Avoid loading compilation unutis twice

Author: nicolasstucki

compiler/src/dotty/tools/dotc/FromTasty.scala

@@ -71,12 +71,13 @@ object FromTasty extends Driver {
       case unit: TASTYCompilationUnit =>
         assert(ctx.settings.YretainTrees.value)
         val className = unit.className.toTypeName
-        val compilationUnits = List(tree(className), tree(className.moduleClassName)).flatMap {
-          case Some((clsd, unpickled)) if !unpickled.isEmpty =>
-            List(CompilationUnit.mkCompilationUnit(clsd, unpickled, forceTrees = true))
-          case _ => Nil
+        def compilationUnit(className: TypeName): Option[CompilationUnit] = {
+          tree(className).flatMap { case (clsd, unpickled) =>
+            if (unpickled.isEmpty) None
+            else Some(CompilationUnit.mkCompilationUnit(clsd, unpickled, forceTrees = true))
+          }
         }
-        compilationUnits
+        compilationUnit(className).orElse(compilationUnit(className.moduleClassName)).toList
     }
 
     private def tree(className: TypeName)(implicit ctx: Context): Option[(ClassDenotation, tpd.Tree)] = {

tests/pos-from-tasty/simpleClassWithObject.scala

@@ -0,0 +1,4 @@
+package foo
+
+class Foo
+object Foo