binder::dummy(element_ty)])
Ok(ty::Binder::dummy(vec![element_ty]))
}

ty::Tuple(tys) => {
// (T1, ..., Tn) -- meets any bound that all of T1...Tn meet
Ok(tys.iter().map(ty::Binder::dummy).collect())
Ok(ty::Binder::dummy(tys.to_vec()))
}

ty::Closure(_, args) => Ok(vec![ty::Binder::dummy(args.as_closure().tupled_upvars_ty())]),
ty::Closure(_, args) => Ok(ty::Binder::dummy(vec![args.as_closure().tupled_upvars_ty()])),

ty::CoroutineClosure(_, args) => {
Ok(vec![ty::Binder::dummy(args.as_coroutine_closure().tupled_upvars_ty())])
Ok(ty::Binder::dummy(vec![args.as_coroutine_closure().tupled_upvars_ty()]))
}

ty::Coroutine(_, args) => {
let coroutine_args = args.as_coroutine();
Ok(vec![
ty::Binder::dummy(coroutine_args.tupled_upvars_ty()),
ty::Binder::dummy(coroutine_args.witness()),
])
Ok(ty::Binder::dummy(vec![coroutine_args.tupled_upvars_ty(), coroutine_args.witness()]))
}

ty::CoroutineWitness(def_id, args) => Ok(ecx
.cx()
.bound_coroutine_hidden_types(def_id)
.into_iter()
.map(|bty| bty.instantiate(cx, args))
.collect()),
.coroutine_hidden_types(def_id)
.instantiate(cx, args)
.map_bound(|tys| tys.to_vec())),

ty::UnsafeBinder(bound_ty) => Ok(vec![bound_ty.into()]),
ty::UnsafeBinder(bound_ty) => Ok(bound_ty.map_bound(|ty| vec![ty])),

// For `PhantomData<T>`, we pass `T`.
ty::Adt(def, args) if def.is_phantom_data() => Ok(vec![ty::Binder::dummy(args.type_at(0))]),
ty::Adt(def, args) if def.is_phantom_data() => Ok(ty::Binder::dummy(vec![args.type_at(0)])),

ty::Adt(def, args) => {
Ok(def.all_field_tys(cx).iter_instantiated(cx, args).map(ty::Binder::dummy).collect())
Ok(ty::Binder::dummy(def.all_field_tys(cx).iter_instantiated(cx, args).collect()))
}

ty::Alias(ty::Opaque, ty::AliasTy { def_id, args, .. }) => {
// We can resolve the `impl Trait` to its concrete type,
// which enforces a DAG between the functions requiring
// the auto trait bounds in question.
Ok(vec![ty::Binder::dummy(cx.type_of(def_id).instantiate(cx, args))])
Ok(ty::Binder::dummy(vec![cx.type_of(def_id).instantiate(cx, args)]))
}
}
}
Expand All @@ -104,7 +100,7 @@ where
pub(in crate::solve) fn instantiate_constituent_tys_for_sized_trait<D, I>(
ecx: &EvalCtxt<'_, D>,
ty: I::Ty,
) -> Result<Vec<ty::Binder<I, I::Ty>>, NoSolution>
) -> Result<ty::Binder<I, Vec<I::Ty>>, NoSolution>
where
D: SolverDelegate<Interner = I>,
I: Interner,
Expand All @@ -130,7 +126,7 @@ where
| ty::CoroutineClosure(..)
| ty::Never
| ty::Dynamic(_, _, ty::DynStar)
| ty::Error(_) => Ok(vec![]),
| ty::Error(_) => Ok(ty::Binder::dummy(vec![])),

ty::Str
| ty::Slice(_)
Expand All @@ -145,11 +141,11 @@ where
panic!("unexpected type `{ty:?}`")
}

ty::UnsafeBinder(bound_ty) => Ok(vec![bound_ty.into()]),
ty::UnsafeBinder(bound_ty) => Ok(bound_ty.map_bound(|ty| vec![ty])),

// impl Sized for ()
// impl Sized for (T1, T2, .., Tn) where Tn: Sized if n >= 1
ty::Tuple(tys) => Ok(tys.last().map_or_else(Vec::new, |ty| vec![ty::Binder::dummy(ty)])),
ty::Tuple(tys) => Ok(ty::Binder::dummy(tys.last().map_or_else(Vec::new, |ty| vec![ty]))),

// impl Sized for Adt<Args...> where sized_constraint(Adt)<Args...>: Sized
// `sized_constraint(Adt)` is the deepest struct trail that can be determined
Expand All @@ -162,9 +158,9 @@ where
// if the ADT is sized for all possible args.
ty::Adt(def, args) => {
if let Some(sized_crit) = def.sized_constraint(ecx.cx()) {
Ok(vec![ty::Binder::dummy(sized_crit.instantiate(ecx.cx(), args))])
Ok(ty::Binder::dummy(vec![sized_crit.instantiate(ecx.cx(), args)]))
} else {
Ok(vec![])
Ok(ty::Binder::dummy(vec![]))
}
}
}
Expand All @@ -174,14 +170,14 @@ where
pub(in crate::solve) fn instantiate_constituent_tys_for_copy_clone_trait<D, I>(
ecx: &EvalCtxt<'_, D>,
ty: I::Ty,
) -> Result<Vec<ty::Binder<I, I::Ty>>, NoSolution>
) -> Result<ty::Binder<I, Vec<I::Ty>>, NoSolution>
where
D: SolverDelegate<Interner = I>,
I: Interner,
{
match ty.kind() {
// impl Copy/Clone for FnDef, FnPtr
ty::FnDef(..) | ty::FnPtr(..) | ty::Error(_) => Ok(vec![]),
ty::FnDef(..) | ty::FnPtr(..) | ty::Error(_) => Ok(ty::Binder::dummy(vec![])),

// Implementations are provided in core
ty::Uint(_)
Expand All @@ -197,7 +193,7 @@ where

// Cannot implement in core, as we can't be generic over patterns yet,
// so we'd have to list all patterns and type combinations.
ty::Pat(ty, ..) => Ok(vec![ty::Binder::dummy(ty)]),
ty::Pat(ty, ..) => Ok(ty::Binder::dummy(vec![ty])),

ty::Dynamic(..)
| ty::Str
Expand All @@ -215,14 +211,14 @@ where
}

// impl Copy/Clone for (T1, T2, .., Tn) where T1: Copy/Clone, T2: Copy/Clone, .. Tn: Copy/Clone
ty::Tuple(tys) => Ok(tys.iter().map(ty::Binder::dummy).collect()),
ty::Tuple(tys) => Ok(ty::Binder::dummy(tys.to_vec())),

// impl Copy/Clone for Closure where Self::TupledUpvars: Copy/Clone
ty::Closure(_, args) => Ok(vec![ty::Binder::dummy(args.as_closure().tupled_upvars_ty())]),
ty::Closure(_, args) => Ok(ty::Binder::dummy(vec![args.as_closure().tupled_upvars_ty()])),

// impl Copy/Clone for CoroutineClosure where Self::TupledUpvars: Copy/Clone
ty::CoroutineClosure(_, args) => {
Ok(vec![ty::Binder::dummy(args.as_coroutine_closure().tupled_upvars_ty())])
Ok(ty::Binder::dummy(vec![args.as_coroutine_closure().tupled_upvars_ty()]))
}

// only when `coroutine_clone` is enabled and the coroutine is movable
Expand All @@ -232,10 +228,7 @@ where
Movability::Movable => {
if ecx.cx().features().coroutine_clone() {
let coroutine = args.as_coroutine();
Ok(vec![
ty::Binder::dummy(coroutine.tupled_upvars_ty()),
ty::Binder::dummy(coroutine.witness()),
])
Ok(ty::Binder::dummy(vec![coroutine.tupled_upvars_ty(), coroutine.witness()]))
} else {
Err(NoSolution)
}
Expand All @@ -247,10 +240,9 @@ where
// impl Copy/Clone for CoroutineWitness where T: Copy/Clone forall T in coroutine_hidden_types
ty::CoroutineWitness(def_id, args) => Ok(ecx
.cx()
.bound_coroutine_hidden_types(def_id)
.into_iter()
.map(|bty| bty.instantiate(ecx.cx(), args))
.collect()),
.coroutine_hidden_types(def_id)
.instantiate(ecx.cx(), args)
.map_bound(|tys| tys.to_vec())),
}
}

Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -913,7 +913,7 @@ where

/// `enter_forall`, but takes `&mut self` and passes it back through the
/// callback since it can't be aliased during the call.
pub(super) fn enter_forall<T: TypeFoldable<I> + Copy, U>(
pub(super) fn enter_forall<T: TypeFoldable<I>, U>(
&mut self,
value: ty::Binder<I, T>,
f: impl FnOnce(&mut Self, T) -> U,
Expand Down
16 changes: 7 additions & 9 deletions compiler/rustc_next_trait_solver/src/solve/trait_goals.rs
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Expand Up @@ -1239,17 +1239,15 @@ where
constituent_tys: impl Fn(
&EvalCtxt<'_, D>,
I::Ty,
) -> Result<Vec<ty::Binder<I, I::Ty>>, NoSolution>,
) -> Result<ty::Binder<I, Vec<I::Ty>>, NoSolution>,
) -> Result<Candidate<I>, NoSolution> {
self.probe_trait_candidate(source).enter(|ecx| {
let goals = constituent_tys(ecx, goal.predicate.self_ty())?
.into_iter()
.map(|ty| {
ecx.enter_forall(ty, |ecx, ty| {
goal.with(ecx.cx(), goal.predicate.with_self_ty(ecx.cx(), ty))
})
})
.collect::<Vec<_>>();
let goals =
ecx.enter_forall(constituent_tys(ecx, goal.predicate.self_ty())?, |ecx, tys| {
tys.into_iter()
.map(|ty| goal.with(ecx.cx(), goal.predicate.with_self_ty(ecx.cx(), ty)))
.collect::<Vec<_>>()
});
ecx.add_goals(GoalSource::ImplWhereBound, goals);
ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
})
Expand Down
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