From 3588527a99e12d3e474899b83dd51cfc9e6dbde9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jean-Micha=C3=ABl=20Celerier?=
 <jeanmichael.celerier@gmail.com>
Date: Mon, 18 Sep 2023 19:31:40 -0400
Subject: [PATCH] [ci] Workaround MSVC issue

---
 include/avnd/binding/vst3/component.hpp  |  4 ++--
 include/avnd/binding/vst3/controller.hpp | 14 ++++++++------
 include/avnd/concepts/generic.hpp        | 15 +++++++++++++++
 3 files changed, 25 insertions(+), 8 deletions(-)

diff --git a/include/avnd/binding/vst3/component.hpp b/include/avnd/binding/vst3/component.hpp
index 040245ea..abaec244 100644
--- a/include/avnd/binding/vst3/component.hpp
+++ b/include/avnd/binding/vst3/component.hpp
@@ -331,7 +331,7 @@ struct Component final
     {
       avnd::parameter_input_introspection<T>::for_nth_raw(
           effect.inputs(), id, [&]<typename C>(C& ctl) {
-            if_possible(ctl.value = avnd::map_control_from_01<C>(value));
+            assign_if_assignable(ctl.value, avnd::map_control_from_01<C>(value));
           });
     };
   }
@@ -527,7 +527,7 @@ struct Component final
             double param = 0.f;
             if(streamer.readDouble(param) == false)
               return false;
-            if_possible(field.value = avnd::map_control_from_01<C>(param));
+            assign_if_assignable(field.value, avnd::map_control_from_01<C>(param));
             return true;
           });
 
diff --git a/include/avnd/binding/vst3/controller.hpp b/include/avnd/binding/vst3/controller.hpp
index c8dc79dc..b09fbd3e 100644
--- a/include/avnd/binding/vst3/controller.hpp
+++ b/include/avnd/binding/vst3/controller.hpp
@@ -16,7 +16,6 @@
 
 namespace stv3
 {
-
 template <typename T>
 class Controller final
     : public stv3::ControllerCommon
@@ -109,7 +108,7 @@ class Controller final
     if constexpr(avnd::has_inputs<T>)
     {
       inputs_info_t::for_nth_raw(this->inputs_mirror, tag, [&]<typename C>(C& field) {
-        if_possible(res = avnd::map_control_from_01_to_fp<C>(valueNormalized));
+        assign_if_assignable(res, avnd::map_control_from_01_to_fp<C>(valueNormalized));
       });
     }
     return res;
@@ -122,7 +121,7 @@ class Controller final
     if constexpr(avnd::has_inputs<T>)
     {
       inputs_info_t::for_nth_raw(this->inputs_mirror, tag, [&]<typename C>(C& field) {
-        if_possible(res = avnd::map_control_from_fp_to_01<C>(plainValue));
+        assign_if_assignable(res, avnd::map_control_from_fp_to_01<C>(plainValue));
       });
     }
     return res;
@@ -135,7 +134,7 @@ class Controller final
     if constexpr(avnd::has_inputs<T>)
     {
       inputs_info_t::for_nth_raw(this->inputs_mirror, tag, [&]<typename C>(C& field) {
-        if_possible(res = avnd::map_control_to_01(field));
+        assign_if_assignable(res, avnd::map_control_to_01(field));
       });
     }
     return res;
@@ -149,7 +148,7 @@ class Controller final
     if constexpr(avnd::has_inputs<T>)
     {
       inputs_info_t::for_nth_raw(this->inputs_mirror, tag, [&]<typename C>(C& field) {
-        if_possible(field.value = avnd::map_control_from_01<C>(value));
+        assign_if_assignable(field.value, avnd::map_control_from_01<C>(value));
       });
     }
 
@@ -171,10 +170,13 @@ class Controller final
     {
       bool ok = inputs_info_t::for_all_unless(
           this->inputs_mirror, [&]<typename C>(C& field) -> bool {
+
             double param = 0.f;
             if(streamer.readDouble(param) == false)
               return false;
-            if_possible(field.value = avnd::map_control_from_01<C>(param));
+
+            assign_if_assignable(field.value, avnd::map_control_from_01<C>(param));
+
             return true;
           });
 
diff --git a/include/avnd/concepts/generic.hpp b/include/avnd/concepts/generic.hpp
index 0b82f519..38dbb29a 100644
--- a/include/avnd/concepts/generic.hpp
+++ b/include/avnd/concepts/generic.hpp
@@ -26,6 +26,21 @@ namespace avnd
   }                                \
   ()
 
+#if defined(_MSC_VER)
+#define assign_if_assignable(dst, src)                             \
+  do                                                               \
+    if constexpr(requires { src; })                                \
+    {                                                              \
+      using val_type = std::add_lvalue_reference_t<decltype(dst)>; \
+      using ret_type = decltype(src);                              \
+      if constexpr(std::is_assignable_v<val_type, ret_type>)       \
+        dst = src;                                                 \
+    }                                                              \
+  while(0)
+#else
+#define assign_if_assignable(dst, src) if_possible(dst = src);
+#endif
+
 // Very generic concepts
 template <typename T>
 concept vector_ish = requires(T t) {