From d113f118ce875c1b5c6823ce1c5cf607eadfd7b1 Mon Sep 17 00:00:00 2001
From: Florian Albrechtskirchinger <falbrechtskirchinger@gmail.com>
Date: Sun, 1 May 2022 14:47:53 +0200
Subject: [PATCH] Fix compilation failure of regression test for #3077 on ICPC

---
 include/nlohmann/detail/meta/type_traits.hpp | 9 ++++++++-
 single_include/nlohmann/json.hpp             | 9 ++++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/include/nlohmann/detail/meta/type_traits.hpp b/include/nlohmann/detail/meta/type_traits.hpp
index 2cc13f3ac..5e3ea3737 100644
--- a/include/nlohmann/detail/meta/type_traits.hpp
+++ b/include/nlohmann/detail/meta/type_traits.hpp
@@ -347,8 +347,15 @@ struct is_compatible_string_type
 template<typename BasicJsonType, typename ConstructibleStringType>
 struct is_constructible_string_type
 {
+    // launder type through decltype() to fix compilation failure on ICPC
+#ifdef __INTEL_COMPILER
+    using laundered_type = decltype(std::declval<ConstructibleStringType>());
+#else
+    using laundered_type = ConstructibleStringType;
+#endif
+
     static constexpr auto value =
-        is_constructible<ConstructibleStringType,
+        is_constructible<laundered_type,
         typename BasicJsonType::string_t>::value;
 };
 
diff --git a/single_include/nlohmann/json.hpp b/single_include/nlohmann/json.hpp
index ad777c92c..949ac14be 100644
--- a/single_include/nlohmann/json.hpp
+++ b/single_include/nlohmann/json.hpp
@@ -3482,8 +3482,15 @@ struct is_compatible_string_type
 template<typename BasicJsonType, typename ConstructibleStringType>
 struct is_constructible_string_type
 {
+    // launder type through decltype() to fix compilation failure on ICPC
+#ifdef __INTEL_COMPILER
+    using laundered_type = decltype(std::declval<ConstructibleStringType>());
+#else
+    using laundered_type = ConstructibleStringType;
+#endif
+
     static constexpr auto value =
-        is_constructible<ConstructibleStringType,
+        is_constructible<laundered_type,
         typename BasicJsonType::string_t>::value;
 };