// computeImplements computes the "implements" relation over all pairs
// of named types in allNamed.
func computeImplements(cache *typeutil.MethodSetCache, allNamed []*types.Named) map[*types.Named]implementsFacts {
// Information about a single type's method set.
type msetInfo struct {
typ types.Type
mset *types.MethodSet
mask1, mask2 uint64
}
initMsetInfo := func(info *msetInfo, typ types.Type) {
info.typ = typ
info.mset = cache.MethodSet(typ)
for i := 0; i < info.mset.Len(); i++ {
name := info.mset.At(i).Obj().Name()
info.mask1 |= 1 << methodBit(name[0])
info.mask2 |= 1 << methodBit(name[len(name)-1])
}
}
// satisfies(T, U) reports whether type T satisfies type U.
// U must be an interface.
//
// Since there are thousands of types (and thus millions of
// pairs of types) and types.Assignable(T, U) is relatively
// expensive, we compute assignability directly from the
// method sets. (At least one of T and U must be an
// interface.)
//
// We use a trick (thanks gri!) related to a Bloom filter to
// quickly reject most tests, which are false. For each
// method set, we precompute a mask, a set of bits, one per
// distinct initial byte of each method name. Thus the mask
// for io.ReadWriter would be {'R','W'}. AssignableTo(T, U)
// cannot be true unless mask(T)&mask(U)==mask(U).
//
// As with a Bloom filter, we can improve precision by testing
// additional hashes, e.g. using the last letter of each
// method name, so long as the subset mask property holds.
//
// When analyzing the standard library, there are about 1e6
// calls to satisfies(), of which 0.6% return true. With a
// 1-hash filter, 95% of calls avoid the expensive check; with
// a 2-hash filter, this grows to 98.2%.
satisfies := func(T, U *msetInfo) bool {
return T.mask1&U.mask1 == U.mask1 &&
T.mask2&U.mask2 == U.mask2 &&
containsAllIdsOf(T.mset, U.mset)
}
// Information about a named type N, and perhaps also *N.
type namedInfo struct {
isInterface bool
base msetInfo // N
ptr msetInfo // *N, iff N !isInterface
}
var infos []namedInfo
// Precompute the method sets and their masks.
for _, N := range allNamed {
var info namedInfo
initMsetInfo(&info.base, N)
_, info.isInterface = N.Underlying().(*types.Interface)
if !info.isInterface {
initMsetInfo(&info.ptr, types.NewPointer(N))
}
if info.base.mask1|info.ptr.mask1 == 0 {
continue // neither N nor *N has methods
}
infos = append(infos, info)
}
facts := make(map[*types.Named]implementsFacts)
// Test all pairs of distinct named types (T, U).
// TODO(adonovan): opt: compute (U, T) at the same time.
for t := range infos {
T := &infos[t]
var to, from, fromPtr []types.Type
for u := range infos {
if t == u {
continue
}
U := &infos[u]
switch {
case T.isInterface && U.isInterface:
if satisfies(&U.base, &T.base) {
to = append(to, U.base.typ)
}
if satisfies(&T.base, &U.base) {
from = append(from, U.base.typ)
}
case T.isInterface: // U concrete
if satisfies(&U.base, &T.base) {
to = append(to, U.base.typ)
} else if satisfies(&U.ptr, &T.base) {
to = append(to, U.ptr.typ)
}
case U.isInterface: // T concrete
if satisfies(&T.base, &U.base) {
from = append(from, U.base.typ)
} else if satisfies(&T.ptr, &U.base) {
fromPtr = append(fromPtr, U.base.typ)
}
}
}
// Sort types (arbitrarily) to avoid nondeterminism.
sort.Sort(typesByString(to))
sort.Sort(typesByString(from))
sort.Sort(typesByString(fromPtr))
facts[T.base.typ.(*types.Named)] = implementsFacts{to, from, fromPtr}
}
return facts
}
// Implements displays the "implements" relation as it pertains to the
// selected type.
// If the selection is a method, 'implements' displays
// the corresponding methods of the types that would have been reported
// by an implements query on the receiver type.
//
func implements(q *Query) error {
lconf := loader.Config{Build: q.Build}
allowErrors(&lconf)
qpkg, err := importQueryPackage(q.Pos, &lconf)
if err != nil {
return err
}
// Set the packages to search.
if len(q.Scope) > 0 {
// Inspect all packages in the analysis scope, if specified.
if err := setPTAScope(&lconf, q.Scope); err != nil {
return err
}
} else {
// Otherwise inspect the forward and reverse
// transitive closure of the selected package.
// (In theory even this is incomplete.)
_, rev, _ := importgraph.Build(q.Build)
for path := range rev.Search(qpkg) {
lconf.ImportWithTests(path)
}
// TODO(adonovan): for completeness, we should also
// type-check and inspect function bodies in all
// imported packages. This would be expensive, but we
// could optimize by skipping functions that do not
// contain type declarations. This would require
// changing the loader's TypeCheckFuncBodies hook to
// provide the []*ast.File.
}
// Load/parse/type-check the program.
lprog, err := lconf.Load()
if err != nil {
return err
}
q.Fset = lprog.Fset
qpos, err := parseQueryPos(lprog, q.Pos, false)
if err != nil {
return err
}
// Find the selected type.
path, action := findInterestingNode(qpos.info, qpos.path)
var method *types.Func
var T types.Type // selected type (receiver if method != nil)
switch action {
case actionExpr:
// method?
if id, ok := path[0].(*ast.Ident); ok {
if obj, ok := qpos.info.ObjectOf(id).(*types.Func); ok {
recv := obj.Type().(*types.Signature).Recv()
if recv == nil {
return fmt.Errorf("this function is not a method")
}
method = obj
T = recv.Type()
}
}
case actionType:
T = qpos.info.TypeOf(path[0].(ast.Expr))
}
if T == nil {
return fmt.Errorf("no type or method here")
}
// Find all named types, even local types (which can have
// methods via promotion) and the built-in "error".
var allNamed []types.Type
for _, info := range lprog.AllPackages {
for _, obj := range info.Defs {
if obj, ok := obj.(*types.TypeName); ok {
allNamed = append(allNamed, obj.Type())
}
}
}
allNamed = append(allNamed, types.Universe.Lookup("error").Type())
var msets typeutil.MethodSetCache
// Test each named type.
var to, from, fromPtr []types.Type
for _, U := range allNamed {
if isInterface(T) {
if msets.MethodSet(T).Len() == 0 {
continue // empty interface
}
if isInterface(U) {
if msets.MethodSet(U).Len() == 0 {
continue // empty interface
}
// T interface, U interface
if !types.Identical(T, U) {
if types.AssignableTo(U, T) {
to = append(to, U)
}
if types.AssignableTo(T, U) {
from = append(from, U)
}
}
} else {
// T interface, U concrete
if types.AssignableTo(U, T) {
to = append(to, U)
} else if pU := types.NewPointer(U); types.AssignableTo(pU, T) {
to = append(to, pU)
}
}
} else if isInterface(U) {
if msets.MethodSet(U).Len() == 0 {
continue // empty interface
}
// T concrete, U interface
if types.AssignableTo(T, U) {
from = append(from, U)
} else if pT := types.NewPointer(T); types.AssignableTo(pT, U) {
fromPtr = append(fromPtr, U)
}
}
}
var pos interface{} = qpos
if nt, ok := deref(T).(*types.Named); ok {
pos = nt.Obj()
}
// Sort types (arbitrarily) to ensure test determinism.
sort.Sort(typesByString(to))
sort.Sort(typesByString(from))
sort.Sort(typesByString(fromPtr))
var toMethod, fromMethod, fromPtrMethod []*types.Selection // contain nils
if method != nil {
for _, t := range to {
toMethod = append(toMethod,
types.NewMethodSet(t).Lookup(method.Pkg(), method.Name()))
}
for _, t := range from {
fromMethod = append(fromMethod,
types.NewMethodSet(t).Lookup(method.Pkg(), method.Name()))
}
for _, t := range fromPtr {
fromPtrMethod = append(fromPtrMethod,
types.NewMethodSet(t).Lookup(method.Pkg(), method.Name()))
}
}
q.result = &implementsResult{
qpos, T, pos, to, from, fromPtr, method, toMethod, fromMethod, fromPtrMethod,
}
return nil
}
// Implements displays the "implements" relation as it pertains to the
// selected type within a single package.
// If the selection is a method, 'implements' displays
// the corresponding methods of the types that would have been reported
// by an implements query on the receiver type.
//
func implements(q *Query) error {
lconf := loader.Config{Build: q.Build}
allowErrors(&lconf)
if err := importQueryPackage(q.Pos, &lconf); err != nil {
return err
}
// Load/parse/type-check the program.
lprog, err := lconf.Load()
if err != nil {
return err
}
q.Fset = lprog.Fset
qpos, err := parseQueryPos(lprog, q.Pos, false)
if err != nil {
return err
}
// Find the selected type.
path, action := findInterestingNode(qpos.info, qpos.path)
var method *types.Func
var T types.Type // selected type (receiver if method != nil)
switch action {
case actionExpr:
// method?
if id, ok := path[0].(*ast.Ident); ok {
if obj, ok := qpos.info.ObjectOf(id).(*types.Func); ok {
recv := obj.Type().(*types.Signature).Recv()
if recv == nil {
return fmt.Errorf("this function is not a method")
}
method = obj
T = recv.Type()
}
}
case actionType:
T = qpos.info.TypeOf(path[0].(ast.Expr))
}
if T == nil {
return fmt.Errorf("no type or method here")
}
// Find all named types, even local types (which can have
// methods via promotion) and the built-in "error".
//
// TODO(adonovan): include all packages in PTA scope too?
// i.e. don't reduceScope?
//
var allNamed []types.Type
for _, info := range lprog.AllPackages {
for _, obj := range info.Defs {
if obj, ok := obj.(*types.TypeName); ok {
allNamed = append(allNamed, obj.Type())
}
}
}
allNamed = append(allNamed, types.Universe.Lookup("error").Type())
var msets typeutil.MethodSetCache
// Test each named type.
var to, from, fromPtr []types.Type
for _, U := range allNamed {
if isInterface(T) {
if msets.MethodSet(T).Len() == 0 {
continue // empty interface
}
if isInterface(U) {
if msets.MethodSet(U).Len() == 0 {
continue // empty interface
}
// T interface, U interface
if !types.Identical(T, U) {
if types.AssignableTo(U, T) {
to = append(to, U)
}
if types.AssignableTo(T, U) {
from = append(from, U)
}
}
} else {
// T interface, U concrete
if types.AssignableTo(U, T) {
to = append(to, U)
} else if pU := types.NewPointer(U); types.AssignableTo(pU, T) {
to = append(to, pU)
}
}
} else if isInterface(U) {
if msets.MethodSet(U).Len() == 0 {
continue // empty interface
}
// T concrete, U interface
if types.AssignableTo(T, U) {
from = append(from, U)
} else if pT := types.NewPointer(T); types.AssignableTo(pT, U) {
fromPtr = append(fromPtr, U)
}
}
}
var pos interface{} = qpos
if nt, ok := deref(T).(*types.Named); ok {
pos = nt.Obj()
}
// Sort types (arbitrarily) to ensure test determinism.
sort.Sort(typesByString(to))
sort.Sort(typesByString(from))
sort.Sort(typesByString(fromPtr))
var toMethod, fromMethod, fromPtrMethod []*types.Selection // contain nils
if method != nil {
for _, t := range to {
toMethod = append(toMethod,
types.NewMethodSet(t).Lookup(method.Pkg(), method.Name()))
}
for _, t := range from {
fromMethod = append(fromMethod,
types.NewMethodSet(t).Lookup(method.Pkg(), method.Name()))
}
for _, t := range fromPtr {
fromPtrMethod = append(fromPtrMethod,
types.NewMethodSet(t).Lookup(method.Pkg(), method.Name()))
}
}
q.result = &implementsResult{
qpos, T, pos, to, from, fromPtr, method, toMethod, fromMethod, fromPtrMethod,
}
return nil
}