echo("Hello World!") # Try a type which may or may not have system.cmp[T]. when true: type X = object var a,b : X else: type X = int var a = 1 b = 2 #echo system.cmp[X](a,b) # does not compile # Test whether this program fails to compile, # even when we do not actually call system.cmp. when true: proc foo(u,v: X, diff: proc (x,y: X): int = system.cmp) = echo diff(u, v) else: proc foo(u,v: X, diff: proc (x,y: X): int) = echo diff(u, v) proc mydiff(x,y: X): int = echo "mydiff" return 0 foo(a, b, mydiff) #foo(a, b) # Obviously, this is not possible, but that's not the point.