recent [128][4]uint64

	// complete history for seen
	mu sync.Mutex
	m  map[uint64]bool
}

// seen records that h has now been seen and reports whether it was seen before.
// When seen returns false, the caller is expected to print a report for h.
func (d *dedup) seen(h uint64) bool {
	d.mu.Lock()
	if d.m == nil {
		d.m = make(map[uint64]bool)
	}
	seen := d.m[h]
	d.m[h] = true
	d.mu.Unlock()

And we know that editors can't provide a lot of support (like completion) for `dict`s, because they can't know their keys and value types.

We can do better...

## What makes a dependency

Up to now you have seen dependencies declared as functions.

But that's not the only way to declare dependencies (although it would probably be the more common).

The key factor is that a dependency should be a "callable".

		size, err := content.Seek(0, io.SeekEnd)
		if err != nil {
			return 0, errSeeker
		}
		_, err = content.Seek(0, io.SeekStart)
		if err != nil {
			return 0, errSeeker
		}
		return size, nil
	}
	serveContent(w, req, name, modtime, sizeFunc, content)
}

// errSeeker is returned by ServeContent's sizeFunc when the content
// doesn't seek properly. The underlying Seeker's error text isn't

// If there is no such path, the result is nil.
func findPath(objMap map[Object]*declInfo, from, to Object, seen map[Object]bool) []Object {
	if seen[from] {
		return nil
	}
	seen[from] = true

	for d := range objMap[from].deps {
		if d == to {
			return []Object{d}
		}
		if P := findPath(objMap, d, to, seen); P != nil {
			return append(P, d)
		}
	}

	return nil
}

// If there is no such path, the result is nil.
func findPath(objMap map[Object]*declInfo, from, to Object, seen map[Object]bool) []Object {
	if seen[from] {
		return nil
	}
	seen[from] = true

	for d := range objMap[from].deps {
		if d == to {
			return []Object{d}
		}
		if P := findPath(objMap, d, to, seen); P != nil {
			return append(P, d)
		}
	}

	return nil
}

// If reportf != nil, it may be used to report why T is not comparable.
func comparable(T Type, dynamic bool, seen map[Type]bool, reportf func(string, ...interface{})) bool {
	if seen[T] {
		return true
	}
	if seen == nil {
		seen = make(map[Type]bool)
	}
	seen[T] = true

	switch t := under(T).(type) {
	case *Basic:
		// assume invalid types to be comparable
		// to avoid follow-up errors

	// eliminate.
	var seen ir.NameSet
	var stores []*Value
	for _, b := range f.Blocks {
		for _, v := range b.Values {
			n, ok := v.Aux.(*ir.Name)
			if !ok {
				continue
			}
			if n.Class != ir.PAUTO {
				continue
			}

			effect := v.Op.SymEffect()
			switch effect {
			case SymNone, SymWrite:
				// If we haven't seen the auto yet
				// then this might be a store we can

	lHash := hash.Sum(nil)
	hash.Reset()

	em := make([]byte, k)
	seed := em[1 : 1+hash.Size()]
	db := em[1+hash.Size():]

	copy(db[0:hash.Size()], lHash)
	db[len(db)-len(msg)-1] = 1
	copy(db[len(db)-len(msg):], msg)

	_, err := io.ReadFull(random, seed)
	if err != nil {
		return nil, err
	}

	mgf1XOR(db, hash, seed)
	mgf1XOR(seed, hash, db)

	if boring.Enabled {
		var bkey *boring.PublicKeyRSA

// yet been checked.
func hasVarSize(t Type, seen map[*Named]bool) (varSized bool) {
	// Cycles are only possible through *Named types.
	// The seen map is used to detect cycles and track
	// the results of previously seen types.
	if named := asNamed(t); named != nil {
		if v, ok := seen[named]; ok {
			return v
		}
		if seen == nil {
			seen = make(map[*Named]bool)
		}

	ldr := ctxt.loader
	seen := make(map[loader.Sym]struct{})
	for _, s := range funcs {
		if _, ok := seen[s]; !ok {
			f(s)
			seen[s] = struct{}{}
		}

		fi := ldr.FuncInfo(s)
		if !fi.Valid() {
			continue
		}
		fi.Preload()
		for i, ni := 0, fi.NumInlTree(); i < int(ni); i++ {
			call := fi.InlTree(i).Func
			if _, ok := seen[call]; !ok {
				f(call)