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Fix derivation macro example #15026

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Merged
merged 2 commits into from
May 5, 2022
Merged

Fix derivation macro example #15026

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426a3d1
Fix derivation macro example
nicolasstucki Apr 25, 2022
a218602
Avoid unchecked Expr casts
nicolasstucki Apr 25, 2022
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19 changes: 10 additions & 9 deletions docs/_docs/reference/contextual/derivation-macro.md
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Original file line number Diff line number Diff line change
Expand Up @@ -49,15 +49,16 @@ given derived[T: Type](using Quotes): Expr[Eq[T]] =
ev match
case '{ $m: Mirror.ProductOf[T] { type MirroredElemTypes = elementTypes }} =>
val elemInstances = summonAll[elementTypes]
val eqProductBody: (Expr[T], Expr[T]) => Expr[Boolean] = (x, y) =>
elemInstances.zipWithIndex.foldLeft(Expr(true: Boolean)) {
case (acc, (elem, index)) =>
val e1 = '{$x.asInstanceOf[Product].productElement(${Expr(index)})}
val e2 = '{$y.asInstanceOf[Product].productElement(${Expr(index)})}
'{ $acc && $elem.asInstanceOf[Eq[Any]].eqv($e1, $e2) }
}

'{ eqProduct((x: T, y: T) => ${eqProductBody('x, 'y)}) }
def eqProductBody(x: Expr[Product], y: Expr[Product])(using Quotes): Expr[Boolean] = {
elemInstances.zipWithIndex.foldLeft(Expr(true)) {
case (acc, ('{ $elem: Eq[t] }, index)) =>
val indexExpr = Expr(index)
val e1 = '{ $x.productElement($indexExpr).asInstanceOf[t] }
val e2 = '{ $y.productElement($indexExpr).asInstanceOf[t] }
'{ $acc && $elem.eqv($e1, $e2) }
}
}
'{ eqProduct((x: T, y: T) => ${eqProductBody('x.asExprOf[Product], 'y.asExprOf[Product])}) }

// case for Mirror.ProductOf[T]
// ...
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16 changes: 8 additions & 8 deletions tests/run-macros/i8007/Macro_3.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -40,17 +40,17 @@ object Eq {
ev match {
case '{ $m: Mirror.ProductOf[T] { type MirroredElemTypes = elementTypes }} =>
val elemInstances = summonAll[elementTypes]
def eqProductBody(x: Expr[T], y: Expr[T])(using Quotes): Expr[Boolean] = {
elemInstances.zipWithIndex.foldLeft(Expr(true: Boolean)) {
case (acc, (elem, index)) =>
val e1 = '{$x.asInstanceOf[Product].productElement(${Expr(index)})}
val e2 = '{$y.asInstanceOf[Product].productElement(${Expr(index)})}

'{ $acc && $elem.asInstanceOf[Eq[Any]].eqv($e1, $e2) }
def eqProductBody(x: Expr[Product], y: Expr[Product])(using Quotes): Expr[Boolean] = {
elemInstances.zipWithIndex.foldLeft(Expr(true)) {
case (acc, ('{ $elem: Eq[t]}, index)) =>
val indexExpr = Expr(index)
val e1 = '{ $x.productElement($indexExpr).asInstanceOf[t] }
val e2 = '{ $y.productElement($indexExpr).asInstanceOf[t] }
'{ $acc && $elem.eqv($e1, $e2) }
}
}
'{
eqProduct((x: T, y: T) => ${eqProductBody('x, 'y)})
eqProduct((x: T, y: T) => ${eqProductBody('x.asExprOf[Product], 'y.asExprOf[Product])})
}

case '{ $m: Mirror.SumOf[T] { type MirroredElemTypes = elementTypes }} =>
Expand Down