Port fix for bugs 4763, 5149, previously 0b417c12e

Adds a compatibility flag so that the behavior of 8.5 can be obtained too.

Original commit:
   unification.ml: fix for bug #4763, unif regression

    Do not force all remaining conversions problems to be solved after
    the _first_ solution of an evar. This was hell to track down, thanks
    for the help of Maxime. contribs pass and HoTT too.

1 files changed, 20 insertions, 1 deletions

diff --git a/test-suite/bugs/closed/HoTT_coq_117.v b/test-suite/bugs/closed/HoTT_coq_117.v
index 5fbcfef4e..de60fd0ae 100644
--- a/test-suite/bugs/closed/HoTT_coq_117.v
+++ b/test-suite/bugs/closed/HoTT_coq_117.v
@@ -16,10 +16,29 @@ Definition path_forall `{Funext} {A : Type} {P : A -> Type} (f g : forall x : A,
 Admitted.
 
 Inductive Empty : Set := .
-Instance contr_from_Empty {_ : Funext} (A : Type) :
+Fail Instance contr_from_Empty {_ : Funext} (A : Type) :
+  Contr_internal (Empty -> A) :=
+  BuildContr _
+             (Empty_rect (fun _ => A))
+             (fun f => path_forall _ f (fun x => Empty_rect _ x)).
+
+Fail Instance contr_from_Empty {F : Funext} (A : Type) :
   Contr_internal (Empty -> A) :=
   BuildContr _
              (Empty_rect (fun _ => A))
              (fun f => path_forall _ f (fun x => Empty_rect _ x)).
+
+(** This could be disallowed, this uses the Funext argument *)
+Instance contr_from_Empty {_ : Funext} (A : Type) :
+  Contr_internal (Empty -> A) :=
+  BuildContr _
+             (Empty_rect (fun _ => A))
+             (fun f => path_forall _ f (fun x => Empty_rect (fun _ => _ x = f x) x)).
+
+Instance contr_from_Empty' {_ : Funext} (A : Type) :
+  Contr_internal (Empty -> A) :=
+  BuildContr _
+             (Empty_rect (fun _ => A))
+             (fun f => path_forall _ f (fun x => Empty_rect (fun _ => _ x = f x) x)).
 (* Toplevel input, characters 15-220:
 Anomaly: unknown meta ?190. Please report. *)