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instantiate canonical vars eagerly

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This commit is contained in:
lcnr 2023-01-17 10:21:30 +01:00
parent b738b06160
commit bf7dbff921
11 changed files with 509 additions and 496 deletions
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11
compiler/rustc_middle/src/ty/sty.rs
View File

@ -1106,17 +1106,6 @@ pub fn no_bound_vars(self) -> Option<T>
if self.0.has_escaping_bound_vars() { None } else { Some(self.skip_binder()) }
}
pub fn no_bound_vars_ignoring_escaping(self, tcx: TyCtxt<'tcx>) -> Option<T>
where
T: TypeFoldable<'tcx>,
{
if !self.0.has_escaping_bound_vars() {
Some(self.skip_binder())
} else {
self.0.try_fold_with(&mut SkipBindersAt { index: ty::INNERMOST, tcx }).ok()
}
}
/// Splits the contents into two things that share the same binder
/// level as the original, returning two distinct binders.
///

78
compiler/rustc_trait_selection/src/solve/assembly.rs
View File

@ -1,20 +1,11 @@
//! Code shared by trait and projection goals for candidate assembly.
use super::infcx_ext::InferCtxtExt;
use super::{
instantiate_canonical_query_response, CanonicalGoal, CanonicalResponse, Certainty, EvalCtxt,
Goal,
};
use super::{CanonicalResponse, Certainty, EvalCtxt, Goal};
use rustc_hir::def_id::DefId;
use rustc_infer::infer::TyCtxtInferExt;
use rustc_infer::infer::{
canonical::{CanonicalVarValues, OriginalQueryValues},
InferCtxt,
};
use rustc_infer::traits::query::NoSolution;
use rustc_middle::ty::TypeFoldable;
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_span::DUMMY_SP;
use std::fmt::Debug;
/// A candidate is a possible way to prove a goal.
@ -40,7 +31,7 @@ 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>,
acx: &mut AssemblyCtxt<'_, '_, 'tcx, Self>,
goal: Goal<'tcx, Self>,
impl_def_id: DefId,
);
@ -49,21 +40,17 @@ fn consider_impl_candidate(
/// 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, 'tcx, G: GoalKind<'tcx>> {
pub(super) cx: &'a mut EvalCtxt<'tcx>,
pub(super) infcx: &'a InferCtxt<'tcx>,
var_values: CanonicalVarValues<'tcx>,
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, 'tcx, G: GoalKind<'tcx>> AssemblyCtxt<'a, '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<'tcx>,
goal: CanonicalGoal<'tcx, G>,
cx: &'a mut EvalCtxt<'b, 'tcx>,
goal: Goal<'tcx, G>,
) -> Vec<Candidate<'tcx, G>> {
let (ref infcx, goal, var_values) =
cx.tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &goal);
let mut acx = AssemblyCtxt { cx, infcx, var_values, candidates: Vec::new() };
let mut acx = AssemblyCtxt { cx, candidates: Vec::new() };
acx.assemble_candidates_after_normalizing_self_ty(goal);
@ -77,7 +64,7 @@ pub(super) fn try_insert_candidate(
source: G::CandidateSource,
certainty: Certainty,
) {
match self.infcx.make_canonical_response(self.var_values.clone(), certainty) {
match self.cx.make_canonical_response(certainty) {
Ok(result) => self.candidates.push(Candidate { source, result }),
Err(NoSolution) => debug!(?source, ?certainty, "failed leakcheck"),
}
@ -89,13 +76,14 @@ pub(super) fn try_insert_candidate(
/// 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 tcx = self.cx.tcx();
let infcx = self.cx.infcx;
// 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
};
self.infcx.probe(|_| {
let normalized_ty = self.infcx.next_ty_infer();
infcx.probe(|_| {
let normalized_ty = infcx.next_ty_infer();
let normalizes_to_goal = goal.with(
tcx,
ty::Binder::dummy(ty::ProjectionPredicate {
@ -103,43 +91,31 @@ fn assemble_candidates_after_normalizing_self_ty(&mut self, goal: Goal<'tcx, G>)
term: normalized_ty.into(),
}),
);
let normalization_certainty =
match self.cx.evaluate_goal(&self.infcx, normalizes_to_goal) {
Ok((_, certainty)) => certainty,
Err(NoSolution) => return,
};
let normalization_certainty = match self.cx.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.
let goal = goal.with(tcx, goal.predicate.with_self_ty(tcx, normalized_ty));
let mut orig_values = OriginalQueryValues::default();
let goal = self.infcx.canonicalize_query(goal, &mut orig_values);
let normalized_candidates =
AssemblyCtxt::assemble_and_evaluate_candidates(self.cx, goal);
// Map each candidate from being canonical wrt the current inference context to being
// canonical wrt the caller.
for Candidate { source, result } in normalized_candidates {
self.infcx.probe(|_| {
let candidate_certainty =
instantiate_canonical_query_response(&self.infcx, &orig_values, result);
// FIXME: This is a bit scary if the `normalizes_to_goal` overflows.
//
// If we have an ambiguous candidate it hides that normalization
// caused an overflow which may cause issues.
self.try_insert_candidate(
source,
normalization_certainty.unify_and(candidate_certainty),
)
})
for mut normalized_candidate in normalized_candidates {
normalized_candidate.result =
normalized_candidate.result.unchecked_map(|mut response| {
response.certainty = response.certainty.unify_and(normalization_certainty);
response
});
self.candidates.push(normalized_candidate);
}
})
}
fn assemble_impl_candidates(&mut self, goal: Goal<'tcx, G>) {
self.cx.tcx.for_each_relevant_impl(
goal.predicate.trait_def_id(self.cx.tcx),
let tcx = self.cx.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),
);

267
compiler/rustc_trait_selection/src/solve/cache.rs
View File

@ -1,267 +0,0 @@
//! This module both handles the global cache which stores "finished" goals,
//! and the provisional cache which contains partially computed goals.
//!
//! The provisional cache is necessary when dealing with coinductive cycles.
//!
//! For more information about the provisional cache and coinduction in general,
//! check out the relevant section of the rustc-dev-guide.
//!
//! FIXME(@lcnr): Write that section, feel free to ping me if you need help here
//! before then or if I still haven't done that before January 2023.
use super::overflow::OverflowData;
use super::{CanonicalGoal, Certainty, MaybeCause, Response};
use super::{EvalCtxt, QueryResult};
use rustc_data_structures::fx::FxHashMap;
use rustc_index::vec::IndexVec;
use rustc_infer::infer::canonical::{Canonical, CanonicalVarKind, CanonicalVarValues};
use rustc_middle::ty::{self, TyCtxt};
use std::collections::hash_map::Entry;
rustc_index::newtype_index! {
pub struct StackDepth {}
}
rustc_index::newtype_index! {
pub struct EntryIndex {}
}
#[derive(Debug, Clone)]
struct ProvisionalEntry<'tcx> {
// In case we have a coinductive cycle, this is the
// the currently least restrictive result of this goal.
response: QueryResult<'tcx>,
// In case of a cycle, the depth of lowest stack entry involved
// in that cycle. This is monotonically decreasing in the stack as all
// elements between the current stack element in the lowest stack entry
// involved have to also be involved in that cycle.
//
// We can only move entries to the global cache once we're complete done
// with the cycle. If this entry has not been involved in a cycle,
// this is just its own depth.
depth: StackDepth,
// The goal for this entry. Should always be equal to the corresponding goal
// in the lookup table.
goal: CanonicalGoal<'tcx>,
}
struct StackElem<'tcx> {
goal: CanonicalGoal<'tcx>,
has_been_used: bool,
}
pub(super) struct ProvisionalCache<'tcx> {
stack: IndexVec<StackDepth, StackElem<'tcx>>,
entries: IndexVec<EntryIndex, ProvisionalEntry<'tcx>>,
// FIXME: This is only used to quickly check whether a given goal
// is in the cache. We should experiment with using something like
// `SsoHashSet` here because in most cases there are only a few entries.
lookup_table: FxHashMap<CanonicalGoal<'tcx>, EntryIndex>,
}
impl<'tcx> ProvisionalCache<'tcx> {
pub(super) fn empty() -> ProvisionalCache<'tcx> {
ProvisionalCache {
stack: Default::default(),
entries: Default::default(),
lookup_table: Default::default(),
}
}
pub(super) fn current_depth(&self) -> usize {
self.stack.len()
}
}
impl<'tcx> EvalCtxt<'tcx> {
/// 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.
pub(super) fn try_push_stack(
&mut self,
goal: CanonicalGoal<'tcx>,
) -> Result<(), QueryResult<'tcx>> {
// FIXME: start by checking the global cache
// Look at the provisional cache to check for cycles.
let cache = &mut self.provisional_cache;
match cache.lookup_table.entry(goal) {
// No entry, simply push this goal on the stack after dealing with overflow.
Entry::Vacant(v) => {
if self.overflow_data.has_overflow(cache.stack.len()) {
return Err(self.deal_with_overflow(goal));
}
let depth = cache.stack.push(StackElem { goal, has_been_used: false });
let response = response_no_constraints(self.tcx, goal, Certainty::Yes);
let entry_index = cache.entries.push(ProvisionalEntry { response, depth, goal });
v.insert(entry_index);
Ok(())
}
// We have a nested goal which relies on a goal `root` deeper in the stack.
//
// We first store that we may have to rerun `evaluate_goal` for `root` in case the
// provisional response is not equal to the final response. We also update the depth
// of all goals which recursively depend on our current goal to depend on `root`
// instead.
//
// Finally we can return either the provisional response for that goal if we have a
// coinductive cycle or an ambiguous result if the cycle is inductive.
Entry::Occupied(entry_index) => {
let entry_index = *entry_index.get();
// FIXME `ProvisionalEntry` should be `Copy`.
let entry = cache.entries.get(entry_index).unwrap().clone();
cache.stack[entry.depth].has_been_used = true;
for provisional_entry in cache.entries.iter_mut().skip(entry_index.index()) {
provisional_entry.depth = provisional_entry.depth.min(entry.depth);
}
// NOTE: The goals on the stack aren't the only goals involved in this cycle.
// We can also depend on goals which aren't part of the stack but coinductively
// depend on the stack themselves. We already checked whether all the goals
// between these goals and their root on the stack. This means that as long as
// each goal in a cycle is checked for coinductivity by itself, simply checking
// the stack is enough.
if cache.stack.raw[entry.depth.index()..]
.iter()
.all(|g| g.goal.value.predicate.is_coinductive(self.tcx))
{
Err(entry.response)
} else {
Err(response_no_constraints(
self.tcx,
goal,
Certainty::Maybe(MaybeCause::Overflow),
))
}
}
}
}
/// We cannot simply store the result of [EvalCtxt::compute_goal] as we have to deal with
/// coinductive cycles.
///
/// When we encounter a coinductive cycle, we have to prove the final result of that cycle
/// while we are still computing that result. Because of this we continously recompute the
/// cycle until the result of the previous iteration is equal to the final result, at which
/// point we are done.
///
/// This function returns `true` if we were able to finalize the goal and `false` if it has
/// updated the provisional cache and we have to recompute the current goal.
///
/// FIXME: Refer to the rustc-dev-guide entry once it exists.
pub(super) fn try_finalize_goal(
&mut self,
actual_goal: CanonicalGoal<'tcx>,
response: QueryResult<'tcx>,
) -> bool {
let cache = &mut self.provisional_cache;
let StackElem { goal, has_been_used } = cache.stack.pop().unwrap();
assert_eq!(goal, actual_goal);
let provisional_entry_index = *cache.lookup_table.get(&goal).unwrap();
let provisional_entry = &mut cache.entries[provisional_entry_index];
// Was the current goal the root of a cycle and was the provisional response
// different from the final one.
if has_been_used && provisional_entry.response != response {
// If so, update the provisional reponse for this goal...
provisional_entry.response = response;
// ...remove all entries whose result depends on this goal
// from the provisional cache...
//
// That's not completely correct, as a nested goal can also
// depend on a goal which is lower in the stack so it doesn't
// actually depend on the current goal. This should be fairly
// rare and is hopefully not relevant for performance.
#[allow(rustc::potential_query_instability)]
cache.lookup_table.retain(|_key, index| *index <= provisional_entry_index);
cache.entries.truncate(provisional_entry_index.index() + 1);
// ...and finally push our goal back on the stack and reevaluate it.
cache.stack.push(StackElem { goal, has_been_used: false });
false
} else {
// If not, we're done with this goal.
//
// Check whether that this goal doesn't depend on a goal deeper on the stack
// and if so, move it and all nested goals to the global cache.
//
// Note that if any nested goal were to depend on something deeper on the stack,
// this would have also updated the depth of this goal.
if provisional_entry.depth == cache.stack.next_index() {
for (i, entry) in cache.entries.drain_enumerated(provisional_entry_index.index()..)
{
let actual_index = cache.lookup_table.remove(&entry.goal);
debug_assert_eq!(Some(i), actual_index);
Self::try_move_finished_goal_to_global_cache(
self.tcx,
&mut self.overflow_data,
&cache.stack,
entry.goal,
entry.response,
);
}
}
true
}
}
fn try_move_finished_goal_to_global_cache(
tcx: TyCtxt<'tcx>,
overflow_data: &mut OverflowData,
stack: &IndexVec<StackDepth, StackElem<'tcx>>,
goal: CanonicalGoal<'tcx>,
response: QueryResult<'tcx>,
) {
// We move goals to the global cache if we either did not hit an overflow or if it's
// the root goal as that will now always hit the same overflow limit.
//
// NOTE: We cannot move any non-root goals to the global cache even if their final result
// isn't impacted by the overflow as that goal still has unstable query dependencies
// because it didn't go its full depth.
//
// FIXME(@lcnr): We could still cache subtrees which are not impacted by overflow though.
// Tracking that info correctly isn't trivial, so I haven't implemented it for now.
let should_cache_globally = !overflow_data.did_overflow() || stack.is_empty();
if should_cache_globally {
// FIXME: move the provisional entry to the global cache.
let _ = (tcx, goal, response);
}
}
}
pub(super) fn response_no_constraints<'tcx>(
tcx: TyCtxt<'tcx>,
goal: Canonical<'tcx, impl Sized>,
certainty: Certainty,
) -> QueryResult<'tcx> {
let var_values = goal
.variables
.iter()
.enumerate()
.map(|(i, info)| match info.kind {
CanonicalVarKind::Ty(_) | CanonicalVarKind::PlaceholderTy(_) => {
tcx.mk_ty(ty::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i).into())).into()
}
CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => {
let br = ty::BoundRegion {
var: ty::BoundVar::from_usize(i),
kind: ty::BrAnon(i as u32, None),
};
tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br)).into()
}
CanonicalVarKind::Const(_, ty) | CanonicalVarKind::PlaceholderConst(_, ty) => tcx
.mk_const(ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i)), ty)
.into(),
})
.collect();
Ok(Canonical {
max_universe: goal.max_universe,
variables: goal.variables,
value: Response {
var_values: CanonicalVarValues { var_values },
external_constraints: Default::default(),
certainty,
},
})
}

26
compiler/rustc_trait_selection/src/solve/fulfill.rs
View File

@ -2,7 +2,7 @@
use rustc_data_structures::fx::FxHashMap;
use rustc_infer::{
infer::InferCtxt,
infer::{canonical::OriginalQueryValues, InferCtxt},
traits::{
query::NoSolution, FulfillmentError, FulfillmentErrorCode, PredicateObligation,
SelectionError, TraitEngine,
@ -67,10 +67,26 @@ fn select_where_possible(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentE
let mut has_changed = false;
for obligation in mem::take(&mut self.obligations) {
let mut cx = EvalCtxt::new(infcx.tcx);
let (changed, certainty) = match cx.evaluate_goal(infcx, obligation.clone().into())
{
Ok(result) => result,
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,
),
)
}
Err(NoSolution) => {
errors.push(FulfillmentError {
obligation: obligation.clone(),

37
compiler/rustc_trait_selection/src/solve/infcx_ext.rs
View File

@ -1,23 +1,11 @@
use rustc_infer::infer::canonical::CanonicalVarValues;
use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use rustc_infer::infer::InferCtxt;
use rustc_infer::traits::query::NoSolution;
use rustc_middle::ty::Ty;
use rustc_span::DUMMY_SP;
use crate::solve::ExternalConstraints;
use super::{Certainty, QueryResult, Response};
/// Methods used inside of the canonical queries of the solver.
pub(super) trait InferCtxtExt<'tcx> {
fn next_ty_infer(&self) -> Ty<'tcx>;
fn make_canonical_response(
&self,
var_values: CanonicalVarValues<'tcx>,
certainty: Certainty,
) -> QueryResult<'tcx>;
}
impl<'tcx> InferCtxtExt<'tcx> for InferCtxt<'tcx> {
@ -27,29 +15,4 @@ fn next_ty_infer(&self) -> Ty<'tcx> {
span: DUMMY_SP,
})
}
fn make_canonical_response(
&self,
var_values: CanonicalVarValues<'tcx>,
certainty: Certainty,
) -> QueryResult<'tcx> {
let external_constraints = take_external_constraints(self)?;
Ok(self.canonicalize_response(Response { var_values, external_constraints, certainty }))
}
}
#[instrument(level = "debug", skip(infcx), ret)]
fn take_external_constraints<'tcx>(
infcx: &InferCtxt<'tcx>,
) -> Result<ExternalConstraints<'tcx>, NoSolution> {
let region_obligations = infcx.take_registered_region_obligations();
let opaque_types = infcx.take_opaque_types_for_query_response();
Ok(ExternalConstraints {
// FIXME: Now that's definitely wrong :)
//
// Should also do the leak check here I think
regions: drop(region_obligations),
opaque_types,
})
}

212
compiler/rustc_trait_selection/src/solve/mod.rs
View File

@ -19,27 +19,23 @@
use std::mem;
use rustc_infer::infer::canonical::{Canonical, CanonicalVarKind, CanonicalVarValues};
use rustc_infer::infer::canonical::{OriginalQueryValues, QueryRegionConstraints, QueryResponse};
use rustc_infer::infer::{InferCtxt, InferOk, TyCtxtInferExt};
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::Obligation;
use rustc_middle::infer::canonical::Certainty as OldCertainty;
use rustc_middle::infer::canonical::{Canonical, CanonicalVarValues};
use rustc_middle::ty::{self, Ty, TyCtxt};
use rustc_middle::ty::{RegionOutlivesPredicate, ToPredicate, TypeOutlivesPredicate};
use rustc_span::DUMMY_SP;
use crate::traits::ObligationCause;
use self::cache::response_no_constraints;
use self::infcx_ext::InferCtxtExt;
mod assembly;
mod cache;
mod fulfill;
mod infcx_ext;
mod overflow;
mod project_goals;
mod search_graph;
mod trait_goals;
pub use fulfill::FulfillmentCtxt;
@ -146,45 +142,25 @@ pub trait TyCtxtExt<'tcx> {
impl<'tcx> TyCtxtExt<'tcx> for TyCtxt<'tcx> {
fn evaluate_goal(self, goal: CanonicalGoal<'tcx>) -> QueryResult<'tcx> {
let mut cx = EvalCtxt::new(self);
cx.evaluate_canonical_goal(goal)
let mut search_graph = search_graph::SearchGraph::new(self);
EvalCtxt::evaluate_canonical_goal(self, &mut search_graph, goal)
}
}
struct EvalCtxt<'tcx> {
tcx: TyCtxt<'tcx>,
struct EvalCtxt<'a, 'tcx> {
infcx: &'a InferCtxt<'tcx>,
var_values: CanonicalVarValues<'tcx>,
provisional_cache: cache::ProvisionalCache<'tcx>,
overflow_data: overflow::OverflowData,
search_graph: &'a mut search_graph::SearchGraph<'tcx>,
}
impl<'tcx> EvalCtxt<'tcx> {
fn new(tcx: TyCtxt<'tcx>) -> EvalCtxt<'tcx> {
EvalCtxt {
tcx,
provisional_cache: cache::ProvisionalCache::empty(),
overflow_data: overflow::OverflowData::new(tcx),
}
}
/// Recursively evaluates `goal`, returning whether any inference vars have
/// been constrained and the certainty of the result.
fn evaluate_goal(
&mut self,
infcx: &InferCtxt<'tcx>,
goal: Goal<'tcx, ty::Predicate<'tcx>>,
) -> Result<(bool, Certainty), NoSolution> {
let mut orig_values = OriginalQueryValues::default();
let canonical_goal = infcx.canonicalize_query(goal, &mut orig_values);
let canonical_response = self.evaluate_canonical_goal(canonical_goal)?;
Ok((
!canonical_response.value.var_values.is_identity(),
instantiate_canonical_query_response(infcx, &orig_values, canonical_response),
))
}
fn evaluate_canonical_goal(&mut self, goal: CanonicalGoal<'tcx>) -> QueryResult<'tcx> {
match self.try_push_stack(goal) {
impl<'a, 'tcx> EvalCtxt<'a, 'tcx> {
fn evaluate_canonical_goal(
tcx: TyCtxt<'tcx>,
search_graph: &'a mut search_graph::SearchGraph<'tcx>,
canonical_goal: CanonicalGoal<'tcx>,
) -> QueryResult<'tcx> {
match search_graph.try_push_stack(tcx, canonical_goal) {
Ok(()) => {}
// Our goal is already on the stack, eager return.
Err(response) => return response,
@ -195,41 +171,65 @@ fn evaluate_canonical_goal(&mut self, goal: CanonicalGoal<'tcx>) -> QueryResult<
//
// FIXME: Similar to `evaluate_all`, this has to check for overflow.
loop {
let result = self.compute_goal(goal);
let (ref infcx, goal, var_values) =
tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical_goal);
let mut ecx = EvalCtxt { infcx, var_values, search_graph };
let result = ecx.compute_goal(goal);
// FIXME: `Response` should be `Copy`
if self.try_finalize_goal(goal, result.clone()) {
if search_graph.try_finalize_goal(tcx, canonical_goal, result.clone()) {
return result;
}
}
}
fn compute_goal(&mut self, canonical_goal: CanonicalGoal<'tcx>) -> QueryResult<'tcx> {
// WARNING: We're looking at a canonical value without instantiating it here.
//
// We have to be incredibly careful to not change the order of bound variables or
// remove any. As we go from `Goal<'tcx, Predicate>` to `Goal` with the variants
// of `PredicateKind` this is the case and it is and faster than instantiating and
// recanonicalizing.
let Goal { param_env, predicate } = canonical_goal.value;
fn tcx(&self) -> TyCtxt<'tcx> {
self.infcx.tcx
}
if let Some(kind) = predicate.kind().no_bound_vars_ignoring_escaping(self.tcx) {
fn make_canonical_response(&self, certainty: Certainty) -> QueryResult<'tcx> {
let external_constraints = take_external_constraints(self.infcx)?;
Ok(self.infcx.canonicalize_response(Response {
var_values: self.var_values.clone(),
external_constraints,
certainty,
}))
}
/// Recursively evaluates `goal`, returning whether any inference vars have
/// been constrained and the certainty of the result.
fn evaluate_goal(
&mut self,
goal: Goal<'tcx, ty::Predicate<'tcx>>,
) -> Result<(bool, Certainty), NoSolution> {
let mut orig_values = OriginalQueryValues::default();
let canonical_goal = self.infcx.canonicalize_query(goal, &mut orig_values);
let canonical_response =
EvalCtxt::evaluate_canonical_goal(self.tcx(), self.search_graph, canonical_goal)?;
Ok((
!canonical_response.value.var_values.is_identity(),
instantiate_canonical_query_response(self.infcx, &orig_values, canonical_response),
))
}
fn compute_goal(&mut self, goal: Goal<'tcx, ty::Predicate<'tcx>>) -> QueryResult<'tcx> {
let Goal { param_env, predicate } = goal;
let kind = predicate.kind();
if let Some(kind) = kind.no_bound_vars() {
match kind {
ty::PredicateKind::Clause(ty::Clause::Trait(predicate)) => self.compute_trait_goal(
canonical_goal.unchecked_rebind(Goal { param_env, predicate }),
),
ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) => self
.compute_projection_goal(
canonical_goal.unchecked_rebind(Goal { param_env, predicate }),
),
ty::PredicateKind::Clause(ty::Clause::TypeOutlives(predicate)) => self
.compute_type_outlives_goal(
canonical_goal.unchecked_rebind(Goal { param_env, predicate }),
),
ty::PredicateKind::Clause(ty::Clause::RegionOutlives(predicate)) => self
.compute_region_outlives_goal(
canonical_goal.unchecked_rebind(Goal { param_env, predicate }),
),
ty::PredicateKind::Clause(ty::Clause::Trait(predicate)) => {
self.compute_trait_goal(Goal { param_env, predicate })
}
ty::PredicateKind::Clause(ty::Clause::Projection(predicate)) => {
self.compute_projection_goal(Goal { param_env, predicate })
}
ty::PredicateKind::Clause(ty::Clause::TypeOutlives(predicate)) => {
self.compute_type_outlives_goal(Goal { param_env, predicate })
}
ty::PredicateKind::Clause(ty::Clause::RegionOutlives(predicate)) => {
self.compute_region_outlives_goal(Goal { param_env, predicate })
}
// FIXME: implement these predicates :)
ty::PredicateKind::WellFormed(_)
| ty::PredicateKind::ObjectSafe(_)
@ -239,49 +239,41 @@ fn compute_goal(&mut self, canonical_goal: CanonicalGoal<'tcx>) -> QueryResult<'
| ty::PredicateKind::ConstEvaluatable(_)
| ty::PredicateKind::ConstEquate(_, _)
| ty::PredicateKind::TypeWellFormedFromEnv(_)
| ty::PredicateKind::Ambiguous => {
// FIXME
response_no_constraints(self.tcx, canonical_goal, Certainty::Yes)
}
| ty::PredicateKind::Ambiguous => self.make_canonical_response(Certainty::Yes),
}
} else {
let (infcx, goal, var_values) =
self.tcx.infer_ctxt().build_with_canonical(DUMMY_SP, &canonical_goal);
let kind = infcx.replace_bound_vars_with_placeholders(goal.predicate.kind());
let goal = goal.with(self.tcx, ty::Binder::dummy(kind));
let (_, certainty) = self.evaluate_goal(&infcx, goal)?;
infcx.make_canonical_response(var_values, certainty)
let kind = self.infcx.replace_bound_vars_with_placeholders(kind);
let goal = goal.with(self.tcx(), ty::Binder::dummy(kind));
let (_, certainty) = self.evaluate_goal(goal)?;
self.make_canonical_response(certainty)
}
}
fn compute_type_outlives_goal(
&mut self,
goal: CanonicalGoal<'tcx, TypeOutlivesPredicate<'tcx>>,
_goal: Goal<'tcx, TypeOutlivesPredicate<'tcx>>,
) -> QueryResult<'tcx> {
// FIXME
response_no_constraints(self.tcx, goal, Certainty::Yes)
self.make_canonical_response(Certainty::Yes)
}
fn compute_region_outlives_goal(
&mut self,
goal: CanonicalGoal<'tcx, RegionOutlivesPredicate<'tcx>>,
_goal: Goal<'tcx, RegionOutlivesPredicate<'tcx>>,
) -> QueryResult<'tcx> {
// FIXME
response_no_constraints(self.tcx, goal, Certainty::Yes)
self.make_canonical_response(Certainty::Yes)
}
}
impl<'tcx> EvalCtxt<'tcx> {
impl<'tcx> EvalCtxt<'_, 'tcx> {
fn evaluate_all(
&mut self,
infcx: &InferCtxt<'tcx>,
mut goals: Vec<Goal<'tcx, ty::Predicate<'tcx>>>,
) -> Result<Certainty, NoSolution> {
let mut new_goals = Vec::new();
self.repeat_while_none(|this| {
let mut has_changed = Err(Certainty::Yes);
for goal in goals.drain(..) {
let (changed, certainty) = match this.evaluate_goal(infcx, goal) {
let (changed, certainty) = match this.evaluate_goal(goal) {
Ok(result) => result,
Err(NoSolution) => return Some(Err(NoSolution)),
};
@ -310,6 +302,21 @@ fn evaluate_all(
}
}
#[instrument(level = "debug", skip(infcx), ret)]
fn take_external_constraints<'tcx>(
infcx: &InferCtxt<'tcx>,
) -> Result<ExternalConstraints<'tcx>, NoSolution> {
let region_obligations = infcx.take_registered_region_obligations();
let opaque_types = infcx.take_opaque_types_for_query_response();
Ok(ExternalConstraints {
// FIXME: Now that's definitely wrong :)
//
// Should also do the leak check here I think
regions: drop(region_obligations),
opaque_types,
})
}
fn instantiate_canonical_query_response<'tcx>(
infcx: &InferCtxt<'tcx>,
original_values: &OriginalQueryValues<'tcx>,
@ -334,3 +341,40 @@ fn instantiate_canonical_query_response<'tcx>(
assert!(obligations.is_empty());
value
}
pub(super) fn response_no_constraints<'tcx>(
tcx: TyCtxt<'tcx>,
goal: Canonical<'tcx, impl Sized>,
certainty: Certainty,
) -> QueryResult<'tcx> {
let var_values = goal
.variables
.iter()
.enumerate()
.map(|(i, info)| match info.kind {
CanonicalVarKind::Ty(_) | CanonicalVarKind::PlaceholderTy(_) => {
tcx.mk_ty(ty::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i).into())).into()
}
CanonicalVarKind::Region(_) | CanonicalVarKind::PlaceholderRegion(_) => {
let br = ty::BoundRegion {
var: ty::BoundVar::from_usize(i),
kind: ty::BrAnon(i as u32, None),
};
tcx.mk_region(ty::ReLateBound(ty::INNERMOST, br)).into()
}
CanonicalVarKind::Const(_, ty) | CanonicalVarKind::PlaceholderConst(_, ty) => tcx
.mk_const(ty::ConstKind::Bound(ty::INNERMOST, ty::BoundVar::from_usize(i)), ty)
.into(),
})
.collect();
Ok(Canonical {
max_universe: goal.max_universe,
variables: goal.variables,
value: Response {
var_values: CanonicalVarValues { var_values },
external_constraints: Default::default(),
certainty,
},
})
}

36
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::{CanonicalGoal, EvalCtxt, Goal, QueryResult};
use super::{EvalCtxt, Goal, QueryResult};
use rustc_errors::ErrorGuaranteed;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::DefId;
@ -26,10 +26,10 @@ pub(super) enum CandidateSource {
type Candidate<'tcx> = assembly::Candidate<'tcx, ProjectionPredicate<'tcx>>;
impl<'tcx> EvalCtxt<'tcx> {
impl<'tcx> EvalCtxt<'_, 'tcx> {
pub(super) fn compute_projection_goal(
&mut self,
goal: CanonicalGoal<'tcx, ProjectionPredicate<'tcx>>,
goal: Goal<'tcx, ProjectionPredicate<'tcx>>,
) -> QueryResult<'tcx> {
let candidates = AssemblyCtxt::assemble_and_evaluate_candidates(self, goal);
self.merge_project_candidates(candidates)
@ -104,11 +104,13 @@ fn trait_def_id(self, tcx: TyCtxt<'tcx>) -> DefId {
}
fn consider_impl_candidate(
acx: &mut AssemblyCtxt<'_, 'tcx, ProjectionPredicate<'tcx>>,
acx: &mut AssemblyCtxt<'_, '_, 'tcx, ProjectionPredicate<'tcx>>,
goal: Goal<'tcx, ProjectionPredicate<'tcx>>,
impl_def_id: DefId,
) {
let tcx = acx.cx.tcx;
let tcx = acx.cx.tcx();
let infcx = acx.cx.infcx;
let goal_trait_ref = goal.predicate.projection_ty.trait_ref(tcx);
let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsPlaceholder };
@ -118,12 +120,11 @@ fn consider_impl_candidate(
return;
}
acx.infcx.probe(|_| {
let impl_substs = acx.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
infcx.probe(|_| {
let impl_substs = 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, .. }) = acx
.infcx
let Ok(InferOk { obligations, .. }) = infcx
.at(&ObligationCause::dummy(), goal.param_env)
.define_opaque_types(false)
.eq(goal_trait_ref, impl_trait_ref)
@ -138,11 +139,12 @@ fn consider_impl_candidate(
.into_iter()
.map(|pred| goal.with(tcx, pred));
let nested_goals = obligations.into_iter().map(|o| o.into()).chain(where_clause_bounds).collect();
let Ok(trait_ref_certainty) = acx.cx.evaluate_all(acx.infcx, nested_goals) else { return };
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 Some(assoc_def) = fetch_eligible_assoc_item_def(
acx.infcx,
infcx,
goal.param_env,
goal_trait_ref,
goal.predicate.def_id(),
@ -174,7 +176,7 @@ fn consider_impl_candidate(
impl_substs,
);
let substs = translate_substs(
acx.infcx,
infcx,
goal.param_env,
impl_def_id,
impl_substs_with_gat,
@ -185,7 +187,8 @@ fn consider_impl_candidate(
let is_const = matches!(tcx.def_kind(assoc_def.item.def_id), DefKind::AssocConst);
let ty = tcx.bound_type_of(assoc_def.item.def_id);
let term: ty::EarlyBinder<ty::Term<'tcx>> = if is_const {
let identity_substs = ty::InternalSubsts::identity_for_item(tcx, assoc_def.item.def_id);
let identity_substs =
ty::InternalSubsts::identity_for_item(tcx, assoc_def.item.def_id);
let did = ty::WithOptConstParam::unknown(assoc_def.item.def_id);
let kind =
ty::ConstKind::Unevaluated(ty::UnevaluatedConst::new(did, identity_substs));
@ -194,8 +197,7 @@ fn consider_impl_candidate(
ty.map_bound(|ty| ty.into())
};
let Ok(InferOk { obligations, .. }) = acx
.infcx
let Ok(InferOk { obligations, .. }) = infcx
.at(&ObligationCause::dummy(), goal.param_env)
.define_opaque_types(false)
.eq(goal.predicate.term, term.subst(tcx, substs))
@ -205,7 +207,7 @@ fn consider_impl_candidate(
};
let nested_goals = obligations.into_iter().map(|o| o.into()).collect();
let Ok(rhs_certainty) = acx.cx.evaluate_all(acx.infcx, nested_goals) else { return };
let Ok(rhs_certainty) = acx.cx.evaluate_all(nested_goals) else { return };
let certainty = trait_ref_certainty.unify_and(rhs_certainty);
acx.try_insert_candidate(CandidateSource::Impl(impl_def_id), certainty);

115
compiler/rustc_trait_selection/src/solve/search_graph/cache.rs Normal file
View File

@ -0,0 +1,115 @@
//! This module both handles the global cache which stores "finished" goals,
//! and the provisional cache which contains partially computed goals.
//!
//! The provisional cache is necessary when dealing with coinductive cycles.
//!
//! For more information about the provisional cache and coinduction in general,
//! check out the relevant section of the rustc-dev-guide.
//!
//! FIXME(@lcnr): Write that section, feel free to ping me if you need help here
//! before then or if I still haven't done that before January 2023.
use super::overflow::OverflowData;
use super::StackDepth;
use crate::solve::{CanonicalGoal, QueryResult};
use rustc_data_structures::fx::FxHashMap;
use rustc_index::vec::IndexVec;
use rustc_middle::ty::TyCtxt;
rustc_index::newtype_index! {
pub struct EntryIndex {}
}
#[derive(Debug, Clone)]
pub(super) struct ProvisionalEntry<'tcx> {
// In case we have a coinductive cycle, this is the
// the currently least restrictive result of this goal.
pub(super) response: QueryResult<'tcx>,
// In case of a cycle, the position of deepest stack entry involved
// in that cycle. This is monotonically decreasing in the stack as all
// elements between the current stack element in the deepest stack entry
// involved have to also be involved in that cycle.
//
// We can only move entries to the global cache once we're complete done
// with the cycle. If this entry has not been involved in a cycle,
// this is just its own depth.
pub(super) depth: StackDepth,
// The goal for this entry. Should always be equal to the corresponding goal
// in the lookup table.
pub(super) goal: CanonicalGoal<'tcx>,
}
pub(super) struct ProvisionalCache<'tcx> {
pub(super) entries: IndexVec<EntryIndex, ProvisionalEntry<'tcx>>,
// FIXME: This is only used to quickly check whether a given goal
// is in the cache. We should experiment with using something like
// `SsoHashSet` here because in most cases there are only a few entries.
pub(super) lookup_table: FxHashMap<CanonicalGoal<'tcx>, EntryIndex>,
}
impl<'tcx> ProvisionalCache<'tcx> {
pub(super) fn empty() -> ProvisionalCache<'tcx> {
ProvisionalCache { entries: Default::default(), lookup_table: Default::default() }
}
/// 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`.
pub(super) fn add_dependency_of_leaf_on(&mut self, target: EntryIndex) {
let depth = self.entries[target].depth;
for provisional_entry in &mut self.entries.raw[target.index()..] {
// The depth of `target` is the position of the deepest goal in the stack
// on which `target` depends. That goal is the `root` of this cycle.
//
// Any entry which was added after `target` is either on the stack itself
// at which point its depth is definitely at least as high as the depth of
// `root`. If it's not on the stack itself it has to depend on a goal
// between `root` and `leaf`. If it were to depend on a goal deeper in the
// stack than `root`, then `root` would also depend on that goal, at which
// point `root` wouldn't be the root anymore.
debug_assert!(provisional_entry.depth >= depth);
provisional_entry.depth = depth;
}
// We only update entries which were added after `target` as no other
// entry should have a higher depth.
//
// Any entry which previously had a higher depth than target has to
// be between `target` and `root`. Because of this we would have updated
// its depth when calling `add_dependency_of_leaf_on(root)` for `target`.
if cfg!(debug_assertions) {
self.entries.iter().all(|e| e.depth <= depth);
}
}
pub(super) fn depth(&self, entry_index: EntryIndex) -> StackDepth {
self.entries[entry_index].depth
}
pub(super) fn provisional_result(&self, entry_index: EntryIndex) -> QueryResult<'tcx> {
self.entries[entry_index].response.clone()
}
}
pub(super) fn try_move_finished_goal_to_global_cache<'tcx>(
tcx: TyCtxt<'tcx>,
overflow_data: &mut OverflowData,
stack: &IndexVec<super::StackDepth, super::StackElem<'tcx>>,
goal: CanonicalGoal<'tcx>,
response: QueryResult<'tcx>,
) {
// We move goals to the global cache if we either did not hit an overflow or if it's
// the root goal as that will now always hit the same overflow limit.
//
// NOTE: We cannot move any non-root goals to the global cache even if their final result
// isn't impacted by the overflow as that goal still has unstable query dependencies
// because it didn't go its full depth.
//
// FIXME(@lcnr): We could still cache subtrees which are not impacted by overflow though.
// Tracking that info correctly isn't trivial, so I haven't implemented it for now.
let should_cache_globally = !overflow_data.did_overflow() || stack.is_empty();
if should_cache_globally {
// FIXME: move the provisional entry to the global cache.
let _ = (tcx, goal, response);
}
}

172
compiler/rustc_trait_selection/src/solve/search_graph/mod.rs Normal file
View File

@ -0,0 +1,172 @@
mod cache;
mod overflow;
use self::cache::ProvisionalEntry;
use super::{CanonicalGoal, Certainty, MaybeCause, QueryResult};
use cache::ProvisionalCache;
use overflow::OverflowData;
use rustc_index::vec::IndexVec;
use rustc_middle::ty::TyCtxt;
use std::collections::hash_map::Entry;
rustc_index::newtype_index! {
pub struct StackDepth {}
}
struct StackElem<'tcx> {
goal: CanonicalGoal<'tcx>,
has_been_used: bool,
}
pub(super) struct SearchGraph<'tcx> {
/// The stack of goals currently being computed.
///
/// An element is *deeper* in the stack if its index is *lower*.
stack: IndexVec<StackDepth, StackElem<'tcx>>,
overflow_data: OverflowData,
provisional_cache: ProvisionalCache<'tcx>,
}
impl<'tcx> SearchGraph<'tcx> {
pub(super) fn new(tcx: TyCtxt<'tcx>) -> SearchGraph<'tcx> {
Self {
stack: Default::default(),
overflow_data: OverflowData::new(tcx),
provisional_cache: ProvisionalCache::empty(),
}
}
/// 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.
pub(super) fn try_push_stack(
&mut self,
tcx: TyCtxt<'tcx>,
goal: CanonicalGoal<'tcx>,
) -> Result<(), QueryResult<'tcx>> {
// FIXME: start by checking the global cache
// Look at the provisional cache to check for cycles.
let cache = &mut self.provisional_cache;
match cache.lookup_table.entry(goal) {
// No entry, simply push this goal on the stack after dealing with overflow.
Entry::Vacant(v) => {
if self.overflow_data.has_overflow(self.stack.len()) {
return Err(self.deal_with_overflow(tcx, goal));
}
let depth = self.stack.push(StackElem { goal, has_been_used: false });
let response = super::response_no_constraints(tcx, goal, Certainty::Yes);
let entry_index = cache.entries.push(ProvisionalEntry { response, depth, goal });
v.insert(entry_index);
Ok(())
}
// We have a nested goal which relies on a goal `root` deeper in the stack.
//
// We first store that we may have to rerun `evaluate_goal` for `root` in case the
// provisional response is not equal to the final response. We also update the depth
// of all goals which recursively depend on our current goal to depend on `root`
// instead.
//
// Finally we can return either the provisional response for that goal if we have a
// coinductive cycle or an ambiguous result if the cycle is inductive.
Entry::Occupied(entry_index) => {
let entry_index = *entry_index.get();
cache.add_dependency_of_leaf_on(entry_index);
let stack_depth = cache.depth(entry_index);
self.stack[stack_depth].has_been_used = true;
// NOTE: The goals on the stack aren't the only goals involved in this cycle.
// We can also depend on goals which aren't part of the stack but coinductively
// depend on the stack themselves. We already checked whether all the goals
// between these goals and their root on the stack. This means that as long as
// each goal in a cycle is checked for coinductivity by itself, simply checking
// the stack is enough.
if self.stack.raw[stack_depth.index()..]
.iter()
.all(|g| g.goal.value.predicate.is_coinductive(tcx))
{
Err(cache.provisional_result(entry_index))
} else {
Err(super::response_no_constraints(
tcx,
goal,
Certainty::Maybe(MaybeCause::Overflow),
))
}
}
}
}
/// We cannot simply store the result of [EvalCtxt::compute_goal] as we have to deal with
/// coinductive cycles.
///
/// When we encounter a coinductive cycle, we have to prove the final result of that cycle
/// while we are still computing that result. Because of this we continously recompute the
/// cycle until the result of the previous iteration is equal to the final result, at which
/// point we are done.
///
/// This function returns `true` if we were able to finalize the goal and `false` if it has
/// updated the provisional cache and we have to recompute the current goal.
///
/// FIXME: Refer to the rustc-dev-guide entry once it exists.
pub(super) fn try_finalize_goal(
&mut self,
tcx: TyCtxt<'tcx>,
actual_goal: CanonicalGoal<'tcx>,
response: QueryResult<'tcx>,
) -> bool {
let StackElem { goal, has_been_used } = self.stack.pop().unwrap();
assert_eq!(goal, actual_goal);
let cache = &mut self.provisional_cache;
let provisional_entry_index = *cache.lookup_table.get(&goal).unwrap();
let provisional_entry = &mut cache.entries[provisional_entry_index];
let depth = provisional_entry.depth;
// Was the current goal the root of a cycle and was the provisional response
// different from the final one.
if has_been_used && provisional_entry.response != response {
// If so, update the provisional reponse for this goal...
provisional_entry.response = response;
// ...remove all entries whose result depends on this goal
// from the provisional cache...
//
// That's not completely correct, as a nested goal can also
// depend on a goal which is lower in the stack so it doesn't
// actually depend on the current goal. This should be fairly
// rare and is hopefully not relevant for performance.
#[allow(rustc::potential_query_instability)]
cache.lookup_table.retain(|_key, index| *index <= provisional_entry_index);
cache.entries.truncate(provisional_entry_index.index() + 1);
// ...and finally push our goal back on the stack and reevaluate it.
self.stack.push(StackElem { goal, has_been_used: false });
false
} else {
// If not, we're done with this goal.
//
// Check whether that this goal doesn't depend on a goal deeper on the stack
// and if so, move it and all nested goals to the global cache.
//
// Note that if any nested goal were to depend on something deeper on the stack,
// this would have also updated the depth of the current goal.
if depth == self.stack.next_index() {
for (i, entry) in cache.entries.drain_enumerated(provisional_entry_index.index()..)
{
let actual_index = cache.lookup_table.remove(&entry.goal);
debug_assert_eq!(Some(i), actual_index);
debug_assert!(entry.depth == depth);
cache::try_move_finished_goal_to_global_cache(
tcx,
&mut self.overflow_data,
&self.stack,
entry.goal,
entry.response,
);
}
}
true
}
}
}

29
compiler/rustc_trait_selection/src/solve/overflow.rs → compiler/rustc_trait_selection/src/solve/search_graph/overflow.rs
View File

@ -3,8 +3,8 @@
use rustc_middle::ty::TyCtxt;
use rustc_session::Limit;
use super::cache::response_no_constraints;
use super::{Certainty, EvalCtxt, MaybeCause, QueryResult};
use super::SearchGraph;
use crate::solve::{response_no_constraints, Certainty, EvalCtxt, MaybeCause, QueryResult};
/// When detecting a solver overflow, we return ambiguity. Overflow can be
/// *hidden* by either a fatal error in an **AND** or a trivial success in an **OR**.
@ -50,32 +50,35 @@ fn deal_with_overflow(&mut self) {
}
}
impl<'tcx> EvalCtxt<'tcx> {
pub(super) fn deal_with_overflow(
impl<'tcx> SearchGraph<'tcx> {
pub fn deal_with_overflow(
&mut self,
tcx: TyCtxt<'tcx>,
goal: Canonical<'tcx, impl Sized>,
) -> QueryResult<'tcx> {
self.overflow_data.deal_with_overflow();
response_no_constraints(self.tcx, goal, Certainty::Maybe(MaybeCause::Overflow))
response_no_constraints(tcx, goal, Certainty::Maybe(MaybeCause::Overflow))
}
}
impl<'tcx> EvalCtxt<'_, 'tcx> {
/// A `while`-loop which tracks overflow.
pub(super) fn repeat_while_none(
pub fn repeat_while_none(
&mut self,
mut loop_body: impl FnMut(&mut Self) -> Option<Result<Certainty, NoSolution>>,
) -> Result<Certainty, NoSolution> {
let start_depth = self.overflow_data.additional_depth;
let depth = self.provisional_cache.current_depth();
while !self.overflow_data.has_overflow(depth) {
let start_depth = self.search_graph.overflow_data.additional_depth;
let depth = self.search_graph.stack.len();
while !self.search_graph.overflow_data.has_overflow(depth) {
if let Some(result) = loop_body(self) {
self.overflow_data.additional_depth = start_depth;
self.search_graph.overflow_data.additional_depth = start_depth;
return result;
}
self.overflow_data.additional_depth += 1;
self.search_graph.overflow_data.additional_depth += 1;
}
self.overflow_data.additional_depth = start_depth;
self.overflow_data.deal_with_overflow();
self.search_graph.overflow_data.additional_depth = start_depth;
self.search_graph.overflow_data.deal_with_overflow();
Ok(Certainty::Maybe(MaybeCause::Overflow))
}
}

22
compiler/rustc_trait_selection/src/solve/trait_goals.rs
View File

@ -3,7 +3,7 @@
use std::iter;
use super::assembly::{self, AssemblyCtxt};
use super::{CanonicalGoal, EvalCtxt, Goal, QueryResult};
use super::{EvalCtxt, Goal, QueryResult};
use rustc_hir::def_id::DefId;
use rustc_infer::infer::InferOk;
use rustc_infer::traits::query::NoSolution;
@ -67,11 +67,12 @@ fn trait_def_id(self, _: TyCtxt<'tcx>) -> DefId {
}
fn consider_impl_candidate(
acx: &mut AssemblyCtxt<'_, 'tcx, Self>,
acx: &mut AssemblyCtxt<'_, '_, 'tcx, Self>,
goal: Goal<'tcx, TraitPredicate<'tcx>>,
impl_def_id: DefId,
) {
let tcx = acx.cx.tcx;
let tcx = acx.cx.tcx();
let infcx = acx.cx.infcx;
let impl_trait_ref = tcx.impl_trait_ref(impl_def_id).unwrap();
let drcx = DeepRejectCtxt { treat_obligation_params: TreatParams::AsPlaceholder };
@ -81,12 +82,11 @@ fn consider_impl_candidate(
return;
}
acx.infcx.probe(|_| {
let impl_substs = acx.infcx.fresh_substs_for_item(DUMMY_SP, impl_def_id);
infcx.probe(|_| {
let impl_substs = 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, .. }) = acx
.infcx
let Ok(InferOk { obligations, .. }) = infcx
.at(&ObligationCause::dummy(), goal.param_env)
.define_opaque_types(false)
.eq(goal.predicate.trait_ref, impl_trait_ref)
@ -104,16 +104,16 @@ fn consider_impl_candidate(
let nested_goals =
obligations.into_iter().map(|o| o.into()).chain(where_clause_bounds).collect();
let Ok(certainty) = acx.cx.evaluate_all(acx.infcx, nested_goals) else { return };
let Ok(certainty) = acx.cx.evaluate_all(nested_goals) else { return };
acx.try_insert_candidate(CandidateSource::Impl(impl_def_id), certainty);
})
}
}
impl<'tcx> EvalCtxt<'tcx> {
impl<'tcx> EvalCtxt<'_, 'tcx> {
pub(super) fn compute_trait_goal(
&mut self,
goal: CanonicalGoal<'tcx, TraitPredicate<'tcx>>,
goal: Goal<'tcx, TraitPredicate<'tcx>>,
) -> QueryResult<'tcx> {
let candidates = AssemblyCtxt::assemble_and_evaluate_candidates(self, goal);
self.merge_trait_candidates_discard_reservation_impls(candidates)
@ -176,7 +176,7 @@ fn trait_candidate_should_be_dropped_in_favor_of(
fn discard_reservation_impl(&self, candidate: Candidate<'tcx>) -> Candidate<'tcx> {
if let CandidateSource::Impl(def_id) = candidate.source {
if let ty::ImplPolarity::Reservation = self.tcx.impl_polarity(def_id) {
if let ty::ImplPolarity::Reservation = self.tcx().impl_polarity(def_id) {
debug!("Selected reservation impl");
// FIXME: reduce candidate to ambiguous
// FIXME: replace `var_values` with identity, yeet external constraints.