Aliasing doc: explain that some cases are detected, reverse order examples.
diff --git a/doc/snippets/TopicAliasing_block.cpp b/doc/snippets/TopicAliasing_block.cpp
index 9e897d0..7d40cfa 100644
--- a/doc/snippets/TopicAliasing_block.cpp
+++ b/doc/snippets/TopicAliasing_block.cpp
@@ -1,4 +1,4 @@
-Matrix3i mat; 
+MatrixXi mat(3,3); 
 mat << 1, 2, 3,   4, 5, 6,   7, 8, 9;
 cout << "Here is the matrix mat:\n" << mat << endl;
 mat.bottomRightCorner(2,2) = mat.topLeftCorner(2,2);