test_unordered_map.cpp: error: modification of 'ze_map' is not a constant expression; error: non-constant condition for static assertion

[Randalphwa]

Migrated from the original repository
Original issue: serge-sans-paille/frozen#163
Originally reported by: @barracuda156

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Build failure on PowerPC macOS (g++-mp-12, C++20, -Werror):

test_unordered_map.cpp:22: error: modification of 'ze_map' is not a constant expression
   22 |   constexpr auto nocount = ze_map.count(3);

test_unordered_map.cpp:180: error: non-constant condition for static assertion
  180 |   static_assert(!ce.count(0), "");

test_unordered_map.cpp:181: error: non-constant condition for static assertion
  181 |   static_assert(ce.find(0) == ce.end(), "");

The root cause traced through the call chain leads to frozen::bits::seed_or_index(), which is apparently not a constant expression in this compiler/platform combination.

The same errors occur in test_unordered_set.cpp for ze_set.count() and similar static_assert checks.

Build environment:

• macOS (PowerPC)
• g++-mp-12
• -std=gnu++20 -arch ppc -mmacosx-version-min=10.6 -Wall -Wextra -Wpedantic -Werror -Wshadow
• frozen 1.1.1