Adapt changes from main repo:

Detect @NotNull fields
Detect @NotNull reference in call chains
Enum constants are non-nullable
by Andrey Ponomarev

tests/testData/ast/annotations/file/jetbrainsNotNullChainExpr.jav

@@ -0,0 +1,22 @@
+package test;
+
+import org.jetbrains.annotations.NotNull;
+
+class Foo {
+   void execute() {}
+}
+
+class Bar {
+  @NotNull
+  Foo fooNotNull = Foo();
+  Foo fooNullable = null;
+}
+
+class Test {
+  public void test(@NotNull Bar barNotNull, Bar barNullable) {
+    barNotNull.fooNotNull.execute();
+    barNotNull.fooNullable.execute();
+    barNullable.fooNotNull.execute();
+    barNullable.fooNullable.execute();
+  }
+}

tests/testData/ast/annotations/file/jetbrainsNotNullChainExpr.kt

@@ -0,0 +1,17 @@
+package test
+open class Foo() {
+open fun execute() : Unit {
+}
+}
+open class Bar() {
+var fooNotNull : Foo = Foo()
+var fooNullable : Foo? = null
+}
+open class Test() {
+public open fun test(barNotNull : Bar, barNullable : Bar?) : Unit {
+barNotNull.fooNotNull.execute()
+barNotNull.fooNullable?.execute()
+barNullable?.fooNotNull?.execute()
+barNullable?.fooNullable?.execute()
+}
+}

tests/testData/ast/enum/class/enumConstantIsNotNull.jav

@@ -0,0 +1,7 @@
+enum E {
+  FOO;
+
+  void foo() {
+    FOO.toString();
+  }
+}

tests/testData/ast/enum/class/enumConstantIsNotNull.kt

@@ -0,0 +1,6 @@
+enum class E {
+FOO
+fun foo() : Unit {
+FOO.toString()
+}
+}