mirror of
https://github.com/rust-lang/rust.git
synced 2025-06-21 12:07:31 +00:00
780 lines
29 KiB
Rust
780 lines
29 KiB
Rust
//! See Rustc Dev Guide chapters on [trait-resolution] and [trait-specialization] for more info on
|
|
//! how this works.
|
|
//!
|
|
//! [trait-resolution]: https://rustc-dev-guide.rust-lang.org/traits/resolution.html
|
|
//! [trait-specialization]: https://rustc-dev-guide.rust-lang.org/traits/specialization.html
|
|
|
|
use std::fmt::Debug;
|
|
|
|
use rustc_data_structures::fx::{FxHashSet, FxIndexSet};
|
|
use rustc_errors::{Diag, EmissionGuarantee};
|
|
use rustc_hir::def::DefKind;
|
|
use rustc_hir::def_id::{CRATE_DEF_ID, DefId};
|
|
use rustc_infer::infer::{DefineOpaqueTypes, InferCtxt, TyCtxtInferExt};
|
|
use rustc_infer::traits::PredicateObligations;
|
|
use rustc_middle::bug;
|
|
use rustc_middle::traits::query::NoSolution;
|
|
use rustc_middle::traits::solve::{CandidateSource, Certainty, Goal};
|
|
use rustc_middle::traits::specialization_graph::OverlapMode;
|
|
use rustc_middle::ty::fast_reject::DeepRejectCtxt;
|
|
use rustc_middle::ty::{
|
|
self, Ty, TyCtxt, TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor, TypingMode,
|
|
};
|
|
pub use rustc_next_trait_solver::coherence::*;
|
|
use rustc_next_trait_solver::solve::SolverDelegateEvalExt;
|
|
use rustc_span::{DUMMY_SP, Span, sym};
|
|
use tracing::{debug, instrument, warn};
|
|
|
|
use super::ObligationCtxt;
|
|
use crate::error_reporting::traits::suggest_new_overflow_limit;
|
|
use crate::infer::InferOk;
|
|
use crate::solve::inspect::{InspectGoal, ProofTreeInferCtxtExt, ProofTreeVisitor};
|
|
use crate::solve::{SolverDelegate, deeply_normalize_for_diagnostics, inspect};
|
|
use crate::traits::query::evaluate_obligation::InferCtxtExt;
|
|
use crate::traits::select::IntercrateAmbiguityCause;
|
|
use crate::traits::{
|
|
FulfillmentErrorCode, NormalizeExt, Obligation, ObligationCause, PredicateObligation,
|
|
SelectionContext, SkipLeakCheck, util,
|
|
};
|
|
|
|
pub struct OverlapResult<'tcx> {
|
|
pub impl_header: ty::ImplHeader<'tcx>,
|
|
pub intercrate_ambiguity_causes: FxIndexSet<IntercrateAmbiguityCause<'tcx>>,
|
|
|
|
/// `true` if the overlap might've been permitted before the shift
|
|
/// to universes.
|
|
pub involves_placeholder: bool,
|
|
|
|
/// Used in the new solver to suggest increasing the recursion limit.
|
|
pub overflowing_predicates: Vec<ty::Predicate<'tcx>>,
|
|
}
|
|
|
|
pub fn add_placeholder_note<G: EmissionGuarantee>(err: &mut Diag<'_, G>) {
|
|
err.note(
|
|
"this behavior recently changed as a result of a bug fix; \
|
|
see rust-lang/rust#56105 for details",
|
|
);
|
|
}
|
|
|
|
pub(crate) fn suggest_increasing_recursion_limit<'tcx, G: EmissionGuarantee>(
|
|
tcx: TyCtxt<'tcx>,
|
|
err: &mut Diag<'_, G>,
|
|
overflowing_predicates: &[ty::Predicate<'tcx>],
|
|
) {
|
|
for pred in overflowing_predicates {
|
|
err.note(format!("overflow evaluating the requirement `{}`", pred));
|
|
}
|
|
|
|
suggest_new_overflow_limit(tcx, err);
|
|
}
|
|
|
|
#[derive(Debug, Clone, Copy)]
|
|
enum TrackAmbiguityCauses {
|
|
Yes,
|
|
No,
|
|
}
|
|
|
|
impl TrackAmbiguityCauses {
|
|
fn is_yes(self) -> bool {
|
|
match self {
|
|
TrackAmbiguityCauses::Yes => true,
|
|
TrackAmbiguityCauses::No => false,
|
|
}
|
|
}
|
|
}
|
|
|
|
/// If there are types that satisfy both impls, returns `Some`
|
|
/// with a suitably-freshened `ImplHeader` with those types
|
|
/// instantiated. Otherwise, returns `None`.
|
|
#[instrument(skip(tcx, skip_leak_check), level = "debug")]
|
|
pub fn overlapping_impls(
|
|
tcx: TyCtxt<'_>,
|
|
impl1_def_id: DefId,
|
|
impl2_def_id: DefId,
|
|
skip_leak_check: SkipLeakCheck,
|
|
overlap_mode: OverlapMode,
|
|
) -> Option<OverlapResult<'_>> {
|
|
// Before doing expensive operations like entering an inference context, do
|
|
// a quick check via fast_reject to tell if the impl headers could possibly
|
|
// unify.
|
|
let drcx = DeepRejectCtxt::relate_infer_infer(tcx);
|
|
let impl1_ref = tcx.impl_trait_ref(impl1_def_id);
|
|
let impl2_ref = tcx.impl_trait_ref(impl2_def_id);
|
|
let may_overlap = match (impl1_ref, impl2_ref) {
|
|
(Some(a), Some(b)) => drcx.args_may_unify(a.skip_binder().args, b.skip_binder().args),
|
|
(None, None) => {
|
|
let self_ty1 = tcx.type_of(impl1_def_id).skip_binder();
|
|
let self_ty2 = tcx.type_of(impl2_def_id).skip_binder();
|
|
drcx.types_may_unify(self_ty1, self_ty2)
|
|
}
|
|
_ => bug!("unexpected impls: {impl1_def_id:?} {impl2_def_id:?}"),
|
|
};
|
|
|
|
if !may_overlap {
|
|
// Some types involved are definitely different, so the impls couldn't possibly overlap.
|
|
debug!("overlapping_impls: fast_reject early-exit");
|
|
return None;
|
|
}
|
|
|
|
if tcx.next_trait_solver_in_coherence() {
|
|
overlap(
|
|
tcx,
|
|
TrackAmbiguityCauses::Yes,
|
|
skip_leak_check,
|
|
impl1_def_id,
|
|
impl2_def_id,
|
|
overlap_mode,
|
|
)
|
|
} else {
|
|
let _overlap_with_bad_diagnostics = overlap(
|
|
tcx,
|
|
TrackAmbiguityCauses::No,
|
|
skip_leak_check,
|
|
impl1_def_id,
|
|
impl2_def_id,
|
|
overlap_mode,
|
|
)?;
|
|
|
|
// In the case where we detect an error, run the check again, but
|
|
// this time tracking intercrate ambiguity causes for better
|
|
// diagnostics. (These take time and can lead to false errors.)
|
|
let overlap = overlap(
|
|
tcx,
|
|
TrackAmbiguityCauses::Yes,
|
|
skip_leak_check,
|
|
impl1_def_id,
|
|
impl2_def_id,
|
|
overlap_mode,
|
|
)
|
|
.unwrap();
|
|
Some(overlap)
|
|
}
|
|
}
|
|
|
|
fn fresh_impl_header<'tcx>(infcx: &InferCtxt<'tcx>, impl_def_id: DefId) -> ty::ImplHeader<'tcx> {
|
|
let tcx = infcx.tcx;
|
|
let impl_args = infcx.fresh_args_for_item(DUMMY_SP, impl_def_id);
|
|
|
|
ty::ImplHeader {
|
|
impl_def_id,
|
|
impl_args,
|
|
self_ty: tcx.type_of(impl_def_id).instantiate(tcx, impl_args),
|
|
trait_ref: tcx.impl_trait_ref(impl_def_id).map(|i| i.instantiate(tcx, impl_args)),
|
|
predicates: tcx
|
|
.predicates_of(impl_def_id)
|
|
.instantiate(tcx, impl_args)
|
|
.iter()
|
|
.map(|(c, _)| c.as_predicate())
|
|
.collect(),
|
|
}
|
|
}
|
|
|
|
fn fresh_impl_header_normalized<'tcx>(
|
|
infcx: &InferCtxt<'tcx>,
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
impl_def_id: DefId,
|
|
) -> ty::ImplHeader<'tcx> {
|
|
let header = fresh_impl_header(infcx, impl_def_id);
|
|
|
|
let InferOk { value: mut header, obligations } =
|
|
infcx.at(&ObligationCause::dummy(), param_env).normalize(header);
|
|
|
|
header.predicates.extend(obligations.into_iter().map(|o| o.predicate));
|
|
header
|
|
}
|
|
|
|
/// Can both impl `a` and impl `b` be satisfied by a common type (including
|
|
/// where-clauses)? If so, returns an `ImplHeader` that unifies the two impls.
|
|
#[instrument(level = "debug", skip(tcx))]
|
|
fn overlap<'tcx>(
|
|
tcx: TyCtxt<'tcx>,
|
|
track_ambiguity_causes: TrackAmbiguityCauses,
|
|
skip_leak_check: SkipLeakCheck,
|
|
impl1_def_id: DefId,
|
|
impl2_def_id: DefId,
|
|
overlap_mode: OverlapMode,
|
|
) -> Option<OverlapResult<'tcx>> {
|
|
if overlap_mode.use_negative_impl() {
|
|
if impl_intersection_has_negative_obligation(tcx, impl1_def_id, impl2_def_id)
|
|
|| impl_intersection_has_negative_obligation(tcx, impl2_def_id, impl1_def_id)
|
|
{
|
|
return None;
|
|
}
|
|
}
|
|
|
|
let infcx = tcx
|
|
.infer_ctxt()
|
|
.skip_leak_check(skip_leak_check.is_yes())
|
|
.with_next_trait_solver(tcx.next_trait_solver_in_coherence())
|
|
.build(TypingMode::Coherence);
|
|
let selcx = &mut SelectionContext::new(&infcx);
|
|
if track_ambiguity_causes.is_yes() {
|
|
selcx.enable_tracking_intercrate_ambiguity_causes();
|
|
}
|
|
|
|
// For the purposes of this check, we don't bring any placeholder
|
|
// types into scope; instead, we replace the generic types with
|
|
// fresh type variables, and hence we do our evaluations in an
|
|
// empty environment.
|
|
let param_env = ty::ParamEnv::empty();
|
|
|
|
let impl1_header = fresh_impl_header_normalized(selcx.infcx, param_env, impl1_def_id);
|
|
let impl2_header = fresh_impl_header_normalized(selcx.infcx, param_env, impl2_def_id);
|
|
|
|
// Equate the headers to find their intersection (the general type, with infer vars,
|
|
// that may apply both impls).
|
|
let mut obligations =
|
|
equate_impl_headers(selcx.infcx, param_env, &impl1_header, &impl2_header)?;
|
|
debug!("overlap: unification check succeeded");
|
|
|
|
obligations.extend(
|
|
[&impl1_header.predicates, &impl2_header.predicates].into_iter().flatten().map(
|
|
|&predicate| Obligation::new(infcx.tcx, ObligationCause::dummy(), param_env, predicate),
|
|
),
|
|
);
|
|
|
|
let mut overflowing_predicates = Vec::new();
|
|
if overlap_mode.use_implicit_negative() {
|
|
match impl_intersection_has_impossible_obligation(selcx, &obligations) {
|
|
IntersectionHasImpossibleObligations::Yes => return None,
|
|
IntersectionHasImpossibleObligations::No { overflowing_predicates: p } => {
|
|
overflowing_predicates = p
|
|
}
|
|
}
|
|
}
|
|
|
|
// We toggle the `leak_check` by using `skip_leak_check` when constructing the
|
|
// inference context, so this may be a noop.
|
|
if infcx.leak_check(ty::UniverseIndex::ROOT, None).is_err() {
|
|
debug!("overlap: leak check failed");
|
|
return None;
|
|
}
|
|
|
|
let intercrate_ambiguity_causes = if !overlap_mode.use_implicit_negative() {
|
|
Default::default()
|
|
} else if infcx.next_trait_solver() {
|
|
compute_intercrate_ambiguity_causes(&infcx, &obligations)
|
|
} else {
|
|
selcx.take_intercrate_ambiguity_causes()
|
|
};
|
|
|
|
debug!("overlap: intercrate_ambiguity_causes={:#?}", intercrate_ambiguity_causes);
|
|
let involves_placeholder = infcx
|
|
.inner
|
|
.borrow_mut()
|
|
.unwrap_region_constraints()
|
|
.data()
|
|
.constraints
|
|
.iter()
|
|
.any(|c| c.0.involves_placeholders());
|
|
|
|
let mut impl_header = infcx.resolve_vars_if_possible(impl1_header);
|
|
|
|
// Deeply normalize the impl header for diagnostics, ignoring any errors if this fails.
|
|
if infcx.next_trait_solver() {
|
|
impl_header = deeply_normalize_for_diagnostics(&infcx, param_env, impl_header);
|
|
}
|
|
|
|
Some(OverlapResult {
|
|
impl_header,
|
|
intercrate_ambiguity_causes,
|
|
involves_placeholder,
|
|
overflowing_predicates,
|
|
})
|
|
}
|
|
|
|
#[instrument(level = "debug", skip(infcx), ret)]
|
|
fn equate_impl_headers<'tcx>(
|
|
infcx: &InferCtxt<'tcx>,
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
impl1: &ty::ImplHeader<'tcx>,
|
|
impl2: &ty::ImplHeader<'tcx>,
|
|
) -> Option<PredicateObligations<'tcx>> {
|
|
let result =
|
|
match (impl1.trait_ref, impl2.trait_ref) {
|
|
(Some(impl1_ref), Some(impl2_ref)) => infcx
|
|
.at(&ObligationCause::dummy(), param_env)
|
|
.eq(DefineOpaqueTypes::Yes, impl1_ref, impl2_ref),
|
|
(None, None) => infcx.at(&ObligationCause::dummy(), param_env).eq(
|
|
DefineOpaqueTypes::Yes,
|
|
impl1.self_ty,
|
|
impl2.self_ty,
|
|
),
|
|
_ => bug!("equate_impl_headers given mismatched impl kinds"),
|
|
};
|
|
|
|
result.map(|infer_ok| infer_ok.obligations).ok()
|
|
}
|
|
|
|
/// The result of [fn impl_intersection_has_impossible_obligation].
|
|
#[derive(Debug)]
|
|
enum IntersectionHasImpossibleObligations<'tcx> {
|
|
Yes,
|
|
No {
|
|
/// With `-Znext-solver=coherence`, some obligations may
|
|
/// fail if only the user increased the recursion limit.
|
|
///
|
|
/// We return those obligations here and mention them in the
|
|
/// error message.
|
|
overflowing_predicates: Vec<ty::Predicate<'tcx>>,
|
|
},
|
|
}
|
|
|
|
/// Check if both impls can be satisfied by a common type by considering whether
|
|
/// any of either impl's obligations is not known to hold.
|
|
///
|
|
/// For example, given these two impls:
|
|
/// `impl From<MyLocalType> for Box<dyn Error>` (in my crate)
|
|
/// `impl<E> From<E> for Box<dyn Error> where E: Error` (in libstd)
|
|
///
|
|
/// After replacing both impl headers with inference vars (which happens before
|
|
/// this function is called), we get:
|
|
/// `Box<dyn Error>: From<MyLocalType>`
|
|
/// `Box<dyn Error>: From<?E>`
|
|
///
|
|
/// This gives us `?E = MyLocalType`. We then certainly know that `MyLocalType: Error`
|
|
/// never holds in intercrate mode since a local impl does not exist, and a
|
|
/// downstream impl cannot be added -- therefore can consider the intersection
|
|
/// of the two impls above to be empty.
|
|
///
|
|
/// Importantly, this works even if there isn't a `impl !Error for MyLocalType`.
|
|
#[instrument(level = "debug", skip(selcx), ret)]
|
|
fn impl_intersection_has_impossible_obligation<'a, 'cx, 'tcx>(
|
|
selcx: &mut SelectionContext<'cx, 'tcx>,
|
|
obligations: &'a [PredicateObligation<'tcx>],
|
|
) -> IntersectionHasImpossibleObligations<'tcx> {
|
|
let infcx = selcx.infcx;
|
|
|
|
if infcx.next_trait_solver() {
|
|
// A fast path optimization, try evaluating all goals with
|
|
// a very low recursion depth and bail if any of them don't
|
|
// hold.
|
|
if !obligations.iter().all(|o| {
|
|
<&SolverDelegate<'tcx>>::from(infcx)
|
|
.root_goal_may_hold_with_depth(8, Goal::new(infcx.tcx, o.param_env, o.predicate))
|
|
}) {
|
|
return IntersectionHasImpossibleObligations::Yes;
|
|
}
|
|
|
|
let ocx = ObligationCtxt::new_with_diagnostics(infcx);
|
|
ocx.register_obligations(obligations.iter().cloned());
|
|
let errors_and_ambiguities = ocx.select_all_or_error();
|
|
// We only care about the obligations that are *definitely* true errors.
|
|
// Ambiguities do not prove the disjointness of two impls.
|
|
let (errors, ambiguities): (Vec<_>, Vec<_>) =
|
|
errors_and_ambiguities.into_iter().partition(|error| error.is_true_error());
|
|
|
|
if errors.is_empty() {
|
|
IntersectionHasImpossibleObligations::No {
|
|
overflowing_predicates: ambiguities
|
|
.into_iter()
|
|
.filter(|error| {
|
|
matches!(
|
|
error.code,
|
|
FulfillmentErrorCode::Ambiguity { overflow: Some(true) }
|
|
)
|
|
})
|
|
.map(|e| infcx.resolve_vars_if_possible(e.obligation.predicate))
|
|
.collect(),
|
|
}
|
|
} else {
|
|
IntersectionHasImpossibleObligations::Yes
|
|
}
|
|
} else {
|
|
for obligation in obligations {
|
|
// We use `evaluate_root_obligation` to correctly track intercrate
|
|
// ambiguity clauses.
|
|
let evaluation_result = selcx.evaluate_root_obligation(obligation);
|
|
|
|
match evaluation_result {
|
|
Ok(result) => {
|
|
if !result.may_apply() {
|
|
return IntersectionHasImpossibleObligations::Yes;
|
|
}
|
|
}
|
|
// If overflow occurs, we need to conservatively treat the goal as possibly holding,
|
|
// since there can be instantiations of this goal that don't overflow and result in
|
|
// success. While this isn't much of a problem in the old solver, since we treat overflow
|
|
// fatally, this still can be encountered: <https://github.com/rust-lang/rust/issues/105231>.
|
|
Err(_overflow) => {}
|
|
}
|
|
}
|
|
|
|
IntersectionHasImpossibleObligations::No { overflowing_predicates: Vec::new() }
|
|
}
|
|
}
|
|
|
|
/// Check if both impls can be satisfied by a common type by considering whether
|
|
/// any of first impl's obligations is known not to hold *via a negative predicate*.
|
|
///
|
|
/// For example, given these two impls:
|
|
/// `struct MyCustomBox<T: ?Sized>(Box<T>);`
|
|
/// `impl From<&str> for MyCustomBox<dyn Error>` (in my crate)
|
|
/// `impl<E> From<E> for MyCustomBox<dyn Error> where E: Error` (in my crate)
|
|
///
|
|
/// After replacing the second impl's header with inference vars, we get:
|
|
/// `MyCustomBox<dyn Error>: From<&str>`
|
|
/// `MyCustomBox<dyn Error>: From<?E>`
|
|
///
|
|
/// This gives us `?E = &str`. We then try to prove the first impl's predicates
|
|
/// after negating, giving us `&str: !Error`. This is a negative impl provided by
|
|
/// libstd, and therefore we can guarantee for certain that libstd will never add
|
|
/// a positive impl for `&str: Error` (without it being a breaking change).
|
|
fn impl_intersection_has_negative_obligation(
|
|
tcx: TyCtxt<'_>,
|
|
impl1_def_id: DefId,
|
|
impl2_def_id: DefId,
|
|
) -> bool {
|
|
debug!("negative_impl(impl1_def_id={:?}, impl2_def_id={:?})", impl1_def_id, impl2_def_id);
|
|
|
|
// N.B. We need to unify impl headers *with* intercrate mode, even if proving negative predicates
|
|
// do not need intercrate mode enabled.
|
|
let ref infcx = tcx.infer_ctxt().with_next_trait_solver(true).build(TypingMode::Coherence);
|
|
let root_universe = infcx.universe();
|
|
assert_eq!(root_universe, ty::UniverseIndex::ROOT);
|
|
|
|
let impl1_header = fresh_impl_header(infcx, impl1_def_id);
|
|
let param_env =
|
|
ty::EarlyBinder::bind(tcx.param_env(impl1_def_id)).instantiate(tcx, impl1_header.impl_args);
|
|
|
|
let impl2_header = fresh_impl_header(infcx, impl2_def_id);
|
|
|
|
// Equate the headers to find their intersection (the general type, with infer vars,
|
|
// that may apply both impls).
|
|
let Some(equate_obligations) =
|
|
equate_impl_headers(infcx, param_env, &impl1_header, &impl2_header)
|
|
else {
|
|
return false;
|
|
};
|
|
|
|
// FIXME(with_negative_coherence): the infcx has constraints from equating
|
|
// the impl headers. We should use these constraints as assumptions, not as
|
|
// requirements, when proving the negated where clauses below.
|
|
drop(equate_obligations);
|
|
drop(infcx.take_registered_region_obligations());
|
|
drop(infcx.take_and_reset_region_constraints());
|
|
|
|
plug_infer_with_placeholders(
|
|
infcx,
|
|
root_universe,
|
|
(impl1_header.impl_args, impl2_header.impl_args),
|
|
);
|
|
let param_env = infcx.resolve_vars_if_possible(param_env);
|
|
|
|
util::elaborate(tcx, tcx.predicates_of(impl2_def_id).instantiate(tcx, impl2_header.impl_args))
|
|
.any(|(clause, _)| try_prove_negated_where_clause(infcx, clause, param_env))
|
|
}
|
|
|
|
fn plug_infer_with_placeholders<'tcx>(
|
|
infcx: &InferCtxt<'tcx>,
|
|
universe: ty::UniverseIndex,
|
|
value: impl TypeVisitable<TyCtxt<'tcx>>,
|
|
) {
|
|
struct PlugInferWithPlaceholder<'a, 'tcx> {
|
|
infcx: &'a InferCtxt<'tcx>,
|
|
universe: ty::UniverseIndex,
|
|
var: ty::BoundVar,
|
|
}
|
|
|
|
impl<'tcx> PlugInferWithPlaceholder<'_, 'tcx> {
|
|
fn next_var(&mut self) -> ty::BoundVar {
|
|
let var = self.var;
|
|
self.var = self.var + 1;
|
|
var
|
|
}
|
|
}
|
|
|
|
impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for PlugInferWithPlaceholder<'_, 'tcx> {
|
|
fn visit_ty(&mut self, ty: Ty<'tcx>) {
|
|
let ty = self.infcx.shallow_resolve(ty);
|
|
if ty.is_ty_var() {
|
|
let Ok(InferOk { value: (), obligations }) =
|
|
self.infcx.at(&ObligationCause::dummy(), ty::ParamEnv::empty()).eq(
|
|
// Comparing against a type variable never registers hidden types anyway
|
|
DefineOpaqueTypes::Yes,
|
|
ty,
|
|
Ty::new_placeholder(
|
|
self.infcx.tcx,
|
|
ty::Placeholder {
|
|
universe: self.universe,
|
|
bound: ty::BoundTy {
|
|
var: self.next_var(),
|
|
kind: ty::BoundTyKind::Anon,
|
|
},
|
|
},
|
|
),
|
|
)
|
|
else {
|
|
bug!("we always expect to be able to plug an infer var with placeholder")
|
|
};
|
|
assert_eq!(obligations.len(), 0);
|
|
} else {
|
|
ty.super_visit_with(self);
|
|
}
|
|
}
|
|
|
|
fn visit_const(&mut self, ct: ty::Const<'tcx>) {
|
|
let ct = self.infcx.shallow_resolve_const(ct);
|
|
if ct.is_ct_infer() {
|
|
let Ok(InferOk { value: (), obligations }) =
|
|
self.infcx.at(&ObligationCause::dummy(), ty::ParamEnv::empty()).eq(
|
|
// The types of the constants are the same, so there is no hidden type
|
|
// registration happening anyway.
|
|
DefineOpaqueTypes::Yes,
|
|
ct,
|
|
ty::Const::new_placeholder(
|
|
self.infcx.tcx,
|
|
ty::Placeholder { universe: self.universe, bound: self.next_var() },
|
|
),
|
|
)
|
|
else {
|
|
bug!("we always expect to be able to plug an infer var with placeholder")
|
|
};
|
|
assert_eq!(obligations.len(), 0);
|
|
} else {
|
|
ct.super_visit_with(self);
|
|
}
|
|
}
|
|
|
|
fn visit_region(&mut self, r: ty::Region<'tcx>) {
|
|
if let ty::ReVar(vid) = r.kind() {
|
|
let r = self
|
|
.infcx
|
|
.inner
|
|
.borrow_mut()
|
|
.unwrap_region_constraints()
|
|
.opportunistic_resolve_var(self.infcx.tcx, vid);
|
|
if r.is_var() {
|
|
let Ok(InferOk { value: (), obligations }) =
|
|
self.infcx.at(&ObligationCause::dummy(), ty::ParamEnv::empty()).eq(
|
|
// Lifetimes don't contain opaque types (or any types for that matter).
|
|
DefineOpaqueTypes::Yes,
|
|
r,
|
|
ty::Region::new_placeholder(
|
|
self.infcx.tcx,
|
|
ty::Placeholder {
|
|
universe: self.universe,
|
|
bound: ty::BoundRegion {
|
|
var: self.next_var(),
|
|
kind: ty::BoundRegionKind::Anon,
|
|
},
|
|
},
|
|
),
|
|
)
|
|
else {
|
|
bug!("we always expect to be able to plug an infer var with placeholder")
|
|
};
|
|
assert_eq!(obligations.len(), 0);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
value.visit_with(&mut PlugInferWithPlaceholder { infcx, universe, var: ty::BoundVar::ZERO });
|
|
}
|
|
|
|
fn try_prove_negated_where_clause<'tcx>(
|
|
root_infcx: &InferCtxt<'tcx>,
|
|
clause: ty::Clause<'tcx>,
|
|
param_env: ty::ParamEnv<'tcx>,
|
|
) -> bool {
|
|
let Some(negative_predicate) = clause.as_predicate().flip_polarity(root_infcx.tcx) else {
|
|
return false;
|
|
};
|
|
|
|
// N.B. We don't need to use intercrate mode here because we're trying to prove
|
|
// the *existence* of a negative goal, not the non-existence of a positive goal.
|
|
// Without this, we over-eagerly register coherence ambiguity candidates when
|
|
// impl candidates do exist.
|
|
// FIXME(#132279): `TypingMode::non_body_analysis` is a bit questionable here as it
|
|
// would cause us to reveal opaque types to leak their auto traits.
|
|
let ref infcx = root_infcx.fork_with_typing_mode(TypingMode::non_body_analysis());
|
|
let ocx = ObligationCtxt::new(infcx);
|
|
ocx.register_obligation(Obligation::new(
|
|
infcx.tcx,
|
|
ObligationCause::dummy(),
|
|
param_env,
|
|
negative_predicate,
|
|
));
|
|
if !ocx.select_all_or_error().is_empty() {
|
|
return false;
|
|
}
|
|
|
|
// FIXME: We could use the assumed_wf_types from both impls, I think,
|
|
// if that wasn't implemented just for LocalDefId, and we'd need to do
|
|
// the normalization ourselves since this is totally fallible...
|
|
let errors = ocx.resolve_regions(CRATE_DEF_ID, param_env, []);
|
|
if !errors.is_empty() {
|
|
return false;
|
|
}
|
|
|
|
true
|
|
}
|
|
|
|
/// Compute the `intercrate_ambiguity_causes` for the new solver using
|
|
/// "proof trees".
|
|
///
|
|
/// This is a bit scuffed but seems to be good enough, at least
|
|
/// when looking at UI tests. Given that it is only used to improve
|
|
/// diagnostics this is good enough. We can always improve it once there
|
|
/// are test cases where it is currently not enough.
|
|
fn compute_intercrate_ambiguity_causes<'tcx>(
|
|
infcx: &InferCtxt<'tcx>,
|
|
obligations: &[PredicateObligation<'tcx>],
|
|
) -> FxIndexSet<IntercrateAmbiguityCause<'tcx>> {
|
|
let mut causes: FxIndexSet<IntercrateAmbiguityCause<'tcx>> = Default::default();
|
|
|
|
for obligation in obligations {
|
|
search_ambiguity_causes(infcx, obligation.as_goal(), &mut causes);
|
|
}
|
|
|
|
causes
|
|
}
|
|
|
|
struct AmbiguityCausesVisitor<'a, 'tcx> {
|
|
cache: FxHashSet<Goal<'tcx, ty::Predicate<'tcx>>>,
|
|
causes: &'a mut FxIndexSet<IntercrateAmbiguityCause<'tcx>>,
|
|
}
|
|
|
|
impl<'a, 'tcx> ProofTreeVisitor<'tcx> for AmbiguityCausesVisitor<'a, 'tcx> {
|
|
fn span(&self) -> Span {
|
|
DUMMY_SP
|
|
}
|
|
|
|
fn visit_goal(&mut self, goal: &InspectGoal<'_, 'tcx>) {
|
|
if !self.cache.insert(goal.goal()) {
|
|
return;
|
|
}
|
|
|
|
let infcx = goal.infcx();
|
|
for cand in goal.candidates() {
|
|
cand.visit_nested_in_probe(self);
|
|
}
|
|
// When searching for intercrate ambiguity causes, we only need to look
|
|
// at ambiguous goals, as for others the coherence unknowable candidate
|
|
// was irrelevant.
|
|
match goal.result() {
|
|
Ok(Certainty::Yes) | Err(NoSolution) => return,
|
|
Ok(Certainty::Maybe(_)) => {}
|
|
}
|
|
|
|
// For bound predicates we simply call `infcx.enter_forall`
|
|
// and then prove the resulting predicate as a nested goal.
|
|
let Goal { param_env, predicate } = goal.goal();
|
|
let trait_ref = match predicate.kind().no_bound_vars() {
|
|
Some(ty::PredicateKind::Clause(ty::ClauseKind::Trait(tr))) => tr.trait_ref,
|
|
Some(ty::PredicateKind::Clause(ty::ClauseKind::Projection(proj)))
|
|
if matches!(
|
|
infcx.tcx.def_kind(proj.projection_term.def_id),
|
|
DefKind::AssocTy | DefKind::AssocConst
|
|
) =>
|
|
{
|
|
proj.projection_term.trait_ref(infcx.tcx)
|
|
}
|
|
_ => return,
|
|
};
|
|
|
|
if trait_ref.references_error() {
|
|
return;
|
|
}
|
|
|
|
let mut candidates = goal.candidates();
|
|
for cand in goal.candidates() {
|
|
if let inspect::ProbeKind::TraitCandidate {
|
|
source: CandidateSource::Impl(def_id),
|
|
result: Ok(_),
|
|
} = cand.kind()
|
|
{
|
|
if let ty::ImplPolarity::Reservation = infcx.tcx.impl_polarity(def_id) {
|
|
let message = infcx
|
|
.tcx
|
|
.get_attr(def_id, sym::rustc_reservation_impl)
|
|
.and_then(|a| a.value_str());
|
|
if let Some(message) = message {
|
|
self.causes.insert(IntercrateAmbiguityCause::ReservationImpl { message });
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
// We also look for unknowable candidates. In case a goal is unknowable, there's
|
|
// always exactly 1 candidate.
|
|
let Some(cand) = candidates.pop() else {
|
|
return;
|
|
};
|
|
|
|
let inspect::ProbeKind::TraitCandidate {
|
|
source: CandidateSource::CoherenceUnknowable,
|
|
result: Ok(_),
|
|
} = cand.kind()
|
|
else {
|
|
return;
|
|
};
|
|
|
|
let lazily_normalize_ty = |mut ty: Ty<'tcx>| {
|
|
if matches!(ty.kind(), ty::Alias(..)) {
|
|
let ocx = ObligationCtxt::new(infcx);
|
|
ty = ocx
|
|
.structurally_normalize_ty(&ObligationCause::dummy(), param_env, ty)
|
|
.map_err(|_| ())?;
|
|
if !ocx.select_where_possible().is_empty() {
|
|
return Err(());
|
|
}
|
|
}
|
|
Ok(ty)
|
|
};
|
|
|
|
infcx.probe(|_| {
|
|
let conflict = match trait_ref_is_knowable(infcx, trait_ref, lazily_normalize_ty) {
|
|
Err(()) => return,
|
|
Ok(Ok(())) => {
|
|
warn!("expected an unknowable trait ref: {trait_ref:?}");
|
|
return;
|
|
}
|
|
Ok(Err(conflict)) => conflict,
|
|
};
|
|
|
|
// It is only relevant that a goal is unknowable if it would have otherwise
|
|
// failed.
|
|
// FIXME(#132279): Forking with `TypingMode::non_body_analysis` is a bit questionable
|
|
// as it would allow us to reveal opaque types, potentially causing unexpected
|
|
// cycles.
|
|
let non_intercrate_infcx = infcx.fork_with_typing_mode(TypingMode::non_body_analysis());
|
|
if non_intercrate_infcx.predicate_may_hold(&Obligation::new(
|
|
infcx.tcx,
|
|
ObligationCause::dummy(),
|
|
param_env,
|
|
predicate,
|
|
)) {
|
|
return;
|
|
}
|
|
|
|
// Normalize the trait ref for diagnostics, ignoring any errors if this fails.
|
|
let trait_ref = deeply_normalize_for_diagnostics(infcx, param_env, trait_ref);
|
|
let self_ty = trait_ref.self_ty();
|
|
let self_ty = self_ty.has_concrete_skeleton().then(|| self_ty);
|
|
self.causes.insert(match conflict {
|
|
Conflict::Upstream => {
|
|
IntercrateAmbiguityCause::UpstreamCrateUpdate { trait_ref, self_ty }
|
|
}
|
|
Conflict::Downstream => {
|
|
IntercrateAmbiguityCause::DownstreamCrate { trait_ref, self_ty }
|
|
}
|
|
});
|
|
});
|
|
}
|
|
}
|
|
|
|
fn search_ambiguity_causes<'tcx>(
|
|
infcx: &InferCtxt<'tcx>,
|
|
goal: Goal<'tcx, ty::Predicate<'tcx>>,
|
|
causes: &mut FxIndexSet<IntercrateAmbiguityCause<'tcx>>,
|
|
) {
|
|
infcx.probe(|_| {
|
|
infcx.visit_proof_tree(
|
|
goal,
|
|
&mut AmbiguityCausesVisitor { cache: Default::default(), causes },
|
|
)
|
|
});
|
|
}
|