oops forgot the inline keyword (though for gcc it was implicit)

Eigen/src/Geometry/AngleAxis.h

@@ -139,12 +139,12 @@ public:
     * then this function smartly returns a const reference to \c *this.
     */
   template<typename NewScalarType>
-  typename ei_cast_return_type<AngleAxis,AngleAxis<NewScalarType> >::type cast() const
+  inline typename ei_cast_return_type<AngleAxis,AngleAxis<NewScalarType> >::type cast() const
   { return typename ei_cast_return_type<AngleAxis,AngleAxis<NewScalarType> >::type(*this); }
 
   /** Copy constructor with scalar type conversion */
   template<typename OtherScalarType>
-  explicit AngleAxis(const AngleAxis<OtherScalarType>& other)
+  inline explicit AngleAxis(const AngleAxis<OtherScalarType>& other)
   {
     m_axis = other.axis().template cast<OtherScalarType>();
     m_angle = other.angle();

Eigen/src/Geometry/Hyperplane.h

@@ -244,7 +244,7 @@ public:
     * then this function smartly returns a const reference to \c *this.
     */
   template<typename NewScalarType>
-  typename ei_cast_return_type<Hyperplane,
+  inline typename ei_cast_return_type<Hyperplane,
            Hyperplane<NewScalarType,AmbientDimAtCompileTime> >::type cast() const
   {
     return typename ei_cast_return_type<Hyperplane,
@@ -253,7 +253,7 @@ public:
 
   /** Copy constructor with scalar type conversion */
   template<typename OtherScalarType>
-  explicit Hyperplane(const Hyperplane<OtherScalarType,AmbientDimAtCompileTime>& other)
+  inline explicit Hyperplane(const Hyperplane<OtherScalarType,AmbientDimAtCompileTime>& other)
   { m_coeffs = other.coeffs().template cast<OtherScalarType>(); }
 
 protected:

Eigen/src/Geometry/ParametrizedLine.h

@@ -107,7 +107,7 @@ public:
     * then this function smartly returns a const reference to \c *this.
     */
   template<typename NewScalarType>
-  typename ei_cast_return_type<ParametrizedLine,
+  inline typename ei_cast_return_type<ParametrizedLine,
            ParametrizedLine<NewScalarType,AmbientDimAtCompileTime> >::type cast() const
   {
     return typename ei_cast_return_type<ParametrizedLine,
@@ -116,7 +116,7 @@ public:
 
   /** Copy constructor with scalar type conversion */
   template<typename OtherScalarType>
-  explicit ParametrizedLine(const ParametrizedLine<OtherScalarType,AmbientDimAtCompileTime>& other)
+  inline explicit ParametrizedLine(const ParametrizedLine<OtherScalarType,AmbientDimAtCompileTime>& other)
   {
     m_origin = other.origin().template cast<OtherScalarType>();
     m_direction = other.direction().template cast<OtherScalarType>();

Eigen/src/Geometry/Quaternion.h

@@ -201,12 +201,12 @@ public:
     * then this function smartly returns a const reference to \c *this.
     */
   template<typename NewScalarType>
-  typename ei_cast_return_type<Quaternion,Quaternion<NewScalarType> >::type cast() const
+  inline typename ei_cast_return_type<Quaternion,Quaternion<NewScalarType> >::type cast() const
   { return typename ei_cast_return_type<Quaternion,Quaternion<NewScalarType> >::type(*this); }
 
   /** Copy constructor with scalar type conversion */
   template<typename OtherScalarType>
-  explicit Quaternion(const Quaternion<OtherScalarType>& other)
+  inline explicit Quaternion(const Quaternion<OtherScalarType>& other)
   {
     m_coeffs = other.coeffs().template cast<OtherScalarType>();
   }

Eigen/src/Geometry/Rotation2D.h

@@ -107,12 +107,12 @@ public:
     * then this function smartly returns a const reference to \c *this.
     */
   template<typename NewScalarType>
-  typename ei_cast_return_type<Rotation2D,Rotation2D<NewScalarType> >::type cast() const
+  inline typename ei_cast_return_type<Rotation2D,Rotation2D<NewScalarType> >::type cast() const
   { return typename ei_cast_return_type<Rotation2D,Rotation2D<NewScalarType> >::type(*this); }
 
   /** Copy constructor with scalar type conversion */
   template<typename OtherScalarType>
-  explicit Rotation2D(const Rotation2D<OtherScalarType>& other)
+  inline explicit Rotation2D(const Rotation2D<OtherScalarType>& other)
   {
     m_angle = other.angle();
   }

Eigen/src/Geometry/Scaling.h

@@ -134,12 +134,12 @@ public:
     * then this function smartly returns a const reference to \c *this.
     */
   template<typename NewScalarType>
-  typename ei_cast_return_type<Scaling,Scaling<NewScalarType,Dim> >::type cast() const
+  inline typename ei_cast_return_type<Scaling,Scaling<NewScalarType,Dim> >::type cast() const
   { return typename ei_cast_return_type<Scaling,Scaling<NewScalarType,Dim> >::type(*this); }
 
   /** Copy constructor with scalar type conversion */
   template<typename OtherScalarType>
-  explicit Scaling(const Scaling<OtherScalarType,Dim>& other)
+  inline explicit Scaling(const Scaling<OtherScalarType,Dim>& other)
   { m_coeffs = other.coeffs().template cast<OtherScalarType>(); }
 
 };

Eigen/src/Geometry/Transform.h

@@ -252,12 +252,12 @@ public:
     * then this function smartly returns a const reference to \c *this.
     */
   template<typename NewScalarType>
-  typename ei_cast_return_type<Transform,Transform<NewScalarType,Dim> >::type cast() const
+  inline typename ei_cast_return_type<Transform,Transform<NewScalarType,Dim> >::type cast() const
   { return typename ei_cast_return_type<Transform,Transform<NewScalarType,Dim> >::type(*this); }
 
   /** Copy constructor with scalar type conversion */
   template<typename OtherScalarType>
-  explicit Transform(const Transform<OtherScalarType,Dim>& other)
+  inline explicit Transform(const Transform<OtherScalarType,Dim>& other)
   { m_matrix = other.matrix().template cast<OtherScalarType>(); }
 
 protected:

Eigen/src/Geometry/Translation.h

@@ -137,12 +137,12 @@ public:
     * then this function smartly returns a const reference to \c *this.
     */
   template<typename NewScalarType>
-  typename ei_cast_return_type<Translation,Translation<NewScalarType,Dim> >::type cast() const
+  inline typename ei_cast_return_type<Translation,Translation<NewScalarType,Dim> >::type cast() const
   { return typename ei_cast_return_type<Translation,Translation<NewScalarType,Dim> >::type(*this); }
 
   /** Copy constructor with scalar type conversion */
   template<typename OtherScalarType>
-  explicit Translation(const Translation<OtherScalarType,Dim>& other)
+  inline explicit Translation(const Translation<OtherScalarType,Dim>& other)
   { m_coeffs = other.vector().template cast<OtherScalarType>(); }
 
 };