Adapt changes from main repo:

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

src/org/jetbrains/jet/j2k/visitors/ExpressionVisitor.kt

@@ -13,6 +13,7 @@ import java.util.Collections
 import com.intellij.psi.CommonClassNames.*
 import com.intellij.psi.util.PsiTreeUtil
 import org.jetbrains.jet.lang.types.lang.PrimitiveType
+import org.jetbrains.jet.j2k.isAnnotatedAsNotNull
 
 public open class ExpressionVisitor(converter: Converter): StatementVisitor(converter) {
     {
@@ -219,7 +220,8 @@ public open class ExpressionVisitor(converter: Converter): StatementVisitor(conv
         val insideSecondaryConstructor: Boolean = isInsideSecondaryConstructor(expression)
         val hasReceiver: Boolean = isFieldReference && insideSecondaryConstructor
         val isThis: Boolean = isThisExpression(expression)
-        val isNullable: Boolean = getConverter().typeToType(expression.getType()).nullable
+        val notNull = isResolvedToNotNull(expression)
+        val isNullable: Boolean = getConverter().typeToType(expression.getType(), notNull).nullable
         val className: String = getClassNameWithConstructor(expression)
         val referencedName = expression.getReferenceName()!!
         var identifier: Expression = Identifier(referencedName, isNullable)
@@ -262,6 +264,17 @@ public open class ExpressionVisitor(converter: Converter): StatementVisitor(conv
         myResult = CallChainExpression(getConverter().expressionToExpression(qualifier), identifier)
     }
 
+    private fun isResolvedToNotNull(expression: PsiReference): Boolean {
+        val target = expression.resolve()
+        if (target is PsiEnumConstant) {
+            return true;
+        }
+        if (target is PsiModifierListOwner) {
+            return isAnnotatedAsNotNull(target.getModifierList());
+        }
+        return false;
+    }
+
     public override fun visitSuperExpression(expression: PsiSuperExpression?): Unit {
         val qualifier: PsiJavaCodeReferenceElement? = expression?.getQualifier()
         myResult = SuperExpression((if (qualifier != null)

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()
+}
+}