[proof] Move proofs that have an associated constant to `Lemmas`

The main idea of this PR is to distinguish the types of "proof object"
`Proof_global.t` and the type of "proof object associated to a
constant, the new `Lemmas.t`.

This way, we can move the terminator setup to the higher layer in
`vernac`, which is the one that really knows about constants, paving
the way for further simplification and in particular for a unified
handling of constant saving by removal of the control inversion here.

Terminators are now internal to `Lemmas`, as it is the only part of
the code applying them.

As a consequence, proof nesting is now handled by `Lemmas`, and
`Proof_global.t` is just a single `Proof.t` plus some environmental
meta-data.

We are also enable considerable simplification in a future PR, as this
patch makes `Proof.t` and `Proof_global.t` essentially the same, so we
should expect to handle them under a unified interface.

1 files changed, 24 insertions, 0 deletions

diff --git a/dev/doc/changes.md b/dev/doc/changes.md
index cc58222fbf..51d90df89f 100644
--- a/dev/doc/changes.md
+++ b/dev/doc/changes.md
@@ -9,6 +9,17 @@
   message. Main change to do generally is to change the flag "Global"
   to "Global ImportDefaultBehavior".
 
+Proof state:
+
+  Proofs that are attached to a top-level constant (such as lemmas)
+  are represented by `Lemmas.t`, as they do contain additional
+  information related to the constant declaration.
+
+  Plugins that require access to the information about currently
+  opened lemmas can add one of the `![proof]` attributes to their
+  `mlg` entry, which will refine the type accordingly. See
+  documentation in `vernacentries` for more information.
+
 ## Changes between Coq 8.9 and Coq 8.10
 
 ### ML4 Pre Processing
@@ -63,6 +74,19 @@ Coqlib:
   command then enables to locate the registered constant through its name. The
   name resolution is dynamic.
 
+Proof state:
+
+- Handling of proof state has been fully functionalized, thus it is
+  not possible to call global functions such as `get_current_context ()`.
+
+  The main type for functions that need to handle proof state is
+  `Proof_global.t`.
+
+  Unfortunately, this change was not possible to do in a
+  backwards-compatible way, but in most case the api changes are
+  straightforward, with functions taking and returning an extra
+  argument.
+
 Macros:
 
 - The RAW_TYPED AS and GLOB_TYPED AS stanzas of the ARGUMENT EXTEND macro are