From d8b676836e2a11e2569cdb2f626263041c537a1d Mon Sep 17 00:00:00 2001
From: Tristan Brindle <t.c.brindle@gmail.com>
Date: Tue, 5 Nov 2024 13:56:35 +0000
Subject: [PATCH 1/3] Add LLVM Clang 19 to MacOS test matrix

---
 .github/workflows/macos.yml | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/macos.yml b/.github/workflows/macos.yml
index 3100679f..aad91333 100644
--- a/.github/workflows/macos.yml
+++ b/.github/workflows/macos.yml
@@ -14,7 +14,7 @@ jobs:
     runs-on: macos-latest
     strategy:
       matrix:
-        compiler: [GCC-13, LLVM-Clang-16, LLVM-Clang-17, LLVM-Clang-18]
+        compiler: [GCC-13, LLVM-Clang-16, LLVM-Clang-17, LLVM-Clang-18, LLVM-Clang-19]
         test_with: [Headers, Module]
         build_type: [Debug, Release]
 
@@ -42,6 +42,10 @@ jobs:
             cxx: $(brew --prefix llvm@18)/bin/clang++
             install: |
               brew install llvm@18 ninja
+          - compiler: LLVM-Clang-19
+            cxx: $(brew --prefix llvm@19)/bin/clang++
+            install: |
+              brew install llvm@19 ninja
 
 
     steps:

From a298e228334bbfb0e3a6aac5ca0f10fb59f4080c Mon Sep 17 00:00:00 2001
From: Tristan Brindle <t.c.brindle@gmail.com>
Date: Tue, 5 Nov 2024 13:57:39 +0000
Subject: [PATCH 2/3] Add Clang 19 to Linux test matrix

---
 .github/workflows/linux.yml | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index 0c805e5b..960608e2 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        compiler: [GCC-11, GCC-12, GCC-13, GCC-14, Clang-17, Clang-18]
+        compiler: [GCC-11, GCC-12, GCC-13, GCC-14, Clang-17, Clang-18, Clang-19]
         test_with: [Headers, Module]
         build_type: [Debug, Release]
 
@@ -56,6 +56,11 @@ jobs:
             install: |
               brew install llvm@18 ninja binutils
               brew link --force binutils
+          - compiler: Clang-19
+            cxx: $(brew --prefix llvm@19)/bin/clang++
+            install: |
+              brew install llvm@19 ninja binutils
+              brew link --force binutils
 
     steps:
     - uses: actions/checkout@master

From e20f4322c29e84007d2560e91a911ef041d17a7d Mon Sep 17 00:00:00 2001
From: Tristan Brindle <t.c.brindle@gmail.com>
Date: Tue, 5 Nov 2024 15:43:25 +0000
Subject: [PATCH 3/3] Fix variant emplace with Clang19/libstdc++

I'm not quite sure what's changed with Clang 19, but it's suddenly complaining about libstdc++12's `variant` using the non-active member of a union in constexpr.

It's possible there was such a bug in libstdc++12, but it seems weird that it wasn't picked up by either GCC12 or an older version of Clang...

Anyway, hopefully this will fix it.
---
 include/flux/adaptor/flatten_with.hpp | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/include/flux/adaptor/flatten_with.hpp b/include/flux/adaptor/flatten_with.hpp
index c3fef214..0b31a93e 100644
--- a/include/flux/adaptor/flatten_with.hpp
+++ b/include/flux/adaptor/flatten_with.hpp
@@ -19,14 +19,10 @@ namespace detail {
 template <std::size_t N>
 inline constexpr auto variant_emplace =
 []<typename... Types>(std::variant<Types...>& variant, auto&&... args) {
-    if constexpr (__cpp_lib_variant >= 202106L) {
-        variant.template emplace<N>(FLUX_FWD(args)...);
+    if (std::is_constant_evaluated()) {
+        variant = std::variant<Types...>(std::in_place_index<N>, FLUX_FWD(args)...); // LCOV_EXCL_LINE
     } else {
-        if (std::is_constant_evaluated()) {
-            variant = std::variant<Types...>(std::in_place_index<N>, FLUX_FWD(args)...); // LCOV_EXCL_LINE
-        } else {
-            variant.template emplace<N>(FLUX_FWD(args)...);
-        }
+        variant.template emplace<N>(FLUX_FWD(args)...);
     }
 };