use v6.c;
say $*PERL.compiler.version;

class ClassA {};
class ClassB {}
class ClassC {
    has $.foo;
    has $!bar;
};

my $class;
given 2 {
    when 0 { $class = ClassA }
    when 1 { $class = ClassB }
    default { $class = ClassC }
}

say my $obj = $class.new( foo => 1, bar => 1 );

##</code><code>##

v2016.04
ClassC.new(foo => 1)

##</code><code>##

class ClassC { has $.foo }
my %args = :foo;
ClassC.new(|%args)

##</code><code>##

class C {}
C.new(1)

##</code><code>##

class Duration ... {
    has Rat $.tai = 0;
    ...
    method new($tai) { self.bless: tai => $tai.Rat }
    ...
}

##</code><code>##

say Duration.new(22); # Duration.new(tai => 22.0)