Demonstrate issue uncovered by previous commit

> run -Xprint-types -Ytest-pickler -Ystop-after:pickler tests/pos/pickleinf.scala
[error] (no source file, offset = 0): error: value of type <notype> does not take parameters

The issue seems to be that the type of $1$.bar is incorrect:
sel: Select(Ident($1$),bar)
sel.tpe.widen: MethodType(List(name, dummy),
  List(TypeRef(TermRef(NoPrefix,$1$),Bar$$N), TypeRef(TermRef(ThisType(TypeRef(NoPrefix,<root>)),scala),Int)),
  TypeRef(TermRef(ThisType(TypeRef(NoPrefix,<root>)),scala),Int))
sel.tpe.signature: Signature(List(java.lang.Object, scala.Int),scala.Int)

In the type, the first argument has type `Bar$$N`, but its type should
be constrained to `Int`, the result is that in the signature the first
parameter has type `Object` instead of `Int`.

Author: smarter

src/dotty/tools/dotc/core/tasty/TreePickler.scala

@@ -311,6 +311,9 @@ class TreePickler(pickler: TastyPickler) {
           case tp: NamedType if tp.name.isShadowedName => tp.name
           case _ => name
         }
+        println("sel: " + tree)
+        println("sel.tpe.widen: " + tree.tpe.widen)
+        println("sel.tpe.signature: " + tree.tpe.signature)
         val sig = tree.tpe.signature
         if (sig == Signature.NotAMethod) pickleName(realName)
         else pickleNameAndSig(realName, sig)

test/dotc/tests.scala

@@ -53,6 +53,7 @@ class tests extends CompilerTest {
 // This directory doesn't exist anymore
 // @Test def pickle_pickling = compileDir(coreDir, "pickling", testPickling)
   @Test def pickle_ast = compileDir(dotcDir, "ast", testPickling)
+  @Test def pickle_inf = compileFile(posDir, "pickleinf", testPickling)
 
   //@Test def pickle_core = compileDir(dotcDir, "core", testPickling, xerrors = 2) // two spurious comparison errors in Types and TypeOps
 

tests/pos/pickleinf.scala

@@ -0,0 +1,9 @@
+class Bar[N] {
+  def bar(name: N, dummy: Int = 42): Int = 0
+}
+
+object Test {
+  def test(): Unit = {
+    (new Bar).bar(10)
+  }
+}