Judicious shadowing of implicits from scope #11052
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sounds good! i'll need to find some time to look into it. want to run a community build on it early? |
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@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. |
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Fixes scala/bug#12351
Fixes scala/bug#9208
Retire both the old and new "implicit shadowing" mechanisms in favor of using
ctx.lookupSymbol.Tweak when
ctx.implicitsscollects implicits from a class by waiting to useowner.thisType.implicitMembers.A notable improvement in correctness is that overloaded implicits are handled correctly (see
neg/t729.scala). The spec for lexically scoped implicits is that the value must be "accessible without a prefix". (Probably a member was seen once in a nested context and then again as an overload in the class type, which was taken as shadowed.)The shadowing test in
isQualifyingImplicitis removed; further clean-up of removed code is still needed after more testing.There are two test tweaks to address which are due to existing cyclic error handling: in one case (
t712), where one implicit member causes a cycle, the other implicit member is not collected; in the other case (virtpatmat_typetag), an explicit type is spuriously required for a class tag, also due to an existing cyclic error.Also 2509 switched order when reporting ambiguous, which is supposed to have "winner" first. Maybe benign or progress.