Definition eq_sind_r :
forall (A:Type) (x:A) (P:A -> SProp), P x -> forall y:A, y = x -> P y.
Register f_equal2 as core.eq.congr2.

Lemma eq_trans_map_distr A B x y z (f:A->B) (e:x=y) (e':y=z) : f_equal f (eq_trans e e') = eq_trans (f_equal f e) (f_equal f e').