--- /dev/null
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package satisfy inspects the type-checked ASTs of Go packages and
+// reports the set of discovered type constraints of the form (lhs, rhs
+// Type) where lhs is a non-trivial interface, rhs satisfies this
+// interface, and this fact is necessary for the package to be
+// well-typed.
+//
+// THIS PACKAGE IS EXPERIMENTAL AND MAY CHANGE AT ANY TIME.
+//
+// It is provided only for the gorename tool. Ideally this
+// functionality will become part of the type-checker in due course,
+// since it is computing it anyway, and it is robust for ill-typed
+// inputs, which this package is not.
+//
+package satisfy // import "golang.org/x/tools/refactor/satisfy"
+
+// NOTES:
+//
+// We don't care about numeric conversions, so we don't descend into
+// types or constant expressions. This is unsound because
+// constant expressions can contain arbitrary statements, e.g.
+// const x = len([1]func(){func() {
+// ...
+// }})
+//
+// TODO(adonovan): make this robust against ill-typed input.
+// Or move it into the type-checker.
+//
+// Assignability conversions are possible in the following places:
+// - in assignments y = x, y := x, var y = x.
+// - from call argument types to formal parameter types
+// - in append and delete calls
+// - from return operands to result parameter types
+// - in composite literal T{k:v}, from k and v to T's field/element/key type
+// - in map[key] from key to the map's key type
+// - in comparisons x==y and switch x { case y: }.
+// - in explicit conversions T(x)
+// - in sends ch <- x, from x to the channel element type
+// - in type assertions x.(T) and switch x.(type) { case T: }
+//
+// The results of this pass provide information equivalent to the
+// ssa.MakeInterface and ssa.ChangeInterface instructions.
+
+import (
+ "fmt"
+ "go/ast"
+ "go/token"
+ "go/types"
+
+ "golang.org/x/tools/go/ast/astutil"
+ "golang.org/x/tools/go/types/typeutil"
+)
+
+// A Constraint records the fact that the RHS type does and must
+// satisfy the LHS type, which is an interface.
+// The names are suggestive of an assignment statement LHS = RHS.
+type Constraint struct {
+ LHS, RHS types.Type
+}
+
+// A Finder inspects the type-checked ASTs of Go packages and
+// accumulates the set of type constraints (x, y) such that x is
+// assignable to y, y is an interface, and both x and y have methods.
+//
+// In other words, it returns the subset of the "implements" relation
+// that is checked during compilation of a package. Refactoring tools
+// will need to preserve at least this part of the relation to ensure
+// continued compilation.
+//
+type Finder struct {
+ Result map[Constraint]bool
+ msetcache typeutil.MethodSetCache
+
+ // per-Find state
+ info *types.Info
+ sig *types.Signature
+}
+
+// Find inspects a single package, populating Result with its pairs of
+// constrained types.
+//
+// The result is non-canonical and thus may contain duplicates (but this
+// tends to preserves names of interface types better).
+//
+// The package must be free of type errors, and
+// info.{Defs,Uses,Selections,Types} must have been populated by the
+// type-checker.
+//
+func (f *Finder) Find(info *types.Info, files []*ast.File) {
+ if f.Result == nil {
+ f.Result = make(map[Constraint]bool)
+ }
+
+ f.info = info
+ for _, file := range files {
+ for _, d := range file.Decls {
+ switch d := d.(type) {
+ case *ast.GenDecl:
+ if d.Tok == token.VAR { // ignore consts
+ for _, spec := range d.Specs {
+ f.valueSpec(spec.(*ast.ValueSpec))
+ }
+ }
+
+ case *ast.FuncDecl:
+ if d.Body != nil {
+ f.sig = f.info.Defs[d.Name].Type().(*types.Signature)
+ f.stmt(d.Body)
+ f.sig = nil
+ }
+ }
+ }
+ }
+ f.info = nil
+}
+
+var (
+ tInvalid = types.Typ[types.Invalid]
+ tUntypedBool = types.Typ[types.UntypedBool]
+ tUntypedNil = types.Typ[types.UntypedNil]
+)
+
+// exprN visits an expression in a multi-value context.
+func (f *Finder) exprN(e ast.Expr) types.Type {
+ typ := f.info.Types[e].Type.(*types.Tuple)
+ switch e := e.(type) {
+ case *ast.ParenExpr:
+ return f.exprN(e.X)
+
+ case *ast.CallExpr:
+ // x, err := f(args)
+ sig := f.expr(e.Fun).Underlying().(*types.Signature)
+ f.call(sig, e.Args)
+
+ case *ast.IndexExpr:
+ // y, ok := x[i]
+ x := f.expr(e.X)
+ f.assign(f.expr(e.Index), x.Underlying().(*types.Map).Key())
+
+ case *ast.TypeAssertExpr:
+ // y, ok := x.(T)
+ f.typeAssert(f.expr(e.X), typ.At(0).Type())
+
+ case *ast.UnaryExpr: // must be receive <-
+ // y, ok := <-x
+ f.expr(e.X)
+
+ default:
+ panic(e)
+ }
+ return typ
+}
+
+func (f *Finder) call(sig *types.Signature, args []ast.Expr) {
+ if len(args) == 0 {
+ return
+ }
+
+ // Ellipsis call? e.g. f(x, y, z...)
+ if _, ok := args[len(args)-1].(*ast.Ellipsis); ok {
+ for i, arg := range args {
+ // The final arg is a slice, and so is the final param.
+ f.assign(sig.Params().At(i).Type(), f.expr(arg))
+ }
+ return
+ }
+
+ var argtypes []types.Type
+
+ // Gather the effective actual parameter types.
+ if tuple, ok := f.info.Types[args[0]].Type.(*types.Tuple); ok {
+ // f(g()) call where g has multiple results?
+ f.expr(args[0])
+ // unpack the tuple
+ for i := 0; i < tuple.Len(); i++ {
+ argtypes = append(argtypes, tuple.At(i).Type())
+ }
+ } else {
+ for _, arg := range args {
+ argtypes = append(argtypes, f.expr(arg))
+ }
+ }
+
+ // Assign the actuals to the formals.
+ if !sig.Variadic() {
+ for i, argtype := range argtypes {
+ f.assign(sig.Params().At(i).Type(), argtype)
+ }
+ } else {
+ // The first n-1 parameters are assigned normally.
+ nnormals := sig.Params().Len() - 1
+ for i, argtype := range argtypes[:nnormals] {
+ f.assign(sig.Params().At(i).Type(), argtype)
+ }
+ // Remaining args are assigned to elements of varargs slice.
+ tElem := sig.Params().At(nnormals).Type().(*types.Slice).Elem()
+ for i := nnormals; i < len(argtypes); i++ {
+ f.assign(tElem, argtypes[i])
+ }
+ }
+}
+
+func (f *Finder) builtin(obj *types.Builtin, sig *types.Signature, args []ast.Expr, T types.Type) types.Type {
+ switch obj.Name() {
+ case "make", "new":
+ // skip the type operand
+ for _, arg := range args[1:] {
+ f.expr(arg)
+ }
+
+ case "append":
+ s := f.expr(args[0])
+ if _, ok := args[len(args)-1].(*ast.Ellipsis); ok && len(args) == 2 {
+ // append(x, y...) including append([]byte, "foo"...)
+ f.expr(args[1])
+ } else {
+ // append(x, y, z)
+ tElem := s.Underlying().(*types.Slice).Elem()
+ for _, arg := range args[1:] {
+ f.assign(tElem, f.expr(arg))
+ }
+ }
+
+ case "delete":
+ m := f.expr(args[0])
+ k := f.expr(args[1])
+ f.assign(m.Underlying().(*types.Map).Key(), k)
+
+ default:
+ // ordinary call
+ f.call(sig, args)
+ }
+
+ return T
+}
+
+func (f *Finder) extract(tuple types.Type, i int) types.Type {
+ if tuple, ok := tuple.(*types.Tuple); ok && i < tuple.Len() {
+ return tuple.At(i).Type()
+ }
+ return tInvalid
+}
+
+func (f *Finder) valueSpec(spec *ast.ValueSpec) {
+ var T types.Type
+ if spec.Type != nil {
+ T = f.info.Types[spec.Type].Type
+ }
+ switch len(spec.Values) {
+ case len(spec.Names): // e.g. var x, y = f(), g()
+ for _, value := range spec.Values {
+ v := f.expr(value)
+ if T != nil {
+ f.assign(T, v)
+ }
+ }
+
+ case 1: // e.g. var x, y = f()
+ tuple := f.exprN(spec.Values[0])
+ for i := range spec.Names {
+ if T != nil {
+ f.assign(T, f.extract(tuple, i))
+ }
+ }
+ }
+}
+
+// assign records pairs of distinct types that are related by
+// assignability, where the left-hand side is an interface and both
+// sides have methods.
+//
+// It should be called for all assignability checks, type assertions,
+// explicit conversions and comparisons between two types, unless the
+// types are uninteresting (e.g. lhs is a concrete type, or the empty
+// interface; rhs has no methods).
+//
+func (f *Finder) assign(lhs, rhs types.Type) {
+ if types.Identical(lhs, rhs) {
+ return
+ }
+ if !isInterface(lhs) {
+ return
+ }
+
+ if f.msetcache.MethodSet(lhs).Len() == 0 {
+ return
+ }
+ if f.msetcache.MethodSet(rhs).Len() == 0 {
+ return
+ }
+ // record the pair
+ f.Result[Constraint{lhs, rhs}] = true
+}
+
+// typeAssert must be called for each type assertion x.(T) where x has
+// interface type I.
+func (f *Finder) typeAssert(I, T types.Type) {
+ // Type assertions are slightly subtle, because they are allowed
+ // to be "impossible", e.g.
+ //
+ // var x interface{f()}
+ // _ = x.(interface{f()int}) // legal
+ //
+ // (In hindsight, the language spec should probably not have
+ // allowed this, but it's too late to fix now.)
+ //
+ // This means that a type assert from I to T isn't exactly a
+ // constraint that T is assignable to I, but for a refactoring
+ // tool it is a conditional constraint that, if T is assignable
+ // to I before a refactoring, it should remain so after.
+
+ if types.AssignableTo(T, I) {
+ f.assign(I, T)
+ }
+}
+
+// compare must be called for each comparison x==y.
+func (f *Finder) compare(x, y types.Type) {
+ if types.AssignableTo(x, y) {
+ f.assign(y, x)
+ } else if types.AssignableTo(y, x) {
+ f.assign(x, y)
+ }
+}
+
+// expr visits a true expression (not a type or defining ident)
+// and returns its type.
+func (f *Finder) expr(e ast.Expr) types.Type {
+ tv := f.info.Types[e]
+ if tv.Value != nil {
+ return tv.Type // prune the descent for constants
+ }
+
+ // tv.Type may be nil for an ast.Ident.
+
+ switch e := e.(type) {
+ case *ast.BadExpr, *ast.BasicLit:
+ // no-op
+
+ case *ast.Ident:
+ // (referring idents only)
+ if obj, ok := f.info.Uses[e]; ok {
+ return obj.Type()
+ }
+ if e.Name == "_" { // e.g. "for _ = range x"
+ return tInvalid
+ }
+ panic("undefined ident: " + e.Name)
+
+ case *ast.Ellipsis:
+ if e.Elt != nil {
+ f.expr(e.Elt)
+ }
+
+ case *ast.FuncLit:
+ saved := f.sig
+ f.sig = tv.Type.(*types.Signature)
+ f.stmt(e.Body)
+ f.sig = saved
+
+ case *ast.CompositeLit:
+ switch T := deref(tv.Type).Underlying().(type) {
+ case *types.Struct:
+ for i, elem := range e.Elts {
+ if kv, ok := elem.(*ast.KeyValueExpr); ok {
+ f.assign(f.info.Uses[kv.Key.(*ast.Ident)].Type(), f.expr(kv.Value))
+ } else {
+ f.assign(T.Field(i).Type(), f.expr(elem))
+ }
+ }
+
+ case *types.Map:
+ for _, elem := range e.Elts {
+ elem := elem.(*ast.KeyValueExpr)
+ f.assign(T.Key(), f.expr(elem.Key))
+ f.assign(T.Elem(), f.expr(elem.Value))
+ }
+
+ case *types.Array, *types.Slice:
+ tElem := T.(interface {
+ Elem() types.Type
+ }).Elem()
+ for _, elem := range e.Elts {
+ if kv, ok := elem.(*ast.KeyValueExpr); ok {
+ // ignore the key
+ f.assign(tElem, f.expr(kv.Value))
+ } else {
+ f.assign(tElem, f.expr(elem))
+ }
+ }
+
+ default:
+ panic("unexpected composite literal type: " + tv.Type.String())
+ }
+
+ case *ast.ParenExpr:
+ f.expr(e.X)
+
+ case *ast.SelectorExpr:
+ if _, ok := f.info.Selections[e]; ok {
+ f.expr(e.X) // selection
+ } else {
+ return f.info.Uses[e.Sel].Type() // qualified identifier
+ }
+
+ case *ast.IndexExpr:
+ x := f.expr(e.X)
+ i := f.expr(e.Index)
+ if ux, ok := x.Underlying().(*types.Map); ok {
+ f.assign(ux.Key(), i)
+ }
+
+ case *ast.SliceExpr:
+ f.expr(e.X)
+ if e.Low != nil {
+ f.expr(e.Low)
+ }
+ if e.High != nil {
+ f.expr(e.High)
+ }
+ if e.Max != nil {
+ f.expr(e.Max)
+ }
+
+ case *ast.TypeAssertExpr:
+ x := f.expr(e.X)
+ f.typeAssert(x, f.info.Types[e.Type].Type)
+
+ case *ast.CallExpr:
+ if tvFun := f.info.Types[e.Fun]; tvFun.IsType() {
+ // conversion
+ arg0 := f.expr(e.Args[0])
+ f.assign(tvFun.Type, arg0)
+ } else {
+ // function call
+ if id, ok := unparen(e.Fun).(*ast.Ident); ok {
+ if obj, ok := f.info.Uses[id].(*types.Builtin); ok {
+ sig := f.info.Types[id].Type.(*types.Signature)
+ return f.builtin(obj, sig, e.Args, tv.Type)
+ }
+ }
+ // ordinary call
+ f.call(f.expr(e.Fun).Underlying().(*types.Signature), e.Args)
+ }
+
+ case *ast.StarExpr:
+ f.expr(e.X)
+
+ case *ast.UnaryExpr:
+ f.expr(e.X)
+
+ case *ast.BinaryExpr:
+ x := f.expr(e.X)
+ y := f.expr(e.Y)
+ if e.Op == token.EQL || e.Op == token.NEQ {
+ f.compare(x, y)
+ }
+
+ case *ast.KeyValueExpr:
+ f.expr(e.Key)
+ f.expr(e.Value)
+
+ case *ast.ArrayType,
+ *ast.StructType,
+ *ast.FuncType,
+ *ast.InterfaceType,
+ *ast.MapType,
+ *ast.ChanType:
+ panic(e)
+ }
+
+ if tv.Type == nil {
+ panic(fmt.Sprintf("no type for %T", e))
+ }
+
+ return tv.Type
+}
+
+func (f *Finder) stmt(s ast.Stmt) {
+ switch s := s.(type) {
+ case *ast.BadStmt,
+ *ast.EmptyStmt,
+ *ast.BranchStmt:
+ // no-op
+
+ case *ast.DeclStmt:
+ d := s.Decl.(*ast.GenDecl)
+ if d.Tok == token.VAR { // ignore consts
+ for _, spec := range d.Specs {
+ f.valueSpec(spec.(*ast.ValueSpec))
+ }
+ }
+
+ case *ast.LabeledStmt:
+ f.stmt(s.Stmt)
+
+ case *ast.ExprStmt:
+ f.expr(s.X)
+
+ case *ast.SendStmt:
+ ch := f.expr(s.Chan)
+ val := f.expr(s.Value)
+ f.assign(ch.Underlying().(*types.Chan).Elem(), val)
+
+ case *ast.IncDecStmt:
+ f.expr(s.X)
+
+ case *ast.AssignStmt:
+ switch s.Tok {
+ case token.ASSIGN, token.DEFINE:
+ // y := x or y = x
+ var rhsTuple types.Type
+ if len(s.Lhs) != len(s.Rhs) {
+ rhsTuple = f.exprN(s.Rhs[0])
+ }
+ for i := range s.Lhs {
+ var lhs, rhs types.Type
+ if rhsTuple == nil {
+ rhs = f.expr(s.Rhs[i]) // 1:1 assignment
+ } else {
+ rhs = f.extract(rhsTuple, i) // n:1 assignment
+ }
+
+ if id, ok := s.Lhs[i].(*ast.Ident); ok {
+ if id.Name != "_" {
+ if obj, ok := f.info.Defs[id]; ok {
+ lhs = obj.Type() // definition
+ }
+ }
+ }
+ if lhs == nil {
+ lhs = f.expr(s.Lhs[i]) // assignment
+ }
+ f.assign(lhs, rhs)
+ }
+
+ default:
+ // y op= x
+ f.expr(s.Lhs[0])
+ f.expr(s.Rhs[0])
+ }
+
+ case *ast.GoStmt:
+ f.expr(s.Call)
+
+ case *ast.DeferStmt:
+ f.expr(s.Call)
+
+ case *ast.ReturnStmt:
+ formals := f.sig.Results()
+ switch len(s.Results) {
+ case formals.Len(): // 1:1
+ for i, result := range s.Results {
+ f.assign(formals.At(i).Type(), f.expr(result))
+ }
+
+ case 1: // n:1
+ tuple := f.exprN(s.Results[0])
+ for i := 0; i < formals.Len(); i++ {
+ f.assign(formals.At(i).Type(), f.extract(tuple, i))
+ }
+ }
+
+ case *ast.SelectStmt:
+ f.stmt(s.Body)
+
+ case *ast.BlockStmt:
+ for _, s := range s.List {
+ f.stmt(s)
+ }
+
+ case *ast.IfStmt:
+ if s.Init != nil {
+ f.stmt(s.Init)
+ }
+ f.expr(s.Cond)
+ f.stmt(s.Body)
+ if s.Else != nil {
+ f.stmt(s.Else)
+ }
+
+ case *ast.SwitchStmt:
+ if s.Init != nil {
+ f.stmt(s.Init)
+ }
+ var tag types.Type = tUntypedBool
+ if s.Tag != nil {
+ tag = f.expr(s.Tag)
+ }
+ for _, cc := range s.Body.List {
+ cc := cc.(*ast.CaseClause)
+ for _, cond := range cc.List {
+ f.compare(tag, f.info.Types[cond].Type)
+ }
+ for _, s := range cc.Body {
+ f.stmt(s)
+ }
+ }
+
+ case *ast.TypeSwitchStmt:
+ if s.Init != nil {
+ f.stmt(s.Init)
+ }
+ var I types.Type
+ switch ass := s.Assign.(type) {
+ case *ast.ExprStmt: // x.(type)
+ I = f.expr(unparen(ass.X).(*ast.TypeAssertExpr).X)
+ case *ast.AssignStmt: // y := x.(type)
+ I = f.expr(unparen(ass.Rhs[0]).(*ast.TypeAssertExpr).X)
+ }
+ for _, cc := range s.Body.List {
+ cc := cc.(*ast.CaseClause)
+ for _, cond := range cc.List {
+ tCase := f.info.Types[cond].Type
+ if tCase != tUntypedNil {
+ f.typeAssert(I, tCase)
+ }
+ }
+ for _, s := range cc.Body {
+ f.stmt(s)
+ }
+ }
+
+ case *ast.CommClause:
+ if s.Comm != nil {
+ f.stmt(s.Comm)
+ }
+ for _, s := range s.Body {
+ f.stmt(s)
+ }
+
+ case *ast.ForStmt:
+ if s.Init != nil {
+ f.stmt(s.Init)
+ }
+ if s.Cond != nil {
+ f.expr(s.Cond)
+ }
+ if s.Post != nil {
+ f.stmt(s.Post)
+ }
+ f.stmt(s.Body)
+
+ case *ast.RangeStmt:
+ x := f.expr(s.X)
+ // No conversions are involved when Tok==DEFINE.
+ if s.Tok == token.ASSIGN {
+ if s.Key != nil {
+ k := f.expr(s.Key)
+ var xelem types.Type
+ // keys of array, *array, slice, string aren't interesting
+ switch ux := x.Underlying().(type) {
+ case *types.Chan:
+ xelem = ux.Elem()
+ case *types.Map:
+ xelem = ux.Key()
+ }
+ if xelem != nil {
+ f.assign(xelem, k)
+ }
+ }
+ if s.Value != nil {
+ val := f.expr(s.Value)
+ var xelem types.Type
+ // values of strings aren't interesting
+ switch ux := x.Underlying().(type) {
+ case *types.Array:
+ xelem = ux.Elem()
+ case *types.Chan:
+ xelem = ux.Elem()
+ case *types.Map:
+ xelem = ux.Elem()
+ case *types.Pointer: // *array
+ xelem = deref(ux).(*types.Array).Elem()
+ case *types.Slice:
+ xelem = ux.Elem()
+ }
+ if xelem != nil {
+ f.assign(xelem, val)
+ }
+ }
+ }
+ f.stmt(s.Body)
+
+ default:
+ panic(s)
+ }
+}
+
+// -- Plundered from golang.org/x/tools/go/ssa -----------------
+
+// deref returns a pointer's element type; otherwise it returns typ.
+func deref(typ types.Type) types.Type {
+ if p, ok := typ.Underlying().(*types.Pointer); ok {
+ return p.Elem()
+ }
+ return typ
+}
+
+func unparen(e ast.Expr) ast.Expr { return astutil.Unparen(e) }
+
+func isInterface(T types.Type) bool { return types.IsInterface(T) }
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