ByName trees

Author: odersky

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

@@ -428,7 +428,7 @@ class RefinedPrinter(_ctx: Context) extends PlainPrinter(_ctx) {
           changePrec (GlobalPrec) {
             keywordStr("throw ") ~ toText(args.head)
           }
-        else if fun.symbol == defn.byNameMethod && !printDebug then
+        else if fun.symbol == defn.byNameMethod && !printDebug && !ctx.settings.YtestPickler.value then
           toText(args.head)
         else if (!printDebug && fun.hasType && fun.symbol == defn.QuotedRuntime_exprQuote)
           keywordStr("'{") ~ toTextGlobal(args, ", ") ~ keywordStr("}")

compiler/src/dotty/tools/dotc/transform/TreeChecker.scala

@@ -222,6 +222,13 @@ class TreeChecker extends Phase with SymTransformer {
       res
     }
 
+    val arguments: mutable.Set[untpd.Tree] = mutable.Set()
+    private def withArgs[T](args: List[untpd.Tree])(op: => T): T =
+      arguments ++= args
+      val res = op
+      arguments --= args
+      res
+
     def assertDefined(tree: untpd.Tree)(using Context): Unit =
       if (tree.symbol.maybeOwner.isTerm) {
         val sym = tree.symbol
@@ -446,6 +453,16 @@ class TreeChecker extends Phase with SymTransformer {
             typed(tree.expr, pt1)
       untpd.cpy.Typed(tree)(expr1, tpt1).withType(tree.typeOpt)
 
+    override def typedApply(tree: untpd.Apply, pt: Type)(using Context): Tree =
+      if tree.fun.symbol == defn.byNameMethod then
+        assert(arguments.contains(tree),
+          i"unexpected <by-name> application $tree,\nwhich is not a method argument")
+        ByName(typedUnadapted(tree.args.head, pt.widenByName))
+      else
+        withArgs(tree.args) {
+          super.typedApply(tree, pt)
+        }
+
     private def checkOwner(tree: untpd.Tree)(using Context): Unit = {
       def ownerMatches(symOwner: Symbol, ctxOwner: Symbol): Boolean =
         symOwner == ctxOwner ||