Add decompiler tests

Author: nicolasstucki

compiler/src/dotty/tools/dotc/decompiler/DecompilationPrinter.scala

@@ -1,9 +1,12 @@
 package dotty.tools.dotc
 package decompiler
 
+import java.io.{OutputStream, PrintStream}
+
 import dotty.tools.dotc.core.Contexts._
 import dotty.tools.dotc.core.Phases.Phase
 import dotty.tools.dotc.core.tasty.TastyPrinter
+import dotty.tools.io.{File, Path}
 
 /** Phase that prints the trees in all loaded compilation units.
  *
@@ -14,23 +17,39 @@ class DecompilationPrinter extends Phase {
   override def phaseName: String = "decompilationPrinter"
 
   override def run(implicit ctx: Context): Unit = {
-    val unit = ctx.compilationUnit
+    val outputDir = ctx.settings.outputDir.value
+    if (outputDir == ".") printToOutput(System.out)
+    else {
+      var os: OutputStream = null
+      var ps: PrintStream = null
+      try {
+        os = File(outputDir + ".decompiled").outputStream()
+        ps = new PrintStream(os)
+        printToOutput(ps)
+      } finally {
+        if (os ne null) os.close()
+        if (ps ne null) ps.close()
+      }
+    }
+  }
 
+  private def printToOutput(out: PrintStream)(implicit ctx: Context): Unit = {
+    val unit = ctx.compilationUnit
     val pageWidth = ctx.settings.pageWidth.value
 
     val doubleLine = "=" * pageWidth
     val line = "-" * pageWidth
 
-    println(doubleLine)
-    println(unit.source)
-    println(line)
+    out.println(doubleLine)
+    out.println(unit.source)
+    out.println(line)
 
-    println(unit.tpdTree.show)
-    println(line)
+    out.println(unit.tpdTree.show)
+    out.println(line)
 
     if (ctx.settings.printTasty.value) {
       new TastyPrinter(unit.pickled.head._2).printContents()
-      println(line)
+      out.println(line)
     }
   }
 }

compiler/test/dotty/tools/dotc/FromTastyTests.scala

@@ -22,7 +22,7 @@ class FromTastyTests extends ParallelTesting {
 
   @Test def posTestFromTasty: Unit = {
     implicit val testGroup: TestGroup = TestGroup("posTestFromTasty")
-    val (step1, step2) = compileTastyInDir("../tests/pos", defaultOptions,
+    val (step1, step2, step3) = compileTastyInDir("../tests/pos", defaultOptions,
       blacklist = Set(
         "Meter.scala",
         "NoCyclicReference.scala",
@@ -56,12 +56,13 @@ class FromTastyTests extends ParallelTesting {
     )
     step1.checkCompile() // Compile all files to generate the class files with tasty
     step2.checkCompile() // Compile from tasty
-    (step1 + step2).delete()
+    step3.checkCompile() // Decompile from tasty
+    (step1 + step2 + step3).delete()
   }
 
   @Test def runTestFromTasty: Unit = {
     implicit val testGroup: TestGroup = TestGroup("runTestFromTasty")
-    val (step1, step2) = compileTastyInDir("../tests/run", defaultOptions,
+    val (step1, step2, step3) = compileTastyInDir("../tests/run", defaultOptions,
        blacklist = Set(
          "Course-2002-13.scala",
          "NestedClasses.scala",
@@ -93,7 +94,8 @@ class FromTastyTests extends ParallelTesting {
     )
     step1.checkCompile() // Compile all files to generate the class files with tasty
     step2.checkRuns() // Compile from tasty and run the result
-    (step1 + step2).delete()
+    step3.checkCompile() // Decompile from tasty
+    (step1 + step2 + step3).delete()
   }
 
   private implicit class tastyCompilationTuples(tup: (CompilationTest, CompilationTest)) {