Remove `_ : Type` from packed classes

This increases performance 10% - 15% for Coq v8.6.1 - v8.9.dev.
Tested on a Debain-based 16-core build server and
a Macbook Pro laptop with 2,3 GHz Intel Core i5.

|                            | Compilation time, old         | Compilation | Speedup |
|                            | (mathcomp commit 967088a6f87) | time, new   |         |
| Coq 8.6.1                  | 10min 33s                     | 9min 10s    | 15%     |
| Coq 8.7.2                  | 10min 12s                     | 8min 50s    | 15%     |
| Coq 8.8.2                  | 9min 39s                      | 8min 32s    | 13%     |
| Coq 8.9.dev(05d827c800544) | 9min 12s                      | 8min 16s    | 11%     |
|                            |                               |             |         |

It seems Coq at some point fixed the problem `_ : Type` was
supposed to solve.

1 files changed, 11 insertions, 11 deletions

diff --git a/mathcomp/algebra/vector.v b/mathcomp/algebra/vector.v
index 542f8ad..75b2073 100644
--- a/mathcomp/algebra/vector.v
+++ b/mathcomp/algebra/vector.v
@@ -117,27 +117,27 @@ Inductive mixin_of (V : lmodType R) := Mixin dim & axiom_def dim (Phant V).
 
 Structure class_of V := Class {
   base : GRing.Lmodule.class_of R V;
-  mixin : mixin_of (GRing.Lmodule.Pack _ base V)
+  mixin : mixin_of (GRing.Lmodule.Pack _ base)
 }.
 Local Coercion base : class_of >-> GRing.Lmodule.class_of.
 
-Structure type (phR : phant R) := Pack {sort; _ : class_of sort; _ : Type}.
+Structure type (phR : phant R) := Pack {sort; _ : class_of sort}.
 Local Coercion sort : type >-> Sortclass.
 Variables (phR : phant R) (T : Type) (cT : type phR).
-Definition class := let: Pack _ c _ := cT return class_of cT in c.
-Definition clone c of phant_id class c := @Pack phR T c T.
-Let xT := let: Pack T _ _ := cT in T.
+Definition class := let: Pack _ c := cT return class_of cT in c.
+Definition clone c of phant_id class c := @Pack phR T c.
+Let xT := let: Pack T _ := cT in T.
 Notation xclass := (class : class_of xT).
 Definition dim := let: Mixin n _ := mixin class in n.
 
-Definition pack b0 (m0 : mixin_of (@GRing.Lmodule.Pack R _ T b0 T)) :=
+Definition pack b0 (m0 : mixin_of (@GRing.Lmodule.Pack R _ T b0)) :=
   fun bT b & phant_id (@GRing.Lmodule.class _ phR bT) b =>
-  fun    m & phant_id m0 m => Pack phR (@Class T b m) T.
+  fun    m & phant_id m0 m => Pack phR (@Class T b m).
 
-Definition eqType := @Equality.Pack cT xclass xT.
-Definition choiceType := @Choice.Pack cT xclass xT.
-Definition zmodType := @GRing.Zmodule.Pack cT xclass xT.
-Definition lmodType := @GRing.Lmodule.Pack R phR cT xclass xT.
+Definition eqType := @Equality.Pack cT xclass.
+Definition choiceType := @Choice.Pack cT xclass.
+Definition zmodType := @GRing.Zmodule.Pack cT xclass.
+Definition lmodType := @GRing.Lmodule.Pack R phR cT xclass.
 
 End ClassDef.
 Notation axiom n V := (axiom_def n (Phant V)).