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Fix test and add more comments
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2 files changed

+27
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compiler/src/dotty/tools/dotc/transform/Dependencies.scala

Lines changed: 24 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -182,32 +182,47 @@ abstract class Dependencies(root: ast.tpd.Tree, @constructorOnly rootContext: Co
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if enclClass.isContainedIn(thisClass) then thisClass
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else enclClass) // unknown this reference, play it safe and assume the narrowest possible owner
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/** Set the first owner of a local method or class that's nested inside a term.
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* This is either the enclosing package or the enclosing class. If the former,
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* the method will be be translated to a static method of its toplevel class.
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* In that case, we might later re-adjust the owner to a nested class via
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* `narrowTo` when we see that the method refers to the this-type of that class.
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* We choose the enclosing package when there's something potentially to gain from this
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* and when it is safe to do so
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*/
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def setLogicOwner(local: Symbol) =
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val encClass = local.owner.enclosingClass
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// When to [efer enclosing class over enclosing package:
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val preferEncClass =
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encClass.isStatic
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// non-static classes can capture owners, so should be avoided
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// If class is not static, we try to hoist the method out of
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// the class to avoid the outer pointer.
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&& (encClass.isProperlyContainedIn(local.topLevelClass)
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// can be false for symbols which are defined in some weird combination of supercalls.
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// If class is nested in an outer object, we prefer to leave the method in the class,
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// since putting it in the outer object makes access more complicated
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|| encClass.is(ModuleClass, butNot = Package)
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// needed to not cause deadlocks in classloader. see t5375.scala
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// If class is an outermost object we also want to avoid making the
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// method static since that could cause deadlocks in interacting
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// with class initialization. See deadlock.scala
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)
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&& (!sym.isAnonymousFunction || sym.owner.ownersIterator.exists(_.isConstructor))
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// For anonymous functions in static objects, we prefer them to be static because
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// that means lambdas are memoized and can be serialized even if the enclosing object
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// The previous conditions mean methods in static objects and nested static classes
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// don't get lifted out to be static. In general it is prudent to do that. However,
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// for anonymous functions, we prefer them to be static because that means lambdas
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// are memoized and can be serialized even if the enclosing object or class
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// is not serializable. See run/lambda-serialization-gc.scala and run/i19224.scala.
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// On the other hand, we don't want to lift anonymous functions from inside the
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// object constructor to be static since that can cause deadlocks by its interaction
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// with class initialization. See run/deadlock.scala, which works in Scala 3
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// but deadlocks in Scala 2.
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// object or class constructor to be static since that can cause again deadlocks
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// by its interaction with class initialization. See run/deadlock.scala, which works
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// in Scala 3 but deadlocks in Scala 2.
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||
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/* Scala.js: Never move any member beyond the boundary of a DynamicImportThunk.
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* DynamicImportThunk subclasses are boundaries between the eventual ES modules
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* that can be dynamically loaded. Moving members across that boundary changes
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* the dynamic and static dependencies between ES modules, which is forbidden.
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*/
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ctx.settings.scalajs.value && encClass.isSubClass(jsdefn.DynamicImportThunkClass)
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logicOwner(sym) = if preferEncClass then encClass else local.enclosingPackageClass
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tree match

tests/run/i19224.scala

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -20,3 +20,6 @@ object Test extends App {
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assert(t1.x() == t2.x()) // true on Scala 2, was false on Scala 3...
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}
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}
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class C {
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def x(): Int => String = (i: Int) => i.toString
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}

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