sounds good! i'll need to find some time to look into it. want to run a community build on it early?

@lrytz thanks, before late bedtime I almost gave you a heads up to ask if you'd like me to continue the PR.

Before spending electrons on CB, I'll try some projects locally. I expect to discover more behaviors.

Edit: the cycle will need fixing first, I hit it right away. I'll leave the PR open out of sheer optimism.

Maybe there's nothing better to do than catch & ignore.

This is current behavior, regular type check fails in "assign type to tree" because asking if it's a refinement (typedDefDef) means checking all overrides. I see dotty has a<refinement> artifact. My bigger idea was thatlookupSymbol need not force inlookupInPrefix, since it just needs to search parents for the name to detect that there is a symbol with that name; actually getting the (possibly overloaded) symbol is not necessary when probing. typedIdent tries a few strategies; I hoped gentler probing might help with cycles, but maybe wishful thinking.

[log typer] collect local implicits List(primary constructor $anon, type T, getter tTag, value tTag )[log typer] collect local implicits List(<$anon: <empty>.this.Extractors>)[log typer] collect local implicits List(type skolem S&0, value a, value evidence$1)[log typer] collect local implicits List()[log typer] collect local implicits List(primary constructor C, method extractorMatch)huh.scala:20: tTag is not a valid implicit value for reflect.this.ClassTag[$anon.this.T] because:illegal cyclic reference involving getter tTag    (new Extractors { type T = S; val tTag = classTag[T] })(a)                                                     ^

I haven't looked at what problem is solved by "pre-filtering".typedImplicit already says we're checking shadowing to reduce ambiguity, andtypedIdent is basically just the lookup. It's nice to think that filtering is efficient, but not at the cost of correctness; and maybe it had more benefit in ancient days.

Has a conflict. I'll try to make some time for reviewing this change.

I'll freshen the PR and look at it with fresh eyes; my eyes will be fresh right after a cup of coffee.