rust-lang/rust — pull request #18921 by oli-obk (2014-11-13 13:26:30+00:00)
Title: libgraphviz: Id::new returns Result<Id, ()> instead of panicking on error

creating a new Id object requires the format to match a subset of `ID` format defined by the DOT language. When the format did not match, the function called assert. This was not mentioned in the docs or the spec. I made the failure explicit by returning an Result.