Fixes x.toString causing auto-application warnings under -Xsource:2.14

Fixes scala/bug#11639
Fixes scala/bug#11657

The compiler gets confused about the lineage of `toString` apparently, so instead of trying to look for the Java flag, I am just going to see if the name exists under `AnyTpe`.

Author: eed3si9n

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

@@ -959,6 +959,7 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
           doIt
         }
 
+        def isAnyDerived(sym: Symbol): Boolean = AnyTpe.nonPrivateMember(sym.name) != NoSymbol
 
         // (4.2) condition for auto-application by -Xsource level
         //
@@ -971,10 +972,11 @@ trait Typers extends Adaptations with Tags with TypersTracking with PatternTyper
         //          > val vparamSymssOrEmptyParamsFromOverride =
         //          This means an accessor that overrides a Java-defined method gets a MethodType instead of a NullaryMethodType, which breaks lots of assumptions about accessors)
         def checkCanAutoApply(): Boolean = {
-          if (sourceLevel2_14 && !meth.isJavaDefined)
+          if (sourceLevel2_14 && !meth.isJavaDefined && !isAnyDerived(meth)) {
             context.deprecationWarning(tree.pos, NoSymbol, s"Auto-application to `()` is deprecated. Supply the empty argument list `()` explicitly to invoke method ${meth.decodedName},\n" +
                                                            s"or remove the empty argument list from its definition (Java-defined methods are exempt).\n"+
                                                            s"In Scala 3, an unapplied method like this will be eta-expanded into a function.", "2.14.0")
+          }
           true
         }
 

test/files/pos/auto-application.scala

@@ -0,0 +1,31 @@
+// scalac: -Werror -deprecation -Xsource:2.14
+//
+class Test {
+  def a1(xs: List[String]): Int = xs.hashCode
+  def a2(xs: List[String]): Int = xs.hashCode()
+  def a3(xs: List[String]): String = xs.toString
+  def a4(xs: List[String]): String = xs.toString()
+  def a5(xs: List[String]): Class[_] = xs.getClass
+  def a6(xs: List[String]): Class[_] = xs.getClass()
+  def a7(xs: List[String]): Int = xs.##
+  def a8(xs: List[String]): Int = xs.##()
+  def a9(x: Address): String = x.toString
+  def a10(x: Address): String = x.toString()
+  def a11(x: A): String = x.toString
+  def a12(x: A): String = x.toString()
+  def a13(x: B): String = x.toString
+  def a14(x: B): String = x.toString()
+}
+
+case class Address()
+
+class A() {
+  override def toString(): String = "A()"
+}
+
+class B() {
+  override def toString: String = "B()"
+}
+
+case class C(c: Int) extends AnyVal
+