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use crate::coherence::CoherenceError;
use crate::ext::GoalExt;
use crate::solve::Solver;
use crate::RustIrDatabase;
use chalk_ir::cast::*;
use chalk_ir::interner::Interner;
use chalk_ir::*;
use tracing::{debug, instrument};
// Test if a local impl violates the orphan rules.
//
// For `impl<T> Trait for MyType<T>` we generate:
//
// forall<T> { LocalImplAllowed(MyType<T>: Trait) }
//
// This must be provable in order to pass the orphan check.
#[instrument(level = "debug", skip(db, solver))]
pub fn perform_orphan_check<I: Interner>(
db: &dyn RustIrDatabase<I>,
solver: &mut dyn Solver<I>,
impl_id: ImplId<I>,
) -> Result<(), CoherenceError<I>> {
let impl_datum = db.impl_datum(impl_id);
debug!(?impl_datum);
let impl_allowed: Goal<I> = impl_datum
.binders
.map_ref(|bound_impl| {
// Ignoring the polarization of the impl's polarized trait ref
DomainGoal::LocalImplAllowed(bound_impl.trait_ref.clone())
})
.cast(db.interner());
let canonical_goal = &impl_allowed.into_closed_goal(db.interner());
let is_allowed = solver.solve(db, canonical_goal).is_some();
debug!("overlaps = {:?}", is_allowed);
if !is_allowed {
let trait_id = impl_datum.trait_id();
return Err(CoherenceError::FailedOrphanCheck(trait_id));
}
Ok(())
}
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