Add CodegenUtil.isNullableType(), fix assertions

JetType.isNullable() is not accurate when the type denotes a type parameter:
a parameter can be not null (isNullable=false), but its upper bound can be
nullable (<T: Any?>), so null may appear in the value of such type. Therefore
it's preferred to use a special check (isNullableType()) in codegen from now on

Do not generate assertion for parameters of not-null types which have a
nullable upper bound + the same with Java method calls

Also fix Intrinsics class internal name in tests

 #KT-3313 Fixed

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

@@ -47,6 +47,7 @@ import java.util.Set;
 
 import static org.jetbrains.asm4.Opcodes.*;
 import static org.jetbrains.jet.codegen.CodegenUtil.isInterface;
+import static org.jetbrains.jet.codegen.CodegenUtil.isNullableType;
 import static org.jetbrains.jet.lang.resolve.DescriptorUtils.isClassObject;
 import static org.jetbrains.jet.lang.resolve.java.AsmTypeConstants.JAVA_STRING_TYPE;
 
@@ -532,7 +533,7 @@ public class AsmUtil {
 
         for (ValueParameterDescriptor parameter : descriptor.getValueParameters()) {
             JetType type = parameter.getReturnType();
-            if (type == null || type.isNullable()) continue;
+            if (type == null || isNullableType(type)) continue;
 
             int index = frameMap.getIndex(parameter);
             Type asmType = state.getTypeMapper().mapReturnType(type);
@@ -574,7 +575,7 @@ public class AsmUtil {
         if (!isDeclaredInJava(descriptor, state.getBindingContext())) return;
 
         JetType type = descriptor.getReturnType();
-        if (type == null || type.isNullable()) return;
+        if (type == null || isNullableType(type)) return;
 
         Type asmType = state.getTypeMapper().mapReturnType(type);
         if (asmType.getSort() == Type.OBJECT || asmType.getSort() == Type.ARRAY) {

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

@@ -41,6 +41,7 @@ import org.jetbrains.jet.lang.resolve.java.JvmStdlibNames;
 import org.jetbrains.jet.lang.resolve.name.Name;
 import org.jetbrains.jet.lang.resolve.scopes.JetScope;
 import org.jetbrains.jet.lang.types.JetType;
+import org.jetbrains.jet.lang.types.TypeUtils;
 import org.jetbrains.jet.lang.types.lang.KotlinBuiltIns;
 
 import java.util.*;
@@ -278,5 +279,16 @@ public class CodegenUtil {
                         return ((MemberDescriptor) declaration).getModality() == ABSTRACT;
                     }
                 });
-}
+    }
+
+    /**
+     * A work-around of the generic nullability problem in the type checker
+     * @return true if a value of this type can be null
+     */
+    public static boolean isNullableType(@NotNull JetType type) {
+        if (type.getConstructor().getDeclarationDescriptor() instanceof TypeParameterDescriptor) {
+            return TypeUtils.hasNullableSuperType(type);
+        }
+        return type.isNullable();
+    }
 }