diff --git a/compiler/src/dotty/tools/dotc/core/NameOps.scala b/compiler/src/dotty/tools/dotc/core/NameOps.scala
index 9d88b8289648..a7490274b0c2 100644
--- a/compiler/src/dotty/tools/dotc/core/NameOps.scala
+++ b/compiler/src/dotty/tools/dotc/core/NameOps.scala
@@ -4,7 +4,7 @@ package core
 import java.security.MessageDigest
 import scala.io.Codec
 import Names._, StdNames._, Contexts._, Symbols._, Flags._, NameKinds._, Types._
-import scala.tasty.util.Chars
+import scala.internal.Chars
 import Chars.isOperatorPart
 import Definitions._
 
diff --git a/compiler/src/dotty/tools/dotc/core/Names.scala b/compiler/src/dotty/tools/dotc/core/Names.scala
index cb987d7ebf16..481a5821dd69 100644
--- a/compiler/src/dotty/tools/dotc/core/Names.scala
+++ b/compiler/src/dotty/tools/dotc/core/Names.scala
@@ -7,7 +7,7 @@ import util.NameTransformer
 import printing.{Showable, Texts, Printer}
 import Texts.Text
 import StdNames.str
-import scala.tasty.util.Chars.isIdentifierStart
+import scala.internal.Chars.isIdentifierStart
 import collection.immutable
 import config.Config
 import java.util.HashMap
diff --git a/compiler/src/dotty/tools/dotc/parsing/CharArrayReader.scala b/compiler/src/dotty/tools/dotc/parsing/CharArrayReader.scala
index ca784d6de87f..14d7a53c0f0f 100644
--- a/compiler/src/dotty/tools/dotc/parsing/CharArrayReader.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/CharArrayReader.scala
@@ -2,7 +2,7 @@ package dotty.tools
 package dotc
 package parsing
 
-import scala.tasty.util.Chars._
+import scala.internal.Chars._
 
 abstract class CharArrayReader { self =>
 
diff --git a/compiler/src/dotty/tools/dotc/parsing/JavaScanners.scala b/compiler/src/dotty/tools/dotc/parsing/JavaScanners.scala
index 0452b9f6e672..81c8ff9b0d6f 100644
--- a/compiler/src/dotty/tools/dotc/parsing/JavaScanners.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/JavaScanners.scala
@@ -8,7 +8,7 @@ import Scanners._
 import util.SourceFile
 import JavaTokens._
 import scala.annotation.{ switch, tailrec }
-import scala.tasty.util.Chars._
+import scala.internal.Chars._
 
 object JavaScanners {
 
diff --git a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
index 10f7d70d3a65..43bc7d50058b 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Parsers.scala
@@ -22,7 +22,7 @@ import Constants._
 import Symbols.defn
 import ScriptParsers._
 import Decorators._
-import scala.tasty.util.Chars.isIdentifierStart
+import scala.internal.Chars.isIdentifierStart
 import scala.annotation.{tailrec, switch}
 import rewrites.Rewrites.patch
 
diff --git a/compiler/src/dotty/tools/dotc/parsing/Scanners.scala b/compiler/src/dotty/tools/dotc/parsing/Scanners.scala
index af0fb9c46190..66dcad5099fc 100644
--- a/compiler/src/dotty/tools/dotc/parsing/Scanners.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/Scanners.scala
@@ -6,7 +6,7 @@ import core.Names._, core.Contexts._, core.Decorators._, util.Spans._
 import core.StdNames._, core.Comments._
 import util.SourceFile
 import java.lang.Character.isDigit
-import scala.tasty.util.Chars._
+import scala.internal.Chars._
 import util.NameTransformer.avoidIllegalChars
 import util.Spans.Span
 import Tokens._
diff --git a/compiler/src/dotty/tools/dotc/parsing/package.scala b/compiler/src/dotty/tools/dotc/parsing/package.scala
index 4871d1b893c1..e039e1bf67fb 100644
--- a/compiler/src/dotty/tools/dotc/parsing/package.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/package.scala
@@ -1,6 +1,6 @@
 package dotty.tools.dotc
 
-import scala.tasty.util.Chars._
+import scala.internal.Chars._
 import core.Names.Name
 import core.StdNames.nme
 import core.NameOps._
diff --git a/compiler/src/dotty/tools/dotc/parsing/xml/MarkupParserCommon.scala b/compiler/src/dotty/tools/dotc/parsing/xml/MarkupParserCommon.scala
index a7a22d1cee34..d51bbfe6f7ca 100644
--- a/compiler/src/dotty/tools/dotc/parsing/xml/MarkupParserCommon.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/xml/MarkupParserCommon.scala
@@ -10,7 +10,7 @@ package parsing
 package xml
 
 import Utility._
-import scala.tasty.util.Chars.SU
+import scala.internal.Chars.SU
 
 
 
diff --git a/compiler/src/dotty/tools/dotc/parsing/xml/MarkupParsers.scala b/compiler/src/dotty/tools/dotc/parsing/xml/MarkupParsers.scala
index a56df8e14906..9279d0b72416 100644
--- a/compiler/src/dotty/tools/dotc/parsing/xml/MarkupParsers.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/xml/MarkupParsers.scala
@@ -6,7 +6,7 @@ package xml
 import scala.collection.mutable
 import mutable.{ Buffer, ArrayBuffer, ListBuffer }
 import scala.util.control.ControlThrowable
-import scala.tasty.util.Chars.SU
+import scala.internal.Chars.SU
 import Parsers._
 import util.Spans._
 import core._
diff --git a/compiler/src/dotty/tools/dotc/parsing/xml/Utility.scala b/compiler/src/dotty/tools/dotc/parsing/xml/Utility.scala
index ad2a5fe54758..5533badbd5c7 100644
--- a/compiler/src/dotty/tools/dotc/parsing/xml/Utility.scala
+++ b/compiler/src/dotty/tools/dotc/parsing/xml/Utility.scala
@@ -12,7 +12,7 @@ import scala.collection.mutable
  * @author Burak Emir
  */
 object Utility {
-  import scala.tasty.util.Chars.SU
+  import scala.internal.Chars.SU
 
   private val unescMap = Map(
     "lt"    -> '<',
diff --git a/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala b/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
index 4b842119e6a9..d7ec980d15ef 100644
--- a/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
+++ b/compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala
@@ -20,7 +20,7 @@ import typer.ProtoTypes._
 import Trees._
 import TypeApplications._
 import Decorators._
-import scala.tasty.util.Chars.isOperatorPart
+import scala.internal.Chars.isOperatorPart
 import transform.TypeUtils._
 
 import language.implicitConversions
diff --git a/compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala b/compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala
index 1b28cbc8996a..9cb9b6057ebc 100644
--- a/compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala
+++ b/compiler/src/dotty/tools/dotc/reporting/MessageRendering.scala
@@ -11,7 +11,7 @@ import printing.SyntaxHighlighting
 import diagnostic.{ErrorMessageID, Message, MessageContainer}
 import diagnostic.messages._
 import util.SourcePosition
-import scala.tasty.util.Chars.{ LF, CR, FF, SU }
+import scala.internal.Chars.{ LF, CR, FF, SU }
 import scala.annotation.switch
 
 import scala.collection.mutable
diff --git a/compiler/src/dotty/tools/dotc/transform/TreeChecker.scala b/compiler/src/dotty/tools/dotc/transform/TreeChecker.scala
index 09d592bcfbc5..2333221b50b2 100644
--- a/compiler/src/dotty/tools/dotc/transform/TreeChecker.scala
+++ b/compiler/src/dotty/tools/dotc/transform/TreeChecker.scala
@@ -18,7 +18,7 @@ import typer.ErrorReporting._
 import reporting.ThrowingReporter
 import ast.Trees._
 import ast.{tpd, untpd}
-import scala.tasty.util.Chars._
+import scala.internal.Chars._
 import collection.mutable
 import ProtoTypes._
 
diff --git a/compiler/src/dotty/tools/dotc/typer/Checking.scala b/compiler/src/dotty/tools/dotc/typer/Checking.scala
index d68e771292de..57279309e719 100644
--- a/compiler/src/dotty/tools/dotc/typer/Checking.scala
+++ b/compiler/src/dotty/tools/dotc/typer/Checking.scala
@@ -37,7 +37,7 @@ import transform.patmat.SpaceEngine.isIrrefutableUnapply
 import collection.mutable
 import reporting.diagnostic.Message
 import reporting.diagnostic.messages._
-import scala.tasty.util.Chars.isOperatorPart
+import scala.internal.Chars.isOperatorPart
 
 object Checking {
   import tpd._
diff --git a/compiler/src/dotty/tools/dotc/util/CommentParsing.scala b/compiler/src/dotty/tools/dotc/util/CommentParsing.scala
index 61c42ced3d92..1c02a473b0b6 100644
--- a/compiler/src/dotty/tools/dotc/util/CommentParsing.scala
+++ b/compiler/src/dotty/tools/dotc/util/CommentParsing.scala
@@ -15,7 +15,7 @@ import scala.collection.mutable
   * handled by dottydoc.
   */
 object CommentParsing {
-  import scala.tasty.util.Chars._
+  import scala.internal.Chars._
 
   /** Returns index of string `str` following `start` skipping longest
    *  sequence of whitespace characters characters (but no newlines)
diff --git a/compiler/src/dotty/tools/dotc/util/SourceFile.scala b/compiler/src/dotty/tools/dotc/util/SourceFile.scala
index c765999cc133..fe87ca9b9043 100644
--- a/compiler/src/dotty/tools/dotc/util/SourceFile.scala
+++ b/compiler/src/dotty/tools/dotc/util/SourceFile.scala
@@ -6,7 +6,7 @@ import scala.collection.mutable.ArrayBuffer
 import dotty.tools.io._
 import java.util.regex.Pattern
 import java.io.IOException
-import scala.tasty.util.Chars._
+import scala.internal.Chars._
 import Spans._
 import scala.io.Codec
 import core.Names.TermName
diff --git a/library/src/scala/tasty/util/Chars.scala b/library/src/scala/tasty/util/Chars.scala
index 795eddea4b1a..e61d1fc65980 100644
--- a/library/src/scala/tasty/util/Chars.scala
+++ b/library/src/scala/tasty/util/Chars.scala
@@ -12,14 +12,19 @@ import java.lang.Character.UPPERCASE_LETTER
 @deprecated("Use scala.internal.Chars", "0.17")
 object Chars {
 
+  @deprecated("Use scala.internal.Chars", "0.18")
   final val LF = '\u000A'
+  @deprecated("Use scala.internal.Chars", "0.18")
   final val FF = '\u000C'
+  @deprecated("Use scala.internal.Chars", "0.18")
   final val CR = '\u000D'
+  @deprecated("Use scala.internal.Chars", "0.18")
   final val SU = '\u001A'
 
   /** Convert a character digit to an Int according to given base,
    *  -1 if no success
    */
+  @deprecated("Use scala.internal.Chars", "0.18")
   def digit2int(ch: Char, base: Int): Int = {
     val num = (
       if (ch <= '9') ch - '0'
@@ -33,6 +38,7 @@ object Chars {
   private[this] val char2uescapeArray = Array[Char]('\\', 'u', 0, 0, 0, 0)
 
   /** Convert a character to a backslash-u escape */
+  @deprecated("Use scala.internal.Chars", "0.18")
   def char2uescape(c: Char): String = {
     @forceInline def hexChar(ch: Int): Char =
       (( if (ch < 10) '0' else 'A' - 10 ) + ch).toChar
@@ -46,36 +52,44 @@ object Chars {
   }
 
   /** Is character a line break? */
+  @deprecated("Use scala.internal.Chars", "0.18")
   def isLineBreakChar(c: Char): Boolean = (c: @switch) match {
     case LF|FF|CR|SU  => true
     case _            => false
   }
 
   /** Is character a whitespace character (but not a new line)? */
+  @deprecated("Use scala.internal.Chars", "0.18")
   def isWhitespace(c: Char): Boolean =
     c == ' ' || c == '\t' || c == CR
 
   /** Can character form part of a doc comment variable $xxx? */
+  @deprecated("Use scala.internal.Chars", "0.18")
   def isVarPart(c: Char): Boolean =
     '0' <= c && c <= '9' || 'A' <= c && c <= 'Z' || 'a' <= c && c <= 'z'
 
   /** Can character start an alphanumeric Scala identifier? */
+  @deprecated("Use scala.internal.Chars", "0.18")
   def isIdentifierStart(c: Char): Boolean =
     (c == '_') || (c == '$') || JCharacter.isUnicodeIdentifierStart(c)
 
   /** Can character form part of an alphanumeric Scala identifier? */
+  @deprecated("Use scala.internal.Chars", "0.18")
   def isIdentifierPart(c: Char): Boolean =
     (c == '$') || JCharacter.isUnicodeIdentifierPart(c)
 
   /** Is character a math or other symbol in Unicode?  */
+  @deprecated("Use scala.internal.Chars", "0.18")
   def isSpecial(c: Char): Boolean = {
     val chtp = JCharacter.getType(c)
     chtp == JCharacter.MATH_SYMBOL.toInt || chtp == JCharacter.OTHER_SYMBOL.toInt
   }
 
+  @deprecated("Use scala.internal.Chars", "0.18")
   def isValidJVMChar(c: Char): Boolean =
     !(c == '.' || c == ';' || c =='[' || c == '/')
 
+  @deprecated("Use scala.internal.Chars", "0.18")
   def isValidJVMMethodChar(c: Char): Boolean =
     !(c == '.' || c == ';' || c =='[' || c == '/' || c == '<' || c == '>')
 
@@ -84,9 +98,11 @@ object Chars {
     import JCharacter._
     Set[Byte](LOWERCASE_LETTER, UPPERCASE_LETTER, OTHER_LETTER, TITLECASE_LETTER, LETTER_NUMBER)
   }
+  @deprecated("Use scala.internal.Chars", "0.18")
   def isScalaLetter(ch: Char): Boolean = letterGroups(JCharacter.getType(ch).toByte) || otherLetters(ch)
 
   /** Can character form part of a Scala operator name? */
+  @deprecated("Use scala.internal.Chars", "0.18")
   def isOperatorPart(c : Char) : Boolean = (c: @switch) match {
     case '~' | '!' | '@' | '#' | '%' |
          '^' | '*' | '+' | '-' | '<' |