Merge pull request #4255 from dotty-staging/pretty-print-lambda

Simplify decompiler printer for lambda

Author: nicolasstucki

compiler/src/dotty/tools/dotc/printing/DecompilerPrinter.scala

@@ -5,6 +5,7 @@ import dotty.tools.dotc.ast.untpd.{PackageDef, Template, TypeDef}
 import dotty.tools.dotc.ast.{Trees, untpd}
 import dotty.tools.dotc.printing.Texts._
 import dotty.tools.dotc.core.Contexts._
+import dotty.tools.dotc.core.StdNames.nme
 import dotty.tools.dotc.core.Flags._
 import dotty.tools.dotc.core.Symbols._
 import dotty.tools.dotc.core.StdNames._
@@ -16,15 +17,19 @@ class DecompilerPrinter(_ctx: Context) extends RefinedPrinter(_ctx) {
   override protected def filterModTextAnnots(annots: List[untpd.Tree]): List[untpd.Tree] =
     annots.filter(_.tpe != defn.SourceFileAnnotType)
 
-  override protected def blockText[T >: Untyped](trees: List[Trees.Tree[T]]): Text = {
-    trees match {
-      case DefDef(_, _, _, _, Trees.If(cond, Trees.Block(body :: Nil, _), _)) :: y :: Nil if y.symbol.name == nme.WHILE_PREFIX =>
+  override protected def blockToText[T >: Untyped](block: Block[T]): Text =
+    block match {
+      case Block(DefDef(_, _, _, _, Trees.If(cond, Trees.Block(body :: Nil, _), _)) :: Nil, y) if y.symbol.name == nme.WHILE_PREFIX =>
         keywordText("while") ~ " (" ~ toText(cond) ~ ")" ~ toText(body)
-      case DefDef(_, _, _, _, Trees.Block(body :: Nil, Trees.If(cond, _, _))) :: y :: Nil if y.symbol.name == nme.DO_WHILE_PREFIX =>
+      case Block(DefDef(_, _, _, _, Trees.Block(body :: Nil, Trees.If(cond, _, _))) :: Nil, y) if y.symbol.name == nme.DO_WHILE_PREFIX =>
         keywordText("do") ~ toText(body) ~ keywordText("while") ~ " (" ~ toText(cond) ~ ")"
-      case _ => super.blockText(trees.filterNot(_.isInstanceOf[Closure[_]]))
+      case Block((meth @ DefDef(nme.ANON_FUN, _, _, _, _)) :: Nil, _: Closure[T]) =>
+        withEnclosingDef(meth) {
+          addVparamssText("", meth.vparamss) ~ " => " ~ toText(meth.rhs)
+        }
+      case _ =>
+        super.blockToText(block)
     }
-  }
 
   override protected def packageDefText(tree: PackageDef): Text = {
     val stats = tree.stats.filter {
@@ -53,16 +58,4 @@ class DecompilerPrinter(_ctx: Context) extends RefinedPrinter(_ctx) {
     val impl1 = impl.copy(parents = impl.parents.filterNot(_.symbol.maybeOwner == defn.ObjectClass))
     super.toTextTemplate(impl1, ofNew)
   }
-
-  override protected def defDefToText[T >: Untyped](tree: DefDef[T]): Text = {
-    import untpd.{modsDeco => _, _}
-    dclTextOr(tree) {
-      val printLambda = tree.symbol.isAnonymousFunction
-      val prefix = modText(tree.mods, keywordStr("def")) ~~ valDefText(nameIdText(tree)) provided (!printLambda)
-      withEnclosingDef(tree) {
-        addVparamssText(prefix ~ tparamsText(tree.tparams), tree.vparamss) ~ optAscription(tree.tpt).provided(!printLambda) ~
-          optText(tree.rhs)((if (printLambda) " => " else " = ") ~ _)
-      }
-    }
-  }
 }

compiler/src/dotty/tools/dotc/printing/RefinedPrinter.scala

@@ -226,6 +226,9 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
   protected def exprToText(tp: ExprType): Text =
     "=> " ~ toText(tp.resType)
 
+  protected def blockToText[T >: Untyped](block: Block[T]): Text =
+    blockText(block.stats :+ block.expr)
+
   protected def blockText[T >: Untyped](trees: List[Tree[T]]): Text =
     ("{" ~ toText(trees, "\n") ~ "}").close
 
@@ -332,8 +335,8 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
         toText(name) ~ " = " ~ toText(arg)
       case Assign(lhs, rhs) =>
         changePrec(GlobalPrec) { toTextLocal(lhs) ~ " = " ~ toText(rhs) }
-      case Block(stats, expr) =>
-        blockText(stats :+ expr)
+      case block: Block =>
+        blockToText(block)
       case If(cond, thenp, elsep) =>
         changePrec(GlobalPrec) {
           keywordStr("if ") ~ toText(cond) ~ (keywordText(" then") provided !cond.isInstanceOf[Parens]) ~~ toText(thenp) ~ optText(elsep)(keywordStr(" else ") ~ _)

tests/pos/lambda.decompiled

@@ -3,10 +3,13 @@ out/posTestFromTasty/pos/lambda/foo/Foo.class
 --------------------------------------------------------------------------------
 package foo {
   class Foo() {
-    val a: Int => Int =
-      {
-        (x: Int) => x.*(x)
-      }
+    {
+      (x: Int) =>
+        {
+          2
+        }
+    }
+    val a: Int => Int = (x: Int) => x.*(x)
   }
 }
 --------------------------------------------------------------------------------

tests/pos/lambda.scala

@@ -1,4 +1,7 @@
 package foo
 class Foo {
+  {
+    (x: Int) => 2
+  }
   val a = (x: Int) => x * x
 }

tests/run-with-compiler/i3876-c.check

@@ -6,9 +6,6 @@
       {
         def apply(x: Int): Int
       }
-   = 
-    {
-      (x: Int) => x.+(x)
-    }
+   = (x: Int) => x.+(x)
   (f: (x: Int) => Int).apply(x$1)
 }

tests/run-with-compiler/quote-run-staged-interpreter.check

@@ -1,6 +1,4 @@
-{
-  (x: Int) => 2.+(x).+(4)
-}
+(x: Int) => 2.+(x).+(4)
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 8
 9