| Terms.Node [ Terms.Leaf eqt ; _; Terms.Node [Terms.Leaf eqt2 ; ty]; l; r]
when eq equivalence_relation eqt && eq setoid_eq eqt2 ->
| Terms.Node [ Terms.Leaf eqt ; _; Terms.Node [Terms.Leaf eqt2 ; ty]; l; r]
when eq equivalence_relation eqt && eq setoid_eq eqt2 ->