nullability tweaks

compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java

@@ -1378,9 +1378,10 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> {
                 }
             }
             //noinspection ConstantConditions
-            if (isInsideClass &&
-                (propertyDescriptor.getSetter() == null ||
-                 propertyDescriptor.getSetter().isDefault() && propertyDescriptor.getSetter().getModality() == Modality.FINAL)) {
+            if (!propertyDescriptor.isVar() || isInsideClass &&
+                                               (propertyDescriptor.getSetter() == null ||
+                                                propertyDescriptor.getSetter().isDefault() &&
+                                                propertyDescriptor.getSetter().getModality() == Modality.FINAL)) {
                 setter = null;
             }
             else {

compiler/backend/src/org/jetbrains/jet/codegen/FunctionCodegen.java

@@ -18,6 +18,7 @@ package org.jetbrains.jet.codegen;
 
 import com.intellij.openapi.progress.ProcessCanceledException;
 import com.intellij.psi.PsiElement;
+import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.asm4.Label;
 import org.jetbrains.asm4.MethodVisitor;
@@ -420,7 +421,7 @@ public class FunctionCodegen {
             GenerationState state,
             ClassBuilder v,
             Method jvmSignature,
-            @Nullable FunctionDescriptor functionDescriptor,
+            @NotNull FunctionDescriptor functionDescriptor,
             OwnerKind kind
     ) {
         DeclarationDescriptor contextClass = owner.getContextDescriptor().getContainingDeclaration();
@@ -431,9 +432,7 @@ public class FunctionCodegen {
             return;
         }
 
-        boolean needed = isDefaultNeeded(functionDescriptor);
-
-        if (!needed) {
+        if (!isDefaultNeeded(functionDescriptor)) {
             return;
         }
 

compiler/backend/src/org/jetbrains/jet/codegen/JetTypeMapper.java

@@ -908,11 +908,9 @@ public class JetTypeMapper {
         return new JvmPropertyAccessorSignature(jvmMethodSignature, jvmMethodSignature.getKotlinReturnType());
     }
 
-    @Nullable
+    @NotNull
     public JvmPropertyAccessorSignature mapSetterSignature(PropertyDescriptor descriptor, OwnerKind kind) {
-        if (!descriptor.isVar()) {
-            return null;
-        }
+        assert descriptor.isVar();
 
         // TODO: generics signature is not always needed
         BothSignatureWriter signatureWriter = new BothSignatureWriter(BothSignatureWriter.Mode.METHOD, true);