[location] [ast] Switch Constrexpr AST to an extensible node type.

Following @gasche idea, and the original intention of #402, we switch
the main parsing AST of Coq from `'a Loc.located` to `'a CAst.ast`
which is private and record-based.

This provides significantly clearer code for the AST, and is robust
wrt attributes.

1 files changed, 24 insertions, 0 deletions

diff --git a/lib/cAst.ml b/lib/cAst.ml
new file mode 100644
index 000000000..5916c9ec1
--- /dev/null
+++ b/lib/cAst.ml
@@ -0,0 +1,24 @@
+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2017     *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+
+(** The ast type contains generic metadata for AST nodes. *)
+type 'a ast = {
+  v   : 'a;
+  loc : Loc.t option;
+}
+
+let make ?loc v = { v; loc }
+
+let map f n = { n with v = f n.v }
+let map_with_loc f n = { n with v = f ?loc:n.loc n.v }
+let map_from_loc f n =
+  let loc, v = Loc.to_pair n in
+  { v = f ?loc v ; loc }
+
+let with_val f n = f n.v
+let with_loc_val f n = f ?loc:n.loc n.v