Add more tests for escaping local roots

tests/neg-custom-args/captures/escaping-local-roots.scala

@@ -0,0 +1,19 @@
+import language.experimental.captureChecking
+
+trait IO:
+  def use: Unit
+
+object test1 {
+  def foo(c: IO^): IO^{cap[foo]} = c  // error
+}
+
+def test2 = {
+  def foo(c: IO^) =  // error
+    def bar: IO^{cap[foo]} = c
+    bar
+}
+
+object test3 {
+  def foo(c: IO^): IO^{cap[bar]} = ???  // error
+  def bar(c: IO^): IO^{cap[foo]} = ???  // error
+}

tests/neg-custom-args/captures/local-roots-inner-classes.scala

@@ -0,0 +1,9 @@
+import language.experimental.captureChecking
+
+class C[T]:
+  object inner:
+    val x: T^{cap[C]} = ???  // error
+
+class C1[T]:
+  private object inner:
+    val x: T^{cap[C1]} = ???  // ok