Hence, also rename (the old) `equiv_entails` → `equiv_entails_1_1` and
`equiv_entails_sym` → `equiv_entails_1_2`, and add `equiv_entails_2` for completeness.

Done with a script by Tej; see
iris/iris!609 for details.

This reverts commit 71a1fbf0, reversing
changes made to ce12f3a6.

Tej Chajed authored Feb 15, 2020 and Ralf Jung committed Feb 15, 2020

Fixes a new warning on Coq 8.12+alpha when implicit annotations are used
in positions where they are ignored.

Tej Chajed authored Feb 02, 2020 and Ralf Jung committed Feb 02, 2020

Coq master is stricter about checking for meaningless implicit binders;
see https://github.com/coq/coq/pull/10202.

The general idea is to first import/export modules which are further
than the current one, and then import/export modules which are close
dependencies.

This commit tries to use the same order of imports for every file, and
describes the convention in ProofGuide.md. There is one exception,
where we do not follow said convention: in program_logic/weakestpre.v,
using that order would break printing of texan triples (??).

This commit closes issue #265.

This is in preparation for coq/coq#9274.

Adding a hint without a database now triggers a deprecation warning in
Coq master (https://github.com/coq/coq/pull/8987).

This needed minor rearrangement.

All the `env` operations are prefixed `env_`, so this is more consistent.

* move PROP-envs definitions to environments.v so that we can control them without pulling in coq_tactics
* use reduction-controlled `pm_default` for proofmode accessors

It used to be an inline pattern match.

This also restores compatibility with Coq 8.6.1.

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.