Flatten bocks in Expr.show

Author: nicolasstucki

compiler/src/dotty/tools/dotc/quoted/QuoteDriver.scala

@@ -44,7 +44,8 @@ class QuoteDriver extends Driver {
     def show(tree: Tree, ctx: Context): String = {
       val printer = new DecompilerPrinter(ctx)
       val pageWidth = ctx.settings.pageWidth.value(ctx)
-      printer.toText(tree).mkString(pageWidth, false)
+      val tree1 = (new TreeCleaner).transform(tree)(ctx)
+      printer.toText(tree1).mkString(pageWidth, false)
     }
     withTree(expr, show, settings)
   }

compiler/src/dotty/tools/dotc/quoted/TreeCleaner.scala

@@ -0,0 +1,28 @@
+package dotty.tools.dotc.quoted
+
+import dotty.tools.dotc.ast.Trees._
+import dotty.tools.dotc.ast.tpd
+import dotty.tools.dotc.core.Contexts._
+import dotty.tools.dotc.core.Constants._
+
+/** Clean up quote artifacts from the tree to make it simpler to read.
+ *  - Flattens block and remove blocks with not statements
+ */
+class TreeCleaner extends tpd.TreeMap {
+  import tpd._
+
+  override def transform(tree: Tree)(implicit ctx: Context): Tree = super.transform(tree) match {
+    case Block(Nil, expr1) => expr1
+    case Block(stats1, expr1) =>
+      val flatStats = stats1.flatMap {
+        case Block(stats2, expr2) => stats2 ::: expr2 :: Nil
+        case Literal(Constant(())) => Nil
+        case stat => stat :: Nil
+      }
+      expr1 match {
+        case Block(stats3, expr3) => Block(flatStats ::: stats3, expr3)
+        case expr3 => Block(flatStats, expr3)
+      }
+    case tree1 => tree1
+  }
+}

tests/run-with-compiler/quote-run-2.check

@@ -1,18 +1,12 @@
 1.0
 5.0
 {
+  val y: Double = 5.0.*(5.0)
+  y
+}
+5.0.*(
   {
     val y: Double = 5.0.*(5.0)
     y
   }
-}
-{
-  5.0.*(
-    {
-      {
-        val y: Double = 5.0.*(5.0)
-        y
-      }
-    }
-  )
-}
+)

tests/run-with-compiler/quote-run-constants-extract-1.check

@@ -0,0 +1,5 @@
+3
+4
+abc
+null
+OK

tests/run-with-compiler/quote-run-constants-extract-1.scala

@@ -0,0 +1,15 @@
+import scala.quoted._
+
+import dotty.tools.dotc.quoted.Toolbox._
+
+object Test {
+
+  def main(args: Array[String]): Unit = {
+    (3: Expr[Int]) match { case Constant(n) => println(n) }
+    '(4) match { case Constant(n) => println(n) }
+    '("abc") match { case Constant(n) => println(n) }
+    '(null) match { case Constant(n) => println(n) }
+
+    '(new Object) match { case Constant(n) => println(n); case _ => println("OK") }
+  }
+}

tests/run-with-compiler/quote-run-constants-extract-2.check

@@ -0,0 +1,5 @@
+{
+  val y: Double = 3.0.*(3.0)
+  y
+}
+9.0

tests/run-with-compiler/quote-run-constants-extract-2.scala

@@ -0,0 +1,30 @@
+import scala.quoted._
+
+import dotty.tools.dotc.quoted.Toolbox._
+
+object Test {
+
+  def main(args: Array[String]): Unit = {
+    // 2 is a lifted constant
+    println(power(2, 3.0).show)
+    println(power(2, 3.0).run)
+  }
+
+  def power(n: Expr[Int], x: Expr[Double]): Expr[Double] = {
+    n match {
+      case Constant(n1) => powerCode(n1, x)
+      case _ => '{ dynamicPower(~n, ~x) }
+    }
+  }
+
+  private def powerCode(n: Int, x: Expr[Double]): Expr[Double] =
+    if (n == 0) '(1.0)
+    else if (n == 1) x
+    else if (n % 2 == 0) '{ { val y = ~x * ~x; ~powerCode(n / 2, '(y)) } }
+    else '{ ~x * ~powerCode(n - 1, x) }
+
+  def dynamicPower(n: Int, x: Double): Double =
+    if (n == 0) 1.0
+    else if (n % 2 == 0) dynamicPower(n / 2, x * x)
+    else x * dynamicPower(n - 1, x)
+}

tests/run-with-compiler/quote-run-constants-extract-3.check

@@ -0,0 +1,5 @@
+{
+  val y: Double = 3.0.*(3.0)
+  y
+}
+9.0

tests/run-with-compiler/quote-run-constants-extract-3.scala

@@ -0,0 +1,30 @@
+import scala.quoted._
+
+import dotty.tools.dotc.quoted.Toolbox._
+
+object Test {
+
+  def main(args: Array[String]): Unit = {
+    // 2 is a lifted constant
+    println(power(2, 3.0).show)
+    println(power(2, 3.0).run)
+  }
+
+  def power(n: Expr[Int], x: Expr[Double]): Expr[Double] = {
+    n match {
+      case Constant(n1) => powerCode(n1, x)
+      case _ => '{ dynamicPower(~n, ~x) }
+    }
+  }
+
+  private def powerCode(n: Int, x: Expr[Double]): Expr[Double] =
+    if (n == 0) '(1.0)
+    else if (n == 1) x
+    else if (n % 2 == 0) '{ { val y = ~x * ~x; ~powerCode(n / 2, '(y)) } }
+    else '{ ~x * ~powerCode(n - 1, x) }
+
+  def dynamicPower(n: Int, x: Double): Double =
+    if (n == 0) 1.0
+    else if (n % 2 == 0) dynamicPower(n / 2, x * x)
+    else x * dynamicPower(n - 1, x)
+}

tests/run-with-compiler/quote-run-constants-extract-4.check

@@ -0,0 +1,5 @@
+{
+  val y: Double = 4.0.*(4.0)
+  y
+}
+16.0