Simplify io_result<> constructors to eliminate include-order dependency

[MungoG]

Replace three separate constructors with a single template constructor that accepts any type convertible to std::error_code. The old approach used #ifdef BOOST_SYSTEM_ERROR_CODE_HPP_INCLUDED to conditionally compile the boost::system::error_code constructor. This created a fragile include-order dependency: if io_result.hpp was included before boost/system/error_code.hpp, the direct constructor wasn't available, forcing MSVC to apply two implicit conversions which triggers warning C4927.

The new single template constructor handles all cases uniformly by relying on std::error_code's existing constructors and conversion operators. This eliminates the C4927 warning and removes the need to carefully order includes in headers that use io_result with Boost error codes.

Summary by CodeRabbit

• Refactor
  • Unified and simplified error-result constructor logic to accept a broader range of error-code types via a single implementation, removing redundant overloads and conditional variants.
• Documentation
  • Updated comments to describe the new constructor behavior and accepted error-code types while preserving existing public behavior and accessors.

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[coderabbitai]

📝 Walkthrough

Walkthrough

Consolidates multiple io_result<> constructors into a single templated constructor that accepts any type convertible to std::error_code, removing the explicit std::error_code and Boost-specific constructors and the enum-based overload. Initializes ec from the provided convertible error type.

Changes

Cohort / File(s)	Summary
Error Code Constructor Consolidation include/boost/capy/io_result.hpp	Removed explicit io_result(std::error_code) and Boost-specific/error-enum constructors. Added a single template<class E, typename std::enable_if<std::is_convertible<E, std::error_code>::value, int>::type = 0> BOOST_CAPY_FORCEINLINE io_result(E const& e) noexcept constructor initializing ec from e. Updated comments accordingly.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 Three doors I hopped through, one by one,
Now a single tunnel gleams in the sun.
A convertible slip, tidy and neat,
io_result hums with one heartbeat. 🥕✨

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: replacing multiple constructors with a templated constructor to eliminate include-order dependency.

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✨ Finishing touches

• 📝 Generate docstrings

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[cppalliance-bot]

An automated preview of the documentation is available at https://115.capy.prtest3.cppalliance.org/index.html

If more commits are pushed to the pull request, the docs will rebuild at the same URL.

2026-01-29 15:03:10 UTC

[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@include/boost/capy/io_result.hpp`:
- Around line 64-74: Update the io_result(E const& e) noexcept constructor
docstring to document the template parameter E, the constructor parameter e, the
template constraint (requires E to be convertible to std::error_code /
std::is_convertible<E, std::error_code>::value), any preconditions (e must
represent a valid error_code) and the noexcept guarantee (constructor is
noexcept and will not throw); mention that the constructor accepts
std::error_code, boost::system::error_code, error-code enums or any type
implicitly convertible to std::error_code and that it initializes the member ec.