spatial: Add fwd decl in some se3 headers to avoid issue with cppadcg

Author: jorisv

include/pinocchio/spatial/se3-expr-base.hpp

@@ -7,6 +7,18 @@
 
 namespace pinocchio
 {
+  // Forward declaration
+  // TODO: This should go into spatial/fwd.hpp but because of a strange include path
+  // in context/cppadcg.hpp we can include se3.hpp without including spatial/fwd.hpp first.
+  template<typename Derived>
+  struct SE3ExprBase;
+  template<typename Derived>
+  struct SE3ExprNoalias;
+  template<typename RotProduct, typename TransProduct>
+  struct SE3ExprProduct;
+  template<typename RotProduct, typename TransProduct>
+  SE3ExprProduct<RotProduct, TransProduct>
+  make_se3_expr_product(RotProduct rot_prod, TransProduct trans_prod);
 
 // Forward traits typedef
 #define PINOCCHIO_SE3_EXPR_TYPEDEF_TPL(Derived)                                                    \

include/pinocchio/spatial/se3-tpl.hpp

@@ -17,6 +17,14 @@
 
 namespace pinocchio
 {
+  // Forward declarations
+  // TODO: This should go into spatial/fwd.hpp but because of a strange include path
+  // in context/cppadcg.hpp we can include se3.hpp without including spatial/fwd.hpp first.
+  template<typename _Scalar, int _Options>
+  struct SE3TplExpr;
+  template<typename _Scalar, int _Options>
+  struct SE3TplConstExpr;
+
   template<typename _Scalar, int _Options>
   struct traits<SE3Tpl<_Scalar, _Options>>
   {