SI-8417 Check adapts of each param section

src/compiler/scala/tools/nsc/typechecker/Adaptations.scala

@@ -80,7 +80,9 @@ trait Adaptations {
           context.deprecationWarning(t.pos, t.symbol, adaptWarningMessage(msg), "2.11.0")
         }
       } else if (settings.warnAdaptedArgs)
-        context.warning(t.pos, adaptWarningMessage(s"Adapting argument list by creating a ${args.size}-tuple: this may not be what you want."))
+        context.warning(t.pos, adaptWarningMessage(
+          s"Adapting argument list by creating a ${args.size}-tuple: this may not be what you want.")
+        )
 
       // return `true` if the adaptation should be kept
       !(settings.noAdaptedArgs || (args.isEmpty && settings.future))

src/compiler/scala/tools/nsc/typechecker/Typers.scala

@@ -3426,29 +3426,29 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
           // repeat vararg as often as needed, remove by-name
           val formals = formalTypes(paramTypes, argslen)
 
-          /* Try packing all arguments into a Tuple and apply `fun`
-           * to that. This is the last thing which is tried (after
-           * default arguments)
+          /* Try packing all arguments into a Tuple and apply `fun` to that.
+           * This is the last thing which is tried (after default arguments).
            */
-          def tryTupleApply: Tree = {
-            if (eligibleForTupleConversion(paramTypes, argslen) && !phase.erasedTypes) {
+          def tryTupleApply: Tree =
+            if (phase.erasedTypes || !eligibleForTupleConversion(paramTypes, argslen)) EmptyTree
+            else {
               val tupleArgs = List(atPos(tree.pos.makeTransparent)(gen.mkTuple(args)))
               // expected one argument, but got 0 or >1 ==>  try applying to tuple
               // the inner "doTypedApply" does "extractUndetparams" => restore when it fails
               val savedUndetparams = context.undetparams
-              silent(_.doTypedApply(tree, fun, tupleArgs, mode, pt)) map { t =>
-                // Depending on user options, may warn or error here if
-                // a Unit or tuple was inserted.
-                val keepTree = (
-                     !mode.typingExprNotFun // why? introduced in 4e488a60, doc welcome
-                  || t.symbol == null       // ditto
-                  || checkValidAdaptation(t, args)
-                )
-                if (keepTree) t else EmptyTree
-              } orElse { _ => context.undetparams = savedUndetparams ; EmptyTree }
+              // May warn or error if a Unit or tuple was inserted.
+              def validate(t: Tree): Tree = {
+                // regardless of typer's mode
+                val invalidAdaptation = t.symbol != null && !checkValidAdaptation(t, args)
+                // only bail if we're typing an expression (and not inside another application)
+                if (invalidAdaptation && mode.typingExprNotFun) EmptyTree else t
+              }
+              def reset(errors: Seq[AbsTypeError]): Tree = {
+                context.undetparams = savedUndetparams
+                EmptyTree
+              }
+              silent(_.doTypedApply(tree, fun, tupleArgs, mode, pt)).map(validate).orElse(reset)
             }
-            else EmptyTree
-          }
 
           /* Treats an application which uses named or default arguments.
            * Also works if names + a vararg used: when names are used, the vararg

test/files/neg/t8417.check

@@ -0,0 +1,15 @@
+t8417.scala:5: warning: Adapting argument list by creating a 2-tuple: this may not be what you want.
+        signature: T.f(x: Any)(y: Any): String
+  given arguments: "hello", "world"
+ after adaptation: T.f(("hello", "world"): (String, String))
+  def g = f("hello", "world")("holy", "moly")
+           ^
+t8417.scala:5: warning: Adapting argument list by creating a 2-tuple: this may not be what you want.
+        signature: T.f(x: Any)(y: Any): String
+  given arguments: "holy", "moly"
+ after adaptation: T.f(("holy", "moly"): (String, String))
+  def g = f("hello", "world")("holy", "moly")
+                             ^
+error: No warnings can be incurred under -Xfatal-warnings.
+two warnings found
+one error found

test/files/neg/t8417.flags

@@ -0,0 +1 @@
+-Xfatal-warnings -Ywarn-adapted-args

test/files/neg/t8417.scala

@@ -0,0 +1,6 @@
+
+
+trait T {
+  def f(x: Any)(y: Any) = "" + x + y
+  def g = f("hello", "world")("holy", "moly")
+}