bump minimum clang version to 16

Author: ericniebler

.github/workflows/ci.cpu.yml

@@ -4,7 +4,6 @@ on:
   push:
     branches:
       - main
-      - "member-function-customization"
       - "pull-request/[0-9]+"
 
 concurrency:
@@ -20,8 +19,8 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - { name: "CPU (clang 14, Debug)",       build: "Debug",   tag: llvm14-cuda12.9, cxxflags: "-stdlib=libc++" }
-          - { name: "CPU (clang 14, Release)",     build: "Release", tag: llvm14-cuda12.9, cxxflags: "-stdlib=libc++" }
+          - { name: "CPU (clang 16, Debug)",       build: "Debug",   tag: llvm16-cuda12.9, cxxflags: "-stdlib=libc++" }
+          - { name: "CPU (clang 16, Release)",     build: "Release", tag: llvm16-cuda12.9, cxxflags: "-stdlib=libc++" }
           - { name: "CPU (gcc 11, Debug)",         build: "Debug",   tag: gcc11-cuda12.9,  cxxflags: "", }
           - { name: "CPU (gcc 11, Release)",       build: "Release", tag: gcc11-cuda12.9,  cxxflags: "", }
           - { name: "CPU (gcc 11, Release, TSAN)", build: "Release", tag: gcc11-cuda12.9,  cxxflags: "-fsanitize=thread" }
@@ -168,7 +167,7 @@ jobs:
       - run: echo "CI (CPU) (Windows) success"
 
   build-cpu-macos:
-    runs-on: macos-14-large
+    runs-on: macos-15-large
     name: macos-${{ matrix.name }}
     strategy:
       fail-fast: false

README.md

@@ -95,8 +95,10 @@ You can also try it directly on [godbolt.org](https://godbolt.org/z/acaE93xq3) w
 ### Requirements
 
 `stdexec` requires compiling with C++20 (`-std=c++20`) but otherwise does not have any dependencies and only requires a sufficiently new compiler:
-- clang 13+
+
 - gcc 11+
+- clang 16+
+- XCode 16+
 - [nvc++ 22.11+](https://developer.nvidia.com/nvidia-hpc-sdk-releases) (required for [GPU support](#gpu-support)). If using `stdexec` from GitHub, then nvc++ 23.3+ is required.
 
 How you configure your environment to use `stdexec` depends on how you got `stdexec`.