Fix firstDiff

Author: nicolasstucki

compiler/src/dotty/tools/dotc/typer/Applications.scala

@@ -590,7 +590,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
     private def firstDiff[T <: Trees.Tree[_]](xs: List[T], ys: List[T], n: Int = 0): Int = xs match {
       case x :: xs1 =>
         ys match {
-          case EmptyTree :: ys1 => firstDiff(xs1, ys1, n)
+          case EmptyTree :: ys1 => firstDiff(xs, ys1, n)
           case y :: ys1 => if (x ne y) n else firstDiff(xs1, ys1, n + 1)
           case nil => n
         }
@@ -609,7 +609,7 @@ trait Applications extends Compatibility { self: Typer with Dynamic =>
       val app1 =
         if (!success) app0.withType(UnspecifiedErrorType)
         else {
-          if (!sameSeq(args, orderedArgs) && !isJavaAnnotConstr(methRef.symbol)) {
+          if (!(sameSeq(args, orderedArgs) && !orderedArgs.contains(EmptyTree)) && !isJavaAnnotConstr(methRef.symbol)) {
             // need to lift arguments to maintain evaluation order in the
             // presence of argument reorderings.
             liftFun()

tests/run/i2916.check

@@ -46,3 +46,7 @@
 4
 2
 5
+
+1
+3
+2

tests/run/i2916.scala

@@ -1,6 +1,7 @@
 object Test {
   def p(x: Int) = { println(x); x }
   def foo(x1: Int, x2: Int, x3: Int, x4: Int = p(4), x5: Int = p(5)) = 1
+  def traceIndented(x1: Int, x2: Int = p(2), x3: Int = p(3)) = ()
   def main(args: Array[String]) = {
     foo(p(1), p(2), p(3)) // 1 2 3 4 5
     println()
@@ -21,5 +22,9 @@ object Test {
     println()
 
     { println(0); Test }.foo(p(1), x3 = p(3), x4 = p(4), x2 = p(2)) // 0 1 3 4 2 5
+    println()
+
+    traceIndented(p(1), x3 = p(3))
+
   }
 }