[M3] detail::erase_if is unused dead code

[csparker247]

Summary

detail::erase_if in HalfEdgeMesh.hpp takes its container by value, modifies the copy, and returns it. There are no call sites in the project — it is dead code.

Fix

Remove the function.

Conductor Track

M3

[csparker247]

Investigation findings

The original spec described detail::erase_if as dead code with no call sites. This is incorrect — investigation found 6 active call sites in HalfEdgeMesh.hpp:

• Lines 800–801 and 813–814: inside boundary-edge validation during face insertion
• Lines 1094–1097 and 1117–1120: inside split_path when rewiring edges at path endpoints

All 6 call sites capture the return value, so the function's by-value semantics are intentional — it is being used as a filtered copy utility (keep only edges matching the predicate), not as an in-place erase.

Revised assessment

The function is not dead code and not buggy for its actual use cases. The real issue is a naming problem: erase_if implies in-place mutation (matching std::erase_if from C++20), but this function returns a filtered copy. A caller unfamiliar with the implementation could easily mistake it for the standard algorithm and be surprised by the by-value semantics.

Suggested resolution

Either:

1. Rename to something like detail::filter or detail::filtered_copy to make the copy semantics explicit, or
2. Replace with a standard range filter at each call site (e.g. std::ranges::filter_view or a local std::copy_if into a new vector) and remove the helper entirely

This issue should be re-scoped from "remove dead code" to "clarify or replace misleading utility function."

[csparker247]

Implemented as a rename in PR #35: → . All 6 call sites updated, no behavioral change.