Guard 64-bit iterator size static_asserts for non 64-bit targets

[adityasingh2400]

Problem

The integer range iterator tests assert the exact byte size of several iterator types with hardcoded values that assume a 64-bit data model, for example:

static_assert(sizeof(IntegerRangeIterator<IteratorDirection::FORWARD, IntegerRange>) == 24);
static_assert(sizeof(CircularIntegerRangeIterator<IteratorDirection::FORWARD, IntegerRange>) == 32);

These iterators are composed of std::size_t-width members. On platforms with narrower pointers and std::size_t, such as wasm32, the iterators are smaller, so these static_asserts fail to compile. This is one of the remaining failures from issue #128 when compiling the project with emscripten, after the unrelated iterator_ two phase lookup fix in #129. The reporter confirmed these size and death test asserts were the only remaining errors.

Root cause

The asserted byte counts are valid only under a 64-bit data model. They are layout sanity checks, not portability requirements, but they were written unconditionally, so any target where sizeof(std::size_t) is not 8 breaks the build. I also verified that the sizes are not a clean multiple of sizeof(std::size_t) on 32-bit targets because of alignment of the iterator wrappers, so a per-platform recomputation would be fragile.

Fix

Wrap the size static_asserts in a defined(__SIZEOF_POINTER__) && __SIZEOF_POINTER__ == 8 guard in the three affected test files:

• test/integer_range_iterator_test.cpp
• test/circular_integer_range_iterator_test.cpp
• test/filtered_integer_range_iterator_test.cpp

This mirrors the existing platform gating already used in these files, keeps the layout checks fully enforced on the primary 64-bit configurations, and skips them where the exact byte count is not meaningful. No library or runtime behavior changes, this only affects compile-time layout assertions in tests.

Verification

• 64-bit native, where __SIZEOF_POINTER__ == 8: all three test translation units compile with -std=c++20, the guarded asserts stay active and pass.
• 32-bit simulation with -m32, where __SIZEOF_POINTER__ == 4, reproducing the narrower wasm32 width: an isolated probe of the same asserts failed before this change with the exact errors reported in the issue, and compiles clean after, since the guard now skips them.
• clang-format applied to all three files, the diff is format stable.

Out of scope: the EXPECT_DEATH errors under emscripten come from gtest death tests not being available on that platform, which is a gtest and toolchain limitation rather than a fixed-containers issue, so they are left untouched.

Fixes #128