[attributes] Allow boolean, single-value attributes.

Following discussion in https://github.com/coq/coq/pull/12586 , we
extend the syntax `val=string` to support also arbitrary values.

In particular we support boolean ones, or arbitrary key-pair lists.

This complements the current form `val="string"`, and makes more sense
in general.

Current syntax for the boolean version is `attr=yes` or `attr=no`, but
we could be more liberal if desired.

The general new guideline is that `foo(vals)` is reserved for
the case where `vals` is a list, whereas `foo=val` is for attributes
that allow a unique assignment.

This commit only introduces the support, next commits will migrate
some attributes to this new syntax and deprecate the old versions.

1 files changed, 8 insertions, 2 deletions

diff --git a/vernac/vernacentries.ml b/vernac/vernacentries.ml
index 4e52af7959..2edd9d4d11 100644
--- a/vernac/vernacentries.ml
+++ b/vernac/vernacentries.ml
@@ -678,9 +678,15 @@ let polymorphic_cumulative =
   in
   let open Attributes in
   let open Notations in
+  (* EJGA: this seems redudant with code in attributes.ml *)
   qualify_attribute "universes"
-    (bool_attribute ~name:"Polymorphism" ~on:"polymorphic" ~off:"monomorphic"
-     ++ bool_attribute ~name:"Cumulativity" ~on:"cumulative" ~off:"noncumulative")
+    (deprecated_bool_attribute
+       ~name:"Polymorphism"
+       ~on:"polymorphic" ~off:"monomorphic"
+     ++
+     deprecated_bool_attribute
+       ~name:"Cumulativity"
+       ~on:"cumulative" ~off:"noncumulative")
   >>= function
   | Some poly, Some cum ->
      (* Case of Polymorphic|Monomorphic Cumulative|NonCumulative Inductive