std.algorithm sort() and reverse() confusion

[Paul via Digitalmars-d-learn]

Given that myVals is a dynamic array of ints...

writeln("Array contents: ", myVals);
writeln("Sorted: ", sort(myVals));
writeln("Sorted, reversed: ", reverse(myVals));

Gives me...

Error: template std.stdio.writeln cannot deduce function from 
argument types !()(string, void)

But, if I bring the reverse out of the call to writeln() it works 
as expected:

writeln("Array contents: ", myVals);
writeln("Sorted: ", sort(myVals));
reverse(myVals);
writeln("Sorted, reversed: ", myVals);

Can someone give me a simple explanation as to why this is so? I 
guess it might be because reverse is 'in place' and the target is 
undefined at compile time but surely that would still be the case 
in the second instance. Somehow it doesn't seem logical to a noob 
like me.