• Robbert Krebbers's avatar
    Improved treatment of anonymous hypotheses in the proof mode. · bb3584e7
    Robbert Krebbers authored
    The proof mode now explicitly keeps track of anonymous hypotheses (i.e.
    hypotheses that are introduced by the introduction pattern `?`). Consider:
    
      Lemma foo {M} (P Q R : uPred M) : P -∗ (Q ∗ R) -∗ Q ∗ P.
      Proof. iIntros "? [H ?]". iFrame "H". iFrame. Qed.
    
    After the `iIntros`, the goal will be:
    
      _ : P
      "H" : Q
      _ : R
      --------------------------------------∗
      Q ∗ P
    
    Anonymous hypotheses are displayed in a special way (`_ : P`). An important
    property of the new anonymous hypotheses is that it is no longer possible to
    refer to them by name, whereas before, anonymous hypotheses were given some
    arbitrary fresh name (typically prefixed by `~`).
    
    Note tactics can still operate on these anonymous hypotheses. For example, both
    `iFrame` and `iAssumption`, as well as the symbolic execution tactics, will
    use them. The only thing that is not possible is to refer to them yourself,
    for example, in an introduction, specialization or selection pattern.
    
    Advantages of the new approach:
    
    - Proofs become more robust as one cannot accidentally refer to anonymous
      hypotheses by their fresh name.
    - Fresh name generation becomes considerably easier. Since anonymous hypotheses
      are internally represented by natural numbers (of type `N`), we can just fold
      over the hypotheses and take the max plus one. This thus solve issue #101.
    bb3584e7
invariants.v 4.78 KB