fix Transform() constructor taking a Transform with other mode.

Not really tested as the geometry tests are currently busted.

2 files changed, 27 insertions, 4 deletions

diff --git a/Eigen/src/Core/util/StaticAssert.h b/Eigen/src/Core/util/StaticAssert.h
index d285f79b1..23fb84c6c 100644
--- a/Eigen/src/Core/util/StaticAssert.h
+++ b/Eigen/src/Core/util/StaticAssert.h
@@ -62,6 +62,7 @@
         THIS_METHOD_IS_ONLY_FOR_MATRICES_OF_A_SPECIFIC_SIZE,
         THIS_METHOD_IS_ONLY_FOR_OBJECTS_OF_A_SPECIFIC_SIZE,
         YOU_MADE_A_PROGRAMMING_MISTAKE,
+        EIGEN_INTERNAL_ERROR_PLEASE_FILE_A_BUG_REPORT,
         EIGEN_INTERNAL_COMPILATION_ERROR_OR_YOU_MADE_A_PROGRAMMING_MISTAKE,
         YOU_CALLED_A_FIXED_SIZE_METHOD_ON_A_DYNAMIC_SIZE_MATRIX_OR_VECTOR,
         YOU_CALLED_A_DYNAMIC_SIZE_METHOD_ON_A_FIXED_SIZE_MATRIX_OR_VECTOR,
@@ -88,7 +89,8 @@
         THE_BRACKET_OPERATOR_IS_ONLY_FOR_VECTORS__USE_THE_PARENTHESIS_OPERATOR_INSTEAD,
         PACKET_ACCESS_REQUIRES_TO_HAVE_INNER_STRIDE_FIXED_TO_1,
         THIS_METHOD_IS_ONLY_FOR_SPECIFIC_TRANSFORMATIONS,
-        YOU_CANNOT_MIX_ARRAYS_AND_MATRICES
+        YOU_CANNOT_MIX_ARRAYS_AND_MATRICES,
+        YOU_CANT_CONVERT_A_PROJECTIVE_TRANSFORM_INTO_AN_AFFINE_TRANSFORM
       };
     };
 
diff --git a/Eigen/src/Geometry/Transform.h b/Eigen/src/Geometry/Transform.h
index 5a0bb5e29..214b286bd 100644
--- a/Eigen/src/Geometry/Transform.h
+++ b/Eigen/src/Geometry/Transform.h
@@ -243,9 +243,30 @@ public:
   template<int OtherMode>
   inline Transform(const Transform<Scalar,Dim,OtherMode>& other)
   {
-    ei_assert(OtherMode!=int(Projective) && "You cannot directly assign a projective transform to an affine one.");
-    typedef typename Transform<Scalar,Dim,OtherMode>::MatrixType OtherMatrixType;
-    ei_transform_construct_from_matrix<OtherMatrixType,Mode,Dim,HDim>::run(this, other.matrix());
+    EIGEN_STATIC_ASSERT(EIGEN_IMPLIES(OtherMode==int(Projective), Mode==int(Projective)),
+                        YOU_CANT_CONVERT_A_PROJECTIVE_TRANSFORM_INTO_AN_AFFINE_TRANSFORM)
+
+    enum { ModeIsAffineCompact = Mode == int(AffineCompact),
+           OtherModeIsAffineCompact = OtherMode == int(AffineCompact)
+    };
+
+    if(ModeIsAffineCompact == OtherModeIsAffineCompact)
+    {
+      m_matrix = other.matrix();
+    }
+    else if(OtherModeIsAffineCompact)
+    {
+      typedef typename Transform<Scalar,Dim,OtherMode>::MatrixType OtherMatrixType;
+      ei_transform_construct_from_matrix<OtherMatrixType,Mode,Dim,HDim>::run(this, other.matrix());
+    }
+    else
+    {
+      // here we know that Mode == AffineCompact and OtherMode != AffineCompact.
+      // if OtherMode were Projective, the static assert above would already have caught it.
+      // So the only possibility is that OtherMode == Affine
+      linear() = other.linear();
+      translation() = other.translation();
+    }
   }
 
   template<typename OtherDerived>