Add FIXME

diff --git a/src/librustc_typeck/check/writeback.rs b/src/librustc_typeck/check/writeback.rs
index 238b087fe32f86b3dc431672d4396aeaba2775cb..00917be538fb3305a6aea4df5ac5b848e99f6acf 100644 (file)
--- a/src/librustc_typeck/check/writeback.rs
+++ b/src/librustc_typeck/check/writeback.rs
@@ -561,6 +561,8 @@ fn visit_opaque_types(&mut self, span: Span) {
                 if def_id == defin_ty_def_id {
                     // Concrete type resolved to the existential type itself
                     // Force a cycle error
+                    // FIXME(oli-obk): we could just not insert it into `concrete_existential_types`
+                    // which simply would make this use not a defining use.
                     self.tcx().at(span).type_of(defin_ty_def_id);
                 }
             }