From d93e8a7e7c9ae08cfedaf4a3db00ae3f9240bfe5 Mon Sep 17 00:00:00 2001
From: Pierre-Marie Pédrot
Date: Fri, 7 Oct 2016 18:06:47 +0200
Subject: Fix bug #4464: "Anomaly: variable H' unbound. Please report.".

We simply catch the RetypeError raised by the retyping function and translate
it into a user error, so that it is captured by the tactic monad instead of
reaching toplevel.
---
 pretyping/retyping.mli        | 2 ++
 tactics/tactics.ml            | 6 +++++-
 test-suite/bugs/closed/4464.v | 4 ++++
 3 files changed, 11 insertions(+), 1 deletion(-)
 create mode 100644 test-suite/bugs/closed/4464.v

diff --git a/pretyping/retyping.mli b/pretyping/retyping.mli
index e4cca2679c..8ca40f829f 100644
--- a/pretyping/retyping.mli
+++ b/pretyping/retyping.mli
@@ -46,3 +46,5 @@ val type_of_global_reference_knowing_conclusion :
 val sorts_of_context : env -> evar_map -> Context.Rel.t -> sorts list
 
 val expand_projection : env -> evar_map -> Names.projection -> constr -> constr list -> constr
+
+val print_retype_error : retype_error -> Pp.std_ppcmds
diff --git a/tactics/tactics.ml b/tactics/tactics.ml
index 0629935e10..893f33f1a8 100644
--- a/tactics/tactics.ml
+++ b/tactics/tactics.ml
@@ -48,7 +48,11 @@ let inj_with_occurrences e = (AllOccurrences,e)
 
 let dloc = Loc.ghost
 
-let typ_of env sigma c = Retyping.get_type_of env (Sigma.to_evar_map sigma) c
+let typ_of env sigma c =
+  let open Retyping in
+  try get_type_of ~lax:true env (Sigma.to_evar_map sigma) c
+  with RetypeError e ->
+    user_err_loc (Loc.ghost, "", print_retype_error e)
 
 open Goptions
 
diff --git a/test-suite/bugs/closed/4464.v b/test-suite/bugs/closed/4464.v
new file mode 100644
index 0000000000..f8e9405d93
--- /dev/null
+++ b/test-suite/bugs/closed/4464.v
@@ -0,0 +1,4 @@
+Goal True -> True.
+Proof.
+  intro H'.
+  let H := H' in destruct H; try destruct H.
-- 
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