// Otherwise, it returns nil.
func (ctxt *Context) lookup(h string, orig Type, targs []Type) Type {
	ctxt.mu.Lock()
	defer ctxt.mu.Unlock()

	for _, e := range ctxt.typeMap[h] {
		if identicalInstance(orig, targs, e.orig, e.targs) {
			return e.instance
		}
		if debug {
			// Panic during development to surface any imperfections in our hash.

// Otherwise, it returns nil.
func (ctxt *Context) lookup(h string, orig Type, targs []Type) Type {
	ctxt.mu.Lock()
	defer ctxt.mu.Unlock()

	for _, e := range ctxt.typeMap[h] {
		if identicalInstance(orig, targs, e.orig, e.targs) {
			return e.instance
		}
		if debug {
			// Panic during development to surface any imperfections in our hash.

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 {
	if len(xargs) != len(yargs) {
		return false
	}

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 {
	if len(xargs) != len(yargs) {
		return false
	}