Can't compare INF or NAN reliably when used on an int var

[vicguedez]

Godot version:
3.1.1.stable.official

OS/device including version:
Windows 7

Issue description:
If you assign an int var with INF, it gets initialized as the min int (-9223372036854775808) which is not useful as it is a negative value. If we are not meant to assign INF to an int then the docs should have a warning on it.

I haven't tested this using floats btw.

Steps to reproduce:

var int_inf : int = INF
var casted_int_inf = int(INF)
var as_inf = INF as int
var untyped_inf = INF

print(int_inf) # -9223372036854775808
print(casted_int_inf) # -9223372036854775808
print(as_inf) # -9223372036854775808
print(untyped_inf) # 1.#INF

print(1 > INF) # False. Ok
print(1 > int_inf) # True. Not ok.
print(1 > casted_int_inf) # True. Not ok.
print(1 > as_inf) # True. Not ok.
print(1 > untyped_inf) # False. Ok.

print(INF == INF) # True. Duh :P
print(INF == int_inf) # True. But what about if I wanted to check a negative INF ?
print(INF == casted_int_inf) # True. Same as above.
print(INF == as_inf) # True. Same as above.
print(INF == untyped_inf) # False. Huh?

[bruvzg]

If we are not meant to assign INF to an int then the docs should have a warning on it.

AFAIK this type of cast is passed directly to underlying C cast, and casting NaN to integer is undefined behavior in C. Debug builds probably should have some check.

6.3.1.4 Real floating and integer: When a finite value of real floating type is converted to an integer type other than_Bool, the fractional part is discarded (i.e., the value is truncated toward zero). If the value ofthe integral part cannot be represented by the integer type, the behavior is undefined.

print(INF == untyped_inf) # False. Huh?

That's correct, comparison with a NaN always return false when comparing with itself (or with anything else), there are is_nan and is_inf function to check if variable is Inf.

[vicguedez]

@bruvzg Didn't know all of that. Thanks. I guess a notice about all of this on the docs could save some debug time.

[AcatXIo]

print(int(NAN))

also outputs -9223372036854775808 as described in #80995.