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|
//! Defines a Chalk-based `TraitEngine`
use crate::infer::canonical::OriginalQueryValues;
use crate::infer::InferCtxt;
use crate::traits::query::NoSolution;
use crate::traits::{
ChalkEnvironmentAndGoal, FulfillmentError, FulfillmentErrorCode, PredicateObligation,
SelectionError, TraitEngine,
};
use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
use rustc_middle::ty::{self, TypeVisitable};
pub struct FulfillmentContext<'tcx> {
obligations: FxIndexSet<PredicateObligation<'tcx>>,
relationships: FxHashMap<ty::TyVid, ty::FoundRelationships>,
usable_in_snapshot: bool,
}
impl FulfillmentContext<'_> {
pub(super) fn new() -> Self {
FulfillmentContext {
obligations: FxIndexSet::default(),
relationships: FxHashMap::default(),
usable_in_snapshot: false,
}
}
pub(crate) fn new_in_snapshot() -> Self {
FulfillmentContext { usable_in_snapshot: true, ..Self::new() }
}
}
impl<'tcx> TraitEngine<'tcx> for FulfillmentContext<'tcx> {
fn register_predicate_obligation(
&mut self,
infcx: &InferCtxt<'tcx>,
obligation: PredicateObligation<'tcx>,
) {
if !self.usable_in_snapshot {
assert!(!infcx.is_in_snapshot());
}
let obligation = infcx.resolve_vars_if_possible(obligation);
super::relationships::update(self, infcx, &obligation);
self.obligations.insert(obligation);
}
fn select_all_or_error(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>> {
{
let errors = self.select_where_possible(infcx);
if !errors.is_empty() {
return errors;
}
}
// any remaining obligations are errors
self.obligations
.iter()
.map(|obligation| FulfillmentError {
obligation: obligation.clone(),
code: FulfillmentErrorCode::CodeAmbiguity,
// FIXME - does Chalk have a notation of 'root obligation'?
// This is just for diagnostics, so it's okay if this is wrong
root_obligation: obligation.clone(),
})
.collect()
}
fn select_where_possible(&mut self, infcx: &InferCtxt<'tcx>) -> Vec<FulfillmentError<'tcx>> {
if !self.usable_in_snapshot {
assert!(!infcx.is_in_snapshot());
}
let mut errors = Vec::new();
let mut next_round = FxIndexSet::default();
let mut making_progress;
loop {
making_progress = false;
// We iterate over all obligations, and record if we are able
// to unambiguously prove at least one obligation.
for obligation in self.obligations.drain(..) {
let obligation = infcx.resolve_vars_if_possible(obligation);
let environment = obligation.param_env.caller_bounds();
let goal = ChalkEnvironmentAndGoal { environment, goal: obligation.predicate };
let mut orig_values = OriginalQueryValues::default();
if goal.references_error() {
continue;
}
let canonical_goal =
infcx.canonicalize_query_preserving_universes(goal, &mut orig_values);
match infcx.tcx.evaluate_goal(canonical_goal) {
Ok(response) => {
if response.is_proven() {
making_progress = true;
match infcx.instantiate_query_response_and_region_obligations(
&obligation.cause,
obligation.param_env,
&orig_values,
&response,
) {
Ok(infer_ok) => next_round.extend(
infer_ok.obligations.into_iter().map(|obligation| {
assert!(!infcx.is_in_snapshot());
infcx.resolve_vars_if_possible(obligation)
}),
),
Err(_err) => errors.push(FulfillmentError {
obligation: obligation.clone(),
code: FulfillmentErrorCode::CodeSelectionError(
SelectionError::Unimplemented,
),
// FIXME - does Chalk have a notation of 'root obligation'?
// This is just for diagnostics, so it's okay if this is wrong
root_obligation: obligation,
}),
}
} else {
// Ambiguous: retry at next round.
next_round.insert(obligation);
}
}
Err(NoSolution) => errors.push(FulfillmentError {
obligation: obligation.clone(),
code: FulfillmentErrorCode::CodeSelectionError(
SelectionError::Unimplemented,
),
// FIXME - does Chalk have a notation of 'root obligation'?
// This is just for diagnostics, so it's okay if this is wrong
root_obligation: obligation,
}),
}
}
next_round = std::mem::replace(&mut self.obligations, next_round);
if !making_progress {
break;
}
}
errors
}
fn pending_obligations(&self) -> Vec<PredicateObligation<'tcx>> {
self.obligations.iter().cloned().collect()
}
fn relationships(&mut self) -> &mut FxHashMap<ty::TyVid, ty::FoundRelationships> {
&mut self.relationships
}
}
|
