From 7050ceaa09a29c3f50620a8d3f8439c3d69a10d0 Mon Sep 17 00:00:00 2001
From: Hugo Herbelin
Date: Wed, 26 Dec 2018 23:46:19 +0100
Subject: Documenting syntax "injection ... as [= pat1 ... patn ]".

To prevent confusion, forbidding a mix of the "injection term as pat1
... patn" and of the "injection term as [= pat1 ... patn]" syntax: If
a "[= ...]" occurs, this should be a singleton list of patterns.
---
 plugins/ltac/extratactics.mlg | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

(limited to 'plugins/ltac')

diff --git a/plugins/ltac/extratactics.mlg b/plugins/ltac/extratactics.mlg
index f5098d2a34..4c186dce09 100644
--- a/plugins/ltac/extratactics.mlg
+++ b/plugins/ltac/extratactics.mlg
@@ -146,6 +146,23 @@ let discrHyp id =
 let injection_main with_evars c =
  elimOnConstrWithHoles (injClause None None) with_evars c
 
+let isInjPat pat = match pat.CAst.v with IntroAction (IntroInjection _) -> Some pat.CAst.loc | _ -> None
+
+let decode_inj_ipat ?loc = function
+  (* For the "as [= pat1 ... patn ]" syntax *)
+  | [{ CAst.v = IntroAction (IntroInjection ipat) }] -> ipat
+  (* For the "as pat1 ... patn" syntax *)
+  | ([] | [_]) as ipat -> ipat
+  | pat1::pat2::_ as ipat ->
+  (* To be sure that there is no confusion of syntax, we check that no [= ...] occurs
+     in the non-singleton list of patterns *)
+  match isInjPat pat1 with
+  | Some _ -> user_err ?loc:pat2.CAst.loc (str "Unexpected pattern.")
+  | None ->
+  match List.map_filter isInjPat ipat with
+  | loc :: _ -> user_err ?loc (str "Unexpected injection pattern.")
+  | [] -> ipat
+
 }
 
 TACTIC EXTEND injection
@@ -158,15 +175,15 @@ TACTIC EXTEND einjection
 END
 TACTIC EXTEND injection_as
 | [ "injection" "as" intropattern_list(ipat)] ->
-    { injClause None (Some ipat) false None }
+    { injClause None (Some (decode_inj_ipat ipat)) false None }
 | [ "injection" destruction_arg(c) "as" intropattern_list(ipat)] ->
-    { mytclWithHoles (injClause None (Some ipat)) false c }
+    { mytclWithHoles (injClause None (Some (decode_inj_ipat ipat))) false c }
 END
 TACTIC EXTEND einjection_as
 | [ "einjection" "as" intropattern_list(ipat)] ->
-    { injClause None (Some ipat) true None }
+    { injClause None (Some (decode_inj_ipat ipat)) true None }
 | [ "einjection" destruction_arg(c) "as" intropattern_list(ipat)] ->
-    { mytclWithHoles (injClause None (Some ipat)) true c }
+    { mytclWithHoles (injClause None (Some (decode_inj_ipat ipat))) true c }
 END
 TACTIC EXTEND simple_injection
 | [ "simple" "injection" ] -> { simpleInjClause None false None }
-- 
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