(* (c) Copyright 2006-2015 Microsoft Corporation and Inria.                  *)
(* Distributed under the terms of CeCILL-B.                                  *)
Require Import mathcomp.ssreflect.ssreflect.
From mathcomp
Require Import ssrbool ssrnat.

Notation "( a 'in' c )" := (a + c) (only parsing) : myscope.
Delimit Scope myscope with myscope.

Notation "( a 'in' c )" := (a + c) (only parsing).

Lemma foo x y : x + x.+1 = x.+1 + y.
move: {x} (x.+1) {1}x y (x.+1 in RHS).
  match goal with |- forall a b c d, b + a = d + c => idtac end.
Admitted.

Lemma bar x y : x + x.+1 = x.+1 + y.
move E: ((x.+1 in y)) => w.
  match goal with |- x + x.+1 = w => rewrite -{w}E end.
move E: (x.+1 in y)%myscope => w.
  match goal with |- x + x.+1 = w => rewrite -{w}E end.
move E: ((x + y).+1 as RHS) => w.
  match goal with |- x + x.+1 = w => rewrite -{}E -addSn end.
Admitted.