Improved custom builder lookup (solves #6) #7
Conversation
mkubala
force-pushed
the
feature/moreElegantBuilderLookup
branch
from
fd5fcf5 to
6f99f7b
Compare
| case foundBuilderTree => foundBuilderTree | ||
| } | ||
|
|
||
| c.Expr[MemoCacheBuilder](Block(List(), builderTree)) |
There was a problem hiding this comment.
So it seems that putting an auxiliary macro call inside a quasiquote makes c.inferImplicitValue() work well, where calling this from an annotation macro context doesn't work in all cases? That's really meta-meta :) But it looks kinda like a bug to me, or at least some weird incosistency I cannot understand...
There was a problem hiding this comment.
I'm going to do some investigation about this behaviour.
My Current clues:
- I can't use auxilary macro directly, I need to weave a call to it in expanded code, because both macros live in the same compilation unit.
- annotation macro can't infer implicits vals from enclosing class scope (implicit val members), but we are able to traverse them manually. This means that problem does not lie in lack of enclosure members visibility. Maybe this behaviour is intended? From @ macros we not only can add new members but even whole companion objects. But then c.inferImplicitVal should not lookup any implicits, for the same reasons..
- based on previous clue - maybe compiler collect informations about implicits and scopes incrementally, during some typechecks or something like that? And static annotation expansions is done before phase in which compiler scan implicit vals within enclosure?
Edit:
AFAIK def macros are an (experimental) part of scala compiler, while annotation macros are still available via macroparadise plugin. Maybe this is the reason?
@xeno-by could you elaborate on this?
There was a problem hiding this comment.
@kciesielski The issue with c.typecheck (and c.inferImplicitValue that's essentially based on c.typecheck) in macro annotations is a yet unsolved problem in the design of macro annotations. That's indeed a bug.
@mkubala Your high-level hypothesis about the reason for this limitation is spot-on (if you're interested in details, scalamacros/paradise#14 provides a lot of information on the nature of the issue).
There was a problem hiding this comment.
Thanks for explanation 👍
Improved custom builder lookup (solves #6)
This implementation uses auxilary macro.