Specs

check(params(), args(), acc()) :: :ok | {:error, term()}

Invoked to handle the corresponding check step.

Returning :ok continues the reduction with the current params and acc passed to the next Exaop step.

Returning a two-element tuple {:error, reason} halts the reduction and the built function __inject__/3 returns the error tuple.

When the final reduction step is check and it returns :ok, the built function __inject__/3 returns the last acc accumulator.