Syntax sugar for function type and rest arguments

[mhagmajer]

Example 1
(int, int) -> int

const sum2: (int, int) -> int = fun (a:int, b:int) { a + b }
const sum2: fun(int, int, int) = fun (a:int, b:int) { a + b }

Example 2
(...array(int)) -> int

const sumN: (...array(int)) -> int = fun (...args:array(int)) { sum(args)) }
const sumN: fun(array(int), true) = fun { sum(resources:at('args')) }

where fun is the function type constructor introduced by #42.