[v4] More CI

[ConorWilliams]

• New CI builds (released, debug, no-exceptions)
• New linear history CI
• Catch2 for tests
• Sketch libfork's module structure

[Copilot]

Pull request overview

This PR refactors the libfork library to use a modular architecture with C++23 modules. It removes the old monolithic module structure and introduces a new libfork.core module with a promise implementation. The PR also updates the test infrastructure to use Catch2, enhances the CI/CD pipeline with multiple build configurations, and improves the CMake toolchain files.

Changes:

• Replaced the monolithic libfork module with a modular libfork.core module structure containing promise types and concepts
• Migrated from a simple main.cpp test to a Catch2-based test framework with promise tests
• Updated CI workflows to test multiple build configurations (debug-hardened, release, no-except-rtti) and split the workflow steps for better clarity

Reviewed changes

Copilot reviewed 16 out of 17 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
test/src/promise.cpp	New test file for promise functionality using Catch2 framework
test/src/main.cpp	Removed old main.cpp test file
test/CMakeLists.txt	Updated to use Catch2 test discovery and glob test sources
src/libfork.cxx	Removed old monolithic module interface
src/libfork.cpp	Removed old module implementation
src/core/promise.cxx	New module partition containing promise types, concepts, and static assertions
src/core/core.cxx	New core module primary interface that exports the promise partition
CMakeLists.txt	Updated module source files to reference new core module structure
cmake/llvm-brew-toolchain.cmake	Enhanced with additional LLVM tools (ar, ranlib, nm) and REQUIRED flags
cmake/gcc-brew-toolchain.cmake	Enhanced with GCC-specific tools and binutils configuration
CMakePresets.json	Refactored to use CI-focused presets with different build configurations
CMakeUserPresets.json	New user preset file for local development workflow
.gitignore	Removed CMakeUserPresets.json from gitignore to track it in version control
.github/workflows/macos.yml	Updated to use matrix strategy with multiple presets and separated workflow steps
.github/workflows/linux.yml	Updated to use matrix strategy with multiple presets and separated workflow steps
.github/workflows/linear.yml	New workflow to enforce linear git history on pull requests
.clangd	Updated compilation database path to match new preset structure

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[Copilot]

The returnable concept does not correctly implement the documentation's requirement for reference types. The condition std::movable<T> evaluates to false for reference types, and std::is_void_v<T> also evaluates to false for references. To correctly handle references as documented, the concept should be: concept returnable = std::is_void_v<T> || std::is_reference_v<T> || std::movable<T>;

Suggested change

	* This requires that `T` is `void` a reference or a `std::movable` type.
	*/
	template <typename T>
	concept returnable = std::is_void_v<T> || std::movable<T>;
	* This requires that `T` is `void`, a reference, or a `std::movable` type.
	*/
	template <typename T>
	concept returnable = std::is_void_v<T> || std::is_reference_v<T> || std::movable<T>;

[Copilot]

The returnable concept, alloc_mixin concept, and basic_promise template structs are not exported from the module, which makes them inaccessible to module consumers. If these are intended to be part of the public API (as suggested by the documentation on returnable), they should be prefixed with the export keyword.

[Copilot]

The test only verifies the placeholder promise struct with its test() method, but does not provide any test coverage for the actual basic_promise implementation, the returnable concept, or the alloc_mixin concept. Consider adding tests for the actual promise implementation and its core functionality.

[Copilot]

The promise template struct appears to be a placeholder for testing purposes only, containing just a test() method that returns "hi". This conflicts with the basic_promise implementation below which appears to be the actual promise type. Consider removing this placeholder or clarifying its purpose and relationship to basic_promise in the code documentation.

[Copilot]

The alloc_mixin concept checks for M::operator new() which is invalid syntax. The operator new is a static member function and should be checked as requires { M::operator new(std::size_t); } or similar with appropriate parameters. The current syntax will not compile as a valid requires expression.

Suggested change

	concept alloc_mixin = std::is_empty_v<M> || requires { M::operator new(); };
	concept alloc_mixin = std::is_empty_v<M> || requires { M::operator new(std::size_t{}); };

[Copilot]

Grammatical error: "a reference" should be "or a reference". The documentation should read "This requires that T is void, a reference, or a std::movable type."

Suggested change

	* This requires that `T` is `void` a reference or a `std::movable` type.
	* This requires that `T` is `void`, a reference, or a `std::movable` type.