C++ named requirements:Erasable(since C++11)

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C++ named requirements

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(C++23)

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Specifies that an object of the type can be destroyed by a givenAllocator.

[edit]Requirements

Given the following types, values and expressions:

Type	Definition
`T`	an object type
`A`	an allocator type
`X`	a container type satisfying all following conditions: `X::value_type` is the same as`T`. `X::allocator_type` is the same asstd::allocator_traits<A>::rebind_alloc<T>.
Value	Definition
m	an lvalue of type`A`
p	a pointer of type`T*`

If the expressionstd::allocator_traits<A>::destroy(m, p) is well-formed,T isErasable fromX.

[edit]Notes

Allstandard library containers require that their value types satisfyErasable.

With the default allocator, this requirement is equivalent to the validity ofp->~T(), which accepts class types with accessible destructors and all scalar types, but rejects array types, function types, reference types, andvoid.	(until C++20)
With the default allocator, this requirement is equivalent to the validity ofstd::destroy_at(p), which accepts class types with accessible destructors and all scalar types, as well as arrays thereof.	(since C++20)

Although it is required that customizeddestroy is used when destroying elements ofstd::basic_string until C++23, all implementations only used the default mechanism. The requirement is corrected byP1072R10 to match existing practice.