---input---
@[FOO::Bar::Baz(opt: "xx")]

---tokens---
'@['          Operator
'FOO::Bar::Baz' Name.Decorator
'('           Punctuation
'opt'         Literal.String.Symbol
':'           Punctuation
' '           Text.Whitespace
'"'           Literal.String.Double
'xx'          Literal.String.Double
'"'           Literal.String.Double
')'           Punctuation
']'           Operator
'\n'          Text.Whitespace