count_until: ensure is_integer when raising argument error

[novaugust]

adds when is_integer(limit) to the Enum.count_until argument errors from #15029, making sure FunctionClauseError is still raised for non integer limits

[davydog187]

IMO FunctionClauseError is internal-facing, and ArgumentError is a better external facing exception for consumers of the API

[zachdaniel]

yeah, I'd prefer a fallback raising an ArgumentError when its not an integer, or a clause at the top matching on non-integers not is_integer raising an ArgumentError

[novaugust]

As is, you'll get neither when a map is passed as the second arg eh? Needs an inspect in the error message if that's the intention

[novaugust]

IMO FunctionClauseError is internal-facing, and ArgumentError is a better external facing exception for consumers of the API

that's not currently a convention i see in elixir, and to zach's point would involve adding a whole lot of final function clauses and when not is_... to existing ones to become the convention. FunctionClauseError is normal and fine when passed a whacky arg (Enum.count_until([], :whoops), especially since the error includes the patterned heads.

[josevalim]

We typically don’t raise argument errors when the value is outside the domain of the function. So if you pass a list as count, it should be a function clause error. Plus the type system can infer proper types in those cases, if you accept the argument and then raise, it cannot.

[josevalim]

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