deduplicating lambda methods

[Brian Goetz]

> A good extension to Liam's proposal, that should arise naturally
> from his AST matching work, would be to recognize the top ten
> (or so) AST patterns, like the above and also e -> k and k::m
> (for constants k).  The desugared methods for these a trivial,
> and as such should deduplicated *across compilation units*.
> They could be defined as part of this work as new members
> of the LMF class.

This seems more like a candidate for a jlink-time optimization.