Add support for Java fields

Author: noti0na1

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

@@ -3688,7 +3688,7 @@ class Typer extends Namer
       // if unsafeNulls is enabled, try to strip nulls from Java function calls
       if Nullables.unsafeNullsEnabled then
         tree match
-          case _: Apply if tree.symbol.is(JavaDefined) =>
+          case _: Apply | _: Select if tree.symbol.is(JavaDefined) =>
             wtp match
               case OrNull(wtp1) => return readapt(tree.cast(wtp1))
               case _ =>

tests/explicit-nulls/unsafe-common/unsafe-java-call/J.java

@@ -10,4 +10,8 @@ public int f2() {
   public <T> T g1() {
     return null;
   }
+}
+
+class J2<T> {
+  public T x = null;
 }

tests/explicit-nulls/unsafe-common/unsafe-java-call/S.scala

@@ -30,4 +30,8 @@ def clo1[T]: T = j.g1[T]()  // error
 
 def clo2[T <: AnyRef]: T = j.g1[T | Null]()  // error
 
-def clo3[T >: Null <: AnyRef | Null]: T = j.g1[T]()
+def clo3[T >: Null <: AnyRef | Null]: T = j.g1[T]()
+
+def testJ2[T]: T =
+  val j2: J2[T] = new J2
+  j2.x // error