This is an old bug.
Case 1)
groovy> String str= "hello 10"
groovy> str as String[]
Result: ["h", "e", "l", "l", "o", " ", "1", "0"]
That is, an array of String with one element per character in the original String.
Case 2)
groovy> def i= 10
groovy> def gstr= "hello $i"
groovy> gstr as String[]
Result: ["hello 10"]
That is, an array of String, with only one element consisting of the whole rendered String.
This is inconsistent behaviour and may give undesired results when calling methods that expect an array of String
Bug
Closed
Major
GString as String[] returns a 1-element array with the whole text
Fixed in head with the following test:
String s = 'hello 10'
def gs = "hello {5+5}"
def expected = ["h", "e", "l", "l", "o", " ", "1", "0"]
assert s.toList() == expected
assert s as String[] == expected
assert gs as String[] == expected