Handling null correctly when wrapping function in SAM wrapper

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

@@ -1928,7 +1928,22 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
             Type functionType = typeMapper.mapType(samInterface.getFunctionTypeForSamInterface());
             expression.accept(visitor, StackValue.none()).put(functionType, v);
 
+            Label ifNonNull = new Label();
+            Label afterAll = new Label();
+
+            v.dup();
+            v.ifnonnull(ifNonNull);
+
+            // if null: pop function value and wrapper objects, put null
+            v.pop();
+            v.pop2();
+            v.aconst(null);
+            v.goTo(afterAll);
+
+            v.mark(ifNonNull);
             v.invokespecial(className.getInternalName(), "<init>", Type.getMethodDescriptor(Type.VOID_TYPE, functionType));
+
+            v.mark(afterAll);
             return StackValue.onStack(className.getAsmType());
         }
     }

compiler/testData/codegen/boxWithJava/samAdapters/nonLiteralNull.java

@@ -0,0 +1,5 @@
+class JavaClass {
+    public static String run(Runnable r) {
+        return r == null ? "OK" : "FAIL";
+    }
+}

compiler/testData/codegen/boxWithJava/samAdapters/nonLiteralNull.kt

@@ -0,0 +1,4 @@
+fun box(): String {
+    val f: (() -> Unit)? = null
+    return JavaClass.run(f)!!
+}

compiler/tests/org/jetbrains/jet/codegen/generated/BlackBoxWithJavaCodegenTestGenerated.java

@@ -191,6 +191,11 @@ public class BlackBoxWithJavaCodegenTestGenerated extends AbstractBlackBoxCodege
             doTestWithJava("compiler/testData/codegen/boxWithJava/samAdapters/nonLiteralInConstructor.kt");
         }
         
+        @TestMetadata("nonLiteralNull.kt")
+        public void testNonLiteralNull() throws Exception {
+            doTestWithJava("compiler/testData/codegen/boxWithJava/samAdapters/nonLiteralNull.kt");
+        }
+        
         @TestMetadata("nonLiteralRunnable.kt")
         public void testNonLiteralRunnable() throws Exception {
             doTestWithJava("compiler/testData/codegen/boxWithJava/samAdapters/nonLiteralRunnable.kt");