Gregory Malecha authored 4 years ago and Robbert Krebbers committed 4 years ago

- it doesn't seem to conflict with anything in Ltac

This lemma is similar to `persistently_impl_wand_2`.

This works because there is already a `Reserved Notation`.

Fix #302, including their ASCII variants.
- Don't use quotes `'` that are not surrounded by spaces.
- However, notation `'(⊢@{' PROP } )` prevents parsing `(⊢@{PROP} Q)` using the
`⊢@{PROP} Q` notation.

To fix that, we force left-factorization: we add a notation for `'(⊢@{' PROP }
Q )`, defined to coincide with '⊢@{' PROP } Q but which can be left-factored
with `( '⊢@{' PROP } )`.

- Add left and right operator sections for (bi)entailment
- Add tests.

Also do all of the above also for ASCII notations, except for operator sections,
which seem to require more discussion.