Add Integer type validation to Literal::Flags.define

[yykamei]

Validate that all flag values are Integers when defining flags to prevent runtime errors caused by non-Integer values in bit operations.

Motivation for the changes

The primary motivation for this change is to prevent potential runtime errors.

For instance, when a class inheriting from Literal::Flags8 was defined as follows:

class Example < Literal::Flags8
  define(a: nil, b: true)
end

I got an error with the following. This is because nil was expanded to an empty String, leading to a syntax error.

/Users/yykamei/literal/lib/literal/flags.rb:34:in 'Module#class_eval': 
/Users/yykamei/literal/lib/literal/flags.rb:38: syntax errors found (SyntaxError)
36 | 
	37 | def b?
	> 38 |  @value & (2 ** ) > 0
	|                 ^ unexpected ')', assuming it is closing the parent parentheses
	|                 ^ unexpected ')'; expected an expression after the operator
	|                      ^ expected an `end` to close the `def` statement
	39 | end
...

In another case, the following class was defined and then initialized with Example.new(a: true).

class Example < Literal::Flags8
  define(a: 0.1, b: 1)
end

This resulted in a TypeError.

/Users/yykamei/literal/lib/literal/flags.rb:67:in 'Integer#|': 2.2973967099940698 can't be 
coerced into Integer (TypeError)

value | (bit ? 2 ** flags.fetch(key) : 0)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
from /Users/yykamei/literal/lib/literal/flags.rb:67:in 'block in Literal::Flags.cal
culate_from_hash'
from /Users/yykamei/literal/lib/literal/flags.rb:66:in 'Hash#each'
from /Users/yykamei/literal/lib/literal/flags.rb:66:in 'Enumerable#reduce'
from /Users/yykamei/literal/lib/literal/flags.rb:66:in 'Literal::Flags.calculate_fr
om_hash'
from /Users/yykamei/literal/lib/literal/flags.rb:8:in 'Literal::Flags#initialize'
...

Based on these two examples, it is evident that the Literal::Flags.define method should only accept integer values for its flags. For this reason, I have proposed the changes to enforce this validation.

[yykamei]

Oh, I should address this error.

NameError: uninitialized constant Literal::Types::InterfaceType

[joeldrapper]

It's not you. It's JRuby. We're waiting for them to fix.

[yykamei]

Thanks!