Java to Kotlin converter: honor external Nullable/NotNull annotations

annotations/com/intellij/codeInsight/annotations.xml

@@ -2,4 +2,8 @@
   <item name='com.intellij.codeInsight.CodeInsightSettings com.intellij.codeInsight.CodeInsightSettings getInstance()'>
     <annotation name='org.jetbrains.annotations.NotNull'/>
   </item>
+  <item
+      name='com.intellij.codeInsight.NullableNotNullManager com.intellij.codeInsight.NullableNotNullManager getInstance(com.intellij.openapi.project.Project)'>
+    <annotation name='org.jetbrains.annotations.NotNull'/>
+  </item>
 </root>

j2k/src/org/jetbrains/jet/j2k/TypeConverter.kt

@@ -28,6 +28,7 @@ import org.jetbrains.jet.j2k.ast.assignPrototype
 import com.intellij.psi.CommonClassNames.JAVA_LANG_OBJECT
 import org.jetbrains.jet.j2k.ast.assignNoPrototype
 import org.jetbrains.jet.j2k.ast.ErrorType
+import com.intellij.codeInsight.NullableNotNullManager
 
 class TypeConverter(val settings: ConverterSettings, val conversionScope: ConversionScope) {
     private val nullabilityCache = HashMap<PsiElement, Nullability>()
@@ -274,4 +275,14 @@ class TypeConverter(val settings: ConverterSettings, val conversionScope: Conver
             else -> false
         }
     }
+
+    private fun PsiModifierListOwner.nullabilityFromAnnotations(): Nullability {
+        val manager = NullableNotNullManager.getInstance(getProject())
+        return if (manager.isNotNull(this, false/* we do not check bases because they are checked by callers of this method*/))
+            Nullability.NotNull
+        else if (manager.isNullable(this, false))
+            Nullability.Nullable
+        else
+            Nullability.Default
+    }
 }

j2k/src/org/jetbrains/jet/j2k/Utils.kt

@@ -22,6 +22,8 @@ import com.intellij.psi.util.PsiUtil
 import com.intellij.psi.search.LocalSearchScope
 import com.intellij.psi.search.searches.ReferencesSearch
 import org.jetbrains.jet.j2k.ast.*
+import com.intellij.codeInsight.AnnotationUtil
+import com.intellij.codeInsight.NullableNotNullManager
 
 fun quoteKeywords(packageName: String): String = packageName.split("\\.").map { Identifier.toKotlin(it) }.makeString(".")
 
@@ -47,16 +49,6 @@ fun PsiVariable.countWriteAccesses(scope: PsiElement?): Int
 fun PsiVariable.hasWriteAccesses(scope: PsiElement?): Boolean
         = if (scope != null) findVariableUsages(this, scope).any { PsiUtil.isAccessedForWriting(it) } else false
 
-fun PsiModifierListOwner.nullabilityFromAnnotations(): Nullability {
-    val annotations = getModifierList()?.getAnnotations() ?: return Nullability.Default
-    return if (annotations.any { NOT_NULL_ANNOTATIONS.contains(it.getQualifiedName()) })
-        Nullability.NotNull
-    else if (annotations.any { NULLABLE_ANNOTATIONS.contains(it.getQualifiedName()) })
-        Nullability.Nullable
-    else
-        Nullability.Default
-}
-
 fun getDefaultInitializer(field: Field): Expression {
     val t = field.`type`
     val result = if (t.isNullable) {

j2k/tests/testData/ast/toKotlinClasses/iterableAndIterator.kt

@@ -1,7 +1,7 @@
 package demo
 
 class Test() : Iterable<String> {
-    override fun iterator(): Iterator<String>? {
+    override fun iterator(): Iterator<String> {
         return null
     }
 
@@ -12,7 +12,7 @@ class Test() : Iterable<String> {
 }
 
 class FullTest() : Iterable<String> {
-    override fun iterator(): Iterator<String>? {
+    override fun iterator(): Iterator<String> {
         return null
     }
 

j2k/tests/testData/ast/toKotlinClasses/iterableAndIterator2.kt

@@ -4,7 +4,7 @@ import java.util.*
 import kotlin.Iterator
 
 class Test() : Iterable<String> {
-    override fun iterator(): Iterator<String>? {
+    override fun iterator(): Iterator<String> {
         return null
     }
 
@@ -15,7 +15,7 @@ class Test() : Iterable<String> {
 }
 
 class FullTest() : Iterable<String> {
-    override fun iterator(): Iterator<String>? {
+    override fun iterator(): Iterator<String> {
         return null
     }
 

j2k/tests/testData/ast/toKotlinClasses/iterableAndIterator3.kt

@@ -1,7 +1,7 @@
 package demo
 
 class Test() : Iterable<String> {
-    override fun iterator(): Iterator<String>? {
+    override fun iterator(): Iterator<String> {
         return null
     }