Hint Resolve reducts_incl_val reducts_incl_loc reducts_incl_listval
reducts_incl_incontext reducts_incl_incontext2_left reducts_incl_incontext2_right.

Lemma step_expr_context:
forall from to C, context from to C ->
forall a m, reducts_incl C (step_expr from a m) (step_expr to (C a) m)
with step_exprlist_context:
forall from C, contextlist from C ->
forall a m, reducts_incl C (step_expr from a m) (step_exprlist (C a) m).