Added two new compiler options:

  -Ywarn-adapted-args   // also included in -Xlint
  -Yno-adapted-args

The former warns when a () is inserted or an argument list is implicitly
tupled. The latter errors under the same conditions. Using these options
I found several bugs in the distribution which would otherwise be nearly
impossible to spot. These bugs were innocuous (I think) but similar bugs
could easily be (and have been) otherwise.

Certain particularly threatening scenarios are at minimum warned about
regardless of options given. Closes SI-4851, no review.

1 files changed, 11 insertions, 6 deletions

diff --git a/src/compiler/scala/tools/nsc/typechecker/Typers.scala b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
index 13e0f13d4c..4125ab0285 100644
--- a/src/compiler/scala/tools/nsc/typechecker/Typers.scala
+++ b/src/compiler/scala/tools/nsc/typechecker/Typers.scala
@@ -27,7 +27,7 @@ import scala.tools.util.StringOps.{ countAsString, countElementsAsString }
  *  @author  Martin Odersky
  *  @version 1.0
  */
-trait Typers extends Modes {
+trait Typers extends Modes with Adaptations {
   self: Analyzer =>
 
   import global._
@@ -77,7 +77,7 @@ trait Typers extends Modes {
   // that are turned private by typedBlock
   private final val SYNTHETIC_PRIVATE = TRANS_FLAG
 
-  abstract class Typer(context0: Context) extends TyperDiagnostics {
+  abstract class Typer(context0: Context) extends TyperDiagnostics with Adaptation {
     import context0.unit
     import typeDebug.{ ptTree, ptBlock, ptLine }
 
@@ -882,7 +882,7 @@ trait Typers extends Modes {
           typed(atPos(tree.pos)(Select(qual, nme.apply)), mode, pt)
         } else if (!context.undetparams.isEmpty && !inPolyMode(mode)) { // (9)
           assert(!inHKMode(mode)) //@M
-          if ((mode & (EXPRmode | FUNmode)) == EXPRmode && (pt.typeSymbol == UnitClass))
+          if (inExprModeButNot(mode, FUNmode) && pt.typeSymbol == UnitClass)
             instantiateExpectingUnit(tree, mode)
           else
             instantiate(tree, mode, pt)
@@ -898,7 +898,7 @@ trait Typers extends Modes {
           val tree1 = constfold(tree, pt) // (10) (11)
           if (tree1.tpe <:< pt) adapt(tree1, mode, pt, original)
           else {
-            if ((mode & (EXPRmode | FUNmode)) == EXPRmode) {
+            if (inExprModeButNot(mode, FUNmode)) {
               pt.normalize match {
                 case TypeRef(_, sym, _) =>
                   // note: was if (pt.typeSymbol == UnitClass) but this leads to a potentially
@@ -2346,8 +2346,13 @@ trait Typers extends Modes {
               val savedUndetparams = context.undetparams
               silent(_.doTypedApply(tree, fun, tupleArgs, mode, pt)) match {
                 case t: Tree =>
-//                  println("tuple conversion to "+t+" for "+mt)//DEBUG
-                  Some(t)
+                  // Depending on user options, may warn or error here if
+                  // a Unit or tuple was inserted.
+                  Some(t) filter (tupledTree =>
+                       !inExprModeButNot(mode, FUNmode)
+                    || tupledTree.symbol == null
+                    || checkValidAdaptation(tupledTree, args)
+                  )
                 case ex =>
                   context.undetparams = savedUndetparams
                   None