})
	method := NewField(src.NoXPos, LocalPkg.Lookup("Error"), sig)
	return NewInterface([]*Field{method})
}

// makeComparableInterface makes the predefined "comparable" interface in the
// built-in package. It has a unique name, but no methods.
func makeComparableInterface() *Type {
	return NewInterface(nil)

var emptyInterface = Interface{complete: true, tset: &topTypeSet}

// NewInterface returns a new interface for the given methods and embedded types.
// NewInterface takes ownership of the provided methods and may modify their types
// by setting missing receivers.
//
// Deprecated: Use NewInterfaceType instead which allows arbitrary embedded types.
func NewInterface(methods []*Func, embeddeds []*Named) *Interface {

func NewInterfaceType(methods []*Func, embeddeds []Type) *Interface {
	if len(methods) == 0 && len(embeddeds) == 0 {
		return &emptyInterface
	}

	// set method receivers if necessary
	typ := (*Checker)(nil).newInterface()
	for _, m := range methods {
		if sig := m.typ.(*Signature); sig.recv == nil {
			sig.recv = NewVar(m.pos, m.pkg, "", typ)
		}
	}

	// sort for API stability
	sortMethods(methods)

				return
			}
			handler(Event{
				New:   o,
				Event: EventAdd,
			})
		},
		UpdateFunc: func(oldInterface, newInterface any) {
			oldObj := ExtractObject(oldInterface)
			if oldObj == nil {
				return
			}
			newObj := ExtractObject(newInterface)
			if newObj == nil {
				return
			}
			handler(Event{
				Old:   oldObj,
				New:   newObj,
				Event: EventUpdate,
			})

			return &Union{terms}
		}

	case *Interface:
		methods, mcopied := subst.funcList(t.methods)
		embeddeds, ecopied := subst.typeList(t.embeddeds)
		if mcopied || ecopied {
			iface := subst.check.newInterface()
			iface.embeddeds = embeddeds
			iface.embedPos = t.embedPos
			iface.implicit = t.implicit
			assert(t.complete) // otherwise we are copying incomplete data
			iface.complete = t.complete

			return &Union{terms}
		}

	case *Interface:
		methods, mcopied := subst.funcList(t.methods)
		embeddeds, ecopied := subst.typeList(t.embeddeds)
		if mcopied || ecopied {
			iface := subst.check.newInterface()
			iface.embeddeds = embeddeds
			iface.embedPos = t.embedPos
			iface.implicit = t.implicit
			assert(t.complete) // otherwise we are copying incomplete data
			iface.complete = t.complete

	nullary := types.NewSignature(nil, nil, nil, false) // func()
	methods := []*types.Func{
		types.NewFunc(token.NoPos, nil, "Lock", nullary),
		types.NewFunc(token.NoPos, nil, "Unlock", nullary),
	}
	lockerType = types.NewInterface(methods, nil).Complete()

			// possible that it wasn't substituted. In this case we need to create
			// a new *Interface before modifying receivers.
			if iface == orig.underlying {
				old := iface
				iface = check.newInterface()
				iface.embeddeds = old.embeddeds
				assert(old.complete) // otherwise we are copying incomplete data
				iface.complete = old.complete
				iface.implicit = old.implicit // should be false but be conservative

			// possible that it wasn't substituted. In this case we need to create
			// a new *Interface before modifying receivers.
			if iface == orig.underlying {
				old := iface
				iface = check.newInterface()
				iface.embeddeds = old.embeddeds
				assert(old.complete) // otherwise we are copying incomplete data
				iface.complete = old.complete
				iface.implicit = old.implicit // should be false but be conservative

	fldt := mkFuncType(types.FakeRecvType(), []*types.Type{},
		[]*types.Type{types.Types[types.TSTRING]})
	field := types.NewField(src.NoXPos, typecheck.Lookup("F"), fldt)
	nei := types.NewInterface([]*types.Field{field})
	i16 := types.Types[types.TINT16]
	tb := types.Types[types.TBOOL]
	s1 := mkstruct(i16, i16, tb)
	ft := mkFuncType(nil, []*types.Type{s1, ei, ei, nei, pei, nei, i16},