From 065d97b585a69c20a30e7ea8ac5413cb6125118a Mon Sep 17 00:00:00 2001
From: tusooa <tusooa@kazv.moe>
Date: Mon, 5 Feb 2024 18:03:51 -0500
Subject: [PATCH] Make zug::compat::invoke work with pointer-to-member function

---
 test/transducer/map.cpp | 19 +++++++++++++++++++
 zug/compat/invoke.hpp   |  9 +++++----
 2 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/test/transducer/map.cpp b/test/transducer/map.cpp
index bec37f5..467e3fc 100644
--- a/test/transducer/map.cpp
+++ b/test/transducer/map.cpp
@@ -36,6 +36,11 @@ namespace {
 
 int free_times2(int x) { return x * 2; }
 
+struct Foo {
+    int a;
+    const int &getA() const { return a; }
+};
+
 } // anonymous namespace
 
 TEST_CASE("map, mapping invoke")
@@ -43,3 +48,17 @@ TEST_CASE("map, mapping invoke")
     auto v = std::vector<int>{1, 2, 3, 6};
     CHECK(transduce(map(&free_times2), std::plus<int>{}, 1, v) == 25);
 }
+
+TEST_CASE("map, pointer to member function")
+{
+    auto v = std::vector<Foo>{{1}};
+    auto r = into_vector(map(&Foo::getA), v);
+    CHECK(r == decltype(r){1});
+}
+
+TEST_CASE("map, pointer to member object")
+{
+    auto v = std::vector<Foo>{{1}};
+    auto r = into_vector(map(&Foo::a), v);
+    CHECK(r == decltype(r){1});
+}
diff --git a/zug/compat/invoke.hpp b/zug/compat/invoke.hpp
index 01bb235..d49405a 100644
--- a/zug/compat/invoke.hpp
+++ b/zug/compat/invoke.hpp
@@ -9,6 +9,7 @@
 #pragma once
 
 #include <utility>
+#include <type_traits>
 
 namespace zug {
 namespace compat {
@@ -22,20 +23,20 @@ template <class F, class... Args>
 inline auto do_invoke(F&& f, Args&&... args) -> ZUG_DETAIL_DECLTYPE_RETURN(
     std::forward<F>(f)(std::forward<Args>(args)...))
 
-template <class Base, class T, class Derived>
+template <class Base, class T, class Derived, class = std::enable_if_t<!std::is_function<T>::value>>
 inline auto do_invoke(T Base::*pmd, Derived&& ref)
     -> ZUG_DETAIL_DECLTYPE_RETURN(std::forward<Derived>(ref).*pmd)
 
-template <class PMD, class Pointer>
+template <class PMD, class Pointer, class = std::enable_if_t<std::is_member_object_pointer<PMD>::value>>
 inline auto do_invoke(PMD pmd, Pointer&& ptr)
     -> ZUG_DETAIL_DECLTYPE_RETURN((*std::forward<Pointer>(ptr)).*pmd)
 
-template <class Base, class T, class Derived, class... Args>
+template <class Base, class T, class Derived, class... Args, class = std::enable_if_t<std::is_function<T>::value>>
 inline auto do_invoke(T Base::*pmf, Derived&& ref, Args&&... args)
     -> ZUG_DETAIL_DECLTYPE_RETURN((std::forward<Derived>(ref).*
                                    pmf)(std::forward<Args>(args)...))
 
-template <class PMF, class Pointer, class... Args>
+template <class PMF, class Pointer, class... Args, class = std::enable_if_t<std::is_member_function_pointer<PMF>::value>>
 inline auto do_invoke(PMF pmf, Pointer&& ptr, Args&&... args)
     -> ZUG_DETAIL_DECLTYPE_RETURN(((*std::forward<Pointer>(ptr)).*
                                    pmf)(std::forward<Args>(args)...))