Validator: No detection of two type issues in [...]

[maxkratz]

Both examples:

constraint -> mapping::n2n {
	[self.variables().v >= 1 => self.value() => 1] & // the last operator is wrong but not detected
	[self.value() >= 1 => self.variables().v >= 1]
}

constraint -> mapping::n2n {
	[self.variables().v >= 1 => self.value()] & // the last expr is missing an arithmetic operator
	[self.value() >= 1 => self.variables().v >= 1]
}

[maxkratz]

TODO: Check if this is a symptom of #102.