Groovy Way to Convert List to Map

gistfile1.groovy

/**
 * Convert any collection to a map by iterating over its contents
 * and taking a result of the entry as the key to the map.  The
 * argument may either be a closure which is invoked once per item
 * in the collection, or may be a string identifying the property
 * to act as the key for each entry.
 */
Collection.metaClass.asMap = { arg ->
    def result = [:]
    delegate.each {
        if (arg instanceof Closure) {
            def key = arg(it)
            result[key] = it
        }
        else {
            def key = it[arg]
            result[key] = it
        }
    }
    return result
}

/* TEST CASES */
class Test {
    def name;
    def description;
}

def list = [ 
    new Test(name:'test1', description:'blah 1'), 
    new Test(name:'test2', description:'blah 2'), 
    new Test(name:'abc', description:'blah 3') 
]

def test1 = list.asMap { it.name }
assert test1 instanceof Map
assert test1.containsKey('test1') && test1.containsKey('test2') && test1.containsKey('abc')

def test2 = list.asMap('name')
assert test2.instanceof Map
assert test2.containsKey('test1') && test2.containsKey('test2') && test2.containsKey('abc')