Refactor TypeUtils

 = 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.

Author: odersky

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

@@ -5,7 +5,6 @@ package ast
 import dotty.tools.dotc.transform.{ExplicitOuter, Erasure}
 import typer.ProtoTypes
 import transform.SymUtils.*
-import transform.TypeUtils.*
 import core.*
 import Scopes.newScope
 import util.Spans.*, Types.*, Contexts.*, Constants.*, Names.*, Flags.*, NameOps.*

compiler/src/dotty/tools/dotc/core/ConstraintHandling.scala

@@ -10,7 +10,6 @@ import Flags.*
 import config.Config
 import config.Printers.typr
 import typer.ProtoTypes.{newTypeVar, representedParamRef}
-import transform.TypeUtils.isTransparent
 import UnificationDirection.*
 import NameKinds.AvoidNameKind
 import util.SimpleIdentitySet

compiler/src/dotty/tools/dotc/core/SymDenotations.scala

@@ -23,7 +23,6 @@ import scala.util.control.NonFatal
 import config.Config
 import reporting.*
 import collection.mutable
-import transform.TypeUtils.*
 import cc.{CapturingType, derivedCapturingType}
 
 import scala.annotation.internal.sharable

compiler/src/dotty/tools/dotc/core/TypeApplications.scala

@@ -12,7 +12,6 @@ import Names.*
 import StdNames.nme
 import Flags.{Module, Provisional}
 import dotty.tools.dotc.config.Config
-import dotty.tools.dotc.transform.TypeUtils.isErasedValueType
 
 object TypeApplications {
 

compiler/src/dotty/tools/dotc/core/TypeComparer.scala

@@ -16,7 +16,6 @@ import TypeErasure.{erasedLub, erasedGlb}
 import TypeApplications.*
 import Variances.{Variance, variancesConform}
 import Constants.Constant
-import transform.TypeUtils.*
 import transform.SymUtils.*
 import scala.util.control.NonFatal
 import typer.ProtoTypes.constrained

compiler/src/dotty/tools/dotc/core/TypeErasure.scala

@@ -9,7 +9,6 @@ import TypeOps.makePackageObjPrefixExplicit
 import backend.sjs.JSDefinitions
 import transform.ExplicitOuter.*
 import transform.ValueClasses.*
-import transform.TypeUtils.*
 import transform.ContextFunctionResults.*
 import unpickleScala2.Scala2Erasure
 import Decorators.*
@@ -404,7 +403,6 @@ object TypeErasure {
       tp1 // After erasure, T | Nothing is just T and C | Null is just C, if C is a reference type.
     else tp1 match {
       case JavaArrayType(elem1) =>
-        import dotty.tools.dotc.transform.TypeUtils.*
         tp2 match {
           case JavaArrayType(elem2) =>
             if (elem1.isPrimitiveValueType || elem2.isPrimitiveValueType)

compiler/src/dotty/tools/dotc/transform/TypeUtils.scala renamed to compiler/src/dotty/tools/dotc/core/TypeUtils.scala

@@ -1,13 +1,12 @@
 package dotty.tools
 package dotc
-package transform
+package core
 
-import core.*
 import TypeErasure.ErasedValueType
 import Types.*, Contexts.*, Symbols.*, Flags.*, Decorators.*
 import Names.Name
 
-object TypeUtils {
+class TypeUtils {
   /** A decorator that provides methods on types
    *  that are needed in the transformer pipeline.
    */

compiler/src/dotty/tools/dotc/core/Types.scala

@@ -43,9 +43,8 @@ import scala.annotation.internal.sharable
 import scala.annotation.threadUnsafe
 
 import dotty.tools.dotc.transform.SymUtils.*
-import dotty.tools.dotc.transform.TypeUtils.isErasedClass
 
-object Types {
+object Types extends TypeUtils {
 
   @sharable private var nextId = 0
 

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

@@ -23,7 +23,6 @@ import Trees.*
 import TypeApplications.*
 import NameKinds.{WildcardParamName, DefaultGetterName}
 import util.Chars.isOperatorPart
-import transform.TypeUtils.*
 import transform.SymUtils.*
 import config.{Config, Feature}
 

compiler/src/dotty/tools/dotc/transform/AccessProxies.scala

@@ -9,7 +9,6 @@ import Flags.*
 import Names.*
 import NameOps.*
 import Decorators.*
-import TypeUtils.*
 import Types.*
 import util.Spans.Span
 import config.Printers.transforms

compiler/src/dotty/tools/dotc/transform/Erasure.scala

@@ -29,7 +29,6 @@ import dotty.tools.dotc.ast.{tpd, untpd}
 import ast.TreeTypeMap
 import dotty.tools.dotc.core.{Constants, Flags}
 import ValueClasses.*
-import TypeUtils.*
 import ContextFunctionResults.*
 import ExplicitOuter.*
 import core.Mode

compiler/src/dotty/tools/dotc/transform/ExtensionMethods.scala

@@ -15,7 +15,6 @@ import SymDenotations.*, Symbols.*, StdNames.*, Denotations.*
 import TypeErasure.{ valueErasure, ErasedValueType }
 import NameKinds.{ExtMethName, BodyRetainerName}
 import Decorators.*
-import TypeUtils.*
 
 /**
  * Perform Step 1 in the inline classes SIP: Creates extension methods for all

compiler/src/dotty/tools/dotc/transform/FirstTransform.scala

@@ -16,7 +16,6 @@ import DenotTransformers.*
 import NameOps.*
 import NameKinds.OuterSelectName
 import StdNames.*
-import TypeUtils.isErasedValueType
 import config.Feature
 import inlines.Inlines.inInlineMethod
 

compiler/src/dotty/tools/dotc/transform/FullParameterization.scala

@@ -6,7 +6,6 @@ import Types.*
 import Contexts.*
 import Symbols.*
 import Decorators.*
-import TypeUtils.*
 import StdNames.nme
 import ast.*
 

compiler/src/dotty/tools/dotc/transform/GenericSignatures.scala

@@ -15,7 +15,6 @@ import core.TypeErasure.{erasedGlb, erasure, fullErasure, isGenericArrayElement,
 import core.Types.*
 import core.classfile.ClassfileConstants
 import SymUtils.*
-import TypeUtils.*
 import config.Printers.transforms
 import reporting.trace
 import java.lang.StringBuilder

compiler/src/dotty/tools/dotc/transform/ParamForwarding.scala

@@ -3,7 +3,7 @@ package dotc
 package transform
 
 import core.*
-import Contexts.*, Types.*, Symbols.*, Flags.*, TypeUtils.*, DenotTransformers.*, StdNames.*
+import Contexts.*, Types.*, Symbols.*, Flags.*, DenotTransformers.*, StdNames.*
 import Decorators.*
 import MegaPhase.*
 import NameKinds.ParamAccessorName

compiler/src/dotty/tools/dotc/transform/PatternMatcher.scala

@@ -9,7 +9,6 @@ import patmat.SpaceEngine
 import util.Spans.*
 import typer.Applications.*
 import SymUtils.*
-import TypeUtils.*
 import Annotations.*
 import Flags.*, Constants.*
 import Decorators.*

compiler/src/dotty/tools/dotc/transform/SuperAccessors.scala

@@ -7,7 +7,7 @@ import scala.collection.mutable
 import ValueClasses.isMethodWithExtension
 import core.*
 import Contexts.*, Flags.*, Symbols.*, Names.*, StdNames.*, NameOps.*, Trees.*
-import TypeUtils.*, SymUtils.*
+import SymUtils.*
 import DenotTransformers.DenotTransformer
 import Symbols.*
 import util.Spans.*

compiler/src/dotty/tools/dotc/transform/TupleOptimizations.scala

@@ -10,7 +10,6 @@ import StdNames.*
 import Symbols.*
 import MegaPhase.*
 import Types.*
-import transform.TypeUtils.*
 import dotty.tools.dotc.ast.tpd
 
 /** Optimize generic operations on tuples */

compiler/src/dotty/tools/dotc/transform/patmat/Space.scala

@@ -5,7 +5,6 @@ package patmat
 
 import core.*
 import Types.*
-import TypeUtils.*
 import Contexts.*
 import Flags.*
 import ast.*

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -21,7 +21,6 @@ import NameKinds.DefaultGetterName
 import ProtoTypes.*
 import Inferencing.*
 import reporting.*
-import transform.TypeUtils.*
 import transform.SymUtils.*
 import Nullables.*, NullOpsDecorator.*
 import config.Feature

compiler/src/dotty/tools/dotc/typer/Checking.scala

@@ -38,7 +38,6 @@ import config.Feature
 import config.Feature.sourceVersion
 import config.SourceVersion.*
 import printing.Formatting.hlAsKeyword
-import transform.TypeUtils.*
 import cc.isCaptureChecking
 
 import collection.mutable

compiler/src/dotty/tools/dotc/typer/ConstFold.scala

@@ -11,7 +11,6 @@ import Constants.*
 import Names.*
 import StdNames.*
 import Contexts.*
-import transform.TypeUtils.*
 
 object ConstFold:
 

compiler/src/dotty/tools/dotc/typer/Dynamic.scala

@@ -18,7 +18,6 @@ import util.Spans.*
 import core.Symbols.*
 import ErrorReporting.*
 import dotty.tools.dotc.transform.ValueClasses
-import dotty.tools.dotc.transform.TypeUtils.isPrimitiveValueType
 import reporting.*
 import inlines.Inlines
 

compiler/src/dotty/tools/dotc/typer/Implicits.scala

@@ -24,7 +24,6 @@ import ErrorReporting.*
 import Inferencing.{fullyDefinedType, isFullyDefined}
 import Scopes.newScope
 import Typer.BindingPrec, BindingPrec.*
-import transform.TypeUtils.*
 import Hashable.*
 import util.{EqHashMap, Stats}
 import config.{Config, Feature}

compiler/src/dotty/tools/dotc/typer/Inferencing.scala

@@ -9,7 +9,6 @@ import ProtoTypes.*
 import NameKinds.UniqueName
 import util.Spans.*
 import util.{Stats, SimpleIdentityMap, SimpleIdentitySet, SrcPos}
-import transform.TypeUtils.isTransparent
 import Decorators._
 import config.Printers.{gadts, typr}
 import annotation.tailrec

compiler/src/dotty/tools/dotc/typer/Namer.scala

@@ -23,7 +23,6 @@ import parsing.Parsers.Parser
 import Annotations.*
 import Inferencing.*
 import transform.ValueClasses.*
-import transform.TypeUtils.*
 import transform.SymUtils.*
 import TypeErasure.erasure
 import reporting.*

compiler/src/dotty/tools/dotc/typer/Synthesizer.scala

@@ -12,7 +12,6 @@ import ProtoTypes.*
 import Inferencing.{fullyDefinedType, isFullyDefined}
 import ast.untpd
 import transform.SymUtils.*
-import transform.TypeUtils.*
 import transform.SyntheticMembers.*
 import util.Property
 import ast.Trees.genericEmptyTree

compiler/src/dotty/tools/dotc/typer/Typer.scala

@@ -46,7 +46,6 @@ import config.SourceVersion.*
 import rewrites.Rewrites.patch
 import staging.StagingLevel
 import transform.SymUtils.*
-import transform.TypeUtils.*
 import reporting.*
 import Nullables.*
 import NullOpsDecorator.*