Update _ wildcard type to ? in compiler (#18810)

Part of #18809

Author: nicolasstucki

compiler/src/dotty/tools/backend/jvm/ClassfileWriters.scala

@@ -186,7 +186,7 @@ class ClassfileWriters(frontendAccess: PostProcessorFrontendAccess) {
 
   private final class DirEntryWriter(base: Path) extends FileWriter {
     val builtPaths = new ConcurrentHashMap[Path, java.lang.Boolean]()
-    val noAttributes = Array.empty[FileAttribute[_]]
+    val noAttributes = Array.empty[FileAttribute[?]]
     private val isWindows = scala.util.Properties.isWin
 
     private def checkName(component: Path): Unit = if (isWindows) {

compiler/src/dotty/tools/backend/jvm/CoreBTypes.scala

@@ -138,7 +138,7 @@ abstract class CoreBTypesFromSymbols[I <: DottyBackendInterface] extends CoreBTy
   lazy val jlStringBuilderRef       : ClassBType = synchClassBTypeFromSymbol(requiredClass[java.lang.StringBuilder])
   lazy val jlStringBufferRef        : ClassBType = synchClassBTypeFromSymbol(requiredClass[java.lang.StringBuffer])
   lazy val jlCharSequenceRef        : ClassBType = synchClassBTypeFromSymbol(requiredClass[java.lang.CharSequence])
-  lazy val jlClassRef               : ClassBType = synchClassBTypeFromSymbol(requiredClass[java.lang.Class[_]])
+  lazy val jlClassRef               : ClassBType = synchClassBTypeFromSymbol(requiredClass[java.lang.Class[?]])
   lazy val jlThrowableRef           : ClassBType = synchClassBTypeFromSymbol(defn.ThrowableClass)
   lazy val jlCloneableRef           : ClassBType = synchClassBTypeFromSymbol(defn.JavaCloneableClass)
   lazy val jiSerializableRef        : ClassBType = synchClassBTypeFromSymbol(requiredClass[java.io.Serializable])

compiler/src/dotty/tools/backend/jvm/DottyBackendInterface.scala

@@ -93,7 +93,7 @@ class DottyBackendInterface(val superCallsMap: ReadOnlyMap[Symbol, Set[ClassSymb
 
 object DottyBackendInterface {
 
-  private def erasureString(clazz: Class[_]): String = {
+  private def erasureString(clazz: Class[?]): String = {
     if (clazz.isArray) "Array[" + erasureString(clazz.getComponentType) + "]"
     else clazz.getName
   }

compiler/src/dotty/tools/backend/jvm/GenericSignatureVisitor.scala

@@ -315,7 +315,7 @@ abstract class NestedClassesCollector[T](nestedOnly: Boolean) extends GenericSig
     if (annot.values != null) annot.values.asScala foreach visitConstant
   }
 
-  def visitAnnotations(annots: java.util.List[_ <: AnnotationNode]) = if (annots != null) annots.asScala foreach visitAnnotation
+  def visitAnnotations(annots: java.util.List[? <: AnnotationNode]) = if (annots != null) annots.asScala foreach visitAnnotation
   def visitAnnotationss(annotss: Array[java.util.List[AnnotationNode]]) = if (annotss != null) annotss foreach visitAnnotations
 
   def visitHandle(handle: Handle): Unit = {

compiler/src/dotty/tools/backend/sjs/JSCodeGen.scala

@@ -1089,7 +1089,7 @@ class JSCodeGen()(using genCtx: Context) {
       val exports = List.newBuilder[jsExportsGen.Exported]
       val jsClassCaptures = List.newBuilder[js.ParamDef]
 
-      def add(tree: ConstructorTree[_ <: JSCtor]): Unit = {
+      def add(tree: ConstructorTree[? <: JSCtor]): Unit = {
         val (e, c) = genJSClassCtorDispatch(tree.ctor.sym,
             tree.ctor.paramsAndInfo, tree.overloadNum)
         exports += e
@@ -1270,7 +1270,7 @@ class JSCodeGen()(using genCtx: Context) {
      * here we use the property from building the trees, that a set of
      * descendants always has a range of overload numbers.
      */
-    def ifOverload(tree: ConstructorTree[_], body: js.Tree): js.Tree = body match {
+    def ifOverload(tree: ConstructorTree[?], body: js.Tree): js.Tree = body match {
       case js.Skip() => js.Skip()
 
       case body =>

compiler/src/dotty/tools/backend/sjs/ScopedVar.scala

@@ -28,7 +28,7 @@ object ScopedVar {
 
   implicit def toValue[T](scVar: ScopedVar[T]): T = scVar.get
 
-  def withScopedVars[T](ass: Assignment[_]*)(body: => T): T = {
+  def withScopedVars[T](ass: Assignment[?]*)(body: => T): T = {
     val stack = ass.map(_.push())
     try body
     finally stack.reverse.foreach(_.pop())

compiler/src/dotty/tools/dotc/ast/TreeInfo.scala

@@ -242,7 +242,7 @@ trait TreeInfo[T <: Untyped] { self: Trees.Instance[T] =>
 
   /** Does this list contain a named argument tree? */
   def hasNamedArg(args: List[Any]): Boolean = args exists isNamedArg
-  val isNamedArg: Any => Boolean = (arg: Any) => arg.isInstanceOf[Trees.NamedArg[_]]
+  val isNamedArg: Any => Boolean = (arg: Any) => arg.isInstanceOf[Trees.NamedArg[?]]
 
   /** Is this pattern node a catch-all (wildcard or variable) pattern? */
   def isDefaultCase(cdef: CaseDef): Boolean = cdef match {
@@ -1060,7 +1060,7 @@ trait TypedTreeInfo extends TreeInfo[Type] { self: Trees.Instance[Type] =>
 
   def assertAllPositioned(tree: Tree)(using Context): Unit =
     tree.foreachSubTree {
-      case t: WithoutTypeOrPos[_] =>
+      case t: WithoutTypeOrPos[?] =>
       case t => assert(t.span.exists, i"$t")
     }
 

compiler/src/dotty/tools/dotc/ast/Trees.scala

@@ -31,7 +31,7 @@ object Trees {
 
   /** Property key for backquoted identifiers and definitions */
   val Backquoted: Property.StickyKey[Unit] = Property.StickyKey()
-  
+
   val SyntheticUnit: Property.StickyKey[Unit] = Property.StickyKey()
 
   /** Trees take a parameter indicating what the type of their `tpe` field
@@ -932,11 +932,11 @@ object Trees {
     def rhs(using Context): Tree[T] = { forceFields(); preRhs.asInstanceOf[Tree[T]] }
 
     def leadingTypeParams(using Context): List[TypeDef[T]] = paramss match
-      case (tparams @ (tparam: TypeDef[_]) :: _) :: _ => tparams.asInstanceOf[List[TypeDef[T]]]
+      case (tparams @ (tparam: TypeDef[?]) :: _) :: _ => tparams.asInstanceOf[List[TypeDef[T]]]
       case _ => Nil
 
     def trailingParamss(using Context): List[ParamClause[T]] = paramss match
-      case ((tparam: TypeDef[_]) :: _) :: paramss1 => paramss1
+      case ((tparam: TypeDef[?]) :: _) :: paramss1 => paramss1
       case _ => paramss
 
     def termParamss(using Context): List[List[ValDef[T]]] =

compiler/src/dotty/tools/dotc/inlines/Inliner.scala

@@ -649,13 +649,13 @@ class Inliner(val call: tpd.Tree)(using Context):
     def treeSize(x: Any): Int =
       var siz = 0
       x match
-        case x: Trees.Inlined[_] =>
+        case x: Trees.Inlined[?] =>
         case x: Positioned =>
           var i = 0
           while i < x.productArity do
             siz += treeSize(x.productElement(i))
             i += 1
-        case x: List[_] =>
+        case x: List[?] =>
           var xs = x
           while xs.nonEmpty do
             siz += treeSize(xs.head)

compiler/src/dotty/tools/dotc/printing/PlainPrinter.scala

@@ -160,7 +160,7 @@ class PlainPrinter(_ctx: Context) extends Printer {
       core ~ cs.optionalInfo
 
   private def toTextRetainedElem[T <: Untyped](ref: Tree[T]): Text = ref match
-    case ref: RefTree[_] if ref.typeOpt.exists =>
+    case ref: RefTree[?] if ref.typeOpt.exists =>
       toTextCaptureRef(ref.typeOpt)
     case Apply(fn, Literal(str) :: Nil) if fn.symbol == defn.Caps_capIn =>
       s"cap[${str.stringValue}]"