fix

Author: YaelDillies

Mathlib/RingTheory/Coalgebra/CoassocSimps.lean

@@ -4,9 +4,12 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Andrew Yang, Yaël Dillies
 -/
 module
+
 public import Mathlib.LinearAlgebra.TensorProduct.Tower
 public import Mathlib.RingTheory.Coalgebra.Basic
 
+import Mathlib.Tactic.Attr.Register
+
 /-!
 # Tactic to reassociate comultiplication in a coalgebra