From 9eb6140d3a60d1b93dd6c62e11c174a992155ad7 Mon Sep 17 00:00:00 2001
From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Mon, 13 May 2024 15:38:02 -0600
Subject: [PATCH] Remove Quadrature(unsigned int) from the public interface.

---
 include/deal.II/base/quadrature.h | 24 +++++++++++++++++-------
 source/base/quadrature.cc         | 12 ++++++++++++
 2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/include/deal.II/base/quadrature.h b/include/deal.II/base/quadrature.h
index d71f739850..c680be4c5f 100644
--- a/include/deal.II/base/quadrature.h
+++ b/include/deal.II/base/quadrature.h
@@ -130,14 +130,9 @@ public:
   using SubQuadrature = Quadrature<dim == 0 ? 0 : dim - 1>;
 
   /**
-   * Constructor.
-   *
-   * This constructor is marked as explicit to avoid involuntary accidents
-   * like in <code>hp::QCollection@<dim@> q_collection(3)</code> where
-   * <code>hp::QCollection@<dim@> q_collection(QGauss@<dim@>(3))</code> was
-   * meant.
+   * Default constructor.
    */
-  explicit Quadrature(const unsigned int n_quadrature_points = 0);
+  Quadrature();
 
   /**
    * Build this quadrature formula as the tensor product of a formula in a
@@ -336,6 +331,21 @@ public:
   get_tensor_basis() const;
 
 protected:
+  /**
+   * Constructor.
+   *
+   * This constructor is marked as explicit to avoid involuntary accidents
+   * like in <code>hp::QCollection@<dim@> q_collection(3)</code> where
+   * <code>hp::QCollection@<dim@> q_collection(QGauss@<dim@>(3))</code> was
+   * meant. Nonetheless, it is easy to accidentally write
+   * @code
+   *   Quadrature<dim> quadrature(3);
+   * @endcode
+   * where QGauss was meant. As a consequence, this constructor is `protected`
+   * and so only available to derived classes initializing their base class.
+   */
+  explicit Quadrature(const unsigned int n_quadrature_points);
+
   /**
    * List of quadrature points. To be filled by the constructors of derived
    * classes.
diff --git a/source/base/quadrature.cc b/source/base/quadrature.cc
index 0aade1577d..d39f88611e 100644
--- a/source/base/quadrature.cc
+++ b/source/base/quadrature.cc
@@ -27,6 +27,11 @@ DEAL_II_NAMESPACE_OPEN
 
 
 #ifndef DOXYGEN
+template <>
+Quadrature<0>::Quadrature()
+  : is_tensor_product_flag(false)
+{}
+
 template <>
 Quadrature<0>::Quadrature(const unsigned int n_q)
   : quadrature_points(n_q)
@@ -37,6 +42,13 @@ Quadrature<0>::Quadrature(const unsigned int n_q)
 
 
 
+template <int dim>
+Quadrature<dim>::Quadrature()
+  : is_tensor_product_flag(dim == 1)
+{}
+
+
+
 template <int dim>
 Quadrature<dim>::Quadrature(const unsigned int n_q)
   : quadrature_points(n_q, Point<dim>())
-- 
2.39.5