AffineConstraints: Improve wording and add a note

diff --git a/include/deal.II/lac/affine_constraints.h b/include/deal.II/lac/affine_constraints.h
index 6b10a5fee8c069e25799934a40b176231a16e4f0..dd92453904585fd58397ec076e57c3820aff37cc 100644 (file)
--- a/include/deal.II/lac/affine_constraints.h
+++ b/include/deal.II/lac/affine_constraints.h
@@ -60,9 +60,13 @@ class AffineConstraints;
  * ConstraintMatrix has been renamed to AffineConstraints. Provide a
  * compatibility typedef that defaults to AffineConstraints<double>.
  *
- * @deprecated Use AffineConstraints
+ * @deprecated Use AffineConstraints<double> instead of ConstraintMatrix
  */
 using ConstraintMatrix = AffineConstraints<double>;
+// Note: Unfortunately, we cannot move this compatibility typedef into
+// constraint_matrix.h directly. This would break a lot of user projects
+// that include constraint_matrix.h transitively due to various deal.II
+// headers that include the file.
 
 
 // TODO[WB]: We should have a function of the kind