}
		return &(*u)(unsafe.Pointer(t)).u
	}
}

// Elem returns the element type for t if t is an array, channel, map, pointer, or slice, otherwise nil.
func (t *Type) Elem() *Type {
	switch t.Kind() {
	case Array:
		tt := (*ArrayType)(unsafe.Pointer(t))
		return tt.Elem
	case Chan:
		tt := (*ChanType)(unsafe.Pointer(t))
		return tt.Elem
	case Map:
		tt := (*MapType)(unsafe.Pointer(t))
		return tt.Elem

// TODO(mdempsky): Store this information directly in the Type's Name.
var typeSymIdx = make(map[*types.Type][2]int64)

func BaseTypeIndex(t *types.Type) int64 {
	tbase := t
	if t.IsPtr() && t.Sym() == nil && t.Elem().Sym() != nil {
		tbase = t.Elem()
	}
	i, ok := typeSymIdx[tbase]
	if !ok {
		return -1
	}
	if t != tbase {
		return i[1]
	}
	return i[0]

func (u *URL) JoinPath(elem ...string) *URL {
	elem = append([]string{u.EscapedPath()}, elem...)
	var p string
	if !strings.HasPrefix(elem[0], "/") {
		// Return a relative path if u is relative,
		// but ensure that it contains no ../ elements.
		elem[0] = "/" + elem[0]
		p = path.Join(elem...)[1:]
	} else {
		p = path.Join(elem...)
	}
	// path.Join will remove any trailing slashes.

			}
		}
		return true
	case reflect.Interface:
		if v1.IsNil() || v2.IsNil() {
			return v1.IsNil() == v2.IsNil()
		}
		return e.deepValueEqual(v1.Elem(), v2.Elem(), visited, equateNilAndEmpty, depth+1)
	case reflect.Ptr:
		return e.deepValueEqual(v1.Elem(), v2.Elem(), visited, equateNilAndEmpty, depth+1)
	case reflect.Struct:
		for i, n := 0, v1.NumField(); i < n; i++ {

// It also reports whether a Pointer was present.
func ReceiverNamed(recv *types.Var) (isPtr bool, named *types.Named) {
	t := recv.Type()
	if ptr, ok := aliases.Unalias(t).(*types.Pointer); ok {
		isPtr = true
		t = ptr.Elem()
	}
	named, _ = aliases.Unalias(t).(*types.Named)
	return
}

// Unpointer returns T given *T or an alias thereof.
// For all other types it is the identity function.
// It does not look at underlying types.

		name  string
		elems []string
		elem  string
		out   bool
	}{
		{"exists", []string{"1", "2", "3"}, "1", true},
		{"not exists", []string{"1", "2", "3"}, "4", false},
	}
	for _, test := range containsTests {
		t.Run(test.name, func(t *testing.T) {
			if out := Contains(test.elems, test.elem); test.out != out {
				t.Errorf("Contains(%v, %s) want: %t, got: %t", test.elems, test.elem, test.out, out)
			}
		})
	}
}

	for len(stack) > 0 && stack[0].m.Version == "" {
		stack = stack[1:]
	}

	if len(stack) == 0 {
		b.WriteString(e.Err.Error())
	} else {
		for _, elem := range stack[:len(stack)-1] {
			fmt.Fprintf(b, "%s %s\n\t", elem.m, elem.nextReason)
		}
		// Ensure that the final module path and version are included as part of the
		// error message.
		m := stack[len(stack)-1].m

	}
	if pt.Elem() == errorType {
		return errors.New("second argument to errors.As should not be *error")
	}
	_, ok = pt.Elem().Underlying().(*types.Interface)
	if ok || types.Implements(pt.Elem(), errorType.Underlying().(*types.Interface)) {
		return nil
	}

	result := url.Values{}
	if obj == nil {
		return result, nil
	}
	var sv reflect.Value
	switch reflect.TypeOf(obj).Kind() {
	case reflect.Pointer, reflect.Interface:
		sv = reflect.ValueOf(obj).Elem()
	default:
		return nil, fmt.Errorf("expecting a pointer or interface")
	}
	st := sv.Type()
	if !isStructKind(st.Kind()) {
		return nil, fmt.Errorf("expecting a pointer to a struct")
	}

	if len(filter) == 0 {
		// No regex defined, we default to NOT matching. This ensures our default skips nothing
		return false
	}
	elem := strings.Split(testName, "/")
	if len(filter) > len(elem) {
		return false
	}
	for i, s := range elem {
		if i >= len(filter) {
			break
		}
		if !filter[i].MatchString(s) {
			return false
		}
	}
	return true
}

// From go/src/testing/match.go