// is not set), MissingMethod only checks that methods of T which are also
// present in V have matching types (e.g., for a type assertion x.(T) where
// x is of interface type V).
func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType bool) {
	return (*Checker)(nil).missingMethod(V, T, static, Identical, nil)
}

// missingMethod is like MissingMethod but accepts a *Checker as receiver,

// is not set), MissingMethod only checks that methods of T which are also
// present in V have matching types (e.g., for a type assertion x.(T) where
// x is of interface type V).
func MissingMethod(V Type, T *Interface, static bool) (method *Func, wrongType bool) {
	return (*Checker)(nil).missingMethod(V, T, static, Identical, nil)
}

// missingMethod is like MissingMethod but accepts a *Checker as receiver,

	RuntimeError()
}

// A TypeAssertionError explains a failed type assertion.
type TypeAssertionError struct {
	_interface    *_type
	concrete      *_type
	asserted      *_type
	missingMethod string // one method needed by Interface, missing from Concrete
}

func (*TypeAssertionError) RuntimeError() {}

func (e *TypeAssertionError) Error() string {
	inter := "interface"
	if e._interface != nil {

					//           We leave it as is for now because missingMethod provides
					//           a failure cause which allows for a better error message.
					//           Eventually, unify should return an error with cause.
					var cause string
					constraint := tpar.iface()
					if m, _ := check.missingMethod(tx, constraint, true, func(x, y Type) bool { return u.unify(x, y, exact) }, &cause); m != nil {

	if Ti.typeSet().IsEmpty() {
		if cause != nil {
			*cause = check.sprintf("cannot %s %s (empty type set)", verb, T)
		}
		return false
	}

	// V must implement T's methods, if any.
	if m, _ := check.missingMethod(V, T, true, Identical, cause); m != nil /* !Implements(V, T) */ {
		if cause != nil {
			*cause = check.sprintf("%s does not %s %s %s", V, verb, T, *cause)
		}
		return false
	}

					//           We leave it as is for now because missingMethod provides
					//           a failure cause which allows for a better error message.
					//           Eventually, unify should return an error with cause.
					var cause string
					constraint := tpar.iface()
					if m, _ := check.missingMethod(tx, constraint, true, func(x, y Type) bool { return u.unify(x, y, exact) }, &cause); m != nil {

	if Ti.typeSet().IsEmpty() {
		if cause != nil {
			*cause = check.sprintf("cannot %s %s (empty type set)", verb, T)
		}
		return false
	}

	// V must implement T's methods, if any.
	if m, _ := check.missingMethod(V, T, true, Identical, cause); m != nil /* !Implements(V, T) */ {
		if cause != nil {
			*cause = check.sprintf("%s does not %s %s %s", V, verb, T, *cause)
		}
		return false
	}

	// The cached result doesn't record which
	// interface function was missing, so initialize
	// the itab again to get the missing function name.
	panic(&TypeAssertionError{concrete: typ, asserted: &inter.Type, missingMethod: itabInit(m, false)})
}

// find finds the given interface/type pair in t.
// Returns nil if the given interface/type pair isn't present.
func (t *itabTableType) find(inter *interfacetype, typ *_type) *itab {