From fcd903c299db00d5c8d3e2fa797404eb880b61ac Mon Sep 17 00:00:00 2001
From: Pierre-Marie Pédrot
Date: Thu, 19 Dec 2019 18:03:34 +0100
Subject: Ensure that a custom entry cannot be defined twice.

This highlights the fact that diamond inheritance of a custom entry
is a tricky problem, as well as merely importing two custom entries with
the same name from two different modules. The only sane way to give a
semantics to that is to stick to module-scoped objects, i.e. give those
entries a kernel name. In the meantime, I went for a warning when
overriding entries.
---
 parsing/pcoq.ml | 1 +
 1 file changed, 1 insertion(+)

(limited to 'parsing')

diff --git a/parsing/pcoq.ml b/parsing/pcoq.ml
index 734dd8ee8a..26afdcb9d5 100644
--- a/parsing/pcoq.ml
+++ b/parsing/pcoq.ml
@@ -533,6 +533,7 @@ let extend_entry_command (type a) (type b) (tag : (a, b) entry_command) (g : a)
       try EntryDataMap.find tag !camlp5_entries
       with Not_found -> EntryData.Ex String.Map.empty
     in
+    let () = assert (not @@ String.Map.mem name old) in
     let entries = String.Map.add name e old in
     camlp5_entries := EntryDataMap.add tag (EntryData.Ex entries) !camlp5_entries
   in
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