Byname implicits parameters with recursive dictionaries

[milessabin]

• Initial implementation — Support by-name implicits with recursive dictionaries scala#6050
• Spec update
• SIP
• Integration with inductive implicits heuristics — replaced by polymorphic implicit pruning
• Coordination with Dotty — in progress

From the initial PR,

This is an implementation of byname implicit parameters with recursive dictionaries, intended as a language-level ... replacement for shapeless's Lazy type. ... implicit arguments can be marked as byname and at call sites will be eligible as parameters in recursively nested positions within their own implicit expansions.

[SethTisue]

@milessabin what milestone should this be on?

[milessabin]

I'd completely forgotten this ticket ... sorry.

It was merged for 2.13.0-M5, so the milestone is already past.

[milessabin]

There are a couple of bugfix PRs in the queue which are targeted at RC1,

• Fix interactions between macros and by-name implicits scala#7199
• By-name implicits: Align detection of implicit recursion with the SIP scala#7368