Work around clang issue

[dietmarkuehl]

No description provided.

[Copilot]

Pull request overview

This PR implements workarounds for a clang compiler issue by modifying the prop deduction guide and refactoring the affine_on implementation to avoid problematic code patterns.

Changes:

• Modified the prop deduction guide to accept an additional non_assignable parameter with a default value
• Introduced a new ao_env helper struct to replace the combination of join_env and env{prop{...}}
• Renamed the env parameter to ev in transform_sender to avoid naming conflicts with the env template

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
include/beman/execution/detail/prop.hpp	Updated deduction guide to include third parameter for workaround
include/beman/execution/detail/affine_on.hpp	Added ao_env helper struct and refactored code to avoid clang issues

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[Copilot]

Creating a constexpr local variable t and then immediately using it to call affine_on is unusual. If this is a workaround for a clang issue, consider adding a comment explaining why this intermediate variable is necessary instead of directly using child_tag_t{}.affine_on(...) as was done previously.

Suggested change

	{
	{
	// NOTE: Some compilers (e.g. certain Clang versions) have had issues
	// when invoking affine_on on a temporary, i.e. child_tag_t{}.affine_on(...).
	// Using a named constexpr instance here avoids those issues; do not
	// simplify back to a temporary without re-validating compiler support.

[Copilot]

The third parameter {} is passed explicitly to the prop constructor even though the deduction guide provides a default value for the non_assignable parameter. If the default value works correctly, this explicit {} may be unnecessary. Consider removing it to simplify the code and rely on the default parameter, or add a comment explaining why the explicit parameter is required.

Suggested change

	::beman::execution::get_stop_token, ::beman::execution::never_stop_token{}, {}}},
	::beman::execution::get_stop_token, ::beman::execution::never_stop_token{}}},

[Copilot]

The deduction guide now requires passing an extra parameter (the non_assignable object with default value) that doesn't correspond to a user-provided value. While this may work around a clang issue, this creates an inconsistency where users of prop must now be aware of this implementation detail. Consider whether this is the intended workaround, as it exposes the internal non_assignable_ member in the public API of the deduction guide.

[coveralls]

coverage: 92.63% (-0.006%) from 92.636%
when pulling ca4a70e on work-around-clang-issue
into 7d2a2b0 on main.