diff --git a/compiler/src/dotty/tools/dotc/config/CliCommand.scala b/compiler/src/dotty/tools/dotc/config/CliCommand.scala
index a0edb2b8cded..53fb21cc9299 100644
--- a/compiler/src/dotty/tools/dotc/config/CliCommand.scala
+++ b/compiler/src/dotty/tools/dotc/config/CliCommand.scala
@@ -1,8 +1,6 @@
 package dotty.tools.dotc
 package config
 
-import scala.language.unsafeNulls
-
 import Settings.*
 import core.Contexts.*
 import printing.Highlighting
diff --git a/compiler/src/dotty/tools/dotc/config/PathResolver.scala b/compiler/src/dotty/tools/dotc/config/PathResolver.scala
index 67be0e3587cb..68960d5134ba 100644
--- a/compiler/src/dotty/tools/dotc/config/PathResolver.scala
+++ b/compiler/src/dotty/tools/dotc/config/PathResolver.scala
@@ -2,8 +2,6 @@ package dotty.tools
 package dotc
 package config
 
-import scala.language.unsafeNulls
-
 import WrappedProperties.AccessControl
 import io.{ClassPath, Directory, Path}
 import classpath.{AggregateClassPath, ClassPathFactory, JrtClassPath}
diff --git a/compiler/src/dotty/tools/dotc/core/classfile/ReusableDataReader.scala b/compiler/src/dotty/tools/dotc/core/classfile/ReusableDataReader.scala
index e9bb7337c948..35716feb7a42 100644
--- a/compiler/src/dotty/tools/dotc/core/classfile/ReusableDataReader.scala
+++ b/compiler/src/dotty/tools/dotc/core/classfile/ReusableDataReader.scala
@@ -3,8 +3,6 @@ package dotc
 package core
 package classfile
 
-import scala.language.unsafeNulls
-
 import java.io.{DataInputStream, InputStream}
 import java.nio.{BufferUnderflowException, ByteBuffer}
 
diff --git a/compiler/src/dotty/tools/dotc/core/tasty/BestEffortTastyWriter.scala b/compiler/src/dotty/tools/dotc/core/tasty/BestEffortTastyWriter.scala
index 13a6a274ed96..a027da8a8a29 100644
--- a/compiler/src/dotty/tools/dotc/core/tasty/BestEffortTastyWriter.scala
+++ b/compiler/src/dotty/tools/dotc/core/tasty/BestEffortTastyWriter.scala
@@ -2,7 +2,6 @@ package dotty.tools.dotc
 package core
 package tasty
 
-import scala.language.unsafeNulls
 import java.nio.file.{Path as JPath, Files as JFiles}
 import java.nio.channels.ClosedByInterruptException
 import java.io.DataOutputStream
diff --git a/compiler/src/dotty/tools/dotc/core/tasty/CommentUnpickler.scala b/compiler/src/dotty/tools/dotc/core/tasty/CommentUnpickler.scala
index d3b5c647b9c5..42c572f0a50e 100644
--- a/compiler/src/dotty/tools/dotc/core/tasty/CommentUnpickler.scala
+++ b/compiler/src/dotty/tools/dotc/core/tasty/CommentUnpickler.scala
@@ -1,8 +1,6 @@
 package dotty.tools.dotc
 package core.tasty
 
-import scala.language.unsafeNulls
-
 import core.Comments.Comment
 import util.Spans.Span
 import util.HashMap
diff --git a/compiler/src/dotty/tools/dotc/core/tasty/TastyPickler.scala b/compiler/src/dotty/tools/dotc/core/tasty/TastyPickler.scala
index e35ed5bb2466..6fc397efea5a 100644
--- a/compiler/src/dotty/tools/dotc/core/tasty/TastyPickler.scala
+++ b/compiler/src/dotty/tools/dotc/core/tasty/TastyPickler.scala
@@ -3,8 +3,6 @@ package dotc
 package core
 package tasty
 
-import scala.language.unsafeNulls
-
 import dotty.tools.tasty.{TastyBuffer, TastyFormat, TastyHash}
 import dotty.tools.tasty.besteffort.BestEffortTastyFormat
 import TastyFormat.*
diff --git a/compiler/src/dotty/tools/dotc/core/tasty/TastyUnpickler.scala b/compiler/src/dotty/tools/dotc/core/tasty/TastyUnpickler.scala
index f034f03298b1..6ce27b8b77af 100644
--- a/compiler/src/dotty/tools/dotc/core/tasty/TastyUnpickler.scala
+++ b/compiler/src/dotty/tools/dotc/core/tasty/TastyUnpickler.scala
@@ -3,8 +3,6 @@ package core
 package tasty
 
 import java.util.UUID
-import scala.language.unsafeNulls
-
 import dotty.tools.tasty.{TastyFormat, TastyVersion, TastyBuffer, TastyReader, TastyHeaderUnpickler, UnpicklerConfig}
 import dotty.tools.tasty.besteffort.{BestEffortTastyHeader, BestEffortTastyHeaderUnpickler}
 
diff --git a/compiler/src/dotty/tools/dotc/decompiler/DecompilationPrinter.scala b/compiler/src/dotty/tools/dotc/decompiler/DecompilationPrinter.scala
index 16e7cc9c7adc..6fe6d4ec22f7 100644
--- a/compiler/src/dotty/tools/dotc/decompiler/DecompilationPrinter.scala
+++ b/compiler/src/dotty/tools/dotc/decompiler/DecompilationPrinter.scala
@@ -1,8 +1,6 @@
 package dotty.tools.dotc
 package decompiler
 
-import scala.language.unsafeNulls
-
 import java.io.{OutputStream, PrintStream}
 import java.nio.charset.StandardCharsets
 
@@ -26,8 +24,8 @@ class DecompilationPrinter extends Phase {
     if (ctx.settings.outputDir.isDefault) printToOutput(System.out)
     else {
       val outputDir = ctx.settings.outputDir.value
-      var os: OutputStream = null
-      var ps: PrintStream = null
+      var os: OutputStream|Null = null
+      var ps: PrintStream|Null = null
       try {
         os = File(outputDir.fileNamed("decompiled.scala").path)(Codec.UTF8).outputStream(append = true)
         ps = new PrintStream(os, /* autoFlush = */ false, StandardCharsets.UTF_8.name)
diff --git a/compiler/src/dotty/tools/dotc/decompiler/IDEDecompilerDriver.scala b/compiler/src/dotty/tools/dotc/decompiler/IDEDecompilerDriver.scala
index 18c5ceb5f346..29acc58c09f4 100644
--- a/compiler/src/dotty/tools/dotc/decompiler/IDEDecompilerDriver.scala
+++ b/compiler/src/dotty/tools/dotc/decompiler/IDEDecompilerDriver.scala
@@ -2,8 +2,6 @@ package dotty.tools
 package dotc
 package decompiler
 
-import scala.language.unsafeNulls
-
 import dotty.tools.dotc.core.Contexts.*
 import dotty.tools.dotc.core.*
 import dotty.tools.dotc.core.tasty.TastyHTMLPrinter
diff --git a/compiler/src/dotty/tools/dotc/fromtasty/Debug.scala b/compiler/src/dotty/tools/dotc/fromtasty/Debug.scala
index 2e6b699b4e36..336d424e545d 100644
--- a/compiler/src/dotty/tools/dotc/fromtasty/Debug.scala
+++ b/compiler/src/dotty/tools/dotc/fromtasty/Debug.scala
@@ -2,8 +2,6 @@ package dotty.tools
 package dotc
 package fromtasty
 
-import scala.language.unsafeNulls
-
 import scala.util.control.NonFatal
 
 import dotty.tools.io.Directory
diff --git a/compiler/src/dotty/tools/dotc/fromtasty/TASTYRun.scala b/compiler/src/dotty/tools/dotc/fromtasty/TASTYRun.scala
index d01f60571601..4ed586e23249 100644
--- a/compiler/src/dotty/tools/dotc/fromtasty/TASTYRun.scala
+++ b/compiler/src/dotty/tools/dotc/fromtasty/TASTYRun.scala
@@ -2,8 +2,6 @@ package dotty.tools
 package dotc
 package fromtasty
 
-import scala.language.unsafeNulls
-
 import io.{JarArchive, AbstractFile, Path, FileExtension}
 import core.Contexts.*
 import core.Decorators.em
diff --git a/compiler/src/dotty/tools/dotc/fromtasty/TastyFileUtil.scala b/compiler/src/dotty/tools/dotc/fromtasty/TastyFileUtil.scala
index b1277accc621..33f2bb2c5e84 100644
--- a/compiler/src/dotty/tools/dotc/fromtasty/TastyFileUtil.scala
+++ b/compiler/src/dotty/tools/dotc/fromtasty/TastyFileUtil.scala
@@ -1,8 +1,6 @@
 package dotty.tools.dotc
 package fromtasty
 
-import scala.language.unsafeNulls
-
 import dotty.tools.dotc.core.tasty.TastyClassName
 import dotty.tools.dotc.core.StdNames.nme.EMPTY_PACKAGE
 import dotty.tools.io.AbstractFile
diff --git a/compiler/src/dotty/tools/dotc/interactive/Interactive.scala b/compiler/src/dotty/tools/dotc/interactive/Interactive.scala
index 973fc2f3d79d..ff73761ad688 100644
--- a/compiler/src/dotty/tools/dotc/interactive/Interactive.scala
+++ b/compiler/src/dotty/tools/dotc/interactive/Interactive.scala
@@ -2,8 +2,6 @@ package dotty.tools
 package dotc
 package interactive
 
-import scala.language.unsafeNulls
-
 import scala.collection.*
 
 import ast.{NavigateAST, Trees, tpd, untpd}
diff --git a/compiler/src/dotty/tools/dotc/printing/SyntaxHighlighting.scala b/compiler/src/dotty/tools/dotc/printing/SyntaxHighlighting.scala
index ce925e336b53..ea58cff357c1 100644
--- a/compiler/src/dotty/tools/dotc/printing/SyntaxHighlighting.scala
+++ b/compiler/src/dotty/tools/dotc/printing/SyntaxHighlighting.scala
@@ -1,8 +1,6 @@
 package dotty.tools.dotc
 package printing
 
-import scala.language.unsafeNulls
-
 import dotty.tools.dotc.ast.untpd
 import dotty.tools.dotc.core.Contexts.*
 import dotty.tools.dotc.core.StdNames.*
diff --git a/compiler/src/dotty/tools/dotc/profile/ChromeTrace.scala b/compiler/src/dotty/tools/dotc/profile/ChromeTrace.scala
index 4950f439640f..8ee81c94f735 100644
--- a/compiler/src/dotty/tools/dotc/profile/ChromeTrace.scala
+++ b/compiler/src/dotty/tools/dotc/profile/ChromeTrace.scala
@@ -13,8 +13,6 @@
 
 package dotty.tools.dotc.profile
 
-import scala.language.unsafeNulls
-
 import java.io.Closeable
 import java.lang.management.ManagementFactory
 import java.nio.file.{Files, Path}
diff --git a/compiler/src/dotty/tools/dotc/profile/Profiler.scala b/compiler/src/dotty/tools/dotc/profile/Profiler.scala
index ab3e73468385..192226d6a883 100644
--- a/compiler/src/dotty/tools/dotc/profile/Profiler.scala
+++ b/compiler/src/dotty/tools/dotc/profile/Profiler.scala
@@ -1,8 +1,6 @@
 package dotty.tools.dotc.profile
 
 import scala.annotation.*
-import scala.language.unsafeNulls
-
 import java.io.{FileWriter, PrintWriter}
 import java.nio.file.Paths
 import java.lang.management.{ManagementFactory, GarbageCollectorMXBean, RuntimeMXBean, MemoryMXBean, ClassLoadingMXBean, CompilationMXBean}
diff --git a/compiler/src/dotty/tools/dotc/profile/ThreadPoolFactory.scala b/compiler/src/dotty/tools/dotc/profile/ThreadPoolFactory.scala
index 1a81153b9b08..d07a38c37485 100644
--- a/compiler/src/dotty/tools/dotc/profile/ThreadPoolFactory.scala
+++ b/compiler/src/dotty/tools/dotc/profile/ThreadPoolFactory.scala
@@ -1,7 +1,5 @@
 package dotty.tools.dotc.profile
 
-import scala.language.unsafeNulls
-
 import java.util.concurrent.ThreadPoolExecutor.AbortPolicy
 import java.util.concurrent.*
 import java.util.concurrent.atomic.AtomicInteger
diff --git a/compiler/src/dotty/tools/dotc/quoted/TastyString.scala b/compiler/src/dotty/tools/dotc/quoted/TastyString.scala
index 369e646e883e..528414654969 100644
--- a/compiler/src/dotty/tools/dotc/quoted/TastyString.scala
+++ b/compiler/src/dotty/tools/dotc/quoted/TastyString.scala
@@ -1,7 +1,5 @@
 package dotty.tools.dotc.quoted
 
-import scala.language.unsafeNulls
-
 import java.util.Base64
 import java.nio.charset.StandardCharsets.UTF_8
 
diff --git a/compiler/src/dotty/tools/dotc/reporting/Diagnostic.scala b/compiler/src/dotty/tools/dotc/reporting/Diagnostic.scala
index 20be33716831..30a9b8f60cf8 100644
--- a/compiler/src/dotty/tools/dotc/reporting/Diagnostic.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/Diagnostic.scala
@@ -2,8 +2,6 @@ package dotty.tools
 package dotc
 package reporting
 
-import scala.language.unsafeNulls
-
 import dotty.tools.dotc.config.Settings.Setting
 import dotty.tools.dotc.core.Contexts.*
 import dotty.tools.dotc.interfaces.Diagnostic.{ERROR, INFO, WARNING}
diff --git a/compiler/src/dotty/tools/dotc/reporting/Message.scala b/compiler/src/dotty/tools/dotc/reporting/Message.scala
index 1e313ca749d3..de0d9fdd7131 100644
--- a/compiler/src/dotty/tools/dotc/reporting/Message.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/Message.scala
@@ -11,7 +11,6 @@ import config.SourceVersion
 import cc.CaptureSet
 import cc.Capabilities.*
 
-import scala.language.unsafeNulls
 import scala.annotation.threadUnsafe
 
 /** ## Tips for error message generation
@@ -177,7 +176,7 @@ object Message:
         case sym: Symbol =>
           val info =
             if (ctx.gadt.contains(sym))
-              sym.info & ctx.gadt.fullBounds(sym)
+              sym.info & ctx.gadt.fullBounds(sym).nn
             else
               sym.info
           s"is a ${ctx.printer.kindString(sym)}${sym.showExtendedLocation}${addendum("bounds", info)}"
@@ -267,7 +266,7 @@ object Message:
         case _ =>
           super.funMiddleText(isContextual, isPure, refs)
 
-    override def toTextMethodAsFunction(info: Type, isPure: Boolean, refs: GeneralCaptureSet): Text =
+    override def toTextMethodAsFunction(info: Type, isPure: Boolean, refs: GeneralCaptureSet | Null): Text =
       info match
         case info: LambdaType =>
           seen.openLambda(info)
diff --git a/compiler/src/dotty/tools/dotc/reporting/messages.scala b/compiler/src/dotty/tools/dotc/reporting/messages.scala
index 44b97790c849..442147f99150 100644
--- a/compiler/src/dotty/tools/dotc/reporting/messages.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/messages.scala
@@ -542,7 +542,6 @@ extends SyntaxMsg(RepeatedModifierID) {
   }
 
   override def actions(using Context) =
-    import scala.language.unsafeNulls
     List(
       CodeAction(title = s"""Remove repeated modifier: "$modifier"""",
         description = None,
@@ -887,7 +886,6 @@ extends Message(PatternMatchExhaustivityID) {
         |"""
 
   override def actions(using Context) =
-    import scala.language.unsafeNulls
     val endPos = tree.cases.lastOption.map(_.endPos)
       .getOrElse(tree.selector.endPos)
     val startColumn = tree.cases.lastOption
@@ -910,7 +908,6 @@ extends Message(PatternMatchExhaustivityID) {
 
 
   private def indent(text:String, margin: Int): String = {
-    import scala.language.unsafeNulls
     " " * margin + text
   }
 }
@@ -1991,7 +1988,6 @@ class OnlyFunctionsCanBeFollowedByUnderscore(tp: Type, tree: untpd.PostfixOp)(us
         |To convert to a function value, you need to explicitly write ${hl("() => x")}"""
 
   override def actions(using Context) =
-    import scala.language.unsafeNulls
     val untpd.PostfixOp(qual, Ident(nme.WILDCARD)) = tree: @unchecked
     List(
       CodeAction(title = "Rewrite to function value",
@@ -2021,7 +2017,6 @@ class MissingEmptyArgumentList(method: String, tree: tpd.Tree)(using Context)
   }
 
   override def actions(using Context) =
-    import scala.language.unsafeNulls
     List(
       CodeAction(title = "Insert ()",
         description = None,
diff --git a/compiler/src/dotty/tools/dotc/reporting/trace.scala b/compiler/src/dotty/tools/dotc/reporting/trace.scala
index 7f05cffb422a..c557a6e4544c 100644
--- a/compiler/src/dotty/tools/dotc/reporting/trace.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/trace.scala
@@ -2,8 +2,6 @@ package dotty.tools
 package dotc
 package reporting
 
-import scala.language.unsafeNulls
-
 import core.*, Contexts.*, Decorators.*
 import config.*
 import printing.Formatting.*
diff --git a/compiler/src/dotty/tools/dotc/sbt/ShowAPI.scala b/compiler/src/dotty/tools/dotc/sbt/ShowAPI.scala
index 61baebbe9517..a16c135deef7 100644
--- a/compiler/src/dotty/tools/dotc/sbt/ShowAPI.scala
+++ b/compiler/src/dotty/tools/dotc/sbt/ShowAPI.scala
@@ -9,8 +9,6 @@
 package dotty.tools.dotc
 package sbt
 
-import scala.language.unsafeNulls
-
 import xsbti.api.*
 
 import scala.util.Try
diff --git a/compiler/src/dotty/tools/scripting/Main.scala b/compiler/src/dotty/tools/scripting/Main.scala
index 0b954cb79b26..16e2fe35e6f1 100755
--- a/compiler/src/dotty/tools/scripting/Main.scala
+++ b/compiler/src/dotty/tools/scripting/Main.scala
@@ -1,7 +1,5 @@
 package dotty.tools.scripting
 
-import scala.language.unsafeNulls
-
 import java.io.File
 import java.nio.file.{Path, Paths}
 import dotty.tools.dotc.config.Properties.isWin
diff --git a/compiler/src/dotty/tools/scripting/StringDriver.scala b/compiler/src/dotty/tools/scripting/StringDriver.scala
index eccd8445c87d..6d4fac719be2 100755
--- a/compiler/src/dotty/tools/scripting/StringDriver.scala
+++ b/compiler/src/dotty/tools/scripting/StringDriver.scala
@@ -1,7 +1,5 @@
 package dotty.tools.scripting
 
-import scala.language.unsafeNulls
-
 import java.nio.file.{ Files, Paths, Path }
 
 import dotty.tools.dotc.Driver
diff --git a/compiler/src/dotty/tools/scripting/Util.scala b/compiler/src/dotty/tools/scripting/Util.scala
index fbbeb13ca13c..99af967143d3 100755
--- a/compiler/src/dotty/tools/scripting/Util.scala
+++ b/compiler/src/dotty/tools/scripting/Util.scala
@@ -1,7 +1,5 @@
 package dotty.tools.scripting
 
-import scala.language.unsafeNulls
-
 import java.nio.file.{ Path }
 import java.io.File
 import java.net.{ URLClassLoader }