Fix #4734: Pickle positions for quotes

compiler/src/dotty/tools/dotc/core/quoted/PickledQuotes.scala

@@ -8,10 +8,11 @@ import dotty.tools.dotc.core.Contexts._
 import dotty.tools.dotc.core.Decorators._
 import dotty.tools.dotc.core.StdNames._
 import dotty.tools.dotc.core.NameKinds
+import dotty.tools.dotc.core.Mode
 import dotty.tools.dotc.core.Symbols._
 import dotty.tools.dotc.core.Types.Type
 import dotty.tools.dotc.core.tasty.TreePickler.Hole
-import dotty.tools.dotc.core.tasty.{TastyPickler, TastyPrinter, TastyString}
+import dotty.tools.dotc.core.tasty.{PositionPickler, TastyPickler, TastyPrinter, TastyString}
 import dotty.tools.dotc.core.tasty.TreeUnpickler.UnpickleMode
 
 import scala.quoted.Types._
@@ -66,13 +67,13 @@ object PickledQuotes {
   /** Unpickle the tree contained in the TastyExpr */
   private def unpickleExpr(expr: TastyExpr[_])(implicit ctx: Context): Tree = {
     val tastyBytes = TastyString.unpickle(expr.tasty)
-    unpickle(tastyBytes, expr.args, isType = false)
+    unpickle(tastyBytes, expr.args, isType = false)(ctx.addMode(Mode.ReadPositions))
   }
 
   /** Unpickle the tree contained in the TastyType */
   private def unpickleType(ttpe: TastyType[_])(implicit ctx: Context): Tree = {
     val tastyBytes = TastyString.unpickle(ttpe.tasty)
-    unpickle(tastyBytes, ttpe.args, isType = true)
+    unpickle(tastyBytes, ttpe.args, isType = true)(ctx.addMode(Mode.ReadPositions))
   }
 
   // TASTY picklingtests/pos/quoteTest.scala
@@ -85,6 +86,8 @@ object PickledQuotes {
     treePkl.compactify()
     pickler.addrOfTree = treePkl.buf.addrOfTree
     pickler.addrOfSym = treePkl.addrOfSym
+    if (tree.pos.exists)
+      new PositionPickler(pickler, treePkl.buf.addrOfTree).picklePositions(tree :: Nil)
 
     if (pickling ne noPrinter)
       println(i"**** pickling quote of \n${tree.show}")

tests/pos/i4734/Macro_1.scala

@@ -0,0 +1,12 @@
+import scala.annotation.tailrec
+import scala.quoted._
+
+object Macros {
+  transparent def unrolledForeach(f: Int => Int): Int =
+  ~unrolledForeachImpl('(f))
+
+  def unrolledForeachImpl(f: Expr[Int => Int]): Expr[Int] = '{
+    val size: Int = 5
+    (~f)(3)
+  }
+}

tests/pos/i4734/Test_2.scala

@@ -0,0 +1,8 @@
+import scala.quoted._
+import Macros._
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    unrolledForeach((x: Int) => 2)
+  }
+}

tests/run/i4734.check

@@ -0,0 +1,21 @@
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tests/run/i4734/Macro_1.scala

@@ -0,0 +1,33 @@
+import scala.annotation.tailrec
+import scala.quoted._
+
+object Macros {
+  transparent def unrolledForeach(seq: IndexedSeq[Int], f: => Int => Unit, transparent unrollSize: Int): Unit = // or f: Int => Unit
+    ~unrolledForeachImpl('(seq), '(f), unrollSize)
+
+  def unrolledForeachImpl(seq: Expr[IndexedSeq[Int]], f: Expr[Int => Unit], unrollSize: Int): Expr[Unit] = '{
+    val size = (~seq).length
+    assert(size % (~unrollSize.toExpr) == 0) // for simplicity of the implementation
+    var i = 0
+    while (i < size) {
+      ~{
+        for (j <- new UnrolledRange(0, unrollSize)) '{
+          val index = i + ~j.toExpr
+          val element = (~seq)(index)
+          ~f('(element)) // or `(~f)(element)` if `f` should not be inlined
+        }
+      }
+      i += ~unrollSize.toExpr
+    }
+
+  }
+
+  class UnrolledRange(start: Int, end: Int) {
+    def foreach(f: Int => Expr[Unit]): Expr[Unit] = {
+      @tailrec def loop(i: Int, acc: Expr[Unit]): Expr[Unit] =
+        if (i >= 0) loop(i - 1, '{ ~f(i); ~acc })
+      else acc
+      loop(end - 1, '())
+    }
+  }
+}

tests/run/i4734/Test_2.scala

@@ -0,0 +1,9 @@
+import scala.quoted._
+import Macros._
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    val seq = IndexedSeq.tabulate[Int](21)(x => x)
+    unrolledForeach(seq, (x: Int) => println(2*x), 3)
+  }
+}