From 69acdf6584be2a04094e27b395c50c071b2b15cf Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Wed, 28 Dec 2022 13:49:54 +0000
Subject: Use the existence of .substr(...) to test if a T is stringlike

---
 lib/stream_support.cpp              | 11 -----------
 lib/stream_support.hpp              |  6 ++++--
 test/Jamfile.jam                    |  1 +
 test/test-static-stream_support.cpp | 11 +++++++++++
 4 files changed, 16 insertions(+), 13 deletions(-)
 delete mode 100644 lib/stream_support.cpp
 create mode 100644 test/test-static-stream_support.cpp

diff --git a/lib/stream_support.cpp b/lib/stream_support.cpp
deleted file mode 100644
index 2054873..0000000
--- a/lib/stream_support.cpp
+++ /dev/null
@@ -1,11 +0,0 @@
-#include "stream_support.hpp"
-
-#include <array>
-#include <vector>
-
-static_assert(spanable<std::vector<int>>);
-// static_assert(spanable<std::vector<char>>);
-static_assert(spanable<std::array<int, 1>>);
-// static_assert(spanable<std::array<char, 1>>);
-static_assert(!spanable<std::string>);
-static_assert(!spanable<std::string_view>);
diff --git a/lib/stream_support.hpp b/lib/stream_support.hpp
index 5f45cbf..a3565d8 100644
--- a/lib/stream_support.hpp
+++ b/lib/stream_support.hpp
@@ -8,14 +8,16 @@
 #include <sstream>
 #include <type_traits>
 
+template<typename S>
+concept stringlike = requires(const S & s) { s.substr(0); };
 template<typename T>
 concept spanable = std::is_constructible_v<std::span<const typename T::value_type>, T> && !
-std::is_same_v<char, std::decay_t<typename T::value_type>>;
+stringlike<T> && !std::is_same_v<std::span<typename T::value_type>, T>;
 
 namespace std {
 	template<typename T, std::size_t L>
 	std::ostream &
-	operator<<(std::ostream & s, const span<const T, L> v)
+	operator<<(std::ostream & s, const span<T, L> v)
 	{
 		s << '(';
 		for (const auto & i : v) {
diff --git a/test/Jamfile.jam b/test/Jamfile.jam
index 32c522b..6a83f9c 100644
--- a/test/Jamfile.jam
+++ b/test/Jamfile.jam
@@ -33,3 +33,4 @@ run test-enumDetails.cpp ;
 run test-render.cpp ;
 run test-glContextBhvr.cpp ;
 compile test-static-enumDetails.cpp ;
+compile test-static-stream_support.cpp ;
diff --git a/test/test-static-stream_support.cpp b/test/test-static-stream_support.cpp
new file mode 100644
index 0000000..367d5a2
--- /dev/null
+++ b/test/test-static-stream_support.cpp
@@ -0,0 +1,11 @@
+#include "stream_support.hpp"
+
+#include <array>
+#include <vector>
+
+static_assert(spanable<std::vector<int>>);
+static_assert(spanable<std::vector<char>>);
+static_assert(spanable<std::array<int, 1>>);
+static_assert(spanable<std::array<char, 1>>);
+static_assert(!spanable<std::string>);
+static_assert(!spanable<std::string_view>);
-- 
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