Question

There are a few cases of source incompatibilities with Scala 2.8.0. For example, creating an anonymous Seq once required defining the abstract def elements : Iterator[A], which is now called def iterator : Iterator[A].

To me, a “brute force” solution is to create two branches that align to the different major scala versions.

Are there general techniques so that code like this will compile under both systems?

// Note: this code resembles techniques used by xml.NodeSeq
trait FooSeq extends Seq[ Foo ] {
   def internal : Seq[ Foo ] 
   def elements = internal.elements
   def iterator = internal.iterator // Only compiles in 2.8
                                    // need to remove for 2.7.X
}

Answer 1

There are a few cases where usage is simply different and you must change. But in almost all cases–such as the elements code above–the 2.7 style is simply deprecated in 2.8, not gone altogether. If you’re okay leaving your 2.8 users with deprecation warnings (edit: if they compile your code, otherwise you’ll just have the warnings yourself), just implement the new features in terms of the old:

def iterator = internal.elements

Otherwise, I would recommend what you call the brute force solution. Use a sufficiently clever VCS so that you don’t actually have to write much code twice (Git, Bazaar, Mercurial) and branch.