bool

Only two objects have type bool: the boolean literals true and false, which are both compile-time constants.

Dart’s type safety means that you can’t use code like if (nonbooleanValue) or assert (nonbooleanValue).

// Check for an empty string. var fullName = ''; assert(fullName.isEmpty); // Check for zero. var hitPoints = 0; assert(hitPoints <= 0); // Check for null. var unicorn; assert(unicorn == null); // Check for NaN. var iMeantToDoThis = 0 / 0; assert(iMeantToDoThis.isNaN);