Method arguments processing in Groovy #groovy

argumentsProcessing.groovy

String f(Object... varArgs) {
    List args = varArgs == null ? [null] : varArgs
    Map named = args 
        ? (args[0] instanceof Map ? args[0] : [:])
        : [:]
    List positional = named ? args.drop(1) : args

    "named: $named; positional: $positional; all: $args"
}

assert f()                   == 'named: [:]; positional: []; all: []'
assert f 1                   == 'named: [:]; positional: [1]; all: [1]'
assert f null                == 'named: [:]; positional: [null]; all: [null]'
assert f x: null             == 'named: [x:null]; positional: []; all: [[x:null]]'
assert f null, null          == 'named: [:]; positional: [null, null]; all: [null, null]'
assert f x: 1                == 'named: [x:1]; positional: []; all: [[x:1]]'
assert f([x: 1])             == 'named: [x:1]; positional: []; all: [[x:1]]'
assert f([x: 1], y: 2)       == 'named: [y:2]; positional: [[x:1]]; all: [[y:2], [x:1]]'
assert f a:5, [x: 1], y: 2   == 'named: [a:5, y:2]; positional: [[x:1]]; all: [[a:5, y:2], [x:1]]'
assert f([x: 1], [y: 2])     == 'named: [x:1]; positional: [[y:2]]; all: [[x:1], [y:2]]'
assert f{}                   == 'named: [:]; positional: [Script1$_run_closure1@4606bcd6]; all: [Script1$_run_closure1@4606bcd6]'
assert f({}, {})             == 'named: [:]; positional: [Script1$_run_closure2@fda98c5, Script1$_run_closure3@7c4975e4]; all: [Script1$_run_closure2@fda98c5, Script1$_run_closure3@7c4975e4]'