Merge pull request #4584 from dotty-staging/fix-inline-function

Fix decompilation of while loops

Author: nicolasstucki

library/src/scala/tasty/util/ShowSourceCode.scala

@@ -149,6 +149,39 @@ class ShowSourceCode[T <: Tasty with Singleton](tasty0: T) extends Show[T](tasty
             this
         }
 
+      case While(cond, stats) =>
+        this += "while ("
+        printTree(cond)
+        this += ") "
+        stats match {
+          case stat :: Nil =>
+            printTree(stat)
+          case stats =>
+            this += "{"
+            indented {
+              this += lineBreak()
+              printTrees(stats, lineBreak())
+            }
+            this += lineBreak() += "}"
+        }
+
+      case DoWhile(stats, cond) =>
+        this += "do "
+        stats match {
+          case stat :: Nil =>
+            printTree(stat)
+          case stats =>
+            this += "{"
+            indented {
+              this += lineBreak()
+              printTrees(stats, lineBreak())
+            }
+            this += lineBreak() += "}"
+        }
+        this += " while ("
+        printTree(cond)
+        this += ")"
+
       case ddef@DefDef(name, targs, argss, tpt, rhs) =>
         val flags = ddef.flags
         if (flags.isOverride) sb.append("override ")
@@ -229,7 +262,14 @@ class ShowSourceCode[T <: Tasty with Singleton](tasty0: T) extends Show[T](tasty
         this += " = "
         printTree(rhs)
 
-      case Term.Block(stats, expr) =>
+      case Term.Block(stats0, expr) =>
+        def isLoopEntryPoint(tree: Tree): Boolean = tree match {
+          case Term.Apply(Term.Ident("while$" | "doWhile$"), _) => true
+          case _ => false
+        }
+
+        val stats = stats0.filterNot(isLoopEntryPoint)
+
         expr match {
           case Term.Lambda(_, _) =>
             // Decompile lambda from { def annon$(...) = ...; closure(annon$, ...)}
@@ -239,31 +279,17 @@ class ShowSourceCode[T <: Tasty with Singleton](tasty0: T) extends Show[T](tasty
             this += " => "
             printTree(rhs)
             this += ")"
-
-          case Term.Apply(Term.Ident("while$"), _) =>
-            val DefDef("while$", _, _, _, Some(Term.If(cond, Term.Block(body :: Nil, _), _))) = stats.head
-            this += "while ("
-            printTree(cond)
-            this += ") "
-            printTree(body)
-
-          case Term.Apply(Term.Ident("doWhile$"), _) =>
-            val DefDef("doWhile$", _, _, _, Some(Term.Block(List(body), Term.If(cond, _, _)))) = stats.head
-            this += "do "
-            printTree(body)
-            this += " while ("
-            printTree(cond)
-            this += ")"
-
           case _ =>
             this += "{"
             indented {
               if (!stats.isEmpty) {
                 this += lineBreak()
                 printTrees(stats, lineBreak())
               }
-              this += lineBreak()
-              printTree(expr)
+              if (!isLoopEntryPoint(expr)) {
+                this += lineBreak()
+                printTree(expr)
+              }
             }
             this += lineBreak() += "}"
         }
@@ -739,6 +765,22 @@ class ShowSourceCode[T <: Tasty with Singleton](tasty0: T) extends Show[T](tasty
     }
   }
 
+  private object While {
+    def unapply(arg: Tree)(implicit ctx: Context): Option[(Term, List[Statement])] = arg match {
+      case DefDef("while$", _, _, _, Some(Term.If(cond, Term.Block(bodyStats, _), _))) => Some((cond, bodyStats))
+      case Term.Block(List(tree), _) => unapply(tree)
+      case _ => None
+    }
+  }
+
+  private object DoWhile {
+    def unapply(arg: Tree)(implicit ctx: Context): Option[(List[Statement], Term)] = arg match {
+      case DefDef("doWhile$", _, _, _, Some(Term.Block(body, Term.If(cond, _, _)))) => Some((body, cond))
+      case Term.Block(List(tree), _) => unapply(tree)
+      case _ => None
+    }
+  }
+
   // TODO Provide some of these in scala.tasty.Tasty.scala and implement them using checks on symbols for performance
   private object Types {
 

tests/run/quote-inline-function.check

@@ -0,0 +1,31 @@
+Normal function
+{
+  var i: scala.Int = 0
+  val j: scala.Int = 5
+  while (i.<(j)) {
+    val x$1: scala.Int = i
+    f.apply(x$1)
+    i = i.+(1)
+  }
+  do {
+    val x$2: scala.Int = i
+    f.apply(x$2)
+    i = i.+(1)
+  } while (i.<(j))
+}
+
+By name function
+{
+  var i: scala.Int = 0
+  val j: scala.Int = 5
+  while (i.<(j)) {
+    val x$1: scala.Int = i
+    scala.Predef.println(x$1)
+    i = i.+(1)
+  }
+  do {
+    val x$2: scala.Int = i
+    scala.Predef.println(x$2)
+    i = i.+(1)
+  } while (i.<(j))
+}

tests/run/quote-inline-function/quoted_1.scala

@@ -0,0 +1,25 @@
+import scala.quoted._
+
+import dotty.tools.dotc.quoted.Toolbox._
+
+object Macros {
+
+  inline def foreach1(start: Int, end: Int, f: Int => Unit): String = ~impl('(start), '(end), '(f))
+  inline def foreach2(start: Int, end: Int, f: => Int => Unit): String = ~impl('(start), '(end), '(f))
+
+  def impl(start: Expr[Int], end: Expr[Int], f: Expr[Int => Unit]): Expr[String] = {
+    val res = '{
+      var i = ~start
+      val j = ~end
+      while (i < j) {
+        ~f.apply('(i))
+        i += 1
+      }
+      do {
+        ~f.apply('(i))
+        i += 1
+      } while (i < j)
+    }
+    res.show.toExpr
+  }
+}

tests/run/quote-inline-function/quoted_2.scala

@@ -0,0 +1,13 @@
+import scala.quoted._
+import Macros._
+
+object Test {
+  def main(args: Array[String]): Unit = {
+    println("Normal function")
+    println(foreach1(0, 5, x => println(x)))
+    println()
+
+    println("By name function")
+    println(foreach2(0, 5, x => println(x)))
+  }
+}