Refactor SymUtils

 - Move to core package. It was for historical reasons in transform because
   it was originally intended as a collection of type operations that were
   were useful in transform phases. But it's now used from everywhere.
 - Make a base class of Types, so that it does not need to be imported explicitly.

Also: move isDerivedValueClass to SymUtils

Author: odersky

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

@@ -19,7 +19,6 @@ import dotty.tools.dotc.core.Types.*
 import dotty.tools.dotc.core.StdNames.{nme, str}
 import dotty.tools.dotc.core.Symbols.*
 import dotty.tools.dotc.transform.Erasure
-import dotty.tools.dotc.transform.SymUtils.*
 import dotty.tools.dotc.util.Spans.*
 import dotty.tools.dotc.core.Contexts.*
 import dotty.tools.dotc.core.Phases.*

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

@@ -20,7 +20,7 @@ import dotty.tools.dotc.core.Types.*
 import dotty.tools.dotc.core.Contexts.*
 import dotty.tools.dotc.util.Spans.*
 import dotty.tools.dotc.report
-import dotty.tools.dotc.transform.SymUtils.*
+
 
 /*
  *

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

@@ -12,7 +12,7 @@ import dotty.tools.dotc.core.Contexts.*
 import dotty.tools.dotc.core.Phases.*
 import dotty.tools.dotc.core.Symbols.*
 import dotty.tools.dotc.core.Phases.Phase
-import dotty.tools.dotc.transform.SymUtils.*
+
 import dotty.tools.dotc.core.StdNames
 import dotty.tools.dotc.core.Phases
 

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

@@ -9,7 +9,7 @@ import dotty.tools.dotc.core.Phases.Phase
 
 import scala.collection.mutable
 import scala.jdk.CollectionConverters.*
-import dotty.tools.dotc.transform.SymUtils.*
+
 import dotty.tools.dotc.interfaces
 import dotty.tools.dotc.report
 

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

@@ -4,7 +4,7 @@ import scala.language.unsafeNulls
 
 import dotty.tools.dotc.ast.tpd
 import dotty.tools.dotc.core.Flags.*
-import dotty.tools.dotc.transform.SymUtils.*
+
 import java.io.{File => _}
 
 import scala.reflect.ClassTag

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

@@ -21,7 +21,7 @@ import StdNames.*
 import TypeErasure.ErasedValueType
 
 import dotty.tools.dotc.transform.{Erasure, ValueClasses}
-import dotty.tools.dotc.transform.SymUtils.*
+
 import dotty.tools.dotc.util.SourcePosition
 import dotty.tools.dotc.report
 

compiler/src/dotty/tools/dotc/CompilationUnit.scala

@@ -12,7 +12,6 @@ import ast.{tpd, untpd}
 import tpd.{Tree, TreeTraverser}
 import ast.Trees.{Import, Ident}
 import typer.Nullables
-import transform.SymUtils.*
 import core.Decorators.*
 import config.{SourceVersion, Feature}
 import StdNames.nme

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

@@ -5,7 +5,7 @@ package ast
 import core.*
 import util.Spans.*, Types.*, Contexts.*, Constants.*, Names.*, NameOps.*, Flags.*
 import Symbols.*, StdNames.*, Trees.*, ContextOps.*
-import Decorators.*, transform.SymUtils.*
+import Decorators.*
 import Annotations.Annotation
 import NameKinds.{UniqueName, ContextBoundParamName, ContextFunctionParamName, DefaultGetterName, WildcardParamName}
 import typer.{Namer, Checking}

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

@@ -7,7 +7,7 @@ import Flags.*, Trees.*, Types.*, Contexts.*
 import Names.*, StdNames.*, NameOps.*, Symbols.*
 import typer.ConstFold
 import reporting.trace
-import dotty.tools.dotc.transform.SymUtils.*
+
 import Decorators.*
 import Constants.Constant
 import scala.collection.mutable

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

@@ -6,7 +6,7 @@ import core.*
 import Types.*, Contexts.*, Flags.*
 import Symbols.*, Annotations.*, Trees.*, Symbols.*, Constants.Constant
 import Decorators.*
-import dotty.tools.dotc.transform.SymUtils.*
+
 
 /** A map that applies three functions and a substitution together to a tree and
  *  makes sure they are coordinated so that the result is well-typed. The functions are