over.app: add proper bool usage check

over/app.py

@@ -79,6 +79,13 @@ class IncompleteArguments(Exception):
 		
 		return "option --%s takes a %d-word argument but has received %s" %(option_name, option_count, received or "none")
 
+class BoolUsageError(Exception):
+	@property
+	def description(self):
+		option_name = self.args[0]
+		
+		return "option --%s is not boolean so you can't use --no-%s" %(option_name, option_name)
+
 class NotAList(Exception):
 	"""
 	Option defaults must be in a list.
@@ -459,6 +466,9 @@ class Main:
 						except KeyError:
 							raise UnknownOption(token)
 						
+						if not option_is_positive and not option.is_boolean:
+							raise BoolUsageError(option.name)
+						
 						last_read_option = option
 						
 						# single booleans are handled specially because of their --option/--no-option forms