Add a no argument case to println!

[zaeleus]

Currently, println! requires an empty string to print an empty line to stdout, i.e, println!(""). I propose an empty argument case for convenience, i.e., println!(). This simply prints a newline.

The idea stems from languages like Java (System.out.println()), Ruby (IO#puts), etc. that do this.

cc @bombless

[bombless]

I like this idea.
panic! already has similar thing for this.
See https://github.com/rust-lang/rust/blob/master/src/libcore/macros.rs#L14-L16

[mellypop]

This seems logical to me.

[bombless]

If we can call println! without round brackets, I think it will be very cool.
I'm tweaking the parser to see if we can do that ideally. If it works out I'll post a new RFC.

[pyfisch]

Please not. I always liked that macros look like a function.

[bombless]

I already have a working implementation and it works well.
Anyway I think it should be post-phone so I just plan to write a RFC around May.

I'll cc you to invite you show your exact idea at that time, @pyfisch .
:)

[zaeleus]

This was implemented by rust-lang/rust#36825 and stablized in 1.14.0.