Introduce explicit error for non-implicit non-case parameters

Fix compilation error when case class has a method named like a case field

Author: NTPape

core/shared/src/main/scala-3.x/monocle/internal/focus/ErrorHandling.scala

@@ -8,6 +8,8 @@ private[focus] trait ErrorHandling {
       s"Cannot generate Lens for field '$fieldName', because '$fromClass' is not a case class"
     case FocusError.NotACaseField(caseClass, fieldName) =>
       s"Can only create lenses for case fields, but '$fieldName' is not a case field of '$caseClass'"
+    case FocusError.NonImplicitNonCaseParameter(caseClass, parameters) =>
+      s"Case class '$caseClass' has non-implicit non-case parameters, which is not supported: ${parameters.map("'" + _ + "'").mkString(", ")}"
     case FocusError.NotAConcreteClass(fromClass) =>
       s"Expecting a concrete case class in the 'From' position; cannot reify type $fromClass"
     case FocusError.NotASimpleLambdaFunction =>
@@ -20,7 +22,7 @@ private[focus] trait ErrorHandling {
     case FocusError.CouldntFindFieldType(fromType, fieldName) => s"Couldn't find type for $fromType.$fieldName"
     case FocusError.InvalidDowncast(fromType, toType)         => s"Type '$fromType' could not be cast to '$toType'"
     case FocusError.ImplicitNotFound(implicitType) =>
-      s"Could not find implicit for '$implicitType'. Note: multiple non-implicit parameter sets or implicits with default values are not supported."
+      s"Could not find implicit for '$implicitType'. Note: implicits with default values are not supported."
     case FocusError.ExpansionFailed(reason) =>
       s"Case class with multiple parameter sets could not be expanded because of: $reason"
   }

core/shared/src/main/scala-3.x/monocle/internal/focus/FocusBase.scala

@@ -7,22 +7,23 @@ private[focus] trait FocusBase {
 
   given Quotes = macroContext
 
+  type Symbol   = macroContext.reflect.Symbol
   type Term     = macroContext.reflect.Term
   type TypeRepr = macroContext.reflect.TypeRepr
 
   case class LambdaConfig(argName: String, lambdaBody: Term)
 
   enum FocusAction {
-    case SelectField(fieldName: String, fromType: TypeRepr, fromTypeArgs: List[TypeRepr], toType: TypeRepr)
-    case SelectFieldWithImplicits(fieldName: String, fromType: TypeRepr, toType: TypeRepr, setter: Term)
+    case SelectField(caseFieldSymbol: Symbol, fromType: TypeRepr, fromTypeArgs: List[TypeRepr], toType: TypeRepr)
+    case SelectFieldWithImplicits(caseFieldSymbol: Symbol, fromType: TypeRepr, toType: TypeRepr, setter: Term)
     case SelectOnlyField(
-      fieldName: String,
+      caseFieldSymbol: Symbol,
       fromType: TypeRepr,
       fromTypeArgs: List[TypeRepr],
       fromCompanion: Term,
       toType: TypeRepr
     )
-    case SelectOnlyFieldWithImplicits(fieldName: String, fromType: TypeRepr, toType: TypeRepr, reverseGet: Term)
+    case SelectOnlyFieldWithImplicits(caseFieldSymbol: Symbol, fromType: TypeRepr, toType: TypeRepr, reverseGet: Term)
     case KeywordSome(toType: TypeRepr)
     case KeywordAs(fromType: TypeRepr, toType: TypeRepr)
     case KeywordEach(fromType: TypeRepr, toType: TypeRepr, eachInstance: Term)
@@ -31,14 +32,14 @@ private[focus] trait FocusBase {
     case KeywordWithDefault(toType: TypeRepr, defaultValue: Term)
 
     override def toString(): String = this match {
-      case SelectField(fieldName, fromType, fromTypeArgs, toType) =>
-        s"SelectField($fieldName, ${fromType.show}, ${fromTypeArgs.map(_.show)}, ${toType.show})"
-      case SelectFieldWithImplicits(fieldName, fromType, toType, setter) =>
-        s"SelectFieldWithImplicits($fieldName, ${fromType.show}, ${toType.show}, ...)"
-      case SelectOnlyField(fieldName, fromType, fromTypeArgs, _, toType) =>
-        s"SelectOnlyField($fieldName, ${fromType.show}, ${fromTypeArgs.map(_.show)}, ..., ${toType.show})"
-      case SelectOnlyFieldWithImplicits(fieldName, fromType, toType, reverseGet) =>
-        s"SelectOnlyFieldWithImplicits($fieldName, ${fromType.show}, ${toType.show}, ...)"
+      case SelectField(caseFieldSymbol, fromType, fromTypeArgs, toType) =>
+        s"SelectField(${caseFieldSymbol.name}, ${fromType.show}, ${fromTypeArgs.map(_.show)}, ${toType.show})"
+      case SelectFieldWithImplicits(caseFieldSymbol, fromType, toType, setter) =>
+        s"SelectFieldWithImplicits(${caseFieldSymbol.name}, ${fromType.show}, ${toType.show}, ...)"
+      case SelectOnlyField(caseFieldSymbol, fromType, fromTypeArgs, _, toType) =>
+        s"SelectOnlyField(${caseFieldSymbol.name}, ${fromType.show}, ${fromTypeArgs.map(_.show)}, ..., ${toType.show})"
+      case SelectOnlyFieldWithImplicits(caseFieldSymbol, fromType, toType, reverseGet) =>
+        s"SelectOnlyFieldWithImplicits(${caseFieldSymbol.name}, ${fromType.show}, ${toType.show}, ...)"
       case KeywordSome(toType)                  => s"KeywordSome(${toType.show})"
       case KeywordAs(fromType, toType)          => s"KeywordAs(${fromType.show}, ${toType.show})"
       case KeywordEach(fromType, toType, _)     => s"KeywordEach(${fromType.show}, ${toType.show}, ...)"
@@ -51,6 +52,7 @@ private[focus] trait FocusBase {
   enum FocusError {
     case NotACaseClass(className: String, fieldName: String)
     case NotACaseField(className: String, fieldName: String)
+    case NonImplicitNonCaseParameter(className: String, parameters: List[String])
     case NotAConcreteClass(className: String)
     case DidNotDirectlyAccessArgument(argName: String)
     case NotASimpleLambdaFunction

core/shared/src/main/scala-3.x/monocle/internal/focus/features/SelectParserBase.scala

@@ -11,11 +11,34 @@ private[focus] trait SelectParserBase extends ParserBase {
 
   import this.macroContext.reflect._
 
-  // Match on a term that is an instance of a case class
-  object CaseClass {
-    def unapply(term: Term): Option[(Term, Symbol)] =
+  case class CaseClass(typeRepr: TypeRepr, classSymbol: Symbol) {
+    val typeArgs: List[TypeRepr] = getSuppliedTypeArgs(typeRepr)
+    val companionObject: Term    = Ref(classSymbol.companionModule)
+
+    private val (typeParams, caseFieldParams :: otherParams) =
+      classSymbol.primaryConstructor.paramSymss.span(_.head.isTypeParam)
+    val hasOnlyOneCaseField: Boolean     = caseFieldParams.length == 1
+    val hasOnlyOneParameterList: Boolean = otherParams.isEmpty
+    private val nonCaseNonImplicitParameters: List[Symbol] =
+      otherParams.flatten.filterNot(symbol => symbol.flags.is(Flags.Implicit) || symbol.flags.is(Flags.Given))
+    val allOtherParametersAreImplicitResult: FocusResult[Unit] = nonCaseNonImplicitParameters match {
+      case Nil  => Right(())
+      case list => FocusError.NonImplicitNonCaseParameter(typeRepr.show, list.map(_.name)).asResult
+    }
+
+    def getCaseFieldSymbol(fieldName: String): FocusResult[Symbol] =
+      classSymbol.caseFields.find(_.name == fieldName) match {
+        case Some(symbol) => Right(symbol)
+        case None         => FocusError.NotACaseField(typeRepr.show, fieldName).asResult
+      }
+    def getCaseFieldType(caseFieldSymbol: Symbol): FocusResult[TypeRepr] =
+      getFieldType(typeRepr, caseFieldSymbol)
+  }
+
+  object CaseClassExtractor {
+    def unapply(term: Term): Option[CaseClass] =
       term.tpe.classSymbol.flatMap { sym =>
-        Option.when(sym.flags.is(Flags.Case))((term, sym))
+        Option.when(sym.flags.is(Flags.Case))(CaseClass(getType(term), sym))
       }
   }
 
@@ -25,32 +48,21 @@ private[focus] trait SelectParserBase extends ParserBase {
       case _                            => Nil
     }
 
-  def getClassSymbol(tpe: TypeRepr): FocusResult[Symbol] = tpe.classSymbol match {
-    case Some(sym) => Right(sym)
-    case None      => FocusError.NotAConcreteClass(tpe.show).asResult
-  }
-
-  def getFieldType(fromType: TypeRepr, fieldName: String): FocusResult[TypeRepr] = {
-    // We need to do this to support tuples, because even though they conform as case classes in other respects,
-    // for some reason their field names (_1, _2, etc) have a space at the end, ie `_1 `.
-    def getTrimmedFieldSymbol(fromTypeSymbol: Symbol): Symbol =
-      fromTypeSymbol.fieldMembers.find(_.name.trim == fieldName).getOrElse(Symbol.noSymbol)
-
-    getClassSymbol(fromType).flatMap { fromTypeSymbol =>
-      getTrimmedFieldSymbol(fromTypeSymbol) match {
-        case FieldType(possiblyTypeArg) => Right(swapWithSuppliedType(fromType, possiblyTypeArg))
-        case _                          => FocusError.CouldntFindFieldType(fromType.show, fieldName).asResult
-      }
+  def getFieldType(fromType: TypeRepr, caseFieldSymbol: Symbol): FocusResult[TypeRepr] =
+    caseFieldSymbol match {
+      case FieldType(possiblyTypeArg) => Right(swapWithSuppliedType(fromType, possiblyTypeArg))
+      case _                          => FocusError.CouldntFindFieldType(fromType.show, caseFieldSymbol.name).asResult
     }
-  }
 
   private object FieldType {
     def unapply(fieldSymbol: Symbol): Option[TypeRepr] = fieldSymbol match {
       case sym if sym.isNoSymbol => None
       case sym =>
         sym.tree match {
           case ValDef(_, typeTree, _) => Some(typeTree.tpe)
-          case _                      => None
+          // Only needed for Tuples because `_1` is a DefDef while `_1 ` is a ValDef.
+          case DefDef(_, _, typeTree, _) => Some(typeTree.tpe)
+          case _                         => None
         }
     }
   }

core/shared/src/main/scala-3.x/monocle/internal/focus/features/selectfield/SelectFieldGenerator.scala

@@ -9,61 +9,61 @@ private[focus] trait SelectFieldGenerator {
 
   import macroContext.reflect._
 
-  private def generateGetter(from: Term, fieldName: String): Term =
-    Select.unique(from, fieldName) // o.field
+  private def generateGetter(from: Term, caseFieldSymbol: Symbol): Term =
+    Select(from, caseFieldSymbol) // o.field
 
   def generateSelectField(action: FocusAction.SelectField): Term = {
-    import action.{fieldName, fromType, fromTypeArgs, toType}
+    import action.{caseFieldSymbol, fromType, fromTypeArgs, toType}
 
     def generateSetter(from: Term, to: Term): Term =
-      Select.overloaded(from, "copy", fromTypeArgs, NamedArg(fieldName, to) :: Nil) // o.copy(field = value)
+      Select.overloaded(from, "copy", fromTypeArgs, NamedArg(caseFieldSymbol.name, to) :: Nil) // o.copy(field = value)
 
     (fromType.asType, toType.asType) match {
       case ('[f], '[t]) =>
         '{
-          Lens.apply[f, t]((from: f) => ${ generateGetter('{ from }.asTerm, fieldName).asExprOf[t] })((to: t) =>
+          Lens.apply[f, t]((from: f) => ${ generateGetter('{ from }.asTerm, caseFieldSymbol).asExprOf[t] })((to: t) =>
             (from: f) => ${ generateSetter('{ from }.asTerm, '{ to }.asTerm).asExprOf[f] }
           )
         }.asTerm
     }
   }
 
   def generateSelectFieldWithImplicits(action: FocusAction.SelectFieldWithImplicits): Term = {
-    import action.{fieldName, fromType, toType, setter}
+    import action.{caseFieldSymbol, fromType, toType, setter}
 
     (fromType.asType, toType.asType) match {
       case ('[f], '[t]) =>
         '{
-          Lens.apply[f, t]((from: f) => ${ generateGetter('{ from }.asTerm, fieldName).asExprOf[t] })(
+          Lens.apply[f, t]((from: f) => ${ generateGetter('{ from }.asTerm, caseFieldSymbol).asExprOf[t] })(
             ${ setter.asExprOf[t => f => f] }
           )
         }.asTerm
     }
   }
 
   def generateSelectOnlyField(action: FocusAction.SelectOnlyField): Term = {
-    import action.{fieldName, fromType, fromTypeArgs, fromCompanion, toType}
+    import action.{caseFieldSymbol, fromType, fromTypeArgs, fromCompanion, toType}
 
     def generateReverseGet(to: Term): Term =
       Select.overloaded(fromCompanion, "apply", fromTypeArgs, List(to)) // Companion.apply(value)
 
     (fromType.asType, toType.asType) match {
       case ('[f], '[t]) =>
         '{
-          Iso.apply[f, t]((from: f) => ${ generateGetter('{ from }.asTerm, fieldName).asExprOf[t] })((to: t) =>
+          Iso.apply[f, t]((from: f) => ${ generateGetter('{ from }.asTerm, caseFieldSymbol).asExprOf[t] })((to: t) =>
             ${ generateReverseGet('{ to }.asTerm).asExprOf[f] }
           )
         }.asTerm
     }
   }
 
   def generateSelectOnlyFieldWithImplicits(action: FocusAction.SelectOnlyFieldWithImplicits): Term = {
-    import action.{fieldName, fromType, toType, reverseGet}
+    import action.{caseFieldSymbol, fromType, toType, reverseGet}
 
     (fromType.asType, toType.asType) match {
       case ('[f], '[t]) =>
         '{
-          Iso.apply[f, t]((from: f) => ${ generateGetter('{ from }.asTerm, fieldName).asExprOf[t] })(
+          Iso.apply[f, t]((from: f) => ${ generateGetter('{ from }.asTerm, caseFieldSymbol).asExprOf[t] })(
             ${ reverseGet.asExprOf[t => f] }
           )
         }.asTerm

core/shared/src/main/scala-3.x/monocle/internal/focus/features/selectfield/SelectFieldParser.scala

@@ -12,20 +12,19 @@ private[focus] trait SelectFieldParser {
 
     def unapply(term: Term): Option[FocusResult[(RemainingCode, FocusAction)]] = term match {
 
-      case Select(CaseClass(remainingCode, classSymbol), fieldName) =>
-        if (isCaseField(classSymbol, fieldName)) {
-          val fromType = getType(remainingCode)
-          val action = (hasOnlyOneParameterList(classSymbol), hasOnlyOneField(classSymbol)) match {
-            case (true, false)  => getSelectFieldAction(fromType, fieldName)
-            case (false, false) => getSelectFieldActionWithImplicits(fromType, fieldName)
-            case (true, true)   => getSelectOnlyFieldAction(fromType, classSymbol, fieldName)
-            case (false, true)  => getSelectOnlyFieldActionWithImplicits(fromType, classSymbol, fieldName)
-          }
-          val remainingCodeWithAction = action.map(a => (RemainingCode(remainingCode), a))
-          Some(remainingCodeWithAction)
-        } else {
-          Some(FocusError.NotACaseField(remainingCode.tpe.show, fieldName).asResult)
-        }
+      case Select(remainingCode @ CaseClassExtractor(caseClass: CaseClass), fieldName) =>
+        Some(
+          for {
+            _               <- caseClass.allOtherParametersAreImplicitResult
+            caseFieldSymbol <- caseClass.getCaseFieldSymbol(fieldName)
+            action <- (caseClass.hasOnlyOneParameterList, caseClass.hasOnlyOneCaseField) match {
+              case (true, false)  => getSelectFieldAction(caseClass, caseFieldSymbol)
+              case (false, false) => getSelectFieldActionWithImplicits(caseClass, caseFieldSymbol)
+              case (true, true)   => getSelectOnlyFieldAction(caseClass, caseFieldSymbol)
+              case (false, true)  => getSelectOnlyFieldActionWithImplicits(caseClass, caseFieldSymbol)
+            }
+          } yield (RemainingCode(remainingCode), action)
+        )
 
       case Select(remainingCode, fieldName) =>
         Some(FocusError.NotACaseClass(remainingCode.tpe.show, fieldName).asResult)
@@ -34,57 +33,60 @@ private[focus] trait SelectFieldParser {
     }
   }
 
-  private def isCaseField(classSymbol: Symbol, fieldName: String): Boolean =
-    classSymbol.caseFields.exists(_.name == fieldName)
-
-  private def hasOnlyOneField(classSymbol: Symbol): Boolean =
-    classSymbol.caseFields.length == 1
-
-  private def hasOnlyOneParameterList(classSymbol: Symbol): Boolean =
-    classSymbol.primaryConstructor.paramSymss match {
-      case _ :: Nil                                    => true
-      case (head :: _) :: _ :: Nil if head.isTypeParam => true
-      case _                                           => false
-    }
-
-  private def getCompanionObject(classSymbol: Symbol): Term =
-    Ref(classSymbol.companionModule)
-
-  private def getSelectFieldAction(fromType: TypeRepr, fieldName: String): FocusResult[FocusAction] =
-    getFieldType(fromType, fieldName).flatMap { toType =>
-      Right(FocusAction.SelectField(fieldName, fromType, getSuppliedTypeArgs(fromType), toType))
-    }
-
-  private def getSelectFieldActionWithImplicits(fromType: TypeRepr, fieldName: String): FocusResult[FocusAction] =
-    getFieldType(fromType, fieldName).flatMap { toType =>
-      val typeArgs = getSuppliedTypeArgs(fromType)
-      constructSetter(fieldName, fromType, toType, typeArgs).map { setter =>
-        FocusAction.SelectFieldWithImplicits(fieldName, fromType, toType, setter)
-      }
-    }
+  private def getSelectFieldAction(
+    caseClass: CaseClass,
+    caseFieldSymbol: Symbol
+  ): FocusResult[FocusAction] =
+    for {
+      toType <- caseClass.getCaseFieldType(caseFieldSymbol)
+    } yield FocusAction.SelectField(
+      caseFieldSymbol,
+      caseClass.typeRepr,
+      caseClass.typeArgs,
+      toType
+    )
+
+  private def getSelectFieldActionWithImplicits(
+    caseClass: CaseClass,
+    caseFieldSymbol: Symbol
+  ): FocusResult[FocusAction] =
+    for {
+      toType <- caseClass.getCaseFieldType(caseFieldSymbol)
+      setter <- constructSetter(caseFieldSymbol.name, caseClass.typeRepr, toType, caseClass.typeArgs)
+    } yield FocusAction.SelectFieldWithImplicits(
+      caseFieldSymbol,
+      caseClass.typeRepr,
+      toType,
+      setter
+    )
 
   private def getSelectOnlyFieldAction(
-    fromType: TypeRepr,
-    fromClassSymbol: Symbol,
-    fieldName: String
+    caseClass: CaseClass,
+    caseFieldSymbol: Symbol
   ): FocusResult[FocusAction] =
     for {
-      toType <- getFieldType(fromType, fieldName)
-      companion = getCompanionObject(fromClassSymbol)
-      supplied  = getSuppliedTypeArgs(fromType)
-    } yield FocusAction.SelectOnlyField(fieldName, fromType, supplied, companion, toType)
+      toType <- caseClass.getCaseFieldType(caseFieldSymbol)
+    } yield FocusAction.SelectOnlyField(
+      caseFieldSymbol,
+      caseClass.typeRepr,
+      caseClass.typeArgs,
+      caseClass.companionObject,
+      toType
+    )
 
   private def getSelectOnlyFieldActionWithImplicits(
-    fromType: TypeRepr,
-    fromClassSymbol: Symbol,
-    fieldName: String
+    caseClass: CaseClass,
+    caseFieldSymbol: Symbol
   ): FocusResult[FocusAction] =
     for {
-      toType <- getFieldType(fromType, fieldName)
-      companion = getCompanionObject(fromClassSymbol)
-      supplied  = getSuppliedTypeArgs(fromType)
-      reverseGet <- constructReverseGet(companion, fromType, toType, supplied)
-    } yield FocusAction.SelectOnlyFieldWithImplicits(fieldName, fromType, toType, reverseGet)
+      toType     <- caseClass.getCaseFieldType(caseFieldSymbol)
+      reverseGet <- constructReverseGet(caseClass.companionObject, caseClass.typeRepr, toType, caseClass.typeArgs)
+    } yield FocusAction.SelectOnlyFieldWithImplicits(
+      caseFieldSymbol,
+      caseClass.typeRepr,
+      toType,
+      reverseGet
+    )
 
   private case class LiftException(error: FocusError) extends Exception
 

macro/src/test/scala/monocle/macros/internal/ContextBoundCompilationIssueSpec.scala

@@ -13,7 +13,9 @@ class ContextBoundCompilationIssueSpec extends DisciplineSuite {
     val lens: Lens[S[T], Bar[T]] = GenLens[S[T]](_.bar)
   }
 
-  private case class S[T: Foo](bar: Bar[T])
+  private case class S[T: Foo](bar: Bar[T]) {
+    def bar(t: T): T = t
+  }
 
   private case object FooImpl extends Foo[Unit]
   private case object BarImpl extends Bar[Unit]