Add function type syntax

[thekid]

PHP

The syntax is callable as per https://wiki.php.net/rfc/callable. Supported in parameter and return types.

XP Language

The syntax is {signature -> return} where signature is either ? (any number of parameters), T (one parameter of type T) or ([T1[, T2[, ...TN]]). Supported in parameter and return types.

public {? -> int} adding() { }
public {() -> int} adding() { }
public {Collection -> int} counting() { }
public {(Collection) -> int} counting() { }
public {(string[], string) -> Map<string, string>} grouping() { }