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Restore pred_known_to_hold_modulo_regions #123578

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50 changes: 47 additions & 3 deletions compiler/rustc_trait_selection/src/traits/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -119,16 +119,60 @@ pub fn predicates_for_generics<'tcx>(

/// Determines whether the type `ty` is known to meet `bound` and
/// returns true if so. Returns false if `ty` either does not meet
/// `bound` or is not known to meet bound.
/// `bound` or is not known to meet bound (note that this is
/// conservative towards *no impl*, which is the opposite of the
/// `evaluate` methods).
pub fn type_known_to_meet_bound_modulo_regions<'tcx>(
infcx: &InferCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
ty: Ty<'tcx>,
def_id: DefId,
) -> bool {
let trait_ref = ty::TraitRef::new(infcx.tcx, def_id, [ty]);
let obligation = Obligation::new(infcx.tcx, ObligationCause::dummy(), param_env, trait_ref);
infcx.predicate_must_hold_modulo_regions(&obligation)
pred_known_to_hold_modulo_regions(infcx, param_env, trait_ref)
}

/// FIXME(@lcnr): this function doesn't seem right and shouldn't exist?
///
/// Ping me on zulip if you want to use this method and need help with finding
/// an appropriate replacement.
#[instrument(level = "debug", skip(infcx, param_env, pred), ret)]
fn pred_known_to_hold_modulo_regions<'tcx>(
infcx: &InferCtxt<'tcx>,
param_env: ty::ParamEnv<'tcx>,
pred: impl ToPredicate<'tcx>,
) -> bool {
let obligation = Obligation::new(infcx.tcx, ObligationCause::dummy(), param_env, pred);

let result = infcx.evaluate_obligation_no_overflow(&obligation);
debug!(?result);

if result.must_apply_modulo_regions() {
true
} else if result.may_apply() {
// Sometimes obligations are ambiguous because the recursive evaluator
// is not smart enough, so we fall back to fulfillment when we're not certain
// that an obligation holds or not. Even still, we must make sure that
// the we do no inference in the process of checking this obligation.
let goal = infcx.resolve_vars_if_possible((obligation.predicate, obligation.param_env));
infcx.probe(|_| {
let ocx = ObligationCtxt::new(infcx);
ocx.register_obligation(obligation);

let errors = ocx.select_all_or_error();
match errors.as_slice() {
// Only known to hold if we did no inference.
[] => infcx.shallow_resolve(goal) == goal,

errors => {
debug!(?errors);
false
}
}
})
} else {
false
}
}

#[instrument(level = "debug", skip(tcx, elaborated_env))]
Expand Down
244 changes: 244 additions & 0 deletions tests/ui/traits/pred-known-to-hold-modulo-regions-unsized-tail.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,244 @@
// This is a non-regression test for issues #108721 and its duplicate #123275 (hopefully, because
// the test is still convoluted and the ICE is fiddly).
//
// `pred_known_to_hold_modulo_regions` prevented "unexpected unsized tail" ICEs with warp/hyper but
// was unknowingly removed in #120463.

//@ build-pass: the ICE happened in codegen

use std::future::Future;
trait TryFuture: Future {
type Ok;
}
impl<F, T> TryFuture for F
where
F: ?Sized + Future<Output = Option<T>>,
{
type Ok = T;
}
trait Executor {}
struct Exec {}
trait HttpBody {
type Data;
}
trait ConnStreamExec<F> {}
impl<F> ConnStreamExec<F> for Exec where H2Stream<F>: Send {}
impl<E, F> ConnStreamExec<F> for E where E: Executor {}
struct H2Stream<F> {
_fut: F,
}
trait NewSvcExec<S, E, W: Watcher<S, E>> {
fn execute_new_svc(&mut self, _fut: NewSvcTask<S, E, W>) {
unimplemented!()
}
}
impl<S, E, W> NewSvcExec<S, E, W> for Exec where W: Watcher<S, E> {}
trait Watcher<S, E> {
type Future;
}
struct NoopWatcher;
impl<S, E> Watcher<S, E> for NoopWatcher
where
S: HttpService,
E: ConnStreamExec<S::Future>,
{
type Future = Option<<<S as HttpService>::ResBody as HttpBody>::Data>;
}
trait Service<Request> {
type Response;
type Future;
}
trait HttpService {
type ResBody: HttpBody;
type Future;
}
struct Body {}
impl HttpBody for Body {
type Data = String;
}
impl<S> HttpService for S
where
S: Service<(), Response = ()>,
{
type ResBody = Body;
type Future = S::Future;
}
trait MakeServiceRef<Target> {
type ResBody;
type Service: HttpService<ResBody = Self::ResBody>;
}
impl<T, Target, S, F> MakeServiceRef<Target> for T
where
T: for<'a> Service<&'a Target, Response = S, Future = F>,
S: HttpService,
{
type Service = S;
type ResBody = S::ResBody;
}
fn make_service_fn<F, Target, Ret>(_f: F) -> MakeServiceFn<F>
where
F: FnMut(&Target) -> Ret,
Ret: Future,
{
unimplemented!()
}
struct MakeServiceFn<F> {
_func: F,
}
impl<'t, F, Ret, Target, Svc> Service<&'t Target> for MakeServiceFn<F>
where
F: FnMut(&Target) -> Ret,
Ret: Future<Output = Option<Svc>>,
{
type Response = Svc;
type Future = Option<()>;
}
struct AddrIncoming {}
struct Server<I, S, E> {
_incoming: I,
_make_service: S,
_protocol: E,
}
impl<I, S, E, B> Server<I, S, E>
where
S: MakeServiceRef<(), ResBody = B>,
B: HttpBody,
E: ConnStreamExec<<S::Service as HttpService>::Future>,
E: NewSvcExec<S::Service, E, NoopWatcher>,
{
fn serve(&mut self) {
let fut = NewSvcTask::new();
self._protocol.execute_new_svc(fut);
}
}
fn serve<S>(_make_service: S) -> Server<AddrIncoming, S, Exec> {
unimplemented!()
}
struct NewSvcTask<S, E, W: Watcher<S, E>> {
_state: State<S, E, W>,
}
struct State<S, E, W: Watcher<S, E>> {
_fut: W::Future,
}
impl<S, E, W: Watcher<S, E>> NewSvcTask<S, E, W> {
fn new() -> Self {
unimplemented!()
}
}
trait Filter {
type Extract;
type Future;
fn map<F>(self, _fun: F) -> MapFilter<Self, F>
where
Self: Sized,
{
unimplemented!()
}
fn wrap_with<W>(self, _wrapper: W) -> W::Wrapped
where
Self: Sized,
W: Wrap<Self>,
{
unimplemented!()
}
}
fn service<F>(_filter: F) -> FilteredService<F>
where
F: Filter,
{
unimplemented!()
}
struct FilteredService<F> {
_filter: F,
}
impl<F> Service<()> for FilteredService<F>
where
F: Filter,
{
type Response = ();
type Future = FilteredFuture<F::Future>;
}
struct FilteredFuture<F> {
_fut: F,
}
struct MapFilter<T, F> {
_filter: T,
_func: F,
}
impl<T, F> Filter for MapFilter<T, F>
where
T: Filter,
F: Func<T::Extract>,
{
type Extract = F::Output;
type Future = MapFilterFuture<T, F>;
}
struct MapFilterFuture<T: Filter, F> {
_extract: T::Future,
_func: F,
}
trait Wrap<F> {
type Wrapped;
}
fn make_filter_fn<F, U>(_func: F) -> FilterFn<F>
where
F: Fn() -> U,
{
unimplemented!()
}
struct FilterFn<F> {
_func: F,
}
impl<F, U> Filter for FilterFn<F>
where
F: Fn() -> U,
U: TryFuture,
U::Ok: Send,
{
type Extract = U::Ok;
type Future = Option<U>;
}
fn trace<F>(_func: F) -> Trace<F>
where
F: Fn(),
{
unimplemented!()
}
struct Trace<F> {
_func: F,
}
impl<FN, F> Wrap<F> for Trace<FN> {
type Wrapped = WithTrace<FN, F>;
}
struct WithTrace<FN, F> {
_filter: F,
_trace: FN,
}
impl<FN, F> Filter for WithTrace<FN, F>
where
F: Filter,
{
type Extract = ();
type Future = (F::Future, fn(F::Extract));
}
trait Func<Args> {
type Output;
}
impl<F, R> Func<()> for F
where
F: Fn() -> R,
{
type Output = R;
}
fn main() {
let make_service = make_service_fn(|_| {
let tracer = trace(|| unimplemented!());
let filter = make_filter_fn(|| std::future::ready(Some(())))
.map(|| "Hello, world")
.wrap_with(tracer);
let svc = service(filter);
std::future::ready(Some(svc))
});
let mut server = serve(make_service);
server.serve();
}
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