checkNoPrivateLeaks: handle defs in local classes

The access boundary of a def in a local class is the owner of that
class, previously it was set to the access boundary of the owner of the
class instead.

Author: smarter

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

@@ -355,7 +355,7 @@ object Checking {
       var errors: Errors = Nil
 
       def accessBoundary(sym: Symbol): Symbol =
-        if (sym.is(Private)) sym.owner
+        if (sym.is(Private) || !sym.owner.isClass) sym.owner
         else if (sym.privateWithin.exists) sym.privateWithin
         else if (sym.is(Package)) sym
         else accessBoundary(sym.owner)

tests/neg/leaks.scala

@@ -5,3 +5,12 @@ class Outer {
     def foo: x.type = x // error: non-private method foo refers to private value x in its type signature
   }
 }
+
+class Outer3Neg {
+  def meth: Unit = {
+    class Inner {
+      private val x: Int = 1
+      def foo: x.type = x // error
+    }
+  }
+}

tests/pos/leaks.scala

@@ -15,3 +15,13 @@ class Outer2 {
     def foo: Outer2.x.type = Outer2.x // OK
   }
 }
+
+class Outer3 {
+  private val x: Int = 1
+
+  def meth: Unit = {
+    class Inner {
+      def foo: x.type = x // OK
+    }
+  }
+}