Minor refactoring. Replaced some ifs with asserts, added @NotNull/@Nullable annotations.

idea/src/org/jetbrains/jet/plugin/codeInsight/ktSignature/AddKotlinSignatureAnnotation.java

@@ -31,6 +31,7 @@ import com.intellij.psi.util.PsiTreeUtil;
 import com.intellij.util.IncorrectOperationException;
 import com.intellij.util.messages.MessageBusConnection;
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.di.InjectorForJavaSemanticServices;
 import org.jetbrains.jet.lang.BuiltinsScopeExtensionMode;
 import org.jetbrains.jet.lang.descriptors.ClassDescriptor;
@@ -99,9 +100,6 @@ public class AddKotlinSignatureAnnotation extends BaseIntentionAction implements
     public void invoke(@NotNull final Project project, final Editor editor, PsiFile file) throws IncorrectOperationException {
         final PsiMethod method = findMethod(file, editor.getCaretModel().getOffset());
         String signature = getDefaultSignature(project, (PsiMethod) method.getOriginalElement());
-        if (signature == null) {
-            return;
-        }
         final MessageBusConnection busConnection = project.getMessageBus().connect();
         busConnection.subscribe(ExternalAnnotationsManager.TOPIC, new ExternalAnnotationsListener.Adapter() {
             @Override
@@ -128,26 +126,35 @@ public class AddKotlinSignatureAnnotation extends BaseIntentionAction implements
         return new AddAnnotationFix(KOTLIN_SIGNATURE_ANNOTATION, method, signatureToNameValuePairs(method.getProject(), signature));
     }
 
+    @NotNull
     private static String getDefaultSignature(@NotNull Project project, @NotNull PsiMethod method) {
         InjectorForJavaSemanticServices injector = new InjectorForJavaSemanticServices(BuiltinsScopeExtensionMode.ALL, project);
         JavaDescriptorResolver javaDescriptorResolver = injector.getJavaDescriptorResolver();
-        FqName classFqName = new FqName(method.getContainingClass().getQualifiedName());
+
+        PsiClass containingClass = method.getContainingClass();
+        assert containingClass != null;
+        String qualifiedName = containingClass.getQualifiedName();
+        assert qualifiedName != null;
+        FqName classFqName = new FqName(qualifiedName);
+
         if (method.getModifierList().hasModifierProperty(PsiModifier.STATIC)) {
             NamespaceDescriptor namespaceDescriptor = javaDescriptorResolver.resolveNamespace(classFqName);
-            if (namespaceDescriptor == null) return null;
+            assert namespaceDescriptor != null: "Couldn't resolve namespace descriptor for " + classFqName;
             namespaceDescriptor.getMemberScope().getFunctions(Name.identifier(method.getName()));
         }
         else {
             ClassDescriptor classDescriptor = javaDescriptorResolver.resolveClass(classFqName);
-            if (classDescriptor == null) return null;
+            assert classDescriptor != null: "Couldn't resolve class descriptor for " + classFqName;
             classDescriptor.getDefaultType().getMemberScope().getFunctions(Name.identifier(method.getName()));
         }
+
         SimpleFunctionDescriptor functionDescriptor = injector.getBindingTrace().getBindingContext().get(BindingContext.FUNCTION, method);
         assert functionDescriptor != null: "Couldn't find function descriptor for " + method.getName() + " in " + classFqName;
         return RENDERER.render(functionDescriptor);
     }
 
-    private static PsiMethod findMethod(PsiFile file, int offset) {
+    @Nullable
+    private static PsiMethod findMethod(@NotNull PsiFile file, int offset) {
         PsiElement element = file.findElementAt(offset);
         PsiMethod res = PsiTreeUtil.getParentOfType(element, PsiMethod.class);
         if (res == null) return null;

idea/src/org/jetbrains/jet/plugin/codeInsight/ktSignature/EditSignatureBalloon.java

@@ -160,9 +160,8 @@ class EditSignatureBalloon {
         settings.setAdditionalPageAtBottom(false);
         settings.setAdditionalLinesCount(2);
 
-        if (editor instanceof EditorEx) {
+        assert editor instanceof EditorEx;
-            ((EditorEx)editor).setEmbeddedIntoDialogWrapper(true);
+        ((EditorEx)editor).setEmbeddedIntoDialogWrapper(true);
-        }
 
         editor.getColorsScheme().setColor(EditorColors.CARET_ROW_COLOR, editor.getColorsScheme().getDefaultBackground());
 
@@ -208,18 +207,20 @@ class EditSignatureBalloon {
     }
 
     private void saveAndHide() {
+        balloon.hide();
+
         final String newSignature = editor.getDocument().getText();
-        if (!previousSignature.equals(newSignature)) {
+        if (previousSignature.equals(newSignature)) {
-            new WriteCommandAction(project) {
+            return;
-                @Override
-                protected void run(Result result) throws Throwable {
-                    ExternalAnnotationsManager.getInstance(project).editExternalAnnotation(
-                            method, KOTLIN_SIGNATURE_ANNOTATION, signatureToNameValuePairs(project, newSignature));
-                }
-            }.execute();
         }
 
-        balloon.hide();
+        new WriteCommandAction(project) {
+            @Override
+            protected void run(Result result) throws Throwable {
+                ExternalAnnotationsManager.getInstance(project).editExternalAnnotation(
+                        method, KOTLIN_SIGNATURE_ANNOTATION, signatureToNameValuePairs(project, newSignature));
+            }
+        }.execute();
     }
 
     static void invokeEditSignature(@NotNull PsiMethod element, @NotNull Editor editor, @Nullable Point point) {
@@ -231,10 +232,11 @@ class EditSignatureBalloon {
                 if (pair.getName() == null || "value".equals(pair.getName())) {
                     PsiAnnotationMemberValue value = pair.getValue();
                     if (value != null) {
-                        PsiElement firstChild = value.getFirstChild();
                         VirtualFile virtualFile = value.getContainingFile().getVirtualFile();
-                        if (firstChild != null && firstChild.getNode().getElementType() == JavaTokenType.STRING_LITERAL
+                        assert virtualFile != null;
-                            && virtualFile != null) {
+
+                        PsiElement firstChild = value.getFirstChild();
+                        if (firstChild != null && firstChild.getNode().getElementType() == JavaTokenType.STRING_LITERAL) {
                             new OpenFileDescriptor(value.getProject(), virtualFile, value.getTextOffset() + 1).navigate(true);
                         }
                         else {

idea/src/org/jetbrains/jet/plugin/codeInsight/ktSignature/KotlinSignatureUtil.java

@@ -38,7 +38,8 @@ class KotlinSignatureUtil {
     private KotlinSignatureUtil() {
     }
 
-    static PsiMethod getAnnotationOwner(PsiElement element) {
+    @NotNull
+    static PsiMethod getAnnotationOwner(@NotNull PsiElement element) {
         PsiMethod annotationOwner = element.getOriginalElement() instanceof PsiMethod
                                     ? (PsiMethod) element.getOriginalElement()
                                     : (PsiMethod) element;