From 64b56ee86fa8e32afd7802a9c5567ee9f15dd386 Mon Sep 17 00:00:00 2001
From: Gaëtan Gilbert
Date: Mon, 12 Oct 2020 16:21:06 +0200
Subject: Check types when converting irrelevant terms in old unification

Fixes probably many strange issues such as the example in #13171
---
 test-suite/success/sprop_uip.v | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

(limited to 'test-suite/success')

diff --git a/test-suite/success/sprop_uip.v b/test-suite/success/sprop_uip.v
index eae1b75689..c9377727db 100644
--- a/test-suite/success/sprop_uip.v
+++ b/test-suite/success/sprop_uip.v
@@ -121,6 +121,33 @@ Proof.
   simpl. Fail check.
 Abort.
 
+Module HoTTStyle.
+  (* a small proof which tests destruct in a tricky case *)
+
+  Definition ap {A B} (f:A -> B) {x y} (e : seq x y) : seq (f x) (f y).
+  Proof. destruct e. reflexivity. Defined.
+
+  Section S.
+    Context
+      (A : Type)
+      (B : Type)
+      (f : A -> B)
+      (g : B -> A)
+      (section : forall a, seq (g (f a)) a)
+      (retraction : forall b, seq (f (g b)) b).
+
+    Lemma bla (P : B -> Type) (a : A) (F : forall a, P (f a))
+      : seq_rect _ (f (g (f a))) (fun a _ => P a) (F (g (f a))) (f a) (retraction (f a)) = F a.
+    Proof.
+      lazy.
+      change (retraction (f a)) with (ap f (section a)).
+      destruct (section a).
+      reflexivity.
+    Qed.
+  End S.
+
+End HoTTStyle.
+
 (* check that extraction doesn't fall apart on matches with special reduction *)
 Require Extraction.
 
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