Do not annotate bare type parameters as @Nullable

This is to account for the case of, say

     class Function<R> { fun invoke(): R }

it would be a shame to put @Nullable on the return type of the function, and force all callers to check for null,
so we put no annotations

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

@@ -25,7 +25,6 @@ import org.jetbrains.jet.lang.descriptors.*;
 import org.jetbrains.jet.lang.descriptors.annotations.Annotated;
 import org.jetbrains.jet.lang.descriptors.annotations.AnnotationArgumentVisitor;
 import org.jetbrains.jet.lang.descriptors.annotations.AnnotationDescriptor;
-import org.jetbrains.jet.lang.evaluate.EvaluatePackage;
 import org.jetbrains.jet.lang.psi.JetAnnotationEntry;
 import org.jetbrains.jet.lang.psi.JetClass;
 import org.jetbrains.jet.lang.psi.JetModifierList;
@@ -36,6 +35,7 @@ import org.jetbrains.jet.lang.resolve.constants.*;
 import org.jetbrains.jet.lang.resolve.constants.StringValue;
 import org.jetbrains.jet.lang.resolve.name.FqName;
 import org.jetbrains.jet.lang.types.JetType;
+import org.jetbrains.jet.lang.types.TypeUtils;
 import org.jetbrains.jet.lang.types.lang.KotlinBuiltIns;
 
 import java.lang.annotation.Retention;
@@ -123,6 +123,14 @@ public abstract class AnnotationCodegen {
     private void generateNullabilityAnnotation(@Nullable JetType type, @NotNull Set<String> annotationDescriptorsAlreadyPresent) {
         if (type == null) return;
 
+        if (isBareTypeParameterWithNullableUpperBound(type)) {
+            // This is to account for the case of, say
+            //   class Function<R> { fun invoke(): R }
+            // it would be a shame to put @Nullable on the return type of the function, and force all callers to check for null,
+            // so we put no annotations
+            return;
+        }
+
         boolean isNullableType = CodegenUtil.isNullableType(type);
         if (!isNullableType && KotlinBuiltIns.getInstance().isPrimitiveType(type)) return;
 
@@ -134,6 +142,11 @@ public abstract class AnnotationCodegen {
         }
     }
 
+    private static boolean isBareTypeParameterWithNullableUpperBound(@NotNull JetType type) {
+        ClassifierDescriptor classifier = type.getConstructor().getDeclarationDescriptor();
+        return !type.isNullable() && classifier instanceof TypeParameterDescriptor && TypeUtils.hasNullableSuperType(type);
+    }
+
     private static boolean isVolatile(@NotNull AnnotationDescriptor annotationDescriptor) {
         ClassifierDescriptor classDescriptor = annotationDescriptor.getType().getConstructor().getDeclarationDescriptor();
         return KotlinBuiltIns.getInstance().getVolatileAnnotationClass().equals(classDescriptor);

compiler/testData/asJava/nullabilityAnnotations/Generic.java

@@ -0,0 +1,12 @@
+public interface Generic <N, NN>  extends jet.JetObject {
+    N a(@jet.runtime.typeinfo.JetValueParameter(name = "n") N n);
+
+    @org.jetbrains.annotations.NotNull
+    NN b(@org.jetbrains.annotations.NotNull @jet.runtime.typeinfo.JetValueParameter(name = "nn") NN nn);
+
+    @org.jetbrains.annotations.Nullable
+    N a1(@org.jetbrains.annotations.Nullable @jet.runtime.typeinfo.JetValueParameter(name = "n", type = "?") N n);
+
+    @org.jetbrains.annotations.Nullable
+    NN b1(@org.jetbrains.annotations.Nullable @jet.runtime.typeinfo.JetValueParameter(name = "nn", type = "?") NN nn);
+}

compiler/testData/asJava/nullabilityAnnotations/Generic.kt

@@ -0,0 +1,7 @@
+trait Generic<N, NN: Any> {
+    fun a(n: N): N
+    fun b(nn: NN): NN
+
+    fun a1(n: N?): N?
+    fun b1(nn: NN?): NN?
+}

compiler/tests/org/jetbrains/jet/asJava/NullabilityAnnotationsTest.java

@@ -86,6 +86,10 @@ public class NullabilityAnnotationsTest extends KotlinAsJavaTestBase {
         doTest(getTestName(false));
     }
 
+    public void testGeneric() throws Exception {
+        doTest(getTestName(false));
+    }
+
     private void doTest(@NotNull String fqName) {
         PsiClass psiClass = finder.findClass(fqName, GlobalSearchScope.allScope(getProject()));
         if (!(psiClass instanceof KotlinLightClass)) {