From 0ac3919e084307e2c6be0d1a549830cfe19aed31 Mon Sep 17 00:00:00 2001
From: ToruNiina <niina.toru.68u@gmail.com>
Date: Fri, 14 May 2021 16:05:54 +0900
Subject: [PATCH] feat: from<T> and from_toml precede constructor

constructor sometimes has `template<T> ctor(const T&)` and it causes
ambiguity. To avoid it, from<T> and T.from_toml precedes any
constructor. But, to check the ambiguity between from<T> and from_toml,
they do not precede each other. If anyone define both from<T> and
from_toml, it causes compilation error.
---
 toml/get.hpp | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/toml/get.hpp b/toml/get.hpp
index 9a5a855..a766f4a 100644
--- a/toml/get.hpp
+++ b/toml/get.hpp
@@ -259,12 +259,15 @@ template<typename T, typename C,
 detail::enable_if_t<detail::has_specialized_from<T>::value, T>
 get(const basic_value<C, M, V>&);
 
-// T(const toml::value&) and T is not toml::basic_value
+// T(const toml::value&) and T is not toml::basic_value,
+// and it does not have `from<T>` nor `from_toml`.
 template<typename T, typename C,
          template<typename ...> class M, template<typename ...> class V>
 detail::enable_if_t<detail::conjunction<
     detail::negation<detail::is_basic_value<T>>,
-    std::is_constructible<T, const basic_value<C, M, V>&>
+    std::is_constructible<T, const basic_value<C, M, V>&>,
+    detail::negation<detail::has_from_toml_method<T, C, M, V>>,
+    detail::negation<detail::has_specialized_from<T>>
     >::value, T>
 get(const basic_value<C, M, V>&);
 
@@ -450,8 +453,10 @@ get(const basic_value<C, M, V>& v)
 template<typename T, typename C,
          template<typename ...> class M, template<typename ...> class V>
 detail::enable_if_t<detail::conjunction<
-    detail::negation<detail::is_basic_value<T>>,
-    std::is_constructible<T, const basic_value<C, M, V>&>
+    detail::negation<detail::is_basic_value<T>>,                // T is not a toml::value
+    std::is_constructible<T, const basic_value<C, M, V>&>,      // T is constructible from toml::value
+    detail::negation<detail::has_from_toml_method<T, C, M, V>>, // and T does not have T.from_toml(v);
+    detail::negation<detail::has_specialized_from<T>>           // and T does not have toml::from<T>{};
     >::value, T>
 get(const basic_value<C, M, V>& v)
 {