Coq is a formal proof management system. It provides a formal language to write mathematical definitions, executable algorithms and theorems together with an environment for semi-interactive development of machine-checked proofs.
Here is some code that works in 8.4 and not in trunk-polyproj:
(* File reduced by coq-bug-finder from 64 lines to 30 lines. *)
Set Implicit Arguments.
Set Universe Polymorphism.
Generalizable All Variables.
Record SpecializedCategory (obj : Type) := { Object :> _ := obj }.
Record > Category :=
{ CObject : Type;
UnderlyingCategory :> @SpecializedCategory CObject }.
Record SpecializedFunctor `(C : @SpecializedCategory objC) `(D : @SpecializedCategory objD) :=
{ ObjectOf :> objC -> objD }.
Definition Functor (C D : Category) := SpecializedFunctor C D.
Parameter TerminalCategory : SpecializedCategory unit.
Definition focus A (_ : A) := True.
Definition CommaCategory_Object (A : Category) (S : Functor TerminalCategory A) : Type.
assert (Hf : focus ((S tt) = (S tt))) by constructor.
progress change CObject with (fun C => @Object (CObject C) C) in *.
(* not convertible *)
Here is some code that works in 8.4 and not in trunk-polyproj: