Add Testcase and handle pointer to interfaces in a guard clause

dingo.go

@@ -17,6 +17,7 @@ const (
 
 var ErrInvalidInjectReceiver = errors.New("usage of 'Inject' method with struct receiver is not allowed")
 var traceCircular []circularTraceEntry
+var errPointersToInterface = errors.New(" Do not use pointers to interface.")
 
 // EnableCircularTracing activates dingo's trace feature to find circular dependencies
 // this is super expensive (memory wise), so it should only be used for debugging purposes
@@ -717,7 +718,7 @@ func (injector *Injector) requestInjection(object interface{}, circularTrace []c
 			for fieldIndex := 0; fieldIndex < ctype.NumField(); fieldIndex++ {
 				if tag, ok := ctype.Field(fieldIndex).Tag.Lookup("inject"); ok {
 					field := current.Field(fieldIndex)
-
+					currentFieldName := ctype.Field(fieldIndex).Name
 					if field.Kind() == reflect.Struct {
 						return fmt.Errorf("can not inject into struct %#v of %#v", field, current)
 					}
@@ -743,6 +744,9 @@ func (injector *Injector) requestInjection(object interface{}, circularTrace []c
 					if field.Kind() != reflect.Ptr && field.Kind() != reflect.Interface && instance.Kind() == reflect.Ptr {
 						field.Set(instance.Elem())
 					} else {
+						if field.Kind() == reflect.Ptr && field.Type().Kind() == reflect.Ptr && field.Type().Elem().Kind() == reflect.Interface {
+							return wrapErr(fmt.Errorf("field %#v is pointer to interface. %w", currentFieldName, errPointersToInterface))
+						}
 						field.Set(instance)
 					}
 				}

dingo_test.go

@@ -335,3 +335,19 @@ func TestInjectStructRec(t *testing.T) {
 	_, err = injector.GetInstance(new(TestInjectStructRecInterface))
 	assert.Error(t, err)
 }
+
+type someStructWithInvalidInterfacePointer struct {
+	A *testInterface `inject:""`
+}
+
+func TestInjectionOfInterfacePointer(t *testing.T) {
+	t.Parallel()
+
+	injector, err := NewInjector()
+	assert.NoError(t, err)
+
+	injector.Bind((*testInterface)(nil)).To(interfaceImpl1{})
+
+	_, err = injector.GetInstance(new(someStructWithInvalidInterfacePointer))
+	assert.Error(t, err, "Expected error")
+}