address reviews

Author: nox213

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

@@ -1690,7 +1690,7 @@ class Typer(@constructorOnly nestingLevel: Int = 0) extends Namer
           val tree =
             if (mt.isResultDependent) {
               if (formals.length != defaultArity)
-                untpd.TypeTree()
+                typeTree(WildcardType)
               else
                 untpd.InLambdaTypeTree(isResult = true, (_, syms) => restpe.substParams(mt, syms.map(_.termRef)))
             } else

tests/neg/i123577.check

@@ -0,0 +1,7 @@
+-- [E007] Type Mismatch Error: tests/neg/i123577.scala:11:4 ------------------------------------------------------------
+11 |    (msg: String) => ??? // error
+   |    ^^^^^^^^^^^^^^^^^^^^
+   |    Found:    String => Nothing
+   |    Required: MillRpcChannel
+   |
+   | longer explanation available when compiling with `-explain`