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remove assembly context and impl a bit more

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This commit is contained in:
lcnr 2023-01-17 11:47:47 +01:00
parent bf7dbff921
commit 660c28391c
8 changed files with 322 additions and 168 deletions
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6
compiler/rustc_middle/src/infer/canonical.rs
View File

@ -339,6 +339,12 @@ TrivialTypeTraversalAndLiftImpls! {
}
impl<'tcx> CanonicalVarValues<'tcx> {
/// Creates dummy var values which should not be used in a
/// canonical response.
pub fn dummy() -> CanonicalVarValues<'tcx> {
CanonicalVarValues { var_values: Default::default() }
}
#[inline]
pub fn len(&self) -> usize {
self.var_values.len()

264
compiler/rustc_trait_selection/src/solve/assembly.rs
View File

@ -12,18 +12,73 @@ use std::fmt::Debug;
///
/// It consists of both the `source`, which describes how that goal would be proven,
/// and the `result` when using the given `source`.
///
/// For the list of possible candidates, please look at the documentation of
/// [super::trait_goals::CandidateSource] and [super::project_goals::CandidateSource].
#[derive(Debug, Clone)]
pub(super) struct Candidate<'tcx, G: GoalKind<'tcx>> {
pub(super) source: G::CandidateSource,
pub(super) struct Candidate<'tcx> {
pub(super) source: CandidateSource,
pub(super) result: CanonicalResponse<'tcx>,
}
pub(super) trait GoalKind<'tcx>: TypeFoldable<'tcx> + Copy {
type CandidateSource: Debug + Copy;
/// Possible ways the given goal can be proven.
#[derive(Debug, Clone, Copy)]
pub(super) enum CandidateSource {
/// A user written impl.
///
/// ## Examples
///
/// ```rust
/// fn main() {
/// let x: Vec<u32> = Vec::new();
/// // This uses the impl from the standard library to prove `Vec<T>: Clone`.
/// let y = x.clone();
/// }
/// ```
Impl(DefId),
/// A builtin impl generated by the compiler. When adding a new special
/// trait, try to use actual impls whenever possible. Builtin impls should
/// only be used in cases where the impl cannot be manually be written.
///
/// Notable examples are auto traits, `Sized`, and `DiscriminantKind`.
/// For a list of all traits with builtin impls, check out the
/// [`EvalCtxt::assemble_builtin_impl_candidates`] method. Not
BuiltinImpl,
/// An assumption from the environment.
///
/// More precicely we've used the `n-th` assumption in the `param_env`.
///
/// ## Examples
///
/// ```rust
/// fn is_clone<T: Clone>(x: T) -> (T, T) {
/// // This uses the assumption `T: Clone` from the `where`-bounds
/// // to prove `T: Clone`.
/// (x.clone(), x)
/// }
/// ```
ParamEnv(usize),
/// If the self type is an alias type, e.g. an opaque type or a projection,
/// we know the bounds on that alias to hold even without knowing its concrete
/// underlying type.
///
/// More precisely this candidate is using the `n-th` bound in the `item_bounds` of
/// the self type.
///
/// ## Examples
///
/// ```rust
/// trait Trait {
/// type Assoc: Clone;
/// }
///
/// fn foo<T: Trait>(x: <T as Trait>::Assoc) {
/// // We prove `<T as Trait>::Assoc` by looking at the bounds on `Assoc` in
/// // in the trait definition.
/// let _y = x.clone();
/// }
/// ```
AliasBound(usize),
}
pub(super) trait GoalKind<'tcx>: TypeFoldable<'tcx> + Copy {
fn self_ty(self) -> Ty<'tcx>;
fn with_self_ty(self, tcx: TyCtxt<'tcx>, self_ty: Ty<'tcx>) -> Self;
@ -31,43 +86,40 @@ pub(super) trait GoalKind<'tcx>: TypeFoldable<'tcx> + Copy {
fn trait_def_id(self, tcx: TyCtxt<'tcx>) -> DefId;
fn consider_impl_candidate(
acx: &mut AssemblyCtxt<'_, '_, 'tcx, Self>,
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
impl_def_id: DefId,
);
) -> Result<Certainty, NoSolution>;
fn consider_builtin_sized_candidate(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Certainty, NoSolution>;
fn consider_assumption(
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
assumption: ty::Predicate<'tcx>,
) -> Result<Certainty, NoSolution>;
}
/// An abstraction which correctly deals with the canonical results for candidates.
///
/// It also deduplicates the behavior between trait and projection predicates.
pub(super) struct AssemblyCtxt<'a, 'b, 'tcx, G: GoalKind<'tcx>> {
pub(super) cx: &'a mut EvalCtxt<'b, 'tcx>,
candidates: Vec<Candidate<'tcx, G>>,
}
impl<'a, 'b, 'tcx, G: GoalKind<'tcx>> AssemblyCtxt<'a, 'b, 'tcx, G> {
pub(super) fn assemble_and_evaluate_candidates(
cx: &'a mut EvalCtxt<'b, 'tcx>,
goal: Goal<'tcx, G>,
) -> Vec<Candidate<'tcx, G>> {
let mut acx = AssemblyCtxt { cx, candidates: Vec::new() };
acx.assemble_candidates_after_normalizing_self_ty(goal);
acx.assemble_impl_candidates(goal);
acx.candidates
}
pub(super) fn try_insert_candidate(
impl<'tcx> EvalCtxt<'_, 'tcx> {
pub(super) fn assemble_and_evaluate_candidates<G: GoalKind<'tcx>>(
&mut self,
source: G::CandidateSource,
certainty: Certainty,
) {
match self.cx.make_canonical_response(certainty) {
Ok(result) => self.candidates.push(Candidate { source, result }),
Err(NoSolution) => debug!(?source, ?certainty, "failed leakcheck"),
}
goal: Goal<'tcx, G>,
) -> Vec<Candidate<'tcx>> {
let mut candidates = Vec::new();
self.assemble_candidates_after_normalizing_self_ty(goal, &mut candidates);
self.assemble_impl_candidates(goal, &mut candidates);
self.assemble_builtin_impl_candidates(goal, &mut candidates);
self.assemble_param_env_candidates(goal, &mut candidates);
self.assemble_alias_bound_candidates(goal, &mut candidates);
candidates
}
/// If the self type of a goal is a projection, computing the relevant candidates is difficult.
@ -75,15 +127,18 @@ impl<'a, 'b, 'tcx, G: GoalKind<'tcx>> AssemblyCtxt<'a, 'b, 'tcx, G> {
/// To deal with this, we first try to normalize the self type and add the candidates for the normalized
/// self type to the list of candidates in case that succeeds. Note that we can't just eagerly return in
/// this case as projections as self types add `
fn assemble_candidates_after_normalizing_self_ty(&mut self, goal: Goal<'tcx, G>) {
let tcx = self.cx.tcx();
let infcx = self.cx.infcx;
fn assemble_candidates_after_normalizing_self_ty<G: GoalKind<'tcx>>(
&mut self,
goal: Goal<'tcx, G>,
candidates: &mut Vec<Candidate<'tcx>>,
) {
let tcx = self.tcx();
// FIXME: We also have to normalize opaque types, not sure where to best fit that in.
let &ty::Alias(ty::Projection, projection_ty) = goal.predicate.self_ty().kind() else {
return
};
infcx.probe(|_| {
let normalized_ty = infcx.next_ty_infer();
self.infcx.probe(|_| {
let normalized_ty = self.infcx.next_ty_infer();
let normalizes_to_goal = goal.with(
tcx,
ty::Binder::dummy(ty::ProjectionPredicate {
@ -91,33 +146,136 @@ impl<'a, 'b, 'tcx, G: GoalKind<'tcx>> AssemblyCtxt<'a, 'b, 'tcx, G> {
term: normalized_ty.into(),
}),
);
let normalization_certainty = match self.cx.evaluate_goal(normalizes_to_goal) {
let normalization_certainty = match self.evaluate_goal(normalizes_to_goal) {
Ok((_, certainty)) => certainty,
Err(NoSolution) => return,
};
// NOTE: Alternatively we could call `evaluate_goal` here and only have a `Normalized` candidate.
// This doesn't work as long as we use `CandidateSource` in both winnowing and to resolve associated items.
// This doesn't work as long as we use `CandidateSource` in winnowing.
let goal = goal.with(tcx, goal.predicate.with_self_ty(tcx, normalized_ty));
let normalized_candidates =
AssemblyCtxt::assemble_and_evaluate_candidates(self.cx, goal);
// FIXME: This is broken if we care about the `usize` of `AliasBound` because the self type
// could be normalized to yet another projection with different item bounds.
let normalized_candidates = self.assemble_and_evaluate_candidates(goal);
for mut normalized_candidate in normalized_candidates {
normalized_candidate.result =
normalized_candidate.result.unchecked_map(|mut response| {
// FIXME: This currently hides overflow in the normalization step of the self type
// which is probably wrong. Maybe `unify_and` should actually keep overflow as
// we treat it as non-fatal anyways.
response.certainty = response.certainty.unify_and(normalization_certainty);
response
});
self.candidates.push(normalized_candidate);
candidates.push(normalized_candidate);
}
})
}
fn assemble_impl_candidates(&mut self, goal: Goal<'tcx, G>) {
let tcx = self.cx.tcx();
fn assemble_impl_candidates<G: GoalKind<'tcx>>(
&mut self,
goal: Goal<'tcx, G>,
candidates: &mut Vec<Candidate<'tcx>>,
) {
let tcx = self.tcx();
tcx.for_each_relevant_impl(
goal.predicate.trait_def_id(tcx),
goal.predicate.self_ty(),
|impl_def_id| G::consider_impl_candidate(self, goal, impl_def_id),
|impl_def_id| match G::consider_impl_candidate(self, goal, impl_def_id)
.and_then(|certainty| self.make_canonical_response(certainty))
{
Ok(result) => candidates
.push(Candidate { source: CandidateSource::Impl(impl_def_id), result }),
Err(NoSolution) => (),
},
);
}
fn assemble_builtin_impl_candidates<G: GoalKind<'tcx>>(
&mut self,
goal: Goal<'tcx, G>,
candidates: &mut Vec<Candidate<'tcx>>,
) {
let lang_items = self.tcx().lang_items();
let trait_def_id = goal.predicate.trait_def_id(self.tcx());
let result = if lang_items.sized_trait() == Some(trait_def_id) {
G::consider_builtin_sized_candidate(self, goal)
} else {
Err(NoSolution)
};
match result.and_then(|certainty| self.make_canonical_response(certainty)) {
Ok(result) => {
candidates.push(Candidate { source: CandidateSource::BuiltinImpl, result })
}
Err(NoSolution) => (),
}
}
fn assemble_param_env_candidates<G: GoalKind<'tcx>>(
&mut self,
goal: Goal<'tcx, G>,
candidates: &mut Vec<Candidate<'tcx>>,
) {
for (i, assumption) in goal.param_env.caller_bounds().iter().enumerate() {
match G::consider_assumption(self, goal, assumption)
.and_then(|certainty| self.make_canonical_response(certainty))
{
Ok(result) => {
candidates.push(Candidate { source: CandidateSource::ParamEnv(i), result })
}
Err(NoSolution) => (),
}
}
}
fn assemble_alias_bound_candidates<G: GoalKind<'tcx>>(
&mut self,
goal: Goal<'tcx, G>,
candidates: &mut Vec<Candidate<'tcx>>,
) {
let alias_ty = match goal.predicate.self_ty().kind() {
ty::Bool
| ty::Char
| ty::Int(_)
| ty::Uint(_)
| ty::Float(_)
| ty::Adt(_, _)
| ty::Foreign(_)
| ty::Str
| ty::Array(_, _)
| ty::Slice(_)
| ty::RawPtr(_)
| ty::Ref(_, _, _)
| ty::FnDef(_, _)
| ty::FnPtr(_)
| ty::Dynamic(..)
| ty::Closure(..)
| ty::Generator(..)
| ty::GeneratorWitness(_)
| ty::Never
| ty::Tuple(_)
| ty::Param(_)
| ty::Placeholder(..)
| ty::Infer(_)
| ty::Error(_) => return,
ty::Bound(..) => bug!("unexpected bound type: {goal:?}"),
ty::Alias(_, alias_ty) => alias_ty,
};
for (i, (assumption, _)) in self
.tcx()
.bound_explicit_item_bounds(alias_ty.def_id)
.subst_iter_copied(self.tcx(), alias_ty.substs)
.enumerate()
{
match G::consider_assumption(self, goal, assumption)
.and_then(|certainty| self.make_canonical_response(certainty))
{
Ok(result) => {
candidates.push(Candidate { source: CandidateSource::AliasBound(i), result })
}
Err(NoSolution) => (),
}
}
}
}

27
compiler/rustc_trait_selection/src/solve/fulfill.rs
View File

@ -2,7 +2,7 @@ use std::mem;
use rustc_data_structures::fx::FxHashMap;
use rustc_infer::{
infer::{canonical::OriginalQueryValues, InferCtxt},
infer::InferCtxt,
traits::{
query::NoSolution, FulfillmentError, FulfillmentErrorCode, PredicateObligation,
SelectionError, TraitEngine,
@ -10,7 +10,7 @@ use rustc_infer::{
};
use rustc_middle::ty;
use super::{Certainty, EvalCtxt};
use super::{search_graph, Certainty, EvalCtxt};
/// A trait engine using the new trait solver.
///
@ -68,25 +68,10 @@ impl<'tcx> TraitEngine<'tcx> for FulfillmentCtxt<'tcx> {
let mut has_changed = false;
for obligation in mem::take(&mut self.obligations) {
let goal = obligation.clone().into();
// FIXME: Add a better API for that '^^
let mut orig_values = OriginalQueryValues::default();
let canonical_goal = infcx.canonicalize_query(goal, &mut orig_values);
let (changed, certainty) = match EvalCtxt::evaluate_canonical_goal(
infcx.tcx,
&mut super::search_graph::SearchGraph::new(infcx.tcx),
canonical_goal,
) {
Ok(canonical_response) => {
(
true, // FIXME: check whether `var_values` are an identity substitution.
super::instantiate_canonical_query_response(
infcx,
&orig_values,
canonical_response,
),
)
}
let search_graph = &mut search_graph::SearchGraph::new(infcx.tcx);
let mut ecx = EvalCtxt::new_outside_solver(infcx, search_graph);
let (changed, certainty) = match ecx.evaluate_goal(goal) {
Ok(result) => result,
Err(NoSolution) => {
errors.push(FulfillmentError {
obligation: obligation.clone(),

21
compiler/rustc_trait_selection/src/solve/mod.rs
View File

@ -155,6 +155,23 @@ struct EvalCtxt<'a, 'tcx> {
}
impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
fn tcx(&self) -> TyCtxt<'tcx> {
self.infcx.tcx
}
/// Creates a new evaluation context outside of the trait solver.
///
/// With this solver making a canonical response doesn't make much sense.
/// The `search_graph` for this solver has to be completely empty.
fn new_outside_solver(
infcx: &'a InferCtxt<'tcx>,
search_graph: &'a mut search_graph::SearchGraph<'tcx>,
) -> EvalCtxt<'a, 'tcx> {
assert!(search_graph.is_empty());
EvalCtxt { infcx, var_values: CanonicalVarValues::dummy(), search_graph }
}
#[instrument(level = "debug", skip(tcx, search_graph), ret)]
fn evaluate_canonical_goal(
tcx: TyCtxt<'tcx>,
search_graph: &'a mut search_graph::SearchGraph<'tcx>,
@ -183,10 +200,6 @@ impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
}
}
fn tcx(&self) -> TyCtxt<'tcx> {
self.infcx.tcx
}
fn make_canonical_response(&self, certainty: Certainty) -> QueryResult<'tcx> {
let external_constraints = take_external_constraints(self.infcx)?;

74
compiler/rustc_trait_selection/src/solve/project_goals.rs
View File

@ -1,7 +1,7 @@
use crate::traits::{specialization_graph, translate_substs};
use super::assembly::{self, AssemblyCtxt};
use super::{EvalCtxt, Goal, QueryResult};
use super::assembly::{self, Candidate, CandidateSource};
use super::{Certainty, EvalCtxt, Goal, QueryResult};
use rustc_errors::ErrorGuaranteed;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::DefId;
@ -16,22 +16,12 @@ use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_span::DUMMY_SP;
use std::iter;
#[allow(dead_code)] // FIXME: implement and use all variants.
#[derive(Debug, Clone, Copy)]
pub(super) enum CandidateSource {
Impl(DefId),
ParamEnv(usize),
Builtin,
}
type Candidate<'tcx> = assembly::Candidate<'tcx, ProjectionPredicate<'tcx>>;
impl<'tcx> EvalCtxt<'_, 'tcx> {
pub(super) fn compute_projection_goal(
&mut self,
goal: Goal<'tcx, ProjectionPredicate<'tcx>>,
) -> QueryResult<'tcx> {
let candidates = AssemblyCtxt::assemble_and_evaluate_candidates(self, goal);
let candidates = self.assemble_and_evaluate_candidates(goal);
self.merge_project_candidates(candidates)
}
@ -83,14 +73,13 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
match (candidate.source, other.source) {
(CandidateSource::Impl(_), _)
| (CandidateSource::ParamEnv(_), _)
| (CandidateSource::Builtin, _) => unimplemented!(),
| (CandidateSource::BuiltinImpl, _)
| (CandidateSource::AliasBound(_), _) => unimplemented!(),
}
}
}
impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
type CandidateSource = CandidateSource;
fn self_ty(self) -> Ty<'tcx> {
self.self_ty()
}
@ -104,12 +93,11 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
}
fn consider_impl_candidate(
acx: &mut AssemblyCtxt<'_, '_, 'tcx, ProjectionPredicate<'tcx>>,
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, ProjectionPredicate<'tcx>>,
impl_def_id: DefId,
) {
let tcx = acx.cx.tcx();
let infcx = acx.cx.infcx;
) -> Result<Certainty, NoSolution> {
let tcx = ecx.tcx();
let goal_trait_ref = goal.predicate.projection_ty.trait_ref(tcx);
let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
@ -117,20 +105,20 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
if iter::zip(goal_trait_ref.substs, impl_trait_ref.skip_binder().substs)
.any(|(goal, imp)| !drcx.generic_args_may_unify(goal, imp))
{
return;
return Err(NoSolution);
}
infcx.probe(|_| {
let impl_substs = infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
ecx.infcx.probe(|_| {
let impl_substs = ecx.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
let impl_trait_ref = impl_trait_ref.subst(tcx, impl_substs);
let Ok(InferOk { obligations, .. }) = infcx
let Ok(InferOk { obligations, .. }) = ecx.infcx
.at(&ObligationCause::dummy(), goal.param_env)
.define_opaque_types(false)
.eq(goal_trait_ref, impl_trait_ref)
.map_err(|e| debug!("failed to equate trait refs: {e:?}"))
else {
return
return Err(NoSolution)
};
let where_clause_bounds = tcx
.predicates_of(impl_def_id)
@ -141,16 +129,16 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
let nested_goals =
obligations.into_iter().map(|o| o.into()).chain(where_clause_bounds).collect();
let Ok(trait_ref_certainty) = acx.cx.evaluate_all(nested_goals) else { return };
let trait_ref_certainty = ecx.evaluate_all(nested_goals)?;
let Some(assoc_def) = fetch_eligible_assoc_item_def(
infcx,
ecx.infcx,
goal.param_env,
goal_trait_ref,
goal.predicate.def_id(),
impl_def_id
) else {
return
return Err(NoSolution);
};
if !assoc_def.item.defaultness(tcx).has_value() {
@ -176,7 +164,7 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
impl_substs,
);
let substs = translate_substs(
infcx,
ecx.infcx,
goal.param_env,
impl_def_id,
impl_substs_with_gat,
@ -197,22 +185,40 @@ impl<'tcx> assembly::GoalKind<'tcx> for ProjectionPredicate<'tcx> {
ty.map_bound(|ty| ty.into())
};
let Ok(InferOk { obligations, .. }) = infcx
let Ok(InferOk { obligations, .. }) = ecx.infcx
.at(&ObligationCause::dummy(), goal.param_env)
.define_opaque_types(false)
.eq(goal.predicate.term, term.subst(tcx, substs))
.map_err(|e| debug!("failed to equate trait refs: {e:?}"))
else {
return
return Err(NoSolution);
};
let nested_goals = obligations.into_iter().map(|o| o.into()).collect();
let Ok(rhs_certainty) = acx.cx.evaluate_all(nested_goals) else { return };
let rhs_certainty = ecx.evaluate_all(nested_goals)?;
let certainty = trait_ref_certainty.unify_and(rhs_certainty);
acx.try_insert_candidate(CandidateSource::Impl(impl_def_id), certainty);
Ok(trait_ref_certainty.unify_and(rhs_certainty))
})
}
fn consider_builtin_sized_candidate(
_ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, Self>,
) -> Result<Certainty, NoSolution> {
bug!("`Sized` does not have an associated type: {:?}", goal);
}
fn consider_assumption(
_ecx: &mut EvalCtxt<'_, 'tcx>,
_goal: Goal<'tcx, Self>,
assumption: ty::Predicate<'tcx>,
) -> Result<Certainty, NoSolution> {
if let Some(_poly_projection_pred) = assumption.to_opt_poly_projection_pred() {
unimplemented!()
} else {
Err(NoSolution)
}
}
}
/// This behavior is also implemented in `rustc_ty_utils` and in the old `project` code.

4
compiler/rustc_trait_selection/src/solve/search_graph/cache.rs
View File

@ -52,6 +52,10 @@ impl<'tcx> ProvisionalCache<'tcx> {
ProvisionalCache { entries: Default::default(), lookup_table: Default::default() }
}
pub(super) fn is_empty(&self) -> bool {
self.entries.is_empty() && self.lookup_table.is_empty()
}
/// Adds a dependency from the current leaf to `target` in the cache
/// to prevent us from moving any goals which depend on the current leaf
/// to the global cache while we're still computing `target`.

6
compiler/rustc_trait_selection/src/solve/search_graph/mod.rs
View File

@ -36,6 +36,12 @@ impl<'tcx> SearchGraph<'tcx> {
}
}
pub(super) fn is_empty(&self) -> bool {
self.stack.is_empty()
&& self.provisional_cache.is_empty()
&& !self.overflow_data.did_overflow()
}
/// Tries putting the new goal on the stack, returning an error if it is already cached.
///
/// This correctly updates the provisional cache if there is a cycle.

88
compiler/rustc_trait_selection/src/solve/trait_goals.rs
View File

@ -2,8 +2,8 @@
use std::iter;
use super::assembly::{self, AssemblyCtxt};
use super::{EvalCtxt, Goal, QueryResult};
use super::assembly::{self, Candidate, CandidateSource};
use super::{Certainty, EvalCtxt, Goal, QueryResult};
use rustc_hir::def_id::DefId;
use rustc_infer::infer::InferOk;
use rustc_infer::traits::query::NoSolution;
@ -13,47 +13,7 @@ use rustc_middle::ty::TraitPredicate;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_span::DUMMY_SP;
#[allow(dead_code)] // FIXME: implement and use all variants.
#[derive(Debug, Clone, Copy)]
pub(super) enum CandidateSource {
/// Some user-defined impl with the given `DefId`.
Impl(DefId),
/// The n-th caller bound in the `param_env` of our goal.
///
/// This is pretty much always a bound from the `where`-clauses of the
/// currently checked item.
ParamEnv(usize),
/// A bound on the `self_ty` in case it is a projection or an opaque type.
///
/// # Examples
///
/// ```ignore (for syntax highlighting)
/// trait Trait {
/// type Assoc: OtherTrait;
/// }
/// ```
///
/// We know that `<Whatever as Trait>::Assoc: OtherTrait` holds by looking at
/// the bounds on `Trait::Assoc`.
AliasBound(usize),
/// A builtin implementation for some specific traits, used in cases
/// where we cannot rely an ordinary library implementations.
///
/// The most notable examples are `Sized`, `Copy` and `Clone`. This is also
/// used for the `DiscriminantKind` and `Pointee` trait, both of which have
/// an associated type.
Builtin,
/// An automatic impl for an auto trait, e.g. `Send`. These impls recursively look
/// at the constituent types of the `self_ty` to check whether the auto trait
/// is implemented for those.
AutoImpl,
}
type Candidate<'tcx> = assembly::Candidate<'tcx, TraitPredicate<'tcx>>;
impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
type CandidateSource = CandidateSource;
fn self_ty(self) -> Ty<'tcx> {
self.self_ty()
}
@ -67,32 +27,31 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
}
fn consider_impl_candidate(
acx: &mut AssemblyCtxt<'_, '_, 'tcx, Self>,
ecx: &mut EvalCtxt<'_, 'tcx>,
goal: Goal<'tcx, TraitPredicate<'tcx>>,
impl_def_id: DefId,
) {
let tcx = acx.cx.tcx();
let infcx = acx.cx.infcx;
) -> Result<Certainty, NoSolution> {
let tcx = ecx.tcx();
let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsPlaceholder };
if iter::zip(goal.predicate.trait_ref.substs, impl_trait_ref.skip_binder().substs)
.any(|(goal, imp)| !drcx.generic_args_may_unify(goal, imp))
{
return;
return Err(NoSolution);
}
infcx.probe(|_| {
let impl_substs = infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
ecx.infcx.probe(|_| {
let impl_substs = ecx.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
let impl_trait_ref = impl_trait_ref.subst(tcx, impl_substs);
let Ok(InferOk { obligations, .. }) = infcx
let Ok(InferOk { obligations, .. }) = ecx.infcx
.at(&ObligationCause::dummy(), goal.param_env)
.define_opaque_types(false)
.eq(goal.predicate.trait_ref, impl_trait_ref)
.map_err(|e| debug!("failed to equate trait refs: {e:?}"))
else {
return
return Err(NoSolution);
};
let where_clause_bounds = tcx
.predicates_of(impl_def_id)
@ -104,10 +63,28 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
let nested_goals =
obligations.into_iter().map(|o| o.into()).chain(where_clause_bounds).collect();
let Ok(certainty) = acx.cx.evaluate_all(nested_goals) else { return };
acx.try_insert_candidate(CandidateSource::Impl(impl_def_id), certainty);
ecx.evaluate_all(nested_goals)
})
}
fn consider_builtin_sized_candidate(
_ecx: &mut EvalCtxt<'_, 'tcx>,
_goal: Goal<'tcx, Self>,
) -> Result<Certainty, NoSolution> {
unimplemented!();
}
fn consider_assumption(
_ecx: &mut EvalCtxt<'_, 'tcx>,
_goal: Goal<'tcx, Self>,
assumption: ty::Predicate<'tcx>,
) -> Result<Certainty, NoSolution> {
if let Some(_poly_trait_pred) = assumption.to_opt_poly_trait_pred() {
unimplemented!()
} else {
Err(NoSolution)
}
}
}
impl<'tcx> EvalCtxt<'_, 'tcx> {
@ -115,7 +92,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
&mut self,
goal: Goal<'tcx, TraitPredicate<'tcx>>,
) -> QueryResult<'tcx> {
let candidates = AssemblyCtxt::assemble_and_evaluate_candidates(self, goal);
let candidates = self.assemble_and_evaluate_candidates(goal);
self.merge_trait_candidates_discard_reservation_impls(candidates)
}
@ -169,8 +146,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
(CandidateSource::Impl(_), _)
| (CandidateSource::ParamEnv(_), _)
| (CandidateSource::AliasBound(_), _)
| (CandidateSource::Builtin, _)
| (CandidateSource::AutoImpl, _) => unimplemented!(),
| (CandidateSource::BuiltinImpl, _) => unimplemented!(),
}
}