@DanielFath - sadly, it’s more of a “fever dream” than something currently being planned. That said, it’s my hope that some of this can be investigated (eg splitting up the compiler into crates that others can consume). Other changes, like the deeper parallel/lazy fixes, would be pretty invasive and would likely have to show strong promise before anyone attempted them.
@repax - right, I don’t think that’d be wise either as a general rule. It’s tempting to think of the possibility of a second compiler being built that could use the newer understanding of the algorithms that are coming along (eg, just start with NLL and the new trait system to begin with). That said, I can’t think of any cases where an alternate compiler became the primary one, cpython is still the main one, the Ruby 1.9->2.0 was a core effort, same for C# and Roslyn, etc. So I agree it would need to be core driven and part of the planning, which this isn’t.