int_cast_for_switch

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.

The rules for coercion when doing a comparison where the RHS is an int are complicated and it's not sufficient to just do straight casts on $value

namespace HH\Lib\Legacy_FIXME;

function int_cast_for_switch(
  mixed $value,
  ?arraykey $first_truthy = NULL,
): int;

Instead, we need to do some data tracking to convert the input to specifics values to match specific cases under different circumstances.

arraykey instead of int second arg courtesy of non-transparent enums

Parameters

• mixed $value
• ?arraykey $first_truthy = NULL

Returns

• int