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

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< cpp‎ | named req

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

### Requirements

The type `T` is Erasable from the Container `X` whose `value_type` is identical to `T` if, given

`A` | an allocator type
`m` | an lvalue of type `A`
`p` | the pointer of type `T*` prepared by the container

where `X::allocator_type` is identical to std::allocator_traits<A>::rebind_alloc<T>,

the following expression is well-formed:

    std::allocator_traits<A>::destroy(m, p);

If `X` is not allocator-aware or is a std::basic_string specialization, the term is defined as if `A` were std::allocator<T>, except that no allocator object needs to be created, and user-defined specializations of std::allocator are not instantiated.

### Notes

All standard library containers require that their element type satisfies Erasable.

With the default allocator, this requirement is equivalent to the validity of p->~T(), which accepts class types with accessible destructors and all scalar types, but rejects array types, function types, reference types, and void. | (until C++20)
With the default allocator, this requirement is equivalent to the validity of std::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 customized `destroy` is used when destroying elements of std::basic_string until C++23, all implementations only used the default mechanism. The requirement is corrected by P1072R10 to match existing practice.

### See also

CopyInsertable
MoveInsertable
EmplaceConstructible
Destructible

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