Pattern: Assignment of Collections.unique()
Issue: -
The Collections.unique() method mutates the list and returns the list as a value. If you are assigning the result of unique() to a variable, then you probably don't realize that you're also modifying the original list as well. This is frequently the cause of subtle bugs. This violation is triggered when a unique() method call appears as the right hand side of an assignment, or when it appears as the first method call in a series of chained method calls.
Example of violations:
def a = someList.unique()
def b = someList.unique() { it }
def c = someList.unique().findAll { x < 1 }