Refactor some tuple methods (#19032)

 - Move from Definitions to TypeUtils
- Unify TypeUtils.tupleElementTypes and Definitions.tupleTypes. They do
the same thing.

I'd like to move more things out of Definitions and into TypeUtils and
SymUtils. Then I'd like to move these files to the core package, and
make their operations accessible automatically by having the companion
objects of Types and Symbols inherit from them. This is a first step
into that direction.

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

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

@@ -4,8 +4,6 @@ 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/cc/CheckCaptures.scala

@@ -15,7 +15,6 @@ import typer.Checking.{checkBounds, checkAppliedTypesIn}
 import typer.ErrorReporting.{Addenda, err}
 import typer.ProtoTypes.{AnySelectionProto, LhsProto}
 import util.{SimpleIdentitySet, EqHashMap, EqHashSet, SrcPos, Property}
-import transform.SymUtils.*
 import transform.{Recheck, PreRecheck, CapturedVars}
 import Recheck.*
 import scala.collection.mutable

compiler/src/dotty/tools/dotc/config/JavaPlatform.scala

@@ -7,7 +7,7 @@ import classpath.AggregateClassPath
 import core.*
 import Symbols.*, Types.*, Contexts.*, StdNames.*
 import Flags.*
-import transform.ExplicitOuter, transform.SymUtils.*
+import transform.ExplicitOuter
 
 class JavaPlatform extends Platform {
 

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/Definitions.scala

@@ -1749,26 +1749,6 @@ class Definitions {
     else TypeOps.nestedPairs(elems)
   }
 
-  def tupleTypes(tp: Type, bound: Int = Int.MaxValue)(using Context): Option[List[Type]] = {
-    @tailrec def rec(tp: Type, acc: List[Type], bound: Int): Option[List[Type]] = tp.normalized.dealias match {
-      case _ if bound < 0 => Some(acc.reverse)
-      case tp: AppliedType if PairClass == tp.classSymbol => rec(tp.args(1), tp.args.head :: acc, bound - 1)
-      case tp: AppliedType if isTupleNType(tp) => Some(acc.reverse ::: tp.args)
-      case tp: TermRef if tp.symbol == defn.EmptyTupleModule => Some(acc.reverse)
-      case _ => None
-    }
-    rec(tp.stripTypeVar, Nil, bound)
-  }
-
-  def isSmallGenericTuple(tp: Type)(using Context): Boolean =
-    if tp.derivesFrom(defn.PairClass) && !defn.isTupleNType(tp.widenDealias) then
-      // If this is a generic tuple we need to cast it to make the TupleN/ members accessible.
-      // This works only for generic tuples of known size up to 22.
-      defn.tupleTypes(tp.widenTermRefExpr) match
-        case Some(elems) if elems.length <= Definitions.MaxTupleArity => true
-        case _ => false
-    else false
-
   def isProductSubType(tp: Type)(using Context): Boolean = tp.derivesFrom(ProductClass)
 
   /** Is `tp` (an alias) of either a scala.FunctionN or a scala.ContextFunctionN

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/transform/SymUtils.scala → compiler/src/dotty/tools/dotc/core/SymUtils.scala

@@ -1,5 +1,5 @@
 package dotty.tools.dotc
-package transform
+package core
 
 import core.*
 import Types.*
@@ -11,18 +11,18 @@ import NameOps.*
 import StdNames.*
 import NameKinds.*
 import Flags.*
-import ValueClasses.isDerivedValueClass
 import Decorators.*
 import Constants.Constant
 import Annotations.Annotation
 import Phases.*
 import ast.tpd.Literal
+import transform.Mixin
 
 import dotty.tools.dotc.transform.sjs.JSSymUtils.sjsNeedsField
 
 import scala.annotation.tailrec
 
-object SymUtils:
+class SymUtils:
 
   extension (self: Symbol)
 
@@ -79,6 +79,14 @@ object SymUtils:
       self.is(Enum, butNot = Case) &&
       self.info.parents.exists(p => p.typeSymbol == defn.JavaEnumClass)
 
+    def isDerivedValueClass(using Context): Boolean = self.isClass && {
+      val d = self.denot
+      !d.isRefinementClass &&
+      d.isValueClass &&
+      (d.initial.symbol ne defn.AnyValClass) && // Compare the initial symbol because AnyVal does not exist after erasure
+      !d.isPrimitiveValueClass
+    }
+
     /** Is this a case class for which a product mirror is generated?
     *  Excluded are value classes, abstract classes and case classes with more than one
     *  parameter section.
@@ -100,7 +108,7 @@ object SymUtils:
       if (!self.is(CaseClass)) "it is not a case class"
       else if (self.is(Abstract)) "it is an abstract class"
       else if (self.primaryConstructor.info.paramInfoss.length != 1) "it takes more than one parameter list"
-      else if (isDerivedValueClass(self)) "it is a value class"
+      else if self.isDerivedValueClass then "it is a value class"
       else if (!(companionMirror || canAccessCtor)) s"the constructor of $self is inaccessible from the calling scope."
       else ""
     end whyNotGenericProduct

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

@@ -18,7 +18,6 @@ import util.Spans.*
 import DenotTransformers.*
 import StdNames.*
 import NameOps.*
-import transform.SymUtils.*
 import NameKinds.LazyImplicitName
 import ast.tpd
 import tpd.{Tree, TreeProvider, TreeOps}
@@ -36,7 +35,7 @@ import dotty.tools.dotc.classpath.FileUtils.isScalaBinary
 import scala.compiletime.uninitialized
 import dotty.tools.tasty.TastyVersion
 
-object Symbols {
+object Symbols extends SymUtils {
 
   implicit def eqSymbol: CanEqual[Symbol, Symbol] = CanEqual.derived
 

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

@@ -16,8 +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
 import typer.Applications.productSelectorTypes

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.*
@@ -72,7 +71,7 @@ end SourceLanguage
 object TypeErasure {
 
   private def erasureDependsOnArgs(sym: Symbol)(using Context) =
-    sym == defn.ArrayClass || sym == defn.PairClass || isDerivedValueClass(sym)
+    sym == defn.ArrayClass || sym == defn.PairClass || sym.isDerivedValueClass
 
   /** The arity of this tuple type, which can be made up of EmptyTuple, TupleX and `*:` pairs.
    *
@@ -126,7 +125,7 @@ object TypeErasure {
     case tp: TypeRef =>
       val sym = tp.symbol
       sym.isClass &&
-      (!erasureDependsOnArgs(sym) || isDerivedValueClass(sym)) &&
+      (!erasureDependsOnArgs(sym) || sym.isDerivedValueClass) &&
       !defn.specialErasure.contains(sym) &&
       !defn.isSyntheticFunctionClass(sym)
     case _: TermRef =>
@@ -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)
@@ -632,15 +630,15 @@ class TypeErasure(sourceLanguage: SourceLanguage, semiEraseVCs: Boolean, isConst
       case tp: TypeRef =>
         val sym = tp.symbol
         if !sym.isClass then this(checkedSuperType(tp))
-        else if semiEraseVCs && isDerivedValueClass(sym) then eraseDerivedValueClass(tp)
+        else if semiEraseVCs && sym.isDerivedValueClass then eraseDerivedValueClass(tp)
         else if defn.isSyntheticFunctionClass(sym) then defn.functionTypeErasure(sym)
         else eraseNormalClassRef(tp)
       case tp: AppliedType =>
         val tycon = tp.tycon
         if (tycon.isRef(defn.ArrayClass)) eraseArray(tp)
         else if (tycon.isRef(defn.PairClass)) erasePair(tp)
         else if (tp.isRepeatedParam) apply(tp.translateFromRepeated(toArray = sourceLanguage.isJava))
-        else if (semiEraseVCs && isDerivedValueClass(tycon.classSymbol)) eraseDerivedValueClass(tp)
+        else if (semiEraseVCs && tycon.classSymbol.isDerivedValueClass) eraseDerivedValueClass(tp)
         else this(checkedSuperType(tp))
       case tp: TermRef =>
         this(underlyingOfTermRef(tp))
@@ -900,7 +898,7 @@ class TypeErasure(sourceLanguage: SourceLanguage, semiEraseVCs: Boolean, isConst
           if (!info.exists) assert(false, i"undefined: $tp with symbol $sym")
           return sigName(info)
         }
-        if (semiEraseVCs && isDerivedValueClass(sym)) {
+        if (semiEraseVCs && sym.isDerivedValueClass) {
           val erasedVCRef = eraseDerivedValueClass(tp)
           if (erasedVCRef.exists) return sigName(erasedVCRef)
         }

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

@@ -13,7 +13,6 @@ import ast.tpd.*
 import reporting.trace
 import config.Printers.typr
 import config.Feature
-import transform.SymUtils.*
 import typer.ProtoTypes.*
 import typer.ForceDegree
 import typer.Inferencing.*

compiler/src/dotty/tools/dotc/transform/TypeUtils.scala → 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.
    */
@@ -45,22 +44,45 @@ object TypeUtils {
       case ps => ps.reduceLeft(AndType(_, _))
     }
 
-    /** The element types of this tuple type, which can be made up of EmptyTuple, TupleX and `*:` pairs */
-    def tupleElementTypes(using Context): Option[List[Type]] = self.dealias match {
-      case AppliedType(tycon, hd :: tl :: Nil) if tycon.isRef(defn.PairClass) =>
-        tl.tupleElementTypes.map(hd :: _)
-      case self: SingletonType =>
-        if self.termSymbol == defn.EmptyTupleModule then Some(Nil) else None
-      case AndType(tp1, tp2) =>
-        // We assume that we have the following property:
-        // (T1, T2, ..., Tn) & (U1, U2, ..., Un) = (T1 & U1, T2 & U2, ..., Tn & Un)
-        tp1.tupleElementTypes.zip(tp2.tupleElementTypes).map { case (t1, t2) => t1.intersect(t2) }
-      case OrType(tp1, tp2) =>
-        None // We can't combine the type of two tuples
-      case _ =>
-        if defn.isTupleClass(self.typeSymbol) then Some(self.dealias.argInfos)
-        else None
-    }
+    /** The element types of this tuple type, which can be made up of EmptyTuple, TupleX and `*:` pairs
+     */
+    def tupleElementTypes(using Context): Option[List[Type]] =
+      tupleElementTypesUpTo(Int.MaxValue)
+
+    /** The element types of this tuple type, which can be made up of EmptyTuple, TupleX and `*:` pairs
+     *  @param bound     The maximum number of elements that needs generating minus 1
+     *                   The generation will stop once more than bound elems have been generated
+     *  @param normalize If true, normalize and dealias at each step.
+     *                   If false, never normalize and dealias only to find *:
+     *                   and EmptyTuple types. This is useful for printing.
+     */
+    def tupleElementTypesUpTo(bound: Int, normalize: Boolean = true)(using Context): Option[List[Type]] =
+      def recur(tp: Type, bound: Int): Option[List[Type]] =
+        if bound < 0 then Some(Nil)
+        else (if normalize then tp.normalized else tp).dealias match
+          case AppliedType(tycon, hd :: tl :: Nil) if tycon.isRef(defn.PairClass) =>
+            recur(tl, bound - 1).map(hd :: _)
+          case tp: AppliedType if defn.isTupleNType(tp) && normalize =>
+            Some(tp.args)  // if normalize is set, use the dealiased tuple
+                           // otherwise rely on the default case below to print unaliased tuples.
+          case tp: SingletonType =>
+            if tp.termSymbol == defn.EmptyTupleModule then Some(Nil) else None
+          case _ =>
+            if defn.isTupleClass(tp.typeSymbol) && !normalize then Some(tp.dealias.argInfos)
+            else None
+      recur(self.stripTypeVar, bound)
+
+    /** Is this a generic tuple that would fit into the range 1..22,
+     *  but is not already an instance of one of Tuple1..22?
+     *  In this case we need to cast it to make the TupleN/ members accessible.
+     *  This works only for generic tuples of known size up to 22.
+     */
+    def isSmallGenericTuple(using Context): Boolean =
+      self.derivesFrom(defn.PairClass)
+      && !defn.isTupleNType(self.widenDealias)
+      && self.widenTermRefExpr.tupleElementTypesUpTo(Definitions.MaxTupleArity).match
+          case Some(elems) if elems.length <= Definitions.MaxTupleArity => true
+          case _ => false
 
     /** The `*:` equivalent of an instance of a Tuple class */
     def toNestedPairs(using Context): Type =