rust-lang/rust — pull request #19385 by chris-morgan (2014-11-29 00:21:28+00:00)
Title: RFC 248? I think you meant RFC 438.

There ain’t an RFC 248, while 438 looks to be what is being referred to:
https://github.com/rust-lang/rfcs/blob/master/text/0438-precedence-of-plus.md