// We have a cycle. If t != t.Origin() then t is an instance of
				// the generic type t.Origin(). Because t is in the nest, t must
				// occur within the definition (RHS) of the generic type t.Origin(),
				// directly or indirectly, after expansion of the RHS.
				// Therefore t.Origin() must be invalid, no matter how it is
				// instantiated since the instantiation t of t.Origin() happens

	if err != nil {
		return nil, &UnknownRevisionError{Rev: rev}
	}
	info, err := r.cmd.parseStat(rev, string(out))
	if err != nil {
		return nil, err
	}
	if info.Origin == nil {
		info.Origin = new(Origin)
	}
	info.Origin.VCS = r.cmd.vcs
	info.Origin.URL = r.remote
	return info, nil
}

func (r *vcsRepo) Latest(ctx context.Context) (*RevInfo, error) {
	return r.Stat(ctx, "latest")
}

// instantiated types, this is same as the type name of the origin type.
func (t *Named) Obj() *TypeName {
	if t.inst == nil {
		return t.obj
	}
	return t.inst.orig.obj
}

// Origin returns the generic type from which the named type t is
// instantiated. If t is not an instantiated type, the result is t.
func (t *Named) Origin() *Named {
	if t.inst == nil {
		return t
	}
	return t.inst.orig

	Sum        string           `json:",omitempty"` // checksum for path, version (as in go.sum)
	GoModSum   string           `json:",omitempty"` // checksum for go.mod (as in go.sum)
	Origin     *codehost.Origin `json:",omitempty"` // provenance of module
	Reuse      bool             `json:",omitempty"` // reuse of old module info is safe
}

type ModuleError struct {
	Err string // error text
}

	if origin == nil {
		return errors.New("nil Origin")
	}

	// Ensure that the Origin actually includes enough fields to resolve the query.
	// If we got the previous Origin data from a proxy, it may be missing something
	// that we would have needed to resolve the query directly from the repo.
	switch {
	case origin.RepoSum != "":

	GoMod    string `json:",omitempty"`
	Zip      string `json:",omitempty"`
	Dir      string `json:",omitempty"`
	Sum      string `json:",omitempty"`
	GoModSum string `json:",omitempty"`

	Origin *codehost.Origin `json:",omitempty"`
	Reuse  bool             `json:",omitempty"`
}

func runDownload(ctx context.Context, cmd *base.Command, args []string) {
	modload.InitWorkfile()

				t.Fatal(err)
			}
			if !reflect.DeepEqual(info, tt.info) {
				t.Errorf("Latest: incorrect info\nhave %+v (origin %+v)\nwant %+v (origin %+v)", info, info.Origin, tt.info, tt.info.Origin)
			}
		}
	}

	for _, tt := range []latestTest{
		{
			gitrepo1,
			&RevInfo{
				Origin: &Origin{
					VCS:  "git",
					URL:  gitrepo1,
					Ref:  "HEAD",
					Hash: "ede458df7cd0fdca520df19a33158086a8a68e81",

//
// [underlying type]: https://go.dev/ref/spec#Underlying_types.
func (a *Alias) Underlying() Type { return unalias(a).Underlying() }

// Origin returns the generic Alias type of which a is an instance.
// If a is not an instance of a generic alias, Origin returns a.
func (a *Alias) Origin() *Alias { return a.orig }

// TypeParams returns the type parameters of the alias type a, or nil.

func identicalOrigin(x, y *Named) bool {
	// TODO(gri) is this correct?
	return x.Origin().obj == y.Origin().obj
}

// identicalInstance reports if two type instantiations are identical.
// Instantiations are identical if their origin and type arguments are
// identical.
func identicalInstance(xorig Type, xargs []Type, yorig Type, yargs []Type) bool {

		}
	}
	for _, t := range l.m[inst.Origin()] {
		if Identical(inst, t) {
			return t
		}
	}
	return nil
}

func (l *instanceLookup) add(inst *Named) {
	for i, t := range l.buf {
		if t == nil {
			l.buf[i] = inst
			return
		}
	}
	if l.m == nil {
		l.m = make(map[*Named][]*Named)
	}
	insts := l.m[inst.Origin()]
	l.m[inst.Origin()] = append(insts, inst)
}