From 402af742c0d23f72b151b1ae637e26f45c4046ab Mon Sep 17 00:00:00 2001
From: Niels Lohmann <mail@nlohmann.me>
Date: Tue, 27 Oct 2026 18:01:12 +0100
Subject: [PATCH] Fix the VS2015 build of unit-json_view_edit_values.cpp

MSVC 2015 treats two function templates that differ only in a decltype
return type as a redefinition (C2995), which breaks all three Visual
Studio 2015 jobs on AppVeyor. Overload on the view's mode in the
parameter type instead; template argument deduction ignores the
read-only-to-editable conversion, so each view still selects the
overload of its own mode.

Signed-off-by: Niels Lohmann <mail@nlohmann.me>
---
 tests/src/unit-json_view_edit_values.cpp | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/tests/src/unit-json_view_edit_values.cpp b/tests/src/unit-json_view_edit_values.cpp
index 39db8d0ba..881d957f8 100644
--- a/tests/src/unit-json_view_edit_values.cpp
+++ b/tests/src/unit-json_view_edit_values.cpp
@@ -54,14 +54,18 @@ int accepts_any(nlohmann::basic_json_view<BasicJsonType, Mode> /*unused*/)
     return Mode == nlohmann::view_mode::editable ? 3 : 4;
 }
 
-template<typename View>
-auto overload(View v) -> decltype(accepts_editable(v))
+// overloads that differ only in the mode; deduction ignores the conversion from
+// read-only to editable views, so each view picks the overload of its own mode
+// (two templates that differ only in a decltype return type are a redefinition
+// for MSVC 2015)
+template<typename BasicJsonType>
+int overload(nlohmann::basic_json_view<BasicJsonType, nlohmann::view_mode::editable> v)
 {
     return accepts_editable(v);
 }
 
-template<typename View>
-auto overload(View v) -> decltype(accepts_read_only(v))
+template<typename BasicJsonType>
+int overload(nlohmann::basic_json_view<BasicJsonType, nlohmann::view_mode::read_only> v)
 {
     return accepts_read_only(v);
 }