[Type] Simplification of the Rebind trait using concepts (#5200)

* [Type] Simplification of the Rebind trait using concepts

* fix

* fix and test

* parentheses

Sofa/framework/Type/src/sofa/type/trait/Rebind.h

@@ -23,19 +23,18 @@
 
 namespace sofa::type
 {
-    // primary template handles types that have no nested ::rebind_to member:
-    template< class T, class OtherType, class = void >
-    struct HasRebindTypedef : std::false_type { };
+    template<class T, class OtherType>
+    concept CanTypeRebind = requires
+    {
+        typename T::template rebind_to<OtherType>;
+    };
 
-    // specialization recognizes types that do have a nested ::rebind_to member:
-    template< class T, class OtherType >
-    struct HasRebindTypedef<T, OtherType, std::void_t<typename T::template rebind_to<OtherType> > > : std::true_type { };
 
     /**
      * Depending on the type _T, has a public member typedef to. Otherwise, there is no member typedef (this is the
      * case of this implementation).
      */
-    template<class _T, class _OtherType, class Enable = void>
+    template<class _T, class _OtherType>
     struct Rebind {};
 
     /**
@@ -45,33 +44,20 @@ namespace sofa::type
      * \tparam _T Type that does have a nested ::rebind_to member
      */
     template<class _T, class _OtherType>
-    struct Rebind<_T, _OtherType, std::enable_if_t<HasRebindTypedef<_T, _OtherType>::value > >
+    requires CanTypeRebind<_T, _OtherType>
+    struct Rebind<_T, _OtherType>
     {
         using to = typename _T::template rebind_to<_OtherType>;
     };
 
-    template <class...>
-    inline constexpr auto deny = false;
-
-    /**
-     * \brief Specialization for types that do NOT have a nested ::rebind_to member. In this implementation, Rebind has
-     * no public member typedef \ref to. If this implementation is chosen by the compiler (the number of template
-     * parameters is probably different from 1), a compilation error occurs.
-     * \tparam _T Type that does NOT have a nested ::rebind_to member
-     */
-    template<class _T, class _OtherType>
-    struct Rebind<_T, _OtherType, std::enable_if_t<!HasRebindTypedef<_T, _OtherType>::value > >
-    {
-        static_assert(deny<_T>, "_T must match _T<A>");
-    };
-
     /**
      * \brief Specialization for types that do NOT have a nested ::rebind_to member. In this implementation, Rebind has
      * a public member typedef \ref to.
      * \tparam _T Type that does NOT have a nested ::rebind_to member
      */
     template<template<class> class _T, class A, class _OtherType>
-    struct Rebind<_T<A>, _OtherType, std::enable_if_t<!HasRebindTypedef<_T<A>, _OtherType >::value > >
+    requires (!CanTypeRebind<_T<A>, _OtherType>)
+    struct Rebind<_T<A>, _OtherType>
     {
         using to = _T<_OtherType>;
     };
@@ -83,7 +69,7 @@ namespace sofa::type
      * 1) sofa::type::rebind_to< sofa::type::vector<int>, float> is of type sofa::type::vector<float>. In this example,
      * sofa::type::vector has a typedef rebind_to that will be used to deduce the type.
      * 2) sofa::type::rebind_to< sofa::type::Quat<float>, double> is of type sofa::type::Quat<double>. In this example,
-     * sofa::type::Quat does not have a typdef rebind_to.
+     * sofa::type::Quat does not have a typedef rebind_to.
      * 3) It makes no sense to use sofa::type::rebind on types having more than one template parameter, such as
      * sofa::type::fixed_array. A compilation error would occur.
      */

Sofa/framework/Type/test/CMakeLists.txt

@@ -8,6 +8,7 @@ set(SOURCE_FILES
     MatTypes_test.cpp
     Material_test.cpp
     Quater_test.cpp
+    Rebind_test.cpp
     RGBAColor_test.cpp
     StrongType_test.cpp
     SVector_test.cpp

Sofa/framework/Type/test/Rebind_test.cpp

@@ -0,0 +1,59 @@
+/******************************************************************************
+*                 SOFA, Simulation Open-Framework Architecture                *
+*                    (c) 2006 INRIA, USTL, UJF, CNRS, MGH                     *
+*                                                                             *
+* This program is free software; you can redistribute it and/or modify it     *
+* under the terms of the GNU Lesser General Public License as published by    *
+* the Free Software Foundation; either version 2.1 of the License, or (at     *
+* your option) any later version.                                             *
+*                                                                             *
+* This program is distributed in the hope that it will be useful, but WITHOUT *
+* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or       *
+* FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License *
+* for more details.                                                           *
+*                                                                             *
+* You should have received a copy of the GNU Lesser General Public License    *
+* along with this program. If not, see <http://www.gnu.org/licenses/>.        *
+*******************************************************************************
+* Authors: The SOFA Team and external contributors (see Authors.txt)          *
+*                                                                             *
+* Contact information: contact@sofa-framework.org                             *
+******************************************************************************/
+#include <sofa/type/trait/Rebind.h>
+#include <sofa/type/vector.h>
+
+static_assert(sofa::type::CanTypeRebind<sofa::type::vector<float>, int>);
+static_assert(sofa::type::CanTypeRebind<sofa::type::vector<int>, int>);
+
+static_assert(
+    std::is_same_v<
+        sofa::type::rebind_to<sofa::type::vector<float>, int>,
+        sofa::type::vector<int>
+    >);
+static_assert(
+    std::is_same_v<
+        sofa::type::rebind_to<sofa::type::vector<int>, int>,
+        sofa::type::vector<int>
+    >);
+
+template<class T>
+struct DummyNoRebind{};
+
+static_assert(!sofa::type::CanTypeRebind<DummyNoRebind<float>, int>);
+
+static_assert(
+    std::is_same_v<
+        sofa::type::rebind_to<DummyNoRebind<float>, int>,
+        DummyNoRebind<int>
+    >);
+
+template<class T>
+struct DummyWithConstraintRebind
+{
+    template<class U>
+    requires std::is_integral_v<U>
+    using rebind_to = U;
+};
+
+static_assert(sofa::type::CanTypeRebind<DummyWithConstraintRebind<float>, int>);
+static_assert(!sofa::type::CanTypeRebind<DummyWithConstraintRebind<float>, std::string>);

Sofa/framework/Type/test/vector_test.cpp

@@ -49,7 +49,7 @@ class vector_test : public NumericTest<>,
     void checkVector(const std::vector<std::string>& params) ;
     void checkVectorAccessFailure() const;
 
-    void checkRebind();
+    void checkRebind() const;
 };
 
 template<class T>
@@ -103,14 +103,18 @@ void vector_test<T>::checkVectorAccessFailure() const
 }
 
 template <class T>
-void vector_test<T>::checkRebind()
+void vector_test<T>::checkRebind() const
 {
-    constexpr bool hasRebind = sofa::type::HasRebindTypedef<vector<T>, int>::value;
+    constexpr bool hasRebind = sofa::type::CanTypeRebind<vector<T>, int>;
+    static_assert(hasRebind);
     EXPECT_TRUE(hasRebind);
-    using rebinded = typename sofa::type::Rebind<vector<T>, int >::to;
-    using vec_int = vector<int>;
-    constexpr bool isRebindOK = std::is_same_v<rebinded, vec_int >;
-    EXPECT_TRUE(isRebindOK);
+    if constexpr (hasRebind)
+    {
+        using rebinded = typename sofa::type::Rebind<vector<T>, int >::to;
+        using vec_int = vector<int>;
+        constexpr bool isRebindOK = std::is_same_v<rebinded, vec_int >;
+        EXPECT_TRUE(isRebindOK);
+    }
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////////////////