Compiler error with slices, .dup and ref Parameter

[anynomous via Digitalmars-d-learn]

module a;

void init (ref string[] argv) { }

void main(string[] args) {
	init(args);           //ok
	auto y = args[1..$];
	init(y);   			  //ok
	auto x = args.dup;
	init(x);			  //ok
	init(args[1..$]);     // Error: function a.init (ref string[]
argv) is not callable using argument types (string[])
	init(args.dup); 	  // Error: function a.init (ref string[] argv)
is not callable using argument types (string[])
}

tested with
dmd 2.066.0
ldc 0.15 beta (Frontend 2.066.1)

Similar Errors occure with int[].

Is this a bug that should be reported or is there some reason for
the errors?
I searched for an issue the bugtracker and did not find a
matching one.

The error messages are strange anyway.