From bf79a3199c87ccfa254b3e4a4111888c010f2c52 Mon Sep 17 00:00:00 2001
From: Hauke Heibel <hauke.heibel@gmail.com>
Date: Fri, 11 Feb 2011 09:41:48 +0100
Subject: [PATCH] Reduced error traces when mixing matrices with different
 scalar types.

---
 Eigen/src/Core/Matrix.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/Eigen/src/Core/Matrix.h b/Eigen/src/Core/Matrix.h
index d304fad60..2b7202c62 100644
--- a/Eigen/src/Core/Matrix.h
+++ b/Eigen/src/Core/Matrix.h
@@ -285,6 +285,11 @@ class Matrix
     EIGEN_STRONG_INLINE Matrix(const MatrixBase<OtherDerived>& other)
              : Base(other.rows() * other.cols(), other.rows(), other.cols())
     {
+      // This test resides here, to bring the error messages closer to the user. Normally, these checks
+      // are performed deeply within the library, thus causing long and scary error traces.
+      EIGEN_STATIC_ASSERT((internal::is_same<Scalar, typename OtherDerived::Scalar>::value),
+        YOU_MIXED_DIFFERENT_NUMERIC_TYPES__YOU_NEED_TO_USE_THE_CAST_METHOD_OF_MATRIXBASE_TO_CAST_NUMERIC_TYPES_EXPLICITLY)
+
       Base::_check_template_params();
       Base::_set_noalias(other);
     }