mozilla/rust — pull request #12384 by seanmonstar (2014-02-19 02:41:10+00:00)
Title: format_args: allow omission of format string

A default format string of Poly {:?} is generated to match the number
of passed arguments. This propagates to all fmt macros, such as println!,
debug!, format!, write!, etc.

Example: println!("{:?}", value); => println!(value);

fixes #12015