ImportObjC pragma

Similar to the importc pragma for C, the importobjc pragma can be used to import Objective C methods. The generated code then uses the Objective C method calling syntax: [obj method param1: arg]. In addition with the header and emit pragmas this allows sloppy interfacing with libraries written in Objective C:

# horrible example of how to interface with GNUStep ...
{.passL: "-lobjc".}
{.emit: """
#include <objc/Object.h>
@interface Greeter:Object
{
}
- (void)greet:(long)x y:(long)dummy;
@end
#include <stdio.h>
@implementation Greeter
- (void)greet:(long)x y:(long)dummy
{
  printf("Hello, World!\n");
}
@end
#include <stdlib.h>
""".}
type
  Id {.importc: "id", header: "<objc/Object.h>", final.} = distinct int
proc newGreeter: Id {.importobjc: "Greeter new", nodecl.}
proc greet(self: Id, x, y: int) {.importobjc: "greet", nodecl.}
proc free(self: Id) {.importobjc: "free", nodecl.}
var g = newGreeter()
g.greet(12, 34)
g.free()

The compiler needs to be told to generate Objective C (command objc) for this to work. The conditional symbol objc is defined when the compiler emits Objective C code.