apply SmallStep.if_true
case hbc.hab

⊢ (Stmt.ifThenElse (fun s => s "x" > s "y")
        ((Stmt.skip; Stmt.assign "x" fun s => s "x" - 1);
          Stmt.whileDo (fun s => s "x" > s "y") (Stmt.skip; Stmt.assign "x" fun s => s "x" - 1))
        Stmt.skip,
      State.update "x" 1 fun x => 0) ⇒
    ?hbc.b
case hbc.hab.hcond

⊢ State.update "x" 1 (fun x => 0) "x" > State.update "x" 1 (fun x => 0) "y"