{print,write}-with-newline: do not suggest empty format string

[euclio]

changelog: do not suggest empty format strings in print-with-newline and write-with-newline

[rust-highfive]

r? @Manishearth

(rust_highfive has picked a reviewer for you, use r? to override)

[euclio]

Oops, this is not quite ready to go: I need to get write_with_newline to work as well.

[euclio]

Updated. I'm not super happy about the span on writeln!, but I'm not sure trying to finagle the span to include the , is worth it. Unfortunately rustfmt won't take care of it.

[flip1995]

I agree that also removing the , would be way too much code for little benefit. This is definitely an improvement of the current suggestion as it is. Thanks!

@bors r+

[bors]

📌 Commit 0261e34 has been approved by flip1995

[bors]

⌛ Testing commit 0261e34 with merge 61dd007...

[bors]

☀️ Test successful - checks-action_dev_test, checks-action_remark_test, checks-action_test
Approved by: flip1995
Pushing 61dd007 to master...