As Mut

:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::

Converts a readonly value type into a mutable one

namespace HH\Readonly;

function as_mut<T>(
  T $x,
): T;

Value types include numerics, strings, bools, null and Hack arrays of value types.

Parameters

• T $x

Returns

• T