The YSLDValidator for the ysld module does not run on aliases (i.e. variables). This can lead to a situation where it uses a 'value' validator when parsing a 'property' tag, causing erroneous parse errors.
For example, given the following YSLD:
The validator reads the fill-color property, and gets a ColorValidator for validating the value. However, since the value is an alias, the validator skips it and uses the ColorValidator on the stroke-color property instead, leading to the error: