Types:
def radioGroup[T](values: Array[T], textProvider: T => String)(setups:(RadioGroup[T] => Unit)*)(parent: Composite): RadioGroup[T]
def label(setups:(Label => Unit)*)(parent:Composite): Label
def contains(setups : (Composite => Unit)*) : Composite // "Pimp my library" on Composite
This works:
new Composite(parent, SWT.NONE).contains(
label() // should have type Composite => Label
)
This doesn't:
new Composite(parent, SWT.NONE).contains(
radioGroup(Array(1,2), (_:Int).toString)()
// should have type Composite => RadioGroup[Int]
)
with the following error:
polymorphic expression cannot be instantiated to expected type;
found : => (org.eclipse.swt.widgets.Composite) => main.scala.RadioGroup[Int]
required: (org.eclipse.swt.widgets.Composite) => Unit
I can annotate the return type of radioGroup
to be Unit
, but I don't understand 1) how the cases of radioGroup
and label
can be different; 2) why is there an extra arrow at the beginning of the "found" type in the error message.