Drop Clang 13 support, I don't want to debug the elusive warning it e…

…mits.

.github/workflows/tests.yml

@@ -20,8 +20,10 @@ jobs:
       run: git clone https://github.com/HolyBlackCat/macro_sequence_for ../macro_sequence_for
     - name: List compilers
       run: make -pq | grep ^COMPILER
+    - name: Confirm installed compilers
+      run: which clang++-17 clang++-16 clang++-15 clang++-14 clang++-13 g++-13 g++-12 g++-11 g++-10
     - name: Run tests
-      run: make COMPILER='clang++-15 clang++-14 clang++-13 g++-12 g++-11 g++-10' CXXFLAGS='-Werror' CXXFLAGS_PER_COMPILER='clang++-13=-Wno-gnu-zero-variadic-macro-arguments'
+      run: make CXXFLAGS='-Werror'
   Tests-MSVC:
     runs-on: windows-latest
     steps:

README.md

@@ -96,7 +96,7 @@ std::copy_n(fib.begin(), 5, std::ostream_iterator<int>(std::cout, "\n")); // 5 8
 
 Header-only. Just clone, add `include/` to the include path, and `#include <rcoro.hpp>`.
 
-Supported compilers are: GCC 10+, Clang 13+, and the latest MSVC. Clang and GCC are recommended, since they're better at optimizing away the coroutine internals, with GCC being slightly behind.
+Supported compilers are: GCC 10+, Clang 14+, and the latest MSVC. Clang and GCC are recommended, since they're better at optimizing away the coroutine internals, with GCC being slightly behind.
 
 Must use C++20 or newer. MSVC users must use [`/Zc:preprocessor`](https://learn.microsoft.com/en-US/cpp/build/reference/zc-preprocessor?view=msvc-170).
 

include/rcoro.hpp

@@ -44,7 +44,7 @@
 #endif
 
 // The version number: `major*10000 + minor*100 + patch`.
-#define RCORO_VERSION 204
+#define RCORO_VERSION 205
 
 // An assertion macro. If not customized, uses the standard `assert()`.
 #ifndef RCORO_ASSERT
@@ -73,15 +73,9 @@
 #endif
 #endif
 
-#ifndef RCORO_TEMPLATE_FRIEND
-#if defined(__clang__)
-// Silence a weird warning from Clang 13.
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wunused-function"
-#define RCORO_TEMPLATE_FRIEND(...) __VA_ARGS__
-#pragma GCC diagnostic pop
-#elif defined(__GNUC__)
 // Silences GCC's silly `-Wnon-template-friend` warning.
+#ifndef RCORO_TEMPLATE_FRIEND
+#if defined(__GNUC__) && !defined(__clang__)
 #define RCORO_TEMPLATE_FRIEND(...) \
     _Pragma("GCC diagnostic push") \
     _Pragma("GCC diagnostic ignored \"-Wnon-template-friend\"") \