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SI-10154 Fix implicit search regression for term-owned objects #5654

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Merged
merged 1 commit into from
Feb 15, 2017
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SI-10154 Fix implicit search regression for term-owned objects #5654

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3 changes: 2 additions & 1 deletion src/compiler/scala/tools/nsc/typechecker/Contexts.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1194,7 +1194,8 @@ trait Contexts { self: Analyzer =>
}

final def lookupCompanionOf(original: Symbol): Symbol = {
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@adriaanm adriaanm Jan 24, 2017 •
edited
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My head started spinning with indirection, so I figure I'll rubber-duck-review this by doing some inlining...

I tried to push all logic into lookupCompanionOf:

final def lookupCompanionOf(original: Symbol): Symbol =
  if (original == NoSymbol) NoSymbol else { // can we collapse the next few lines by using original.exists in the condition here?
    original.failIfStub()

    if (original.needsFlatClasses) original.info // use initialize() ?
    val flatOwnerInfo = original.owner.rawInfo

    // can we find it using the owner structure -- i.e., is it a member of some other symbol?
    val member =
      original match {
        case mcs: ModuleClassSymbol if mcs.module ne null => mcs.module
        case _ =>
          flatOwnerInfo.decl(original.name.companionName).suchThat(sym =>
            sym != original && (if (original.isClass) sym.isModule else sym.isClass) && sym.isCoDefinedWith(original)
          )
      }

    // can we decide which branch to take here directly rather than by trying the search?
    // i.e., is it a term-owned symbol??
    if (member == NoSymbol) 
      lookupScopeEntry(original) match {
        case null => NoSymbol
        case entry => entry.owner.lookupCompanion(original)
      }
    else member
  }

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@retronym retronym Jan 24, 2017 •
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can we decide which branch to take here directly rather than by trying the search? i.e., is it a term-owned symbol??

I think we also get into this code path for class-owned symbols where the class info is incomplete. So the check would need to be something like owner.isTerm || !owner.hasCompleteInfo

lookupScopeEntry(original) match {
if (original.isModuleClass) original.sourceModule
else lookupScopeEntry(original) match {
case null => NoSymbol
case entry => entry.owner.lookupCompanion(original)
}
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11 changes: 11 additions & 0 deletions test/files/pos/t10154.scala
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@@ -0,0 +1,11 @@
trait Bar2[T]

object Test2 {
def wrap {
object Foo {
implicit def fooBar: Bar2[Foo.type] = ???
}

implicitly[Bar2[Foo.type]]
}
}
16 changes: 16 additions & 0 deletions test/files/pos/t10154b.scala
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@@ -0,0 +1,16 @@
import scala.language.existentials

class Bar[T]
class Test {
def method = {
object Foo {
implicit def x: Bar[Foo.type] = new Bar[Foo.type]
}
type T = Foo.type

{
object Foo
implicitly[Bar[T]]
}
}
}