From 123d3a2d7d1e2fb81ad75d227423c5e442625a11 Mon Sep 17 00:00:00 2001
From: Liu Fengyun <liu@fengy.me>
Date: Wed, 19 Aug 2020 12:07:48 +0200
Subject: [PATCH 1/6] Reduce allocations when loading packages from classpath

This is a port of the following PR in scalac:

https://github.com/scala/scala/pull/8927
---
 .../tools/dotc/classpath/ClassPath.scala      | 21 ++++++-----
 .../src/dotty/tools/dotc/core/Contexts.scala  | 12 +++++++
 .../dotty/tools/dotc/core/Definitions.scala   |  2 +-
 .../dotty/tools/dotc/core/SymbolLoaders.scala | 36 +++++++++++--------
 compiler/src/dotty/tools/io/ClassPath.scala   | 13 +++++++
 5 files changed, 60 insertions(+), 24 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/classpath/ClassPath.scala b/compiler/src/dotty/tools/dotc/classpath/ClassPath.scala
index 1c95589d3fb7..9557a55e25d2 100644
--- a/compiler/src/dotty/tools/dotc/classpath/ClassPath.scala
+++ b/compiler/src/dotty/tools/dotc/classpath/ClassPath.scala
@@ -23,24 +23,27 @@ trait PackageEntry {
 }
 
 private[dotty] case class ClassFileEntryImpl(file: AbstractFile) extends ClassFileEntry {
-  override def name: String = FileUtils.stripClassExtension(file.name) // class name
+  final def fileName: String = file.name
+  def name: String = FileUtils.stripClassExtension(file.name) // class name
 
-  override def binary: Option[AbstractFile] = Some(file)
-  override def source: Option[AbstractFile] = None
+  def binary: Option[AbstractFile] = Some(file)
+  def source: Option[AbstractFile] = None
 }
 
 private[dotty] case class SourceFileEntryImpl(file: AbstractFile) extends SourceFileEntry {
-  override def name: String = FileUtils.stripSourceExtension(file.name)
+  final def fileName: String = file.name
+  def name: String = FileUtils.stripSourceExtension(file.name)
 
-  override def binary: Option[AbstractFile] = None
-  override def source: Option[AbstractFile] = Some(file)
+  def binary: Option[AbstractFile] = None
+  def source: Option[AbstractFile] = Some(file)
 }
 
 private[dotty] case class ClassAndSourceFilesEntry(classFile: AbstractFile, srcFile: AbstractFile) extends ClassRepresentation {
-  override def name: String = FileUtils.stripClassExtension(classFile.name)
+  final def fileName: String = classFile.name
+  def name: String = FileUtils.stripClassExtension(classFile.name)
 
-  override def binary: Option[AbstractFile] = Some(classFile)
-  override def source: Option[AbstractFile] = Some(srcFile)
+  def binary: Option[AbstractFile] = Some(classFile)
+  def source: Option[AbstractFile] = Some(srcFile)
 }
 
 private[dotty] case class PackageEntryImpl(name: String) extends PackageEntry
diff --git a/compiler/src/dotty/tools/dotc/core/Contexts.scala b/compiler/src/dotty/tools/dotc/core/Contexts.scala
index fdba7003a9d1..5db5335912d9 100644
--- a/compiler/src/dotty/tools/dotc/core/Contexts.scala
+++ b/compiler/src/dotty/tools/dotc/core/Contexts.scala
@@ -89,6 +89,16 @@ object Contexts {
   inline def withoutMode[T](mode: Mode)(inline op: Context ?=> T)(using ctx: Context): T =
     inMode(ctx.mode &~ mode)(op)
 
+  private[dotc] inline def withNameBuffer(inline op: Array[Char] => Int)(using ctx: Context): Names.TermName = {
+    val base = ctx.base
+    var len = op(base.nameCharBuffer)
+    while(len == -1) {
+      base.nameCharBuffer = new Array[Char](base.nameCharBuffer.length * 2)
+      len = op(base.nameCharBuffer)
+    }
+    Names.termName(base.nameCharBuffer, 0, len)
+  }
+
   /** A context is passed basically everywhere in dotc.
    *  This is convenient but carries the risk of captured contexts in
    *  objects that turn into space leaks. To combat this risk, here are some
@@ -894,6 +904,8 @@ object Contexts {
     private[Contexts] val comparers = new mutable.ArrayBuffer[TypeComparer]
     private[Contexts] var comparersInUse: Int = 0
 
+    private[dotc] var nameCharBuffer = new Array[Char](256)
+
     def reset(): Unit = {
       for ((_, set) <- uniqueSets) set.clear()
       errorTypeMsg.clear()
diff --git a/compiler/src/dotty/tools/dotc/core/Definitions.scala b/compiler/src/dotty/tools/dotc/core/Definitions.scala
index 418d7f3027c9..dde6baa47325 100644
--- a/compiler/src/dotty/tools/dotc/core/Definitions.scala
+++ b/compiler/src/dotty/tools/dotc/core/Definitions.scala
@@ -682,10 +682,10 @@ class Definitions {
   @tu lazy val NonLocalReturnControlClass: ClassSymbol = requiredClass("scala.runtime.NonLocalReturnControl")
   @tu lazy val SelectableClass: ClassSymbol = requiredClass("scala.Selectable")
 
+  @tu lazy val ReflectPackageClass: Symbol = requiredPackage("scala.reflect.package").moduleClass
   @tu lazy val ClassTagClass: ClassSymbol = requiredClass("scala.reflect.ClassTag")
   @tu lazy val ClassTagModule: Symbol = ClassTagClass.companionModule
     @tu lazy val ClassTagModule_apply: Symbol = ClassTagModule.requiredMethod(nme.apply)
-  @tu lazy val ReflectPackageClass: Symbol = requiredPackage("scala.reflect.package").moduleClass
 
 
   @tu lazy val QuotedExprClass: ClassSymbol = requiredClass("scala.quoted.Expr")
diff --git a/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala b/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
index 0d23f0df1d51..a122e1959e6b 100644
--- a/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
@@ -4,24 +4,29 @@ package core
 
 import java.io.{IOException, File}
 import java.nio.channels.ClosedByInterruptException
+
 import scala.compat.Platform.currentTime
+import scala.util.control.NonFatal
+
 import dotty.tools.io.{ ClassPath, ClassRepresentation, AbstractFile }
-import config.Config
+import dotty.tools.backend.jvm.DottyBackendInterface.symExtensions
+
 import Contexts._, Symbols._, Flags._, SymDenotations._, Types._, Scopes._, Names._
 import NameOps._
-import StdNames.str
-import Decorators._
+import StdNames._
 import classfile.ClassfileParser
-import util.Stats
 import Decorators._
-import scala.util.control.NonFatal
+
+import util.Stats
+import reporting.trace
+import config.Config
+
 import ast.Trees._
+import ast.desugar
+
 import parsing.JavaParsers.OutlineJavaParser
 import parsing.Parsers.OutlineParser
-import reporting.trace
-import ast.desugar
 
-import dotty.tools.backend.jvm.DottyBackendInterface.symExtensions
 
 object SymbolLoaders {
   import ast.untpd._
@@ -178,27 +183,30 @@ object SymbolLoaders {
    *  Note: We do a name-base comparison here because the method is called before we even
    *  have ReflectPackage defined.
    */
-  def binaryOnly(owner: Symbol, name: String)(using Context): Boolean =
-    name == "package" &&
+  def binaryOnly(owner: Symbol, name: TermName)(using Context): Boolean =
+    name == nme.PACKAGEkw &&
       (owner.fullName.toString == "scala" || owner.fullName.toString == "scala.reflect")
 
   /** Initialize toplevel class and module symbols in `owner` from class path representation `classRep`
    */
   def initializeFromClassPath(owner: Symbol, classRep: ClassRepresentation)(using Context): Unit =
     ((classRep.binary, classRep.source): @unchecked) match {
-      case (Some(bin), Some(src)) if needCompile(bin, src) && !binaryOnly(owner, classRep.name) =>
+      case (Some(bin), Some(src)) if needCompile(bin, src) && !binaryOnly(owner, nameOf(classRep)) =>
         if (ctx.settings.verbose.value) report.inform("[symloader] picked up newer source file for " + src.path)
-        enterToplevelsFromSource(owner, classRep.name, src)
+        enterToplevelsFromSource(owner, nameOf(classRep), src)
       case (None, Some(src)) =>
         if (ctx.settings.verbose.value) report.inform("[symloader] no class, picked up source file for " + src.path)
-        enterToplevelsFromSource(owner, classRep.name, src)
+        enterToplevelsFromSource(owner, nameOf(classRep), src)
       case (Some(bin), _) =>
-        enterClassAndModule(owner, classRep.name, ctx.platform.newClassLoader(bin))
+        enterClassAndModule(owner, nameOf(classRep), ctx.platform.newClassLoader(bin))
     }
 
   def needCompile(bin: AbstractFile, src: AbstractFile): Boolean =
     src.lastModified >= bin.lastModified
 
+  private def nameOf(classRep: ClassRepresentation)(using Context): TermName =
+    withNameBuffer(classRep.nameChars)
+
   /** Load contents of a package
    */
   class PackageLoader(_sourceModule: TermSymbol, classPath: ClassPath)
diff --git a/compiler/src/dotty/tools/io/ClassPath.scala b/compiler/src/dotty/tools/io/ClassPath.scala
index f8fa6c2c35be..b3d75001838f 100644
--- a/compiler/src/dotty/tools/io/ClassPath.scala
+++ b/compiler/src/dotty/tools/io/ClassPath.scala
@@ -170,9 +170,22 @@ object ClassPath {
 }
 
 trait ClassRepresentation {
+  def fileName: String
   def name: String
   def binary: Option[AbstractFile]
   def source: Option[AbstractFile]
+
+  /** Low level way to extract the entry name without allocation. */
+  final def nameChars(buffer: Array[Char]): Int = {
+    val ix = fileName.lastIndexOf('.')
+    val nameLength = if (ix < 0) fileName.length else ix
+    if (nameLength > buffer.length)
+      -1
+    else {
+      fileName.getChars(0, nameLength, buffer, 0)
+      nameLength
+    }
+  }
 }
 
 @deprecated("shim for sbt's compiler interface", since = "2.12.0")

From cfd2937dd3fc21a18a667e89e756e371ac0637a7 Mon Sep 17 00:00:00 2001
From: Liu Fengyun <liu@fengy.me>
Date: Wed, 19 Aug 2020 16:14:46 +0200
Subject: [PATCH 2/6] Avoid string equality

---
 compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala b/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
index a122e1959e6b..9f1b6a8ca44f 100644
--- a/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
@@ -185,7 +185,7 @@ object SymbolLoaders {
    */
   def binaryOnly(owner: Symbol, name: TermName)(using Context): Boolean =
     name == nme.PACKAGEkw &&
-      (owner.fullName.toString == "scala" || owner.fullName.toString == "scala.reflect")
+      (owner.name == nme.scala || owner.name == nme.reflect && owner.owner.name == nme.scala)
 
   /** Initialize toplevel class and module symbols in `owner` from class path representation `classRep`
    */

From 1fd0844d5e976bb4a5080906c9b3562aa15c2f2c Mon Sep 17 00:00:00 2001
From: Liu Fengyun <liu@fengy.me>
Date: Wed, 19 Aug 2020 19:11:29 +0200
Subject: [PATCH 3/6] Generalize buffering for Name construction from substring

---
 compiler/src/dotty/tools/dotc/core/Contexts.scala | 10 ----------
 compiler/src/dotty/tools/dotc/core/Names.scala    | 13 +++++++++++++
 .../src/dotty/tools/dotc/core/SymbolLoaders.scala |  2 +-
 compiler/src/dotty/tools/io/ClassPath.scala       | 15 ++++++---------
 4 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/core/Contexts.scala b/compiler/src/dotty/tools/dotc/core/Contexts.scala
index 5db5335912d9..c805be876868 100644
--- a/compiler/src/dotty/tools/dotc/core/Contexts.scala
+++ b/compiler/src/dotty/tools/dotc/core/Contexts.scala
@@ -89,16 +89,6 @@ object Contexts {
   inline def withoutMode[T](mode: Mode)(inline op: Context ?=> T)(using ctx: Context): T =
     inMode(ctx.mode &~ mode)(op)
 
-  private[dotc] inline def withNameBuffer(inline op: Array[Char] => Int)(using ctx: Context): Names.TermName = {
-    val base = ctx.base
-    var len = op(base.nameCharBuffer)
-    while(len == -1) {
-      base.nameCharBuffer = new Array[Char](base.nameCharBuffer.length * 2)
-      len = op(base.nameCharBuffer)
-    }
-    Names.termName(base.nameCharBuffer, 0, len)
-  }
-
   /** A context is passed basically everywhere in dotc.
    *  This is convenient but carries the risk of captured contexts in
    *  objects that turn into space leaks. To combat this risk, here are some
diff --git a/compiler/src/dotty/tools/dotc/core/Names.scala b/compiler/src/dotty/tools/dotc/core/Names.scala
index cd58977f9dda..674c3c721f01 100644
--- a/compiler/src/dotty/tools/dotc/core/Names.scala
+++ b/compiler/src/dotty/tools/dotc/core/Names.scala
@@ -644,6 +644,19 @@ object Names {
   /** Create a type name from a string, without encoding operators */
   def typeName(s: String): TypeName = typeName(s.toCharArray, 0, s.length)
 
+  def termName(s: String, from: Int, len: Int)(using ctx: Contexts.Context): TermName = {
+    val base = ctx.base
+
+    while (len > base.nameCharBuffer.length)
+      base.nameCharBuffer = new Array[Char](base.nameCharBuffer.length * 2)
+
+    s.getChars(from, from + len, base.nameCharBuffer, 0)
+    termName(base.nameCharBuffer, 0, len)
+  }
+
+  def typeName(s: String, from: Int, len: Int)(using ctx: Contexts.Context): TypeName =
+    termName(s, from, len).toTypeName
+
   table(0) = new SimpleName(-1, 0, null)
 
   /** The term name represented by the empty string */
diff --git a/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala b/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
index 9f1b6a8ca44f..b53ab7c885bf 100644
--- a/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
@@ -205,7 +205,7 @@ object SymbolLoaders {
     src.lastModified >= bin.lastModified
 
   private def nameOf(classRep: ClassRepresentation)(using Context): TermName =
-    withNameBuffer(classRep.nameChars)
+    termName(classRep.fileName, 0, classRep.nameLength)
 
   /** Load contents of a package
    */
diff --git a/compiler/src/dotty/tools/io/ClassPath.scala b/compiler/src/dotty/tools/io/ClassPath.scala
index b3d75001838f..97d678901a6d 100644
--- a/compiler/src/dotty/tools/io/ClassPath.scala
+++ b/compiler/src/dotty/tools/io/ClassPath.scala
@@ -175,16 +175,13 @@ trait ClassRepresentation {
   def binary: Option[AbstractFile]
   def source: Option[AbstractFile]
 
-  /** Low level way to extract the entry name without allocation. */
-  final def nameChars(buffer: Array[Char]): Int = {
+  /** returns the length of `name` by stripping the extension of `fileName`
+   *
+   *  Used to avoid creating String instance of `name`.
+   */
+  final def nameLength: Int = {
     val ix = fileName.lastIndexOf('.')
-    val nameLength = if (ix < 0) fileName.length else ix
-    if (nameLength > buffer.length)
-      -1
-    else {
-      fileName.getChars(0, nameLength, buffer, 0)
-      nameLength
-    }
+    if (ix < 0) fileName.length else ix
   }
 }
 

From 6ccfdc18c4684383e5b4a00e7a564014d6a91659 Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Thu, 20 Aug 2020 11:19:35 +0200
Subject: [PATCH 4/6] Add some explaining comments

---
 compiler/src/dotty/tools/dotc/core/Names.scala | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/core/Names.scala b/compiler/src/dotty/tools/dotc/core/Names.scala
index 674c3c721f01..f84eca7b88bb 100644
--- a/compiler/src/dotty/tools/dotc/core/Names.scala
+++ b/compiler/src/dotty/tools/dotc/core/Names.scala
@@ -11,6 +11,7 @@ import scala.internal.Chars.isIdentifierStart
 import collection.immutable
 import config.Config
 import java.util.HashMap
+import Contexts.{Context, ctx}
 
 import scala.annotation.internal.sharable
 
@@ -638,12 +639,18 @@ object Names {
   def typeName(bs: Array[Byte], offset: Int, len: Int): TypeName =
     termName(bs, offset, len).toTypeName
 
-  /** Create a term name from a string, without encoding operators */
+  /** Create a term name from a string.
+   *  See `termName(s: String, from: Int, len: Int) for a more efficient version
+   *  which however requires a Context for its operation
+   */
   def termName(s: String): SimpleName = termName(s.toCharArray, 0, s.length)
 
-  /** Create a type name from a string, without encoding operators */
+  /** Create a type name from a string */
   def typeName(s: String): TypeName = typeName(s.toCharArray, 0, s.length)
 
+  /** Create a term name from a string slice, using a common buffer.
+   *  This avoids some allocation relative to `termName(s: String)`
+   */
   def termName(s: String, from: Int, len: Int)(using ctx: Contexts.Context): TermName = {
     val base = ctx.base
 
@@ -654,7 +661,10 @@ object Names {
     termName(base.nameCharBuffer, 0, len)
   }
 
-  def typeName(s: String, from: Int, len: Int)(using ctx: Contexts.Context): TypeName =
+  /** Create a type name from a string slice, using a common buffer.
+   *  This avoids some allocation relative to `typeName(s: String)`
+   */
+  def typeName(s: String, from: Int, len: Int)(using Context): TypeName =
     termName(s, from, len).toTypeName
 
   table(0) = new SimpleName(-1, 0, null)

From fb736068d52ed00b4196f8da67a759b557e390da Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Thu, 20 Aug 2020 11:50:23 +0200
Subject: [PATCH 5/6] Move sliceToTermName logic to Decorators

That way we can keep Contexts out of Names.
---
 .../src/dotty/tools/dotc/config/Feature.scala |  2 +-
 .../tools/dotc/config/SourceVersion.scala     |  2 +-
 .../dotty/tools/dotc/core/Decorators.scala    | 28 +++++++++++++------
 .../src/dotty/tools/dotc/core/Names.scala     | 24 ++--------------
 .../dotty/tools/dotc/core/SymbolLoaders.scala |  2 +-
 5 files changed, 25 insertions(+), 33 deletions(-)

diff --git a/compiler/src/dotty/tools/dotc/config/Feature.scala b/compiler/src/dotty/tools/dotc/config/Feature.scala
index ed804ff4a7af..63ac69b94eba 100644
--- a/compiler/src/dotty/tools/dotc/config/Feature.scala
+++ b/compiler/src/dotty/tools/dotc/config/Feature.scala
@@ -5,7 +5,7 @@ package config
 import core._
 import Contexts._, Symbols._, Names._, NameOps._, Phases._
 import StdNames.nme
-import Decorators.{given _}
+import Decorators.{_, given _}
 import util.SrcPos
 import SourceVersion._
 import reporting.Message
diff --git a/compiler/src/dotty/tools/dotc/config/SourceVersion.scala b/compiler/src/dotty/tools/dotc/config/SourceVersion.scala
index cc9221bad6cf..e7b39ac769ac 100644
--- a/compiler/src/dotty/tools/dotc/config/SourceVersion.scala
+++ b/compiler/src/dotty/tools/dotc/config/SourceVersion.scala
@@ -5,7 +5,7 @@ package config
 import core.Contexts._
 import core.Names.TermName
 import core.StdNames.nme
-import core.Decorators.{given _}
+import core.Decorators.{_, given _}
 import util.Property
 
 enum SourceVersion:
diff --git a/compiler/src/dotty/tools/dotc/core/Decorators.scala b/compiler/src/dotty/tools/dotc/core/Decorators.scala
index afb356db2d52..f695923d517b 100644
--- a/compiler/src/dotty/tools/dotc/core/Decorators.scala
+++ b/compiler/src/dotty/tools/dotc/core/Decorators.scala
@@ -20,22 +20,34 @@ object Decorators {
    *  with a normal wildcard. In the future, once #9255 is in trunk, replace with
    *  a simple collective extension.
    */
-  implicit object PreNamedString:
-    extension (pn: PreName) def toTypeName: TypeName = pn match
-      case s: String => typeName(s)
-      case n: Name => n.toTypeName
-    extension (pn: PreName) def toTermName: TermName = pn match
+  extension (pn: PreName)
+    def toTermName: TermName = pn match
       case s: String => termName(s)
       case n: Name => n.toTermName
+    def toTypeName: TypeName = pn match
+      case s: String => typeName(s)
+      case n: Name => n.toTypeName
 
   extension (s: String):
-    def splitWhere(f: Char => Boolean, doDropIndex: Boolean): Option[(String, String)] = {
+    def splitWhere(f: Char => Boolean, doDropIndex: Boolean): Option[(String, String)] =
       def splitAt(idx: Int, doDropIndex: Boolean): Option[(String, String)] =
         if (idx == -1) None
         else Some((s.take(idx), s.drop(if (doDropIndex) idx + 1 else idx)))
-
       splitAt(s.indexWhere(f), doDropIndex)
-    }
+
+    /** Create a term name from a string slice, using a common buffer.
+     *  This avoids some allocation relative to `termName(s)`
+     */
+    def sliceToTermName(start: Int, end: Int)(using Context): SimpleName =
+      val base = ctx.base
+      val len = end - start
+      while len > base.nameCharBuffer.length do
+        base.nameCharBuffer = new Array[Char](base.nameCharBuffer.length * 2)
+      s.getChars(start, end, base.nameCharBuffer, 0)
+      termName(base.nameCharBuffer, 0, len)
+
+    def sliceToTypeName(start: Int, end: Int)(using Context): TypeName =
+      sliceToTermName(start, end).toTypeName
 
   /** Implements a findSymbol method on iterators of Symbols that
    *  works like find but avoids Option, replacing None with NoSymbol.
diff --git a/compiler/src/dotty/tools/dotc/core/Names.scala b/compiler/src/dotty/tools/dotc/core/Names.scala
index f84eca7b88bb..89adab098abb 100644
--- a/compiler/src/dotty/tools/dotc/core/Names.scala
+++ b/compiler/src/dotty/tools/dotc/core/Names.scala
@@ -11,7 +11,6 @@ import scala.internal.Chars.isIdentifierStart
 import collection.immutable
 import config.Config
 import java.util.HashMap
-import Contexts.{Context, ctx}
 
 import scala.annotation.internal.sharable
 
@@ -640,33 +639,14 @@ object Names {
     termName(bs, offset, len).toTypeName
 
   /** Create a term name from a string.
-   *  See `termName(s: String, from: Int, len: Int) for a more efficient version
-   *  which however requires a Context for its operation
+   *  See `sliceToTermName` in `Decorators` for a more efficient version
+   *  which however requires a Context for its operation.
    */
   def termName(s: String): SimpleName = termName(s.toCharArray, 0, s.length)
 
   /** Create a type name from a string */
   def typeName(s: String): TypeName = typeName(s.toCharArray, 0, s.length)
 
-  /** Create a term name from a string slice, using a common buffer.
-   *  This avoids some allocation relative to `termName(s: String)`
-   */
-  def termName(s: String, from: Int, len: Int)(using ctx: Contexts.Context): TermName = {
-    val base = ctx.base
-
-    while (len > base.nameCharBuffer.length)
-      base.nameCharBuffer = new Array[Char](base.nameCharBuffer.length * 2)
-
-    s.getChars(from, from + len, base.nameCharBuffer, 0)
-    termName(base.nameCharBuffer, 0, len)
-  }
-
-  /** Create a type name from a string slice, using a common buffer.
-   *  This avoids some allocation relative to `typeName(s: String)`
-   */
-  def typeName(s: String, from: Int, len: Int)(using Context): TypeName =
-    termName(s, from, len).toTypeName
-
   table(0) = new SimpleName(-1, 0, null)
 
   /** The term name represented by the empty string */
diff --git a/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala b/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
index b53ab7c885bf..52431854f64b 100644
--- a/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
+++ b/compiler/src/dotty/tools/dotc/core/SymbolLoaders.scala
@@ -205,7 +205,7 @@ object SymbolLoaders {
     src.lastModified >= bin.lastModified
 
   private def nameOf(classRep: ClassRepresentation)(using Context): TermName =
-    termName(classRep.fileName, 0, classRep.nameLength)
+    classRep.fileName.sliceToTermName(0, classRep.nameLength)
 
   /** Load contents of a package
    */

From aebb209604cda8cfd6c9a4cd00b92a3e7372a92d Mon Sep 17 00:00:00 2001
From: Martin Odersky <odersky@gmail.com>
Date: Thu, 20 Aug 2020 12:32:59 +0200
Subject: [PATCH 6/6] Fix test

---
 .../test/dotty/tools/dotc/core/tasty/CommentPicklingTest.scala  | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/test/dotty/tools/dotc/core/tasty/CommentPicklingTest.scala b/compiler/test/dotty/tools/dotc/core/tasty/CommentPicklingTest.scala
index 62d95843e0f3..28779fe9b697 100644
--- a/compiler/test/dotty/tools/dotc/core/tasty/CommentPicklingTest.scala
+++ b/compiler/test/dotty/tools/dotc/core/tasty/CommentPicklingTest.scala
@@ -5,7 +5,7 @@ import dotty.tools.dotc.ast.tpd.TreeOps
 import dotty.tools.dotc.{Driver, Main}
 import dotty.tools.dotc.core.Comments.CommentsContext
 import dotty.tools.dotc.core.Contexts.Context
-import dotty.tools.dotc.core.Decorators.PreNamedString
+import dotty.tools.dotc.core.Decorators.{toTermName, toTypeName}
 import dotty.tools.dotc.core.Mode
 import dotty.tools.dotc.core.Names.Name
 import dotty.tools.dotc.interfaces.Diagnostic.ERROR