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Revert "Auto merge of #91491 - spastorino:revert-91354, r=oli-obk"

Browse source 
This reverts commit ff2439b7b9, reversing
changes made to 2a9e0831d6.
This commit is contained in:
Deadbeef 2021-12-12 12:34:46 +08:00
parent c5f8788d8d
commit 84b1d859c8
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GPG key ID: 6D017A96D8E6C2F9
49 changed files with 400 additions and 424 deletions
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236
compiler/rustc_trait_selection/src/traits/select/mod.rs
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@ -39,7 +39,6 @@ use rustc_middle::ty::fast_reject;
use rustc_middle::ty::print::with_no_trimmed_paths;
use rustc_middle::ty::relate::TypeRelation;
use rustc_middle::ty::subst::{GenericArgKind, Subst, SubstsRef};
use rustc_middle::ty::WithConstness;
use rustc_middle::ty::{self, PolyProjectionPredicate, ToPolyTraitRef, ToPredicate};
use rustc_middle::ty::{Ty, TyCtxt, TypeFoldable};
use rustc_span::symbol::sym;
@ -128,9 +127,6 @@ pub struct SelectionContext<'cx, 'tcx> {
/// and a negative impl
allow_negative_impls: bool,
/// Are we in a const context that needs `~const` bounds to be const?
is_in_const_context: bool,
/// The mode that trait queries run in, which informs our error handling
/// policy. In essence, canonicalized queries need their errors propagated
/// rather than immediately reported because we do not have accurate spans.
@ -141,9 +137,9 @@ pub struct SelectionContext<'cx, 'tcx> {
struct TraitObligationStack<'prev, 'tcx> {
obligation: &'prev TraitObligation<'tcx>,
/// The trait ref from `obligation` but "freshened" with the
/// The trait predicate from `obligation` but "freshened" with the
/// selection-context's freshener. Used to check for recursion.
fresh_trait_ref: ty::ConstnessAnd<ty::PolyTraitRef<'tcx>>,
fresh_trait_pred: ty::PolyTraitPredicate<'tcx>,
/// Starts out equal to `depth` -- if, during evaluation, we
/// encounter a cycle, then we will set this flag to the minimum
@ -222,7 +218,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
is_in_const_context: false,
query_mode: TraitQueryMode::Standard,
}
}
@ -234,7 +229,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: true,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
is_in_const_context: false,
query_mode: TraitQueryMode::Standard,
}
}
@ -250,7 +244,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls,
is_in_const_context: false,
query_mode: TraitQueryMode::Standard,
}
}
@ -266,26 +259,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
is_in_const_context: false,
query_mode,
}
}
pub fn with_constness(
infcx: &'cx InferCtxt<'cx, 'tcx>,
constness: hir::Constness,
) -> SelectionContext<'cx, 'tcx> {
SelectionContext {
infcx,
freshener: infcx.freshener_keep_static(),
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
is_in_const_context: matches!(constness, hir::Constness::Const),
query_mode: TraitQueryMode::Standard,
}
}
/// Enables tracking of intercrate ambiguity causes. These are
/// used in coherence to give improved diagnostics. We don't do
/// this until we detect a coherence error because it can lead to
@ -318,20 +295,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
self.intercrate
}
/// Returns `true` if the trait predicate is considerd `const` to this selection context.
pub fn is_trait_predicate_const(&self, pred: ty::TraitPredicate<'_>) -> bool {
matches!(pred.constness, ty::BoundConstness::ConstIfConst) && self.is_in_const_context
}
/// Returns `true` if the predicate is considered `const` to
/// this selection context.
pub fn is_predicate_const(&self, pred: ty::Predicate<'_>) -> bool {
match pred.kind().skip_binder() {
ty::PredicateKind::Trait(pred) => self.is_trait_predicate_const(pred),
_ => false,
}
}
///////////////////////////////////////////////////////////////////////////
// Selection
//
@ -716,20 +679,22 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}
let stack = self.push_stack(previous_stack, &obligation);
let fresh_trait_ref = stack.fresh_trait_ref;
let mut fresh_trait_pred = stack.fresh_trait_pred;
let mut param_env = obligation.param_env;
debug!(?fresh_trait_ref);
fresh_trait_pred = fresh_trait_pred.map_bound(|mut pred| {
param_env = param_env.with_constness(pred.constness.and(param_env.constness()));
pred
});
if let Some(result) = self.check_evaluation_cache(
obligation.param_env,
fresh_trait_ref,
obligation.polarity(),
) {
debug!(?fresh_trait_pred);
if let Some(result) = self.check_evaluation_cache(param_env, fresh_trait_pred) {
debug!(?result, "CACHE HIT");
return Ok(result);
}
if let Some(result) = stack.cache().get_provisional(fresh_trait_ref) {
if let Some(result) = stack.cache().get_provisional(fresh_trait_pred) {
debug!(?result, "PROVISIONAL CACHE HIT");
stack.update_reached_depth(result.reached_depth);
return Ok(result.result);
@ -754,19 +719,12 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let reached_depth = stack.reached_depth.get();
if reached_depth >= stack.depth {
debug!(?result, "CACHE MISS");
self.insert_evaluation_cache(
obligation.param_env,
fresh_trait_ref,
obligation.polarity(),
dep_node,
result,
);
self.insert_evaluation_cache(param_env, fresh_trait_pred, dep_node, result);
stack.cache().on_completion(stack.dfn, |fresh_trait_ref, provisional_result| {
stack.cache().on_completion(stack.dfn, |fresh_trait_pred, provisional_result| {
self.insert_evaluation_cache(
obligation.param_env,
fresh_trait_ref,
obligation.polarity(),
param_env,
fresh_trait_pred,
dep_node,
provisional_result.max(result),
);
@ -776,10 +734,10 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
debug!(
"caching provisionally because {:?} \
is a cycle participant (at depth {}, reached depth {})",
fresh_trait_ref, stack.depth, reached_depth,
fresh_trait_pred, stack.depth, reached_depth,
);
stack.cache().insert_provisional(stack.dfn, reached_depth, fresh_trait_ref, result);
stack.cache().insert_provisional(stack.dfn, reached_depth, fresh_trait_pred, result);
}
Ok(result)
@ -813,7 +771,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
.skip(1) // Skip top-most frame.
.find(|prev| {
stack.obligation.param_env == prev.obligation.param_env
&& stack.fresh_trait_ref == prev.fresh_trait_ref
&& stack.fresh_trait_pred == prev.fresh_trait_pred
})
.map(|stack| stack.depth)
{
@ -876,7 +834,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// terms of `Fn` etc, but we could probably make this more
// precise still.
let unbound_input_types =
stack.fresh_trait_ref.value.skip_binder().substs.types().any(|ty| ty.is_fresh());
stack.fresh_trait_pred.skip_binder().trait_ref.substs.types().any(|ty| ty.is_fresh());
if stack.obligation.polarity() != ty::ImplPolarity::Negative {
// This check was an imperfect workaround for a bug in the old
@ -914,8 +872,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
&& stack.iter().skip(1).any(|prev| {
stack.obligation.param_env == prev.obligation.param_env
&& self.match_fresh_trait_refs(
stack.fresh_trait_ref,
prev.fresh_trait_ref,
stack.fresh_trait_pred,
prev.fresh_trait_pred,
prev.obligation.param_env,
)
})
@ -993,7 +951,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// not just the lifetime choice for this particular (non-erased)
// predicate.
// See issue #80691
if stack.fresh_trait_ref.has_erased_regions() {
if stack.fresh_trait_pred.has_erased_regions() {
result = result.max(EvaluatedToOkModuloRegions);
}
@ -1004,8 +962,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
fn check_evaluation_cache(
&self,
param_env: ty::ParamEnv<'tcx>,
trait_ref: ty::ConstnessAnd<ty::PolyTraitRef<'tcx>>,
polarity: ty::ImplPolarity,
trait_pred: ty::PolyTraitPredicate<'tcx>,
) -> Option<EvaluationResult> {
// Neither the global nor local cache is aware of intercrate
// mode, so don't do any caching. In particular, we might
@ -1017,19 +974,17 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
let tcx = self.tcx();
if self.can_use_global_caches(param_env) {
if let Some(res) = tcx.evaluation_cache.get(&(param_env.and(trait_ref), polarity), tcx)
{
if let Some(res) = tcx.evaluation_cache.get(&param_env.and(trait_pred), tcx) {
return Some(res);
}
}
self.infcx.evaluation_cache.get(&(param_env.and(trait_ref), polarity), tcx)
self.infcx.evaluation_cache.get(&param_env.and(trait_pred), tcx)
}
fn insert_evaluation_cache(
&mut self,
param_env: ty::ParamEnv<'tcx>,
trait_ref: ty::ConstnessAnd<ty::PolyTraitRef<'tcx>>,
polarity: ty::ImplPolarity,
trait_pred: ty::PolyTraitPredicate<'tcx>,
dep_node: DepNodeIndex,
result: EvaluationResult,
) {
@ -1048,23 +1003,19 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
}
if self.can_use_global_caches(param_env) {
if !trait_ref.needs_infer() {
debug!(?trait_ref, ?result, "insert_evaluation_cache global");
if !trait_pred.needs_infer() {
debug!(?trait_pred, ?result, "insert_evaluation_cache global");
// This may overwrite the cache with the same value
// FIXME: Due to #50507 this overwrites the different values
// This should be changed to use HashMapExt::insert_same
// when that is fixed
self.tcx().evaluation_cache.insert(
(param_env.and(trait_ref), polarity),
dep_node,
result,
);
self.tcx().evaluation_cache.insert(param_env.and(trait_pred), dep_node, result);
return;
}
}
debug!(?trait_ref, ?result, "insert_evaluation_cache");
self.infcx.evaluation_cache.insert((param_env.and(trait_ref), polarity), dep_node, result);
debug!(?trait_pred, ?result, "insert_evaluation_cache");
self.infcx.evaluation_cache.insert(param_env.and(trait_pred), dep_node, result);
}
/// For various reasons, it's possible for a subobligation
@ -1142,16 +1093,15 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
for candidate in candidates {
// Respect const trait obligations
if self.is_trait_predicate_const(obligation.predicate.skip_binder()) {
if obligation.is_const() {
match candidate {
// const impl
ImplCandidate(def_id)
if tcx.impl_constness(def_id) == hir::Constness::Const => {}
// const param
ParamCandidate((
ty::ConstnessAnd { constness: ty::BoundConstness::ConstIfConst, .. },
_,
)) => {}
ParamCandidate(trait_pred)
if trait_pred.skip_binder().constness
== ty::BoundConstness::ConstIfConst => {}
// auto trait impl
AutoImplCandidate(..) => {}
// generator, this will raise error in other places
@ -1260,7 +1210,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
fn check_candidate_cache(
&mut self,
param_env: ty::ParamEnv<'tcx>,
mut param_env: ty::ParamEnv<'tcx>,
cache_fresh_trait_pred: ty::PolyTraitPredicate<'tcx>,
) -> Option<SelectionResult<'tcx, SelectionCandidate<'tcx>>> {
// Neither the global nor local cache is aware of intercrate
@ -1271,19 +1221,15 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
return None;
}
let tcx = self.tcx();
let pred = &cache_fresh_trait_pred.skip_binder();
let trait_ref = pred.trait_ref;
let mut pred = cache_fresh_trait_pred.skip_binder();
param_env = param_env.with_constness(pred.constness.and(param_env.constness()));
if self.can_use_global_caches(param_env) {
if let Some(res) = tcx
.selection_cache
.get(&(param_env.and(trait_ref).with_constness(pred.constness), pred.polarity), tcx)
{
if let Some(res) = tcx.selection_cache.get(&param_env.and(pred), tcx) {
return Some(res);
}
}
self.infcx
.selection_cache
.get(&(param_env.and(trait_ref).with_constness(pred.constness), pred.polarity), tcx)
self.infcx.selection_cache.get(&param_env.and(pred), tcx)
}
/// Determines whether can we safely cache the result
@ -1321,43 +1267,36 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
fn insert_candidate_cache(
&mut self,
param_env: ty::ParamEnv<'tcx>,
mut param_env: ty::ParamEnv<'tcx>,
cache_fresh_trait_pred: ty::PolyTraitPredicate<'tcx>,
dep_node: DepNodeIndex,
candidate: SelectionResult<'tcx, SelectionCandidate<'tcx>>,
) {
let tcx = self.tcx();
let pred = cache_fresh_trait_pred.skip_binder();
let trait_ref = pred.trait_ref;
let mut pred = cache_fresh_trait_pred.skip_binder();
param_env = param_env.with_constness(pred.constness.and(param_env.constness()));
if !self.can_cache_candidate(&candidate) {
debug!(?trait_ref, ?candidate, "insert_candidate_cache - candidate is not cacheable");
debug!(?pred, ?candidate, "insert_candidate_cache - candidate is not cacheable");
return;
}
if self.can_use_global_caches(param_env) {
if let Err(Overflow) = candidate {
// Don't cache overflow globally; we only produce this in certain modes.
} else if !trait_ref.needs_infer() {
} else if !pred.needs_infer() {
if !candidate.needs_infer() {
debug!(?trait_ref, ?candidate, "insert_candidate_cache global");
debug!(?pred, ?candidate, "insert_candidate_cache global");
// This may overwrite the cache with the same value.
tcx.selection_cache.insert(
(param_env.and(trait_ref).with_constness(pred.constness), pred.polarity),
dep_node,
candidate,
);
tcx.selection_cache.insert(param_env.and(pred), dep_node, candidate);
return;
}
}
}
debug!(?trait_ref, ?candidate, "insert_candidate_cache local");
self.infcx.selection_cache.insert(
(param_env.and(trait_ref).with_constness(pred.constness), pred.polarity),
dep_node,
candidate,
);
debug!(?pred, ?candidate, "insert_candidate_cache local");
self.infcx.selection_cache.insert(param_env.and(pred), dep_node, candidate);
}
/// Matches a predicate against the bounds of its self type.
@ -1548,7 +1487,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// Check if a bound would previously have been removed when normalizing
// the param_env so that it can be given the lowest priority. See
// #50825 for the motivation for this.
let is_global = |cand: &ty::PolyTraitRef<'tcx>| {
let is_global = |cand: &ty::PolyTraitPredicate<'tcx>| {
cand.is_global(self.infcx.tcx) && !cand.has_late_bound_regions()
};
@ -1581,25 +1520,22 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
| ConstDropCandidate,
) => false,
(
ParamCandidate((other, other_polarity)),
ParamCandidate((victim, victim_polarity)),
) => {
let same_except_bound_vars = other.value.skip_binder()
== victim.value.skip_binder()
&& other.constness == victim.constness
&& other_polarity == victim_polarity
&& !other.value.skip_binder().has_escaping_bound_vars();
(ParamCandidate(other), ParamCandidate(victim)) => {
let same_except_bound_vars = other.skip_binder().trait_ref
== victim.skip_binder().trait_ref
&& other.skip_binder().constness == victim.skip_binder().constness
&& other.skip_binder().polarity == victim.skip_binder().polarity
&& !other.skip_binder().trait_ref.has_escaping_bound_vars();
if same_except_bound_vars {
// See issue #84398. In short, we can generate multiple ParamCandidates which are
// the same except for unused bound vars. Just pick the one with the fewest bound vars
// or the current one if tied (they should both evaluate to the same answer). This is
// probably best characterized as a "hack", since we might prefer to just do our
// best to *not* create essentially duplicate candidates in the first place.
other.value.bound_vars().len() <= victim.value.bound_vars().len()
} else if other.value == victim.value
&& victim.constness == ty::BoundConstness::NotConst
&& other_polarity == victim_polarity
other.bound_vars().len() <= victim.bound_vars().len()
} else if other.skip_binder().trait_ref == victim.skip_binder().trait_ref
&& victim.skip_binder().constness == ty::BoundConstness::NotConst
&& other.skip_binder().polarity == victim.skip_binder().polarity
{
// Drop otherwise equivalent non-const candidates in favor of const candidates.
true
@ -1629,11 +1565,11 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
| TraitAliasCandidate(..)
| ObjectCandidate(_)
| ProjectionCandidate(_),
) => !is_global(&cand.0.value),
) => !is_global(cand),
(ObjectCandidate(_) | ProjectionCandidate(_), ParamCandidate(ref cand)) => {
// Prefer these to a global where-clause bound
// (see issue #50825).
is_global(&cand.0.value)
is_global(cand)
}
(
ImplCandidate(_)
@ -1649,7 +1585,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
) => {
// Prefer these to a global where-clause bound
// (see issue #50825).
is_global(&cand.0.value) && other.evaluation.must_apply_modulo_regions()
is_global(cand) && other.evaluation.must_apply_modulo_regions()
}
(ProjectionCandidate(i), ProjectionCandidate(j))
@ -2209,8 +2145,8 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
fn match_fresh_trait_refs(
&self,
previous: ty::ConstnessAnd<ty::PolyTraitRef<'tcx>>,
current: ty::ConstnessAnd<ty::PolyTraitRef<'tcx>>,
previous: ty::PolyTraitPredicate<'tcx>,
current: ty::PolyTraitPredicate<'tcx>,
param_env: ty::ParamEnv<'tcx>,
) -> bool {
let mut matcher = ty::_match::Match::new(self.tcx(), param_env);
@ -2222,17 +2158,13 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
previous_stack: TraitObligationStackList<'o, 'tcx>,
obligation: &'o TraitObligation<'tcx>,
) -> TraitObligationStack<'o, 'tcx> {
let fresh_trait_ref = obligation
.predicate
.to_poly_trait_ref()
.fold_with(&mut self.freshener)
.with_constness(obligation.predicate.skip_binder().constness);
let fresh_trait_pred = obligation.predicate.fold_with(&mut self.freshener);
let dfn = previous_stack.cache.next_dfn();
let depth = previous_stack.depth() + 1;
TraitObligationStack {
obligation,
fresh_trait_ref,
fresh_trait_pred,
reached_depth: Cell::new(depth),
previous: previous_stack,
dfn,
@ -2426,7 +2358,7 @@ impl<'o, 'tcx> TraitObligationStack<'o, 'tcx> {
debug!(reached_depth, "update_reached_depth");
let mut p = self;
while reached_depth < p.depth {
debug!(?p.fresh_trait_ref, "update_reached_depth: marking as cycle participant");
debug!(?p.fresh_trait_pred, "update_reached_depth: marking as cycle participant");
p.reached_depth.set(p.reached_depth.get().min(reached_depth));
p = p.previous.head.unwrap();
}
@ -2505,7 +2437,7 @@ struct ProvisionalEvaluationCache<'tcx> {
/// - then we determine that `E` is in error -- we will then clear
/// all cache values whose DFN is >= 4 -- in this case, that
/// means the cached value for `F`.
map: RefCell<FxHashMap<ty::ConstnessAnd<ty::PolyTraitRef<'tcx>>, ProvisionalEvaluation>>,
map: RefCell<FxHashMap<ty::PolyTraitPredicate<'tcx>, ProvisionalEvaluation>>,
}
/// A cache value for the provisional cache: contains the depth-first
@ -2537,28 +2469,28 @@ impl<'tcx> ProvisionalEvaluationCache<'tcx> {
/// `reached_depth` (from the returned value).
fn get_provisional(
&self,
fresh_trait_ref: ty::ConstnessAnd<ty::PolyTraitRef<'tcx>>,
fresh_trait_pred: ty::PolyTraitPredicate<'tcx>,
) -> Option<ProvisionalEvaluation> {
debug!(
?fresh_trait_ref,
?fresh_trait_pred,
"get_provisional = {:#?}",
self.map.borrow().get(&fresh_trait_ref),
self.map.borrow().get(&fresh_trait_pred),
);
Some(*self.map.borrow().get(&fresh_trait_ref)?)
Some(*self.map.borrow().get(&fresh_trait_pred)?)
}
/// Insert a provisional result into the cache. The result came
/// from the node with the given DFN. It accessed a minimum depth
/// of `reached_depth` to compute. It evaluated `fresh_trait_ref`
/// of `reached_depth` to compute. It evaluated `fresh_trait_pred`
/// and resulted in `result`.
fn insert_provisional(
&self,
from_dfn: usize,
reached_depth: usize,
fresh_trait_ref: ty::ConstnessAnd<ty::PolyTraitRef<'tcx>>,
fresh_trait_pred: ty::PolyTraitPredicate<'tcx>,
result: EvaluationResult,
) {
debug!(?from_dfn, ?fresh_trait_ref, ?result, "insert_provisional");
debug!(?from_dfn, ?fresh_trait_pred, ?result, "insert_provisional");
let mut map = self.map.borrow_mut();
@ -2582,7 +2514,7 @@ impl<'tcx> ProvisionalEvaluationCache<'tcx> {
}
}
map.insert(fresh_trait_ref, ProvisionalEvaluation { from_dfn, reached_depth, result });
map.insert(fresh_trait_pred, ProvisionalEvaluation { from_dfn, reached_depth, result });
}
/// Invoked when the node with dfn `dfn` does not get a successful
@ -2633,16 +2565,16 @@ impl<'tcx> ProvisionalEvaluationCache<'tcx> {
fn on_completion(
&self,
dfn: usize,
mut op: impl FnMut(ty::ConstnessAnd<ty::PolyTraitRef<'tcx>>, EvaluationResult),
mut op: impl FnMut(ty::PolyTraitPredicate<'tcx>, EvaluationResult),
) {
debug!(?dfn, "on_completion");
for (fresh_trait_ref, eval) in
for (fresh_trait_pred, eval) in
self.map.borrow_mut().drain_filter(|_k, eval| eval.from_dfn >= dfn)
{
debug!(?fresh_trait_ref, ?eval, "on_completion");
debug!(?fresh_trait_pred, ?eval, "on_completion");
op(fresh_trait_ref, eval.result);
op(fresh_trait_pred, eval.result);
}
}
}