[eigen] clang-3.1 issue

[Benjamin Schindler <bschindler@xxxxxxxxxxx>]

Hi

I just stumbled over this issue, may be you have some input on it, but
I'm really thinking I have found a clang bug. Consider the attached code
(I used latest tip of Eigen). It fails to compile with

test.cpp:11:18: error: use of overloaded operator '=' is ambiguous (with
operand types 'typename FixedSegmentReturnType<3>::Type' (aka
'VectorBlock<Eigen::Matrix<float, 4, 1, 0, 4, 1>, 3>') and 'const
ConstantReturnType' (aka 'const
      CwiseNullaryOp<internal::scalar_constant_op<Scalar>,
Eigen::Matrix<float, 3, 1, 0, 3, 1> >'))
        input.head<3>() = Vector3f::Zero();
        ~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~
test.cpp:17:2: note: in instantiation of function template
specialization 'myFunction<float>' requested here
        myFunction<float>();
        ^
/local/bschindler/projects/eigen/Eigen/src/Core/MatrixBase.h:169:14:
note: candidate function [with OtherDerived =
Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<float>,
Eigen::Matrix<float, 3, 1, 0, 3, 1> >]
    Derived& operator=(const DenseBase<OtherDerived>& other);
             ^
/local/bschindler/projects/eigen/Eigen/src/Core/MatrixBase.h:172:14:
note: candidate function [with OtherDerived =
Eigen::CwiseNullaryOp<Eigen::internal::scalar_constant_op<float>,
Eigen::Matrix<float, 3, 1, 0, 3, 1> >]
    Derived& operator=(const EigenBase<OtherDerived>& other);


Now, If I move lines 10 and 11 into the main function it compiles.
clang bug?

Cheers
Benjamin

#include <Eigen/Core>

using namespace Eigen;

template<typename T>
void myFunction()
{
	T someValue = 1.0f;

	Vector4f input = Vector4f::Zero();
	input.head<3>() = Vector3f::Zero();
}


int main(int, char**)
{
	myFunction<float>();
	return 0;
}