Fixing bug #4216:

Internal error: Anomaly: Uncaught exception Not_found. Please report.

An evarmap was lost because of an unsound typing primitive.

2 files changed, 24 insertions, 4 deletions

diff --git a/tactics/equality.ml b/tactics/equality.ml
index fb7237e4b2..ea74dc37ea 100644
--- a/tactics/equality.ml
+++ b/tactics/equality.ml
@@ -165,10 +165,10 @@ let instantiate_lemma_all frzevars gl c ty l l2r concl =
   in List.map try_occ occs
 
 let instantiate_lemma gl c ty l l2r concl =
-  let ct = pf_unsafe_type_of gl c in
-  let t = try snd (pf_reduce_to_quantified_ind gl ct) with UserError _ -> ct in
-  let eqclause = pf_apply Clenv.make_clenv_binding gl (c,t) l in
-   [eqclause]
+  let sigma, ct = pf_type_of gl c in
+  let t = try snd (reduce_to_quantified_ind (pf_env gl) sigma ct) with UserError _ -> ct in
+  let eqclause = Clenv.make_clenv_binding (pf_env gl) sigma (c,t) l in
+  [eqclause]
 
 let rewrite_conv_closed_core_unif_flags = {
   modulo_conv_on_closed_terms = Some full_transparent_state;
diff --git a/test-suite/bugs/closed/4216.v b/test-suite/bugs/closed/4216.v
new file mode 100644
index 0000000000..ae7f746778
--- /dev/null
+++ b/test-suite/bugs/closed/4216.v
@@ -0,0 +1,20 @@
+Generalizable Variables T A.
+
+Inductive path `(a: A): A -> Type := idpath: path a a.
+
+Class TMonad (T: Type -> Type) := {
+  bind: forall {A B: Type}, (T A) -> (A -> T B) -> T B;
+  ret: forall {A: Type}, A -> T A;
+  ret_unit_left: forall {A B: Type} (k: A -> T B) (a: A),
+                 path (bind (ret a) k) (k a)
+  }.
+
+Let T_fzip `{TMonad T} := fun (A B: Type) (f: T (A -> B)) (t: T A)
+                  => bind t (fun a => bind f (fun g => ret (g a) )).
+Let T_pure `{TMonad T} := @ret _ _.
+
+Let T_pure_id `{TMonad T} {A: Type} (t: A -> A) (x: T A): 
+        path (T_fzip A A (T_pure (A -> A) t) x) x.
+  unfold T_fzip, T_pure.
+  Fail rewrite (ret_unit_left (fun g a => ret (g a)) (fun x => x)).
+