// MethodSet returns the method set of type T.  It is thread-safe.
//
// If cache is nil, this function is equivalent to types.NewMethodSet(T).
// Utility functions can thus expose an optional *MethodSetCache
// parameter to clients that care about performance.
//
func (cache *MethodSetCache) MethodSet(T types.Type) *types.MethodSet {
	if cache == nil {
		return types.NewMethodSet(T)
	}
	cache.mu.Lock()
	defer cache.mu.Unlock()

	switch T := T.(type) {
	case *types.Named:
		return cache.lookupNamed(T).value

	case *types.Pointer:
		if N, ok := T.Elem().(*types.Named); ok {
			return cache.lookupNamed(N).pointer
		}
	}

	// all other types
	// (The map uses pointer equivalence, not type identity.)
	mset := cache.others[T]
	if mset == nil {
		mset = types.NewMethodSet(T)
		if cache.others == nil {
			cache.others = make(map[types.Type]*types.MethodSet)
		}
		cache.others[T] = mset
	}
	return mset
}

// lockPath returns a typePath describing the location of a lock value
// contained in typ. If there is no contained lock, it returns nil.
func lockPath(tpkg *types.Package, typ types.Type) typePath {
	if typ == nil {
		return nil
	}

	// We're only interested in the case in which the underlying
	// type is a struct. (Interfaces and pointers are safe to copy.)
	styp, ok := typ.Underlying().(*types.Struct)
	if !ok {
		return nil
	}

	// We're looking for cases in which a reference to this type
	// can be locked, but a value cannot. This differentiates
	// embedded interfaces from embedded values.
	if plock := types.NewMethodSet(types.NewPointer(typ)).Lookup(tpkg, "Lock"); plock != nil {
		if lock := types.NewMethodSet(typ).Lookup(tpkg, "Lock"); lock == nil {
			return []types.Type{typ}
		}
	}

	nfields := styp.NumFields()
	for i := 0; i < nfields; i++ {
		ftyp := styp.Field(i).Type()
		subpath := lockPath(tpkg, ftyp)
		if subpath != nil {
			return append(subpath, typ)
		}
	}

	return nil
}

func (cache *MethodSetCache) lookupNamed(named *types.Named) struct{ value, pointer *types.MethodSet } {
	if cache.named == nil {
		cache.named = make(map[*types.Named]struct{ value, pointer *types.MethodSet })
	}
	// Avoid recomputing mset(*T) for each distinct Pointer
	// instance whose underlying type is a named type.
	msets, ok := cache.named[named]
	if !ok {
		msets.value = types.NewMethodSet(named)
		msets.pointer = types.NewMethodSet(types.NewPointer(named))
		cache.named[named] = msets
	}
	return msets
}

//!+
func PrintSkeleton(pkg *types.Package, ifacename, concname string) error {
	obj := pkg.Scope().Lookup(ifacename)
	if obj == nil {
		return fmt.Errorf("%s.%s not found", pkg.Path(), ifacename)
	}
	if _, ok := obj.(*types.TypeName); !ok {
		return fmt.Errorf("%v is not a named type", obj)
	}
	iface, ok := obj.Type().Underlying().(*types.Interface)
	if !ok {
		return fmt.Errorf("type %v is a %T, not an interface",
			obj, obj.Type().Underlying())
	}
	// Use first letter of type name as receiver parameter.
	if !isValidIdentifier(concname) {
		return fmt.Errorf("invalid concrete type name: %q", concname)
	}
	r, _ := utf8.DecodeRuneInString(concname)

	fmt.Printf("// *%s implements %s.%s.\n", concname, pkg.Path(), ifacename)
	fmt.Printf("type %s struct{}\n", concname)
	mset := types.NewMethodSet(iface)
	for i := 0; i < mset.Len(); i++ {
		meth := mset.At(i).Obj()
		sig := types.TypeString(meth.Type(), (*types.Package).Name)
		fmt.Printf("func (%c *%s) %s%s {\n\tpanic(\"unimplemented\")\n}\n",
			r, concname, meth.Name(),
			strings.TrimPrefix(sig, "func"))
	}
	return nil
}

func makeIfaceSummary(iface *types.Interface) ifaceSummary {
	summary := ifaceSummary{
		iface:         iface,
		implementable: true,
	}
	methodset := types.NewMethodSet(iface)
	for i := 0; i < methodset.Len(); i++ {
		obj := methodset.At(i).Obj()
		if !obj.Exported() {
			summary.implementable = false
			continue
		}
		m, ok := obj.(*types.Func)
		if !ok {
			log.Panicf("unexpected methodset obj: %s (%T)", obj, obj)
		}
		if !isImplementable(m.Type().(*types.Signature)) {
			summary.implementable = false
		}
		if isCallable(m) {
			summary.callable = append(summary.callable, m)
		}
	}
	return summary
}

func getMethods(pkg *types.Package, typename string) map[string]*types.Func {
	r := make(map[string]*types.Func)
	mset := types.NewMethodSet(types.NewPointer(pkg.Scope().Lookup(typename).Type()))
	for i := 0; i < mset.Len(); i++ {
		fn := mset.At(i).Obj().(*types.Func)
		r[fn.Name()] = fn
	}
	return r
}

// combinedMethodSet returns the method set for a named type T
// merged with all the methods of *T that have different names than
// the methods of T.
//
// combinedMethodSet is analogous to types/typeutil.IntuitiveMethodSet
// but doesn't require a MethodSetCache.
// TODO(gri) If this functionality doesn't change over time, consider
// just calling IntuitiveMethodSet eventually.
func combinedMethodSet(T *types.Named) []*types.Selection {
	// method set for T
	mset := types.NewMethodSet(T)
	var res []*types.Selection
	for i, n := 0, mset.Len(); i < n; i++ {
		res = append(res, mset.At(i))
	}

	// add all *T methods with names different from T methods
	pmset := types.NewMethodSet(types.NewPointer(T))
	for i, n := 0, pmset.Len(); i < n; i++ {
		pm := pmset.At(i)
		if obj := pm.Obj(); mset.Lookup(obj.Pkg(), obj.Name()) == nil {
			res = append(res, pm)
		}
	}

	return res
}

func (w *Walker) emitType(obj *types.TypeName) {
	name := obj.Name()
	typ := obj.Type()
	switch typ := typ.Underlying().(type) {
	case *types.Struct:
		w.emitStructType(name, typ)
	case *types.Interface:
		w.emitIfaceType(name, typ)
		return // methods are handled by emitIfaceType
	default:
		w.emitf("type %s %s", name, w.typeString(typ.Underlying()))
	}

	// emit methods with value receiver
	var methodNames map[string]bool
	vset := types.NewMethodSet(typ)
	for i, n := 0, vset.Len(); i < n; i++ {
		m := vset.At(i)
		if m.Obj().Exported() {
			w.emitMethod(m)
			if methodNames == nil {
				methodNames = make(map[string]bool)
			}
			methodNames[m.Obj().Name()] = true
		}
	}

	// emit methods with pointer receiver; exclude
	// methods that we have emitted already
	// (the method set of *T includes the methods of T)
	pset := types.NewMethodSet(types.NewPointer(typ))
	for i, n := 0, pset.Len(); i < n; i++ {
		m := pset.At(i)
		if m.Obj().Exported() && !methodNames[m.Obj().Name()] {
			w.emitMethod(m)
		}
	}
}

func exportedMethodSet(T types.Type) []*types.Func {
	var methods []*types.Func
	methodset := types.NewMethodSet(T)
	for i := 0; i < methodset.Len(); i++ {
		obj := methodset.At(i).Obj()
		if !obj.Exported() {
			continue
		}
		switch obj := obj.(type) {
		case *types.Func:
			methods = append(methods, obj)
		default:
			log.Panicf("unexpected methodset obj: %s", obj)
		}
	}
	return methods
}

// ExampleMethodSet prints the method sets of various types.
func ExampleMethodSet() {
	// Parse a single source file.
	const input = `
package temperature
import "fmt"
type Celsius float64
func (c Celsius) String() string  { return fmt.Sprintf("%g°C", c) }
func (c *Celsius) SetF(f float64) { *c = Celsius(f - 32 / 9 * 5) }
`
	fset := token.NewFileSet()
	f, err := parser.ParseFile(fset, "celsius.go", input, 0)
	if err != nil {
		log.Fatal(err)
	}

	// Type-check a package consisting of this file.
	// Type information for the imported packages
	// comes from $GOROOT/pkg/$GOOS_$GOOARCH/fmt.a.
	conf := types.Config{Importer: importer.Default()}
	pkg, err := conf.Check("temperature", fset, []*ast.File{f}, nil)
	if err != nil {
		log.Fatal(err)
	}

	// Print the method sets of Celsius and *Celsius.
	celsius := pkg.Scope().Lookup("Celsius").Type()
	for _, t := range []types.Type{celsius, types.NewPointer(celsius)} {
		fmt.Printf("Method set of %s:\n", t)
		mset := types.NewMethodSet(t)
		for i := 0; i < mset.Len(); i++ {
			fmt.Println(mset.At(i))
		}
		fmt.Println()
	}

	// Output:
	// Method set of temperature.Celsius:
	// method (temperature.Celsius) String() string
	//
	// Method set of *temperature.Celsius:
	// method (*temperature.Celsius) SetF(f float64)
	// method (*temperature.Celsius) String() string
}

func methodDocComment(prog *loader.Program, tname *types.TypeName, methodName string) (string, error) {
	t := tname.Type()
	if !types.IsInterface(t) {
		// Use the pointer type to get as many methods as possible.
		t = types.NewPointer(t)
	}

	mset := types.NewMethodSet(t)
	sel := mset.Lookup(nil, methodName)
	if sel == nil {
		return "", errgo.Newf("cannot find method %v on %v", methodName, t)
	}
	obj := sel.Obj()
	decl, err := findDecl(prog, obj.Pos())
	if err != nil {
		return "", errgo.Mask(err)
	}
	switch decl := decl.(type) {
	case *ast.GenDecl:
		if decl.Tok != token.TYPE {
			return "", errgo.Newf("found non-type decl %#v", decl)
		}
		for _, spec := range decl.Specs {
			tspec := spec.(*ast.TypeSpec)
			it := tspec.Type.(*ast.InterfaceType)
			for _, m := range it.Methods.List {
				for _, id := range m.Names {
					if id.Pos() == obj.Pos() {
						return m.Doc.Text(), nil
					}
				}
			}
		}
		return "", errgo.Newf("method definition not found in type")
	case *ast.FuncDecl:
		if decl.Name.Pos() != obj.Pos() {
			return "", errgo.Newf("method definition not found (at %#v)", prog.Fset.Position(obj.Pos()))
		}
		return decl.Doc.Text(), nil
	default:
		return "", errgo.Newf("unexpected declaration %T found", decl)
	}
}

func (w *Walker) emitIfaceType(name string, typ *types.Interface) {
	pop := w.pushScope("type " + name + " interface")

	var methodNames []string
	complete := true
	mset := types.NewMethodSet(typ)
	for i, n := 0, mset.Len(); i < n; i++ {
		m := mset.At(i).Obj().(*types.Func)
		if !m.Exported() {
			complete = false
			continue
		}
		methodNames = append(methodNames, m.Name())
		w.emitf("%s%s", m.Name(), w.signatureString(m.Type().(*types.Signature)))
	}

	if !complete {
		// The method set has unexported methods, so all the
		// implementations are provided by the same package,
		// so the method set can be extended. Instead of recording
		// the full set of names (below), record only that there were
		// unexported methods. (If the interface shrinks, we will notice
		// because a method signature emitted during the last loop
		// will disappear.)
		w.emitf("unexported methods")
	}

	pop()

	if !complete {
		return
	}

	if len(methodNames) == 0 {
		w.emitf("type %s interface {}", name)
		return
	}

	sort.Strings(methodNames)
	w.emitf("type %s interface { %s }", name, strings.Join(methodNames, ", "))
}

func exportedMethodSet(T types.Type) []*types.Func {
	var methods []*types.Func
	methodset := types.NewMethodSet(T)
	for i := 0; i < methodset.Len(); i++ {
		obj := methodset.At(i).Obj()
		if !obj.Exported() {
			continue
		}
		// Skip methods from the embedded classes, so that
		// only methods that are implemented in Go are included.
		if pref := pkgFirstElem(obj.Pkg()); pref == "Java" || pref == "ObjC" {
			continue
		}
		switch obj := obj.(type) {
		case *types.Func:
			methods = append(methods, obj)
		default:
			log.Panicf("unexpected methodset obj: %s", obj)
		}
	}
	return methods
}

// Smoke test to ensure that imported methods get the correct package.
func TestCorrectMethodPackage(t *testing.T) {
	skipSpecialPlatforms(t)

	// This package only handles gc export data.
	if runtime.Compiler != "gc" {
		t.Skipf("gc-built packages not available (compiler = %s)", runtime.Compiler)
		return
	}

	imports := make(map[string]*types.Package)
	_, err := Import(imports, "net/http")
	if err != nil {
		t.Fatal(err)
	}

	mutex := imports["sync"].Scope().Lookup("Mutex").(*types.TypeName).Type()
	mset := types.NewMethodSet(types.NewPointer(mutex)) // methods of *sync.Mutex
	sel := mset.Lookup(nil, "Lock")
	lock := sel.Obj().(*types.Func)
	if got, want := lock.Pkg().Path(), "sync"; got != want {
		t.Errorf("got package path %q; want %q", got, want)
	}
}

// process collects informations about a go package.
func (p *Package) process() error {
	var err error

	funcs := make(map[string]Func)
	structs := make(map[string]Struct)

	scope := p.pkg.Scope()
	for _, name := range scope.Names() {
		obj := scope.Lookup(name)
		if !obj.Exported() {
			continue
		}

		p.n++
		p.syms.addSymbol(obj)
	}

	for _, name := range scope.Names() {
		obj := scope.Lookup(name)
		if !obj.Exported() {
			continue
		}

		switch obj := obj.(type) {
		case *types.Const:
			p.addConst(obj)

		case *types.Var:
			p.addVar(obj)

		case *types.Func:
			funcs[name], err = newFuncFrom(p, "", obj, obj.Type().(*types.Signature))
			if err != nil {
				return err
			}

		case *types.TypeName:
			named := obj.Type().(*types.Named)
			switch typ := named.Underlying().(type) {
			case *types.Struct:
				structs[name], err = newStruct(p, obj)
				if err != nil {
					return err
				}

			case *types.Basic:
				// ok. handled by p.syms-types

			case *types.Array:
				// ok. handled by p.syms-types

			case *types.Interface:
				// ok. handled by p.syms-types

			case *types.Signature:
				// ok. handled by p.syms-types

			case *types.Slice:
				// ok. handled by p.syms-types

			default:
				//TODO(sbinet)
				panic(fmt.Errorf("not yet supported: %v (%T)", typ, obj))
			}

		default:
			//TODO(sbinet)
			panic(fmt.Errorf("not yet supported: %v (%T)", obj, obj))
		}

	}

	// remove ctors from funcs.
	// add methods.
	for sname, s := range structs {
		for name, fct := range funcs {
			if fct.Return() == nil {
				continue
			}
			if fct.Return() == s.GoType() {
				delete(funcs, name)
				fct.doc = p.getDoc(sname, scope.Lookup(name))
				fct.ctor = true
				s.ctors = append(s.ctors, fct)
				structs[sname] = s
			}
		}

		ptyp := types.NewPointer(s.GoType())
		p.syms.addType(nil, ptyp)
		mset := types.NewMethodSet(ptyp)
		for i := 0; i < mset.Len(); i++ {
			meth := mset.At(i)
			if !meth.Obj().Exported() {
				continue
			}
			m, err := newFuncFrom(p, sname, meth.Obj(), meth.Type().(*types.Signature))
			if err != nil {
				return err
//.........这里部分代码省略.........

//.........这里部分代码省略.........
				}
				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
}

func (r *implementsResult) display(printf printfFunc) {
	relation := "is implemented by"

	meth := func(sel *types.Selection) {
		if sel != nil {
			printf(sel.Obj(), "\t%s method (%s).%s",
				relation, r.qpos.typeString(sel.Recv()), sel.Obj().Name())
		}
	}

	if isInterface(r.t) {
		if types.NewMethodSet(r.t).Len() == 0 { // TODO(adonovan): cache mset
			printf(r.pos, "empty interface type %s", r.qpos.typeString(r.t))
			return
		}

		if r.method == nil {
			printf(r.pos, "interface type %s", r.qpos.typeString(r.t))
		} else {
			printf(r.method, "abstract method %s", r.qpos.objectString(r.method))
		}

		// Show concrete types (or methods) first; use two passes.
		for i, sub := range r.to {
			if !isInterface(sub) {
				if r.method == nil {
					printf(deref(sub).(*types.Named).Obj(), "\t%s %s type %s",
						relation, typeKind(sub), r.qpos.typeString(sub))
				} else {
					meth(r.toMethod[i])
				}
			}
		}
		for i, sub := range r.to {
			if isInterface(sub) {
				if r.method == nil {
					printf(sub.(*types.Named).Obj(), "\t%s %s type %s",
						relation, typeKind(sub), r.qpos.typeString(sub))
				} else {
					meth(r.toMethod[i])
				}
			}
		}

		relation = "implements"
		for i, super := range r.from {
			if r.method == nil {
				printf(super.(*types.Named).Obj(), "\t%s %s",
					relation, r.qpos.typeString(super))
			} else {
				meth(r.fromMethod[i])
			}
		}
	} else {
		relation = "implements"

		if r.from != nil {
			if r.method == nil {
				printf(r.pos, "%s type %s",
					typeKind(r.t), r.qpos.typeString(r.t))
			} else {
				printf(r.method, "concrete method %s",
					r.qpos.objectString(r.method))
			}
			for i, super := range r.from {
				if r.method == nil {
					printf(super.(*types.Named).Obj(), "\t%s %s",
						relation, r.qpos.typeString(super))
				} else {
					meth(r.fromMethod[i])
				}
			}
		}
		if r.fromPtr != nil {
			if r.method == nil {
				printf(r.pos, "pointer type *%s", r.qpos.typeString(r.t))
			} else {
				// TODO(adonovan): de-dup (C).f and (*C).f implementing (I).f.
				printf(r.method, "concrete method %s",
					r.qpos.objectString(r.method))
			}

			for i, psuper := range r.fromPtr {
				if r.method == nil {
					printf(psuper.(*types.Named).Obj(), "\t%s %s",
						relation, r.qpos.typeString(psuper))
				} else {
					meth(r.fromPtrMethod[i])
				}
			}
		} else if r.from == nil {
			printf(r.pos, "%s type %s implements only interface{}",
				typeKind(r.t), r.qpos.typeString(r.t))
		}
	}
}