intern external constraints

compiler/rustc_middle/src/traits/solve.rs

@@ -0,0 +1,55 @@
+use std::ops::ControlFlow;
+
+use rustc_data_structures::intern::Interned;
+
+use crate::ty::{FallibleTypeFolder, Ty, TypeFoldable, TypeFolder, TypeVisitable, TypeVisitor};
+
+#[derive(Debug, PartialEq, Eq, Copy, Clone, Hash)]
+pub struct ExternalConstraints<'tcx>(pub(crate) Interned<'tcx, ExternalConstraintsData<'tcx>>);
+
+impl<'tcx> std::ops::Deref for ExternalConstraints<'tcx> {
+    type Target = ExternalConstraintsData<'tcx>;
+
+    fn deref(&self) -> &Self::Target {
+        &*self.0
+    }
+}
+
+/// Additional constraints returned on success.
+#[derive(Debug, PartialEq, Eq, Clone, Hash, Default)]
+pub struct ExternalConstraintsData<'tcx> {
+    // FIXME: implement this.
+    pub regions: (),
+    pub opaque_types: Vec<(Ty<'tcx>, Ty<'tcx>)>,
+}
+
+impl<'tcx> TypeFoldable<'tcx> for ExternalConstraints<'tcx> {
+    fn try_fold_with<F: FallibleTypeFolder<'tcx>>(self, folder: &mut F) -> Result<Self, F::Error> {
+        Ok(FallibleTypeFolder::tcx(folder).intern_external_constraints(ExternalConstraintsData {
+            regions: (),
+            opaque_types: self
+                .opaque_types
+                .iter()
+                .map(|opaque| opaque.try_fold_with(folder))
+                .collect::<Result<_, F::Error>>()?,
+        }))
+    }
+
+    fn fold_with<F: TypeFolder<'tcx>>(self, folder: &mut F) -> Self {
+        TypeFolder::tcx(folder).intern_external_constraints(ExternalConstraintsData {
+            regions: (),
+            opaque_types: self.opaque_types.iter().map(|opaque| opaque.fold_with(folder)).collect(),
+        })
+    }
+}
+
+impl<'tcx> TypeVisitable<'tcx> for ExternalConstraints<'tcx> {
+    fn visit_with<V: TypeVisitor<'tcx>>(
+        &self,
+        visitor: &mut V,
+    ) -> std::ops::ControlFlow<V::BreakTy> {
+        self.regions.visit_with(visitor)?;
+        self.opaque_types.visit_with(visitor)?;
+        ControlFlow::Continue(())
+    }
+}