Merge branch 'cpp-variadic-template' into cpp-template-2

src/backports/concepts.h

@@ -44,11 +44,13 @@
 #define QL_CONCEPT_OR_TYPENAME(...) typename
 #define CPP_template_2 CPP_template_2_SFINAE
 #define CPP_and_2 CPP_and_2_sfinae
+#define CPP_variadic_template CPP_template_NO_DEFAULT_SFINAE
 #else
 #define QL_CONCEPT_OR_NOTHING(...) __VA_ARGS__
 #define QL_CONCEPT_OR_TYPENAME(...) __VA_ARGS__
 #define CPP_template_2 CPP_template
 #define CPP_and_2 CPP_and
+#define CPP_variadic_template CPP_template
 #endif
 
 // The namespace `ql::concepts` includes concepts that are contained in the

src/backports/cppTemplate2.h

@@ -5,6 +5,27 @@
 #pragma once
 #include <concepts/concepts.hpp>
 
+// The internal reimplementation of a `CPP_variadic_template` macro
+// that can be used for variadic template functions.
+#define CPP_TEMPLATE_NO_DEFAULT_SFINAE_AUX_0(...)                         \
+  , std::enable_if_t<CPP_PP_CAT(CPP_TEMPLATE_SFINAE_AUX_3_, __VA_ARGS__), \
+                     int> = 0 > CPP_PP_IGNORE_CXX2A_COMPAT_END
+
+#define CPP_TEMPLATE_NO_DEFAULT_SFINAE_AUX_3_requires
+
+#define CPP_TEMPLATE_NO_DEFAULT_SFINAE_AUX_WHICH_(FIRST, ...) \
+  CPP_PP_EVAL(CPP_PP_CHECK,                                   \
+              CPP_PP_CAT(CPP_TEMPLATE_SFINAE_PROBE_CONCEPT_, FIRST))
+
+#define CPP_TEMPLATE_NO_DEFAULT_SFINAE_AUX_(...)                       \
+  CPP_PP_CAT(CPP_TEMPLATE_NO_DEFAULT_SFINAE_AUX_,                      \
+             CPP_TEMPLATE_NO_DEFAULT_SFINAE_AUX_WHICH_(__VA_ARGS__, )) \
+  (__VA_ARGS__)
+
+#define CPP_template_NO_DEFAULT_SFINAE(...) \
+  CPP_PP_IGNORE_CXX2A_COMPAT_BEGIN          \
+  template <__VA_ARGS__ CPP_TEMPLATE_NO_DEFAULT_SFINAE_AUX_
+
 // The internal reimplementation of a `CPP_template_2` and `CPP_and_2` macro
 // that can be used for class members when the outer class has already been
 // constrained using `CPP_template`.

test/backports/ConceptsTest.cpp

@@ -2,12 +2,14 @@
 // Created by kalmbacj on 2/10/25.
 //
 
+#include <gmock/gmock.h>
+
 #include "backports/concepts.h"
 
 template <typename... T>
 CPP_concept Something = (... && (sizeof(T) <= 4));
 
-// Those are rewritten as follows:
+// A templated class with a variety of members.
 CPP_template(typename T)(requires(Something<T>)) struct C {
   // A constructor that takes an int only exists for certain `T`
   explicit constexpr CPP_ctor(C)([[maybe_unused]] int i)(
@@ -17,8 +19,10 @@ CPP_template(typename T)(requires(Something<T>)) struct C {
   // type `F`.
   CPP_template_2(typename F)(requires Something<F>) void f(F arg) { (void)arg; }
 
-  // Same, but the constraint combines F and T.
-  CPP_template_2(typename F)(requires(Something<F, T>)) auto i() {
+  // Same, but the constraint combines F and T. Note that you have to use
+  // `CPP_and_2` instead of `CPP_and`.
+  CPP_template_2(typename F)(
+      requires Something<F> CPP_and_2 Something<T>) auto i() {
   }  // Additional template parameter + `auto`
 
   // Member function with explicit return type that has no other template
@@ -30,3 +34,8 @@ CPP_template(typename T)(requires(Something<T>)) struct C {
   // arguments but poses additional constraints on `T`.
   CPP_auto_member auto CPP_fun(h)()(requires Something<T>) {}
 };
+
+// A variadic function template.  NOTE: you currently have to use plain `&&`,
+// the `CPP_and...` macros won't work here.
+CPP_variadic_template(typename... Ts)(
+    requires(Something<Ts...>&& Something<Ts...>)) void f(Ts...) {}