Merge PR #6413: [econstr] Switch constrintern API to non-imperative style.

1 files changed, 2 insertions, 3 deletions

diff --git a/plugins/derive/derive.ml b/plugins/derive/derive.ml
index fb65a8639a..c8c4c2dad9 100644
--- a/plugins/derive/derive.ml
+++ b/plugins/derive/derive.ml
@@ -38,9 +38,8 @@ let start_deriving f suchthat lemma =
         let f_type = EConstr.Unsafe.to_constr f_type in
         let ef = EConstr.Unsafe.to_constr ef in
         let env' = Environ.push_named (LocalDef (f, ef, f_type)) env in
-        let evdref = ref sigma in
-        let suchthat = Constrintern.interp_type_evars env' evdref suchthat in
-        TCons ( env' , !evdref , suchthat , (fun sigma _ ->
+        let sigma, suchthat = Constrintern.interp_type_evars env' sigma suchthat in
+        TCons ( env' , sigma , suchthat , (fun sigma _ ->
         TNil sigma))))))
     in