1 files changed, 44 insertions, 0 deletions
diff --git a/vendor/chalk-solve-0.87.0/src/coherence/orphan.rs b/vendor/chalk-solve-0.87.0/src/coherence/orphan.rs
new file mode 100644
index 000000000..f8e06b901
--- /dev/null
+++ b/vendor/chalk-solve-0.87.0/src/coherence/orphan.rs
@@ -0,0 +1,44 @@
+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(())
+}