Java to Kotlin converter: more smartness about nullability

j2k/tests/testData/ast/nullability/FieldComparedWithNull.java

@@ -1,6 +1,6 @@
 //file
 class C {
-    private String s = "";
+    private String s = x();
 
     void foo() {
         if (s == null) {

j2k/tests/testData/ast/nullability/FieldComparedWithNull.kt

@@ -1,5 +1,5 @@
 class C() {
-    private var s: String? = ""
+    private var s: String? = x()
 
     fun foo() {
         if (s == null) {

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull2.java

@@ -0,0 +1,13 @@
+//file
+interface I {
+    String getString();
+}
+
+class C {
+    void foo(I i) {
+        final String result = i.getString();
+        if (result != null) {
+            print(result);
+        }
+    }
+}

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull2.kt

@@ -0,0 +1,12 @@
+trait I {
+    public fun getString(): String?
+}
+
+class C() {
+    fun foo(i: I) {
+        val result = i.getString()
+        if (result != null) {
+            print(result)
+        }
+    }
+}

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull3.java

@@ -0,0 +1,13 @@
+//file
+interface I {
+    String getString();
+}
+
+class C {
+    void foo(I i) {
+        String result = i.getString();
+        if (result != null) {
+            print(result);
+        }
+    }
+}

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull3.kt

@@ -0,0 +1,12 @@
+trait I {
+    public fun getString(): String?
+}
+
+class C() {
+    fun foo(i: I) {
+        val result = i.getString()
+        if (result != null) {
+            print(result)
+        }
+    }
+}

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull4.java

@@ -0,0 +1,14 @@
+//file
+interface I {
+    String getString();
+}
+
+class C {
+    void foo(I i, boolean b) {
+        String result = i.getString();
+        if (b) result = null;
+        if (result != null) {
+            print(result);
+        }
+    }
+}

j2k/tests/testData/ast/nullability/MethodResultComparedWithNull4.kt

@@ -0,0 +1,14 @@
+trait I {
+    public fun getString(): String
+}
+
+class C() {
+    fun foo(i: I, b: Boolean) {
+        val result = i.getString()
+        if (b)
+            result = null
+        if (result != null) {
+            print(result)
+        }
+    }
+}

j2k/tests/testData/ast/nullability/MethodResultInitializesNullableField.java

@@ -0,0 +1,8 @@
+//file
+import org.jetbrains.annotations.Nullable;
+
+class C {
+    @Nullable private final String string = getString();
+
+    static String getString() { return x(); }
+}

j2k/tests/testData/ast/nullability/MethodResultInitializesNullableField.kt

@@ -0,0 +1,10 @@
+class C() {
+    private val string: String? = getString()
+
+    class object {
+
+        fun getString(): String? {
+            return x()
+        }
+    }
+}