Trying a hack to support {'pat|P} without breaking compatibility.

Concretely, we bypass the following limitation: The notation
"{ ' pat | P }" broke the parsing of expressions of the form
"{ forall x, P } + { Q }". Indeed the latter works thanks to a
tolerance of Camlp5 in parsing "forall x, P" at level 200 while the
rule asks to actually parse the interior of "{ ... }" at level 99 (the
reason for 99 is to be below the rule for "M : T" which is at level
100, so that "{ x : A | P }" does not see "x : A" as a cast). Adding
an extra "'"; pat = pattern in parallel to c = constr LEVEL "99" broke
the tolerance for constr at level 200.

We fix this by adding an ad hoc rule for "{ binder_constr }" in the
native grammar (g_constr.ml4).

Actually, this is inconsistent with having a rule for "{ constr at level 99 }"
in Notations.v. We should have both rules in Notations.v or both rules
hard-wired in the native grammar. But I still don't know what is the best
decision to take, so leaving as it at the current time.

Advantages of hard-wiring both rules in g_constr.ml4: a bit simpler in
metasyntax.ml (no need to ensure that the rule exist). Disadvantages:
if one wants a different initial state without the business needing
the "{ }" for sumbool, sumor, sig, sigT, one still have the rules
there.

Advantages of having them in Notations.v: more modular, we can change
the initial state. Disadvantages: one would need a new kind of
modifier, something like "x at level 99 || binder_constr", with all
the difficulty to find a nice, intuitive, name for "binder_constr",
and the difficulty of understanding if there is a generality to this
"||" disjunction operator, and whether it should be documented or not.

2 files changed, 15 insertions, 17 deletions

diff --git a/theories/Init/Notations.v b/theories/Init/Notations.v
index 0c212b025..a9051e761 100644
--- a/theories/Init/Notations.v
+++ b/theories/Init/Notations.v
@@ -78,6 +78,21 @@ Reserved Notation "{ x : A  |  P  & Q }" (at level 0, x at level 99).
 Reserved Notation "{ x : A  & P }" (at level 0, x at level 99).
 Reserved Notation "{ x : A  & P  & Q }" (at level 0, x at level 99).
 
+Reserved Notation "{ ' pat | P }"
+  (at level 0, pat strict pattern, format "{ ' pat  |  P  }").
+Reserved Notation "{ ' pat | P & Q }"
+  (at level 0, pat strict pattern, format "{ ' pat  |  P  & Q }").
+
+Reserved Notation "{ ' pat : A | P }"
+  (at level 0, pat strict pattern, format "{ ' pat  :  A  |  P }").
+Reserved Notation "{ ' pat : A | P & Q }"
+  (at level 0, pat strict pattern, format "{ ' pat  :  A  |  P  & Q }").
+
+Reserved Notation "{ ' pat : A & P }"
+  (at level 0, pat strict pattern, format "{ ' pat  :  A  & P }").
+Reserved Notation "{ ' pat : A & P & Q }"
+  (at level 0, pat strict pattern, format "{ ' pat  :  A  & P  & Q }").
+
 (** Support for Gonthier-Ssreflect's "if c is pat then u else v" *)
 
 Module IfNotations.
diff --git a/theories/Init/Specif.v b/theories/Init/Specif.v
index ef95aef50..47e8a7558 100644
--- a/theories/Init/Specif.v
+++ b/theories/Init/Specif.v
@@ -53,21 +53,6 @@ Notation "{ x : A  & P }" := (sigT (A:=A) (fun x => P)) : type_scope.
 Notation "{ x : A  & P  & Q }" := (sigT2 (A:=A) (fun x => P) (fun x => Q)) :
   type_scope.
 
-Module SpecifPatternNotations.
-
-Reserved Notation "{ ' pat | P }"
-  (at level 0, pat strict pattern, format "{ ' pat  |  P  }").
-Reserved Notation "{ ' pat | P & Q }"
-  (at level 0, pat strict pattern, format "{ ' pat  |  P  & Q }").
-Reserved Notation "{ ' pat : A | P }"
-  (at level 0, pat strict pattern, format "{ ' pat  :  A  |  P }").
-Reserved Notation "{ ' pat : A | P & Q }"
-  (at level 0, pat strict pattern, format "{ ' pat  :  A  |  P  & Q }").
-Reserved Notation "{ ' pat : A & P }"
-  (at level 0, pat strict pattern, format "{ ' pat  :  A  & P }").
-Reserved Notation "{ ' pat : A & P & Q }"
-  (at level 0, pat strict pattern, format "{ ' pat  :  A  & P  & Q }").
-
 Notation "{ ' pat  |  P }" := (sig (fun pat => P)) : type_scope.
 Notation "{ ' pat  |  P  & Q }" := (sig2 (fun pat => P) (fun pat => Q)) : type_scope.
 Notation "{ ' pat : A  |  P }" := (sig (A:=A) (fun pat => P)) : type_scope.
@@ -77,8 +62,6 @@ Notation "{ ' pat : A  & P }" := (sigT (A:=A) (fun pat => P)) : type_scope.
 Notation "{ ' pat : A  & P  & Q }" := (sigT2 (A:=A) (fun pat => P) (fun pat => Q)) :
   type_scope.
 
-End SpecifPatternNotations.
-
 Add Printing Let sig.
 Add Printing Let sig2.
 Add Printing Let sigT.