fix computation of fixed size sub/super diagonal size

diff --git a/Eigen/src/Core/Diagonal.h b/Eigen/src/Core/Diagonal.h
index 1876932..3af3c69 100644
--- a/Eigen/src/Core/Diagonal.h
+++ b/Eigen/src/Core/Diagonal.h

@@ -56,16 +56,15 @@
   typedef typename remove_reference<MatrixTypeNested>::type _MatrixTypeNested;
   typedef typename MatrixType::StorageKind StorageKind;
   enum {
-    AbsDiagIndex = DiagIndex<0 ? -DiagIndex : DiagIndex, // only used if DiagIndex != Dynamic
-    // FIXME these computations are broken in the case where the matrix is rectangular and DiagIndex!=0
     RowsAtCompileTime = (int(DiagIndex) == Dynamic || int(MatrixType::SizeAtCompileTime) == Dynamic) ? Dynamic
-                      : (EIGEN_SIZE_MIN_PREFER_DYNAMIC(MatrixType::RowsAtCompileTime,
-                                        MatrixType::ColsAtCompileTime) - AbsDiagIndex),
+    : (EIGEN_PLAIN_ENUM_MIN(MatrixType::RowsAtCompileTime - EIGEN_PLAIN_ENUM_MAX(-DiagIndex, 0),
+                            MatrixType::ColsAtCompileTime - EIGEN_PLAIN_ENUM_MAX( DiagIndex, 0))),
     ColsAtCompileTime = 1,
     MaxRowsAtCompileTime = int(MatrixType::MaxSizeAtCompileTime) == Dynamic ? Dynamic
                          : DiagIndex == Dynamic ? EIGEN_SIZE_MIN_PREFER_FIXED(MatrixType::MaxRowsAtCompileTime,
-                                                                    MatrixType::MaxColsAtCompileTime)
-                         : (EIGEN_SIZE_MIN_PREFER_FIXED(MatrixType::MaxRowsAtCompileTime, MatrixType::MaxColsAtCompileTime) - AbsDiagIndex),
+                                                                              MatrixType::MaxColsAtCompileTime)
+                         : (EIGEN_PLAIN_ENUM_MIN(MatrixType::MaxRowsAtCompileTime - EIGEN_PLAIN_ENUM_MAX(-DiagIndex, 0),
+                                                 MatrixType::MaxColsAtCompileTime - EIGEN_PLAIN_ENUM_MAX( DiagIndex, 0))),
     MaxColsAtCompileTime = 1,
     MaskLvalueBit = is_lvalue<MatrixType>::value ? LvalueBit : 0,
     Flags = (unsigned int)_MatrixTypeNested::Flags & (HereditaryBits | LinearAccessBit | MaskLvalueBit | DirectAccessBit) & ~RowMajorBit,

diff --git a/test/diagonal.cpp b/test/diagonal.cpp
index 94a30e2..191a91b 100644
--- a/test/diagonal.cpp
+++ b/test/diagonal.cpp

@@ -51,19 +51,32 @@
     };
 
     // check sub/super diagonal
+    if(m1.template diagonal<N1>().RowsAtCompileTime!=Dynamic)
+    {
+      VERIFY(m1.template diagonal<N1>().RowsAtCompileTime == m1.diagonal(N1).size());
+    }
+    if(m1.template diagonal<N2>().RowsAtCompileTime!=Dynamic)
+    {
+      VERIFY(m1.template diagonal<N2>().RowsAtCompileTime == m1.diagonal(N2).size());
+    }
+
     m2.template diagonal<N1>() = 2 * m1.template diagonal<N1>();
+    VERIFY_IS_APPROX(m2.template diagonal<N1>(), static_cast<Scalar>(2) * m1.diagonal(N1));
     m2.template diagonal<N1>()[0] *= 3;
     VERIFY_IS_APPROX(m2.template diagonal<N1>()[0], static_cast<Scalar>(6) * m1.template diagonal<N1>()[0]);
 
+
     m2.template diagonal<N2>() = 2 * m1.template diagonal<N2>();
     m2.template diagonal<N2>()[0] *= 3;
     VERIFY_IS_APPROX(m2.template diagonal<N2>()[0], static_cast<Scalar>(6) * m1.template diagonal<N2>()[0]);
 
     m2.diagonal(N1) = 2 * m1.diagonal(N1);
+    VERIFY_IS_APPROX(m2.diagonal<N1>(), static_cast<Scalar>(2) * m1.diagonal(N1));
     m2.diagonal(N1)[0] *= 3;
     VERIFY_IS_APPROX(m2.diagonal(N1)[0], static_cast<Scalar>(6) * m1.diagonal(N1)[0]);
 
     m2.diagonal(N2) = 2 * m1.diagonal(N2);
+    VERIFY_IS_APPROX(m2.diagonal<N2>(), static_cast<Scalar>(2) * m1.diagonal(N2));
     m2.diagonal(N2)[0] *= 3;
     VERIFY_IS_APPROX(m2.diagonal(N2)[0], static_cast<Scalar>(6) * m1.diagonal(N2)[0]);
   }
@@ -73,6 +86,8 @@
 {
   for(int i = 0; i < g_repeat; i++) {
     CALL_SUBTEST_1( diagonal(Matrix<float, 1, 1>()) );
+    CALL_SUBTEST_1( diagonal(Matrix<float, 4, 9>()) );
+    CALL_SUBTEST_1( diagonal(Matrix<float, 7, 3>()) );
     CALL_SUBTEST_2( diagonal(Matrix4d()) );
     CALL_SUBTEST_2( diagonal(MatrixXcf(internal::random<int>(1,EIGEN_TEST_MAX_SIZE), internal::random<int>(1,EIGEN_TEST_MAX_SIZE))) );
     CALL_SUBTEST_2( diagonal(MatrixXi(internal::random<int>(1,EIGEN_TEST_MAX_SIZE), internal::random<int>(1,EIGEN_TEST_MAX_SIZE))) );