| (Ast.CONTEXT(_,Ast.BEFORE(l1)),
Ast.CONTEXT(_,Ast.AFTER(l2))) ->
Some (Ast.CONTEXT(Ast.NoPos,Ast.BEFORE(l1@l2)))
| (Ast.CONTEXT(_,Ast.BEFORE(_)),Ast.CONTEXT(_,Ast.NOTHING))
| (Ast.CONTEXT(_,Ast.NOTHING),Ast.CONTEXT(_,Ast.NOTHING)) ->
Some retmc
| (Ast.CONTEXT(_,Ast.BEFORE(l1)),
Ast.CONTEXT(_,Ast.AFTER(l2))) ->
Some (Ast.CONTEXT(Ast.NoPos,Ast.BEFORE(l1@l2)))
| (Ast.CONTEXT(_,Ast.BEFORE(_)),Ast.CONTEXT(_,Ast.NOTHING))
| (Ast.CONTEXT(_,Ast.NOTHING),Ast.CONTEXT(_,Ast.NOTHING)) ->
Some retmc