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Backport "Warn unused member of anonymous class" to 3.3 LTS #286

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Backport "Warn unused member of anonymous class" to 3.3 LTS #286

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da7ac7d
First cut at nowarn refinement members
som-snytt Mar 8, 2025
bd6ce48
First cut at nowarn refinement members
tgodzik Apr 24, 2025
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22 changes: 20 additions & 2 deletions compiler/src/dotty/tools/dotc/transform/CheckUnused.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -150,6 +150,9 @@ class CheckUnused private (phaseMode: PhaseMode, suffix: String) extends MiniPha
override def prepareForValDef(tree: ValDef)(using Context): Context =
if !tree.symbol.is(Deferred) && tree.rhs.symbol != defn.Predef_undefined then
refInfos.register(tree)
tree.tpt match
case RefinedTypeTree(_, refinements) => relax(tree.rhs, refinements)
case _ =>
ctx
override def transformValDef(tree: ValDef)(using Context): tree.type =
traverseAnnotations(tree.symbol)
Expand All @@ -168,11 +171,15 @@ class CheckUnused private (phaseMode: PhaseMode, suffix: String) extends MiniPha
override def prepareForDefDef(tree: DefDef)(using Context): Context =
def trivial = tree.symbol.is(Deferred) || isUnconsuming(tree.rhs)
def nontrivial = tree.symbol.isConstructor || tree.symbol.isAnonymousFunction
if !nontrivial && trivial then refInfos.skip.addOne(tree.symbol)
if !nontrivial && trivial then
refInfos.skip.addOne(tree.symbol)
if tree.symbol.is(Inline) then
refInfos.inliners += 1
else if !tree.symbol.is(Deferred) && tree.rhs.symbol != defn.Predef_undefined then
refInfos.register(tree)
tree.tpt match
case RefinedTypeTree(_, refinements) => relax(tree.rhs, refinements)
case _ =>
ctx
override def transformDefDef(tree: DefDef)(using Context): tree.type =
traverseAnnotations(tree.symbol)
Expand Down Expand Up @@ -447,7 +454,7 @@ object CheckUnused:
if !tree.name.isInstanceOf[DerivedName] then
pats.addOne((tree.symbol, tree.namePos))
case tree: NamedDefTree =>
if (tree.symbol ne NoSymbol) && !tree.name.isWildcard then
if (tree.symbol ne NoSymbol) && !tree.name.isWildcard && !tree.hasAttachment(NoWarn) then
defs.addOne((tree.symbol, tree.namePos))
case _ =>
if tree.symbol ne NoSymbol then
Expand Down Expand Up @@ -843,6 +850,17 @@ object CheckUnused:
args.foreach(traverse)
case tree => traverseChildren(tree)

// NoWarn members in tree that correspond to refinements; currently uses only names.
def relax(tree: Tree, refinements: List[Tree])(using Context): Unit =
val names = refinements.collect { case named: NamedDefTree => named.name }.toSet
val relaxer = new TreeTraverser:
def traverse(tree: Tree)(using Context) =
tree match
case tree: NamedDefTree if names(tree.name) => tree.withAttachment(NoWarn, ())
case _ =>
traverseChildren(tree)
relaxer.traverse(tree)

extension (nm: Name)
inline def exists(p: Name => Boolean): Boolean = nm.ne(nme.NO_NAME) && p(nm)
inline def isWildcard: Boolean = nm == nme.WILDCARD || nm.is(WildcardParamName)
Expand Down
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