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nicolasstuckinicolasstucki
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Add portotype for Expr[Mirror] methods (#18072)
Getting the info from the mirror in a macro is a bit tricky and verbose. The methods in this portotype intend to make this process trivial. ```scala private def myMacroExpr[T: Type](mirror: Expr[Mirror.Of[T]])(using Quotes): Expr[Any] = import MirroredExpr.* // TODO where we could define this? val mirroredLabel: Option[String] = mirror.mirroredLabel val mirroredElemLabels: Option[List[String]] = mirror.mirroredElemLabels val mirroredMonoType: Option[Type[?]] = mirror.mirroredMonoType val mirroredType: Option[Type[?]] = mirror.mirroredType val mirroredElemTypes: Option[List[Type[?]]] = mirror.mirroredElemTypes ... ``` [skip community_build] [skip docs] [skip mima]
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‎tests/run-macros/expr-mirror-info.check

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(Foo,List(x, y, z),Foo[scala.Long],Foo[scala.Long],List(scala.Int, scala.Double, scala.Long))
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(Foo,List(x, y, z),Foo[scala.Long],Foo[scala.Long],List(scala.Int, scala.Double, scala.Long))
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(Bar,List(A, B),Bar,Bar,List(Bar.A.type, Bar.B))
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(Bar,List(A, B),Bar,Bar,List(Bar.A.type, Bar.B))

‎tests/run-macros/expr-mirror-info/Lib_1.scala

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import scala.deriving.Mirror
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import scala.quoted.*
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object MirroredExpr:
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extension (mirror: Expr[Mirror])
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def mirroredMonoType(using Quotes): Option[Type[?]] =
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mirror match
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case '{ $_ : Mirror { type MirroredMonoType = t } } => Some(Type.of[t])
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case _ => None
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def mirroredType(using Quotes): Option[Type[?]] =
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mirror match
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case '{ $_ : Mirror { type MirroredType = t } } => Some(Type.of[t])
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case _ => None
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def mirroredLabel(using Quotes): Option[String] =
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mirror match
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case '{ type label <: String; $_ : Mirror { type MirroredLabel = label } } =>
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Type.valueOfConstant[label]
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case _ => None
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def mirroredElemTypes(using Quotes): Option[List[Type[?]]] =
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mirror match
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case '{ type labels <: Tuple; $_ : Mirror { type MirroredElemTypes = labels } } =>
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tupleTypes[labels]
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case _ => None
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def mirroredElemLabels(using Quotes): Option[List[String]] =
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mirror match
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case '{ type labels <: Tuple; $_ : Mirror { type MirroredElemLabels = labels } } =>
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Type.valueOfTuple[labels].map(_.toList.asInstanceOf[List[String]])
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case _ => None
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private def tupleTypes[T <: Tuple : Type](using Quotes): Option[List[Type[?]]] =
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import quotes.reflect.*
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val cons = Symbol.classSymbol("scala.*:")
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def rec(tpe: TypeRepr): Option[List[Type[?]]] =
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tpe.widenTermRefByName.dealias match
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case AppliedType(fn, tpes) if defn.isTupleClass(fn.typeSymbol) =>
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tpes.foldRight(Option(List.empty[Type[?]])) {
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case (_, None) => None
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case (tpe, Some(acc)) => Some(tpe.asType :: acc)
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case _ => None
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}
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case AppliedType(tp, List(headType, tail)) if tp.derivesFrom(cons) =>
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rec(tail) match
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case Some(tailTypes) => Some(headType.asType :: tailTypes)
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case None => None
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case tpe =>
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if tpe.derivesFrom(Symbol.classSymbol("scala.EmptyTuple")) then Some(Nil)
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else None
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rec(TypeRepr.of[T])

‎tests/run-macros/expr-mirror-info/Macro_1.scala

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import scala.deriving.Mirror
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import scala.quoted.*
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inline def reflectMirrorInfo[T](using mirror: Mirror.Of[T]): Any = ${ reflectMirrorInfoExpr[T]('mirror) }
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private def reflectMirrorInfoExpr[T: Type](mirror: Expr[Mirror.Of[T]])(using Quotes): Expr[Any] =
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val mirroredLabel: String = MirroredExpr.mirroredLabel(mirror).getOrElse(quotes.reflect.report.errorAndAbort("MirroredLabel not found"))
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val mirroredElemLabels = MirroredExpr.mirroredElemLabels(mirror).getOrElse(quotes.reflect.report.errorAndAbort("MirroredElemLabels not found"))
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val mirroredMonoType: Type[?] = MirroredExpr.mirroredMonoType(mirror).getOrElse(quotes.reflect.report.errorAndAbort("MirroredMonoType not found"))
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val mirroredType: Type[?] = MirroredExpr.mirroredType(mirror).getOrElse(quotes.reflect.report.errorAndAbort("MirroredType not found"))
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val mirroredElemTypes: List[Type[?]] = MirroredExpr.mirroredElemTypes(mirror).getOrElse(quotes.reflect.report.errorAndAbort("MirroredElemTypes not found"))
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val mirroredMonoTypeString = mirroredMonoType match
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case '[t] => Type.show[t]
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val mirroredTypeString = mirroredType match
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case '[t] => Type.show[t]
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val mirroredElemTypesStrings = mirroredElemTypes.map {
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case '[t] => Type.show[t]
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}
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Expr((mirroredLabel, mirroredElemLabels, mirroredMonoTypeString, mirroredTypeString, mirroredElemTypesStrings))
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inline def reflectMirrorInfo2[T](using mirror: Mirror.Of[T]): Any = ${ reflectMirrorInfoExpr2[T]('mirror) }
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private def reflectMirrorInfoExpr2[T: Type](mirror: Expr[Mirror.Of[T]])(using Quotes): Expr[Any] =
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import MirroredExpr.*
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val mirroredLabel: String = mirror.mirroredLabel.getOrElse(quotes.reflect.report.errorAndAbort("MirroredLabel not found"))
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val mirroredElemLabels = mirror.mirroredElemLabels.getOrElse(quotes.reflect.report.errorAndAbort("MirroredElemLabels not found"))
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val mirroredMonoType: Type[?] = mirror.mirroredMonoType.getOrElse(quotes.reflect.report.errorAndAbort("MirroredMonoType not found"))
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val mirroredType: Type[?] = mirror.mirroredType.getOrElse(quotes.reflect.report.errorAndAbort("MirroredType not found"))
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val mirroredElemTypes: List[Type[?]] = mirror.mirroredElemTypes.getOrElse(quotes.reflect.report.errorAndAbort("MirroredElemTypes not found"))
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val mirroredMonoTypeString = mirroredMonoType match
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case '[t] => Type.show[t]
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val mirroredTypeString = mirroredType match
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case '[t] => Type.show[t]
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val mirroredElemTypesStrings = mirroredElemTypes.map {
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case '[t] => Type.show[t]
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}
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Expr((mirroredLabel, mirroredElemLabels, mirroredMonoTypeString, mirroredTypeString, mirroredElemTypesStrings))

‎tests/run-macros/expr-mirror-info/Test_2.scala

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import scala.deriving.Mirror
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case class Foo[T](x: Int, y: Double, z: T)
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enum Bar:
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case A
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case B(b: Int)
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@main def Test: Unit =
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println(reflectMirrorInfo[Foo[Long]])
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println(reflectMirrorInfo2[Foo[Long]])
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println(reflectMirrorInfo[Bar])
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println(reflectMirrorInfo2[Bar])

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