As proposed on the list:

- rename EvalBeforeAssignBit to MayAliasBit
- make .lazy() remove the MayAliasBit only, and mark it as deprecated
- add a NoAlias pseudo expression, and MatrixBase::noalias() function
Todo:
- we have to decide whether += and -= assume no aliasing by default ?
- once we agree on the API: update the Sparse module and the unit tests respectively.

Eigen/src/Core/util/ForwardDeclarations.h

@@ -35,6 +35,7 @@ template<typename _Scalar, int _Rows, int _Cols,
          int _MaxRows = _Rows, int _MaxCols = _Cols> class Matrix;
 
 template<typename ExpressionType, unsigned int Added, unsigned int Removed> class Flagged;
+template<typename ExpressionType> class NoAlias;
 template<typename ExpressionType> class NestByValue;
 template<typename ExpressionType> class SwapWrapper;
 template<typename MatrixType> class Minor;