1 files changed, 31 insertions, 0 deletions
diff --git a/compiler/rustc_mir_build/src/thir/util.rs b/compiler/rustc_mir_build/src/thir/util.rs
new file mode 100644
index 000000000..c58ed1ac0
--- /dev/null
+++ b/compiler/rustc_mir_build/src/thir/util.rs
@@ -0,0 +1,31 @@
+use rustc_hir as hir;
+use rustc_middle::ty::{self, CanonicalUserType, TyCtxt, UserType};
+
+pub(crate) trait UserAnnotatedTyHelpers<'tcx> {
+    fn tcx(&self) -> TyCtxt<'tcx>;
+
+    fn typeck_results(&self) -> &ty::TypeckResults<'tcx>;
+
+    /// Looks up the type associated with this hir-id and applies the
+    /// user-given substitutions; the hir-id must map to a suitable
+    /// type.
+    fn user_substs_applied_to_ty_of_hir_id(
+        &self,
+        hir_id: hir::HirId,
+    ) -> Option<CanonicalUserType<'tcx>> {
+        let user_provided_types = self.typeck_results().user_provided_types();
+        let mut user_ty = *user_provided_types.get(hir_id)?;
+        debug!("user_subts_applied_to_ty_of_hir_id: user_ty={:?}", user_ty);
+        let ty = self.typeck_results().node_type(hir_id);
+        match ty.kind() {
+            ty::Adt(adt_def, ..) => {
+                if let UserType::TypeOf(ref mut did, _) = &mut user_ty.value {
+                    *did = adt_def.did();
+                }
+                Some(user_ty)
+            }
+            ty::FnDef(..) => Some(user_ty),
+            _ => bug!("ty: {:?} should not have user provided type {:?} recorded ", ty, user_ty),
+        }
+    }
+}