Error compile

[rogerwilcos]

Hi guys.
Sorry, i'm newbie in Rust, but when I tried to compile Polkadot PoC-1, i've catched this panic -

error[E0283]: type annotations required: cannot resolve std::string::String: std::convert::AsRef<_>
--> /home/personal-space/.cargo/git/checkouts/parity-dc9825eb65b3adf1/0ecbb3e/util/network-devp2p/src/service.rs:35:91
info!(target: "network", "Public node URL: {}", Colour::White.bold().paint(public_url.as_ref()));
error: aborting due to previous error

Then, I deleted as_ref() into paint(public_url.as_ref()) and compile without any panics. What's problem? Tell me what I'm doing wrong?

[rogerwilcos]

openethereum/parity-ethereum#8707