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Make hitting the recursion limit in projection non-fatal #81055

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Jan 28, 2021
Merged

Make hitting the recursion limit in projection non-fatal #81055

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11 changes: 3 additions & 8 deletions compiler/rustc_trait_selection/src/traits/project.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -736,14 +736,9 @@ fn project_type<'cx, 'tcx>(

if !selcx.tcx().sess.recursion_limit().value_within_limit(obligation.recursion_depth) {
debug!("project: overflow!");
match selcx.query_mode() {
super::TraitQueryMode::Standard => {
selcx.infcx().report_overflow_error(&obligation, true);
}
super::TraitQueryMode::Canonical => {
return Err(ProjectionTyError::TraitSelectionError(SelectionError::Overflow));
}
}
// This should really be an immediate error, but some existing code
// relies on being able to recover from this.
return Err(ProjectionTyError::TraitSelectionError(SelectionError::Overflow));
}

let obligation_trait_ref = &obligation.predicate.trait_ref(selcx.tcx());
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4 changes: 0 additions & 4 deletions compiler/rustc_trait_selection/src/traits/select/mod.rs
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Expand Up @@ -291,10 +291,6 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
self.infcx.tcx
}

pub(super) fn query_mode(&self) -> TraitQueryMode {
self.query_mode
}

///////////////////////////////////////////////////////////////////////////
// Selection
//
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58 changes: 58 additions & 0 deletions src/test/ui/associated-types/project-recursion-limit-non-fatal.rs
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@@ -0,0 +1,58 @@
// Regression test for #80953. Hitting the recursion limit in projection
// is non-fatal. The above code, minimised from wundergraph shows a case
// where this is relied on.

// check-pass

struct AlternateTable {}
struct AlternateQuery {}

pub trait Query {}
pub trait AsQuery {
type Query;
}
impl<T: Query> AsQuery for T {
type Query = Self;
}
impl AsQuery for AlternateTable {
type Query = AlternateQuery;
}

pub trait Table: AsQuery {
type PrimaryKey;
}
impl Table for AlternateTable {
type PrimaryKey = ();
}

pub trait FilterDsl<Predicate> {
type Output;
}
pub type Filter<Source, Predicate> = <Source as FilterDsl<Predicate>>::Output;
impl<T, Predicate> FilterDsl<Predicate> for T
where
T: Table,
T::Query: FilterDsl<Predicate>,
{
type Output = Filter<T::Query, Predicate>;
}
impl<Predicate> FilterDsl<Predicate> for AlternateQuery {
type Output = &'static str;
}

pub trait HandleDelete {
type Filter;
}
impl<T> HandleDelete for T
where
T: Table,
T::Query: FilterDsl<T::PrimaryKey>,
Filter<T::Query, T::PrimaryKey>: ,
{
type Filter = Filter<T::Query, T::PrimaryKey>;
}

fn main() {
let x: <AlternateTable as HandleDelete>::Filter = "Hello, world";
println!("{}", x);
}
3 changes: 2 additions & 1 deletion src/test/ui/issues/issue-23122-2.stderr
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@@ -1,10 +1,11 @@
error[E0275]: overflow evaluating the requirement `<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<T as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next`
error[E0275]: overflow evaluating the requirement `<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<T as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next: Sized`
--> $DIR/issue-23122-2.rs:9:5
|
LL | type Next = <GetNext<T::Next> as Next>::Next;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= help: consider adding a `#![recursion_limit="256"]` attribute to your crate (`issue_23122_2`)
= note: required because of the requirements on the impl of `Next` for `GetNext<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<T as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next>`

error: aborting due to previous error

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