[libc++][test] Fix MaybePOCCAAllocator to finally meet the allocator requirements

[StephanTLavavej]

Found while running libc++'s test suite with MSVC's STL.

After @CaseyCarter's LLVM-D118279 c5ba46e "[libcxx][test] MaybePOCCAAllocator should meet the Cpp17Allocator requirements" followed by @philnik777's LLVM-D68365 98d3d5b "[libc++] Implement P1004R2 (constexpr std::vector)", one more change is necessary.

MSVC's constexpr vector implementation noticed this because we always rebind allocators.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Stephan T. Lavavej (StephanTLavavej)

Changes

Found while running libc++'s test suite with MSVC's STL.

After @CaseyCarter's LLVM-D118279 c5ba46e "[libcxx][test] MaybePOCCAAllocator should meet the Cpp17Allocator requirements" followed by @philnik777's LLVM-D68365 98d3d5b "[libc++] Implement P1004R2 (constexpr std::vector)", one more change is necessary.

MSVC's constexpr vector implementation noticed this because we always rebind allocators.

---

Full diff: https://github.com/llvm/llvm-project/pull/74960.diff

1 Files Affected:

• (modified) libcxx/test/support/allocators.h (+1-1)

diff --git a/libcxx/test/support/allocators.h b/libcxx/test/support/allocators.h
index 2b987ad872783e..02436fd9c35ef1 100644
--- a/libcxx/test/support/allocators.h
+++ b/libcxx/test/support/allocators.h
@@ -209,7 +209,7 @@ class MaybePOCCAAllocator {
         : id_(id), copy_assigned_into_(copy_assigned_into) {}
 
     template <class U>
-    MaybePOCCAAllocator(const MaybePOCCAAllocator<U, POCCAValue>& that)
+    TEST_CONSTEXPR MaybePOCCAAllocator(const MaybePOCCAAllocator<U, POCCAValue>& that)
         : id_(that.id_), copy_assigned_into_(that.copy_assigned_into_) {}
 
     MaybePOCCAAllocator(const MaybePOCCAAllocator&) = default;

[StephanTLavavej]

Thanks! The checks are green, modulo what #74987 is about to fix, and unrelated sporadic timeouts/failures. Merging...