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Add quoted.Expr.block #6747

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Jun 26, 2019
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9 changes: 9 additions & 0 deletions library/src-3.x/scala/quoted/Expr.scala
Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,15 @@ package quoted {
tg.untupled(args => new FunctionAppliedTo[R](f, args.toArray.map(_.asInstanceOf[Expr[_]])))
}

/** Returns A expression containing a block with the given statements and ending with the expresion
* Given list of statements `s1 :: s2 :: ... :: Nil` and an expression `e` the resulting expression
* will be equivalent to `'{ $s1; $s2; ...; $e }`.
*/
def block[T](statements: List[Expr[_]], expr: Expr[T])(implicit refl: tasty.Reflection): Expr[T] = {
import refl._
Block(statements.map(_.unseal), expr.unseal).seal.asInstanceOf[Expr[T]]
}

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It seems this can be done using toExprList and then use quote and splices?

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Functionally it can but it would not solve the recursion issue. But actually I could use this one to improve toExprOfList

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By improve I mean not have a recursive implementation that nests all the trees creating an extremely deep tree.

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I hit a bug trying to implement it. I will leave it for another PR.

}

}
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10 changes: 10 additions & 0 deletions tests/run-macros/quoted-expr-block/quoted_1.scala
Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
import scala.quoted._

inline def replicate(inline times: Int, code: => Any) = ${replicateImpl(times, 'code)}

private def replicateImpl(times: Int, code: Expr[Any]) given tasty.Reflection = {
@annotation.tailrec def loop(n: Int, accum: List[Expr[Any]]): List[Expr[Any]] =
if (n > 0) loop(n - 1, code :: accum) else accum
Expr.block(loop(times, Nil), '{})

}
8 changes: 8 additions & 0 deletions tests/run-macros/quoted-expr-block/quoted_2.scala
Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@

object Test {
def main(args: Array[String]): Unit = {
var a = 0
replicate(500, a += 1)
assert(a == 500, a)
}
}