| // Copyright 2013 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. |
| |
| // This file implements type-checking of identifiers and type expressions. |
| |
| package types |
| |
| import ( |
| "go/ast" |
| "go/constant" |
| "go/token" |
| "sort" |
| "strconv" |
| ) |
| |
| // ident type-checks identifier e and initializes x with the value or type of e. |
| // If an error occurred, x.mode is set to invalid. |
| // For the meaning of def, see Checker.definedType, below. |
| // If wantType is set, the identifier e is expected to denote a type. |
| // |
| func (check *Checker) ident(x *operand, e *ast.Ident, def *Named, wantType bool) { |
| x.mode = invalid |
| x.expr = e |
| |
| // Note that we cannot use check.lookup here because the returned scope |
| // may be different from obj.Parent(). See also Scope.LookupParent doc. |
| scope, obj := check.scope.LookupParent(e.Name, check.pos) |
| if obj == nil { |
| if e.Name == "_" { |
| check.errorf(e, _InvalidBlank, "cannot use _ as value or type") |
| } else { |
| check.errorf(e, _UndeclaredName, "undeclared name: %s", e.Name) |
| } |
| return |
| } |
| check.recordUse(e, obj) |
| |
| // Type-check the object. |
| // Only call Checker.objDecl if the object doesn't have a type yet |
| // (in which case we must actually determine it) or the object is a |
| // TypeName and we also want a type (in which case we might detect |
| // a cycle which needs to be reported). Otherwise we can skip the |
| // call and avoid a possible cycle error in favor of the more |
| // informative "not a type/value" error that this function's caller |
| // will issue (see issue #25790). |
| typ := obj.Type() |
| if _, gotType := obj.(*TypeName); typ == nil || gotType && wantType { |
| check.objDecl(obj, def) |
| typ = obj.Type() // type must have been assigned by Checker.objDecl |
| } |
| assert(typ != nil) |
| |
| // The object may be dot-imported: If so, remove its package from |
| // the map of unused dot imports for the respective file scope. |
| // (This code is only needed for dot-imports. Without them, |
| // we only have to mark variables, see *Var case below). |
| if pkg := obj.Pkg(); pkg != check.pkg && pkg != nil { |
| delete(check.unusedDotImports[scope], pkg) |
| } |
| |
| switch obj := obj.(type) { |
| case *PkgName: |
| check.errorf(e, _InvalidPkgUse, "use of package %s not in selector", obj.name) |
| return |
| |
| case *Const: |
| check.addDeclDep(obj) |
| if typ == Typ[Invalid] { |
| return |
| } |
| if obj == universeIota { |
| if check.iota == nil { |
| check.errorf(e, _InvalidIota, "cannot use iota outside constant declaration") |
| return |
| } |
| x.val = check.iota |
| } else { |
| x.val = obj.val |
| } |
| assert(x.val != nil) |
| x.mode = constant_ |
| |
| case *TypeName: |
| x.mode = typexpr |
| |
| case *Var: |
| // It's ok to mark non-local variables, but ignore variables |
| // from other packages to avoid potential race conditions with |
| // dot-imported variables. |
| if obj.pkg == check.pkg { |
| obj.used = true |
| } |
| check.addDeclDep(obj) |
| if typ == Typ[Invalid] { |
| return |
| } |
| x.mode = variable |
| |
| case *Func: |
| check.addDeclDep(obj) |
| x.mode = value |
| |
| case *Builtin: |
| x.id = obj.id |
| x.mode = builtin |
| |
| case *Nil: |
| x.mode = value |
| |
| default: |
| unreachable() |
| } |
| |
| x.typ = typ |
| } |
| |
| // typ type-checks the type expression e and returns its type, or Typ[Invalid]. |
| func (check *Checker) typ(e ast.Expr) Type { |
| return check.definedType(e, nil) |
| } |
| |
| // definedType is like typ but also accepts a type name def. |
| // If def != nil, e is the type specification for the defined type def, declared |
| // in a type declaration, and def.underlying will be set to the type of e before |
| // any components of e are type-checked. |
| // |
| func (check *Checker) definedType(e ast.Expr, def *Named) (T Type) { |
| if trace { |
| check.trace(e.Pos(), "%s", e) |
| check.indent++ |
| defer func() { |
| check.indent-- |
| check.trace(e.Pos(), "=> %s", T) |
| }() |
| } |
| |
| T = check.typInternal(e, def) |
| assert(isTyped(T)) |
| check.recordTypeAndValue(e, typexpr, T, nil) |
| |
| return |
| } |
| |
| // funcType type-checks a function or method type. |
| func (check *Checker) funcType(sig *Signature, recvPar *ast.FieldList, ftyp *ast.FuncType) { |
| scope := NewScope(check.scope, token.NoPos, token.NoPos, "function") |
| scope.isFunc = true |
| check.recordScope(ftyp, scope) |
| |
| recvList, _ := check.collectParams(scope, recvPar, false) |
| params, variadic := check.collectParams(scope, ftyp.Params, true) |
| results, _ := check.collectParams(scope, ftyp.Results, false) |
| |
| if recvPar != nil { |
| // recv parameter list present (may be empty) |
| // spec: "The receiver is specified via an extra parameter section preceding the |
| // method name. That parameter section must declare a single parameter, the receiver." |
| var recv *Var |
| switch len(recvList) { |
| case 0: |
| check.error(recvPar, _BadRecv, "method is missing receiver") |
| recv = NewParam(0, nil, "", Typ[Invalid]) // ignore recv below |
| default: |
| // more than one receiver |
| check.error(recvList[len(recvList)-1], _BadRecv, "method must have exactly one receiver") |
| fallthrough // continue with first receiver |
| case 1: |
| recv = recvList[0] |
| } |
| // spec: "The receiver type must be of the form T or *T where T is a type name." |
| // (ignore invalid types - error was reported before) |
| if t, _ := deref(recv.typ); t != Typ[Invalid] { |
| var err string |
| if T, _ := t.(*Named); T != nil { |
| // spec: "The type denoted by T is called the receiver base type; it must not |
| // be a pointer or interface type and it must be declared in the same package |
| // as the method." |
| if T.obj.pkg != check.pkg { |
| err = "type not defined in this package" |
| } else { |
| // TODO(gri) This is not correct if the underlying type is unknown yet. |
| switch u := T.underlying.(type) { |
| case *Basic: |
| // unsafe.Pointer is treated like a regular pointer |
| if u.kind == UnsafePointer { |
| err = "unsafe.Pointer" |
| } |
| case *Pointer, *Interface: |
| err = "pointer or interface type" |
| } |
| } |
| } else { |
| err = "basic or unnamed type" |
| } |
| if err != "" { |
| check.errorf(recv, _InvalidRecv, "invalid receiver %s (%s)", recv.typ, err) |
| // ok to continue |
| } |
| } |
| sig.recv = recv |
| } |
| |
| sig.scope = scope |
| sig.params = NewTuple(params...) |
| sig.results = NewTuple(results...) |
| sig.variadic = variadic |
| } |
| |
| // typInternal drives type checking of types. |
| // Must only be called by definedType. |
| // |
| func (check *Checker) typInternal(e ast.Expr, def *Named) Type { |
| switch e := e.(type) { |
| case *ast.BadExpr: |
| // ignore - error reported before |
| |
| case *ast.Ident: |
| var x operand |
| check.ident(&x, e, def, true) |
| |
| switch x.mode { |
| case typexpr: |
| typ := x.typ |
| def.setUnderlying(typ) |
| return typ |
| case invalid: |
| // ignore - error reported before |
| case novalue: |
| check.errorf(&x, _NotAType, "%s used as type", &x) |
| default: |
| check.errorf(&x, _NotAType, "%s is not a type", &x) |
| } |
| |
| case *ast.SelectorExpr: |
| var x operand |
| check.selector(&x, e) |
| |
| switch x.mode { |
| case typexpr: |
| typ := x.typ |
| def.setUnderlying(typ) |
| return typ |
| case invalid: |
| // ignore - error reported before |
| case novalue: |
| check.errorf(&x, _NotAType, "%s used as type", &x) |
| default: |
| check.errorf(&x, _NotAType, "%s is not a type", &x) |
| } |
| |
| case *ast.ParenExpr: |
| return check.definedType(e.X, def) |
| |
| case *ast.ArrayType: |
| if e.Len != nil { |
| typ := new(Array) |
| def.setUnderlying(typ) |
| typ.len = check.arrayLength(e.Len) |
| typ.elem = check.typ(e.Elt) |
| return typ |
| |
| } else { |
| typ := new(Slice) |
| def.setUnderlying(typ) |
| typ.elem = check.typ(e.Elt) |
| return typ |
| } |
| |
| case *ast.StructType: |
| typ := new(Struct) |
| def.setUnderlying(typ) |
| check.structType(typ, e) |
| return typ |
| |
| case *ast.StarExpr: |
| typ := new(Pointer) |
| def.setUnderlying(typ) |
| typ.base = check.typ(e.X) |
| return typ |
| |
| case *ast.FuncType: |
| typ := new(Signature) |
| def.setUnderlying(typ) |
| check.funcType(typ, nil, e) |
| return typ |
| |
| case *ast.InterfaceType: |
| typ := new(Interface) |
| def.setUnderlying(typ) |
| check.interfaceType(typ, e, def) |
| return typ |
| |
| case *ast.MapType: |
| typ := new(Map) |
| def.setUnderlying(typ) |
| |
| typ.key = check.typ(e.Key) |
| typ.elem = check.typ(e.Value) |
| |
| // spec: "The comparison operators == and != must be fully defined |
| // for operands of the key type; thus the key type must not be a |
| // function, map, or slice." |
| // |
| // Delay this check because it requires fully setup types; |
| // it is safe to continue in any case (was issue 6667). |
| check.atEnd(func() { |
| if !Comparable(typ.key) { |
| check.errorf(e.Key, _IncomparableMapKey, "incomparable map key type %s", typ.key) |
| } |
| }) |
| |
| return typ |
| |
| case *ast.ChanType: |
| typ := new(Chan) |
| def.setUnderlying(typ) |
| |
| dir := SendRecv |
| switch e.Dir { |
| case ast.SEND | ast.RECV: |
| // nothing to do |
| case ast.SEND: |
| dir = SendOnly |
| case ast.RECV: |
| dir = RecvOnly |
| default: |
| check.invalidAST(e, "unknown channel direction %d", e.Dir) |
| // ok to continue |
| } |
| |
| typ.dir = dir |
| typ.elem = check.typ(e.Value) |
| return typ |
| |
| default: |
| check.errorf(e, _NotAType, "%s is not a type", e) |
| } |
| |
| typ := Typ[Invalid] |
| def.setUnderlying(typ) |
| return typ |
| } |
| |
| // typeOrNil type-checks the type expression (or nil value) e |
| // and returns the typ of e, or nil. |
| // If e is neither a type nor nil, typOrNil returns Typ[Invalid]. |
| // |
| func (check *Checker) typOrNil(e ast.Expr) Type { |
| var x operand |
| check.rawExpr(&x, e, nil) |
| switch x.mode { |
| case invalid: |
| // ignore - error reported before |
| case novalue: |
| check.errorf(&x, _NotAType, "%s used as type", &x) |
| case typexpr: |
| return x.typ |
| case value: |
| if x.isNil() { |
| return nil |
| } |
| fallthrough |
| default: |
| check.errorf(&x, _NotAType, "%s is not a type", &x) |
| } |
| return Typ[Invalid] |
| } |
| |
| // arrayLength type-checks the array length expression e |
| // and returns the constant length >= 0, or a value < 0 |
| // to indicate an error (and thus an unknown length). |
| func (check *Checker) arrayLength(e ast.Expr) int64 { |
| var x operand |
| check.expr(&x, e) |
| if x.mode != constant_ { |
| if x.mode != invalid { |
| check.errorf(&x, _InvalidArrayLen, "array length %s must be constant", &x) |
| } |
| return -1 |
| } |
| if isUntyped(x.typ) || isInteger(x.typ) { |
| if val := constant.ToInt(x.val); val.Kind() == constant.Int { |
| if representableConst(val, check, Typ[Int], nil) { |
| if n, ok := constant.Int64Val(val); ok && n >= 0 { |
| return n |
| } |
| check.errorf(&x, _InvalidArrayLen, "invalid array length %s", &x) |
| return -1 |
| } |
| } |
| } |
| check.errorf(&x, _InvalidArrayLen, "array length %s must be integer", &x) |
| return -1 |
| } |
| |
| func (check *Checker) collectParams(scope *Scope, list *ast.FieldList, variadicOk bool) (params []*Var, variadic bool) { |
| if list == nil { |
| return |
| } |
| |
| var named, anonymous bool |
| for i, field := range list.List { |
| ftype := field.Type |
| if t, _ := ftype.(*ast.Ellipsis); t != nil { |
| ftype = t.Elt |
| if variadicOk && i == len(list.List)-1 && len(field.Names) <= 1 { |
| variadic = true |
| } else { |
| check.softErrorf(t, _MisplacedDotDotDot, "can only use ... with final parameter in list") |
| // ignore ... and continue |
| } |
| } |
| typ := check.typ(ftype) |
| // The parser ensures that f.Tag is nil and we don't |
| // care if a constructed AST contains a non-nil tag. |
| if len(field.Names) > 0 { |
| // named parameter |
| for _, name := range field.Names { |
| if name.Name == "" { |
| check.invalidAST(name, "anonymous parameter") |
| // ok to continue |
| } |
| par := NewParam(name.Pos(), check.pkg, name.Name, typ) |
| check.declare(scope, name, par, scope.pos) |
| params = append(params, par) |
| } |
| named = true |
| } else { |
| // anonymous parameter |
| par := NewParam(ftype.Pos(), check.pkg, "", typ) |
| check.recordImplicit(field, par) |
| params = append(params, par) |
| anonymous = true |
| } |
| } |
| |
| if named && anonymous { |
| check.invalidAST(list, "list contains both named and anonymous parameters") |
| // ok to continue |
| } |
| |
| // For a variadic function, change the last parameter's type from T to []T. |
| // Since we type-checked T rather than ...T, we also need to retro-actively |
| // record the type for ...T. |
| if variadic { |
| last := params[len(params)-1] |
| last.typ = &Slice{elem: last.typ} |
| check.recordTypeAndValue(list.List[len(list.List)-1].Type, typexpr, last.typ, nil) |
| } |
| |
| return |
| } |
| |
| func (check *Checker) declareInSet(oset *objset, pos token.Pos, obj Object) bool { |
| if alt := oset.insert(obj); alt != nil { |
| check.errorf(atPos(pos), _DuplicateDecl, "%s redeclared", obj.Name()) |
| check.reportAltDecl(alt) |
| return false |
| } |
| return true |
| } |
| |
| func (check *Checker) interfaceType(ityp *Interface, iface *ast.InterfaceType, def *Named) { |
| for _, f := range iface.Methods.List { |
| if len(f.Names) > 0 { |
| // We have a method with name f.Names[0]. |
| // (The parser ensures that there's only one method |
| // and we don't care if a constructed AST has more.) |
| name := f.Names[0] |
| if name.Name == "_" { |
| check.errorf(name, _BlankIfaceMethod, "invalid method name _") |
| continue // ignore |
| } |
| |
| typ := check.typ(f.Type) |
| sig, _ := typ.(*Signature) |
| if sig == nil { |
| if typ != Typ[Invalid] { |
| check.invalidAST(f.Type, "%s is not a method signature", typ) |
| } |
| continue // ignore |
| } |
| |
| // use named receiver type if available (for better error messages) |
| var recvTyp Type = ityp |
| if def != nil { |
| recvTyp = def |
| } |
| sig.recv = NewVar(name.Pos(), check.pkg, "", recvTyp) |
| |
| m := NewFunc(name.Pos(), check.pkg, name.Name, sig) |
| check.recordDef(name, m) |
| ityp.methods = append(ityp.methods, m) |
| } else { |
| // We have an embedded interface and f.Type is its |
| // (possibly qualified) embedded type name. Collect |
| // it if it's a valid interface. |
| typ := check.typ(f.Type) |
| |
| utyp := check.underlying(typ) |
| if _, ok := utyp.(*Interface); !ok { |
| if utyp != Typ[Invalid] { |
| check.errorf(f.Type, _InvalidIfaceEmbed, "%s is not an interface", typ) |
| } |
| continue |
| } |
| |
| ityp.embeddeds = append(ityp.embeddeds, typ) |
| check.posMap[ityp] = append(check.posMap[ityp], f.Type.Pos()) |
| } |
| } |
| |
| if len(ityp.methods) == 0 && len(ityp.embeddeds) == 0 { |
| // empty interface |
| ityp.allMethods = markComplete |
| return |
| } |
| |
| // sort for API stability |
| sort.Sort(byUniqueMethodName(ityp.methods)) |
| sort.Stable(byUniqueTypeName(ityp.embeddeds)) |
| |
| check.later(func() { check.completeInterface(ityp) }) |
| } |
| |
| func (check *Checker) completeInterface(ityp *Interface) { |
| if ityp.allMethods != nil { |
| return |
| } |
| |
| // completeInterface may be called via the LookupFieldOrMethod, |
| // MissingMethod, Identical, or IdenticalIgnoreTags external API |
| // in which case check will be nil. In this case, type-checking |
| // must be finished and all interfaces should have been completed. |
| if check == nil { |
| panic("internal error: incomplete interface") |
| } |
| |
| if trace { |
| check.trace(token.NoPos, "complete %s", ityp) |
| check.indent++ |
| defer func() { |
| check.indent-- |
| check.trace(token.NoPos, "=> %s", ityp) |
| }() |
| } |
| |
| // An infinitely expanding interface (due to a cycle) is detected |
| // elsewhere (Checker.validType), so here we simply assume we only |
| // have valid interfaces. Mark the interface as complete to avoid |
| // infinite recursion if the validType check occurs later for some |
| // reason. |
| ityp.allMethods = markComplete |
| |
| // Methods of embedded interfaces are collected unchanged; i.e., the identity |
| // of a method I.m's Func Object of an interface I is the same as that of |
| // the method m in an interface that embeds interface I. On the other hand, |
| // if a method is embedded via multiple overlapping embedded interfaces, we |
| // don't provide a guarantee which "original m" got chosen for the embedding |
| // interface. See also issue #34421. |
| // |
| // If we don't care to provide this identity guarantee anymore, instead of |
| // reusing the original method in embeddings, we can clone the method's Func |
| // Object and give it the position of a corresponding embedded interface. Then |
| // we can get rid of the mpos map below and simply use the cloned method's |
| // position. |
| |
| var seen objset |
| var methods []*Func |
| mpos := make(map[*Func]token.Pos) // method specification or method embedding position, for good error messages |
| addMethod := func(pos token.Pos, m *Func, explicit bool) { |
| switch other := seen.insert(m); { |
| case other == nil: |
| methods = append(methods, m) |
| mpos[m] = pos |
| case explicit: |
| check.errorf(atPos(pos), _DuplicateDecl, "duplicate method %s", m.name) |
| check.errorf(atPos(mpos[other.(*Func)]), _DuplicateDecl, "\tother declaration of %s", m.name) // secondary error, \t indented |
| default: |
| // check method signatures after all types are computed (issue #33656) |
| check.atEnd(func() { |
| if !check.identical(m.typ, other.Type()) { |
| check.errorf(atPos(pos), _DuplicateDecl, "duplicate method %s", m.name) |
| check.errorf(atPos(mpos[other.(*Func)]), _DuplicateDecl, "\tother declaration of %s", m.name) // secondary error, \t indented |
| } |
| }) |
| } |
| } |
| |
| for _, m := range ityp.methods { |
| addMethod(m.pos, m, true) |
| } |
| |
| posList := check.posMap[ityp] |
| for i, typ := range ityp.embeddeds { |
| pos := posList[i] // embedding position |
| typ, ok := check.underlying(typ).(*Interface) |
| if !ok { |
| // An error was reported when collecting the embedded types. |
| // Ignore it. |
| continue |
| } |
| check.completeInterface(typ) |
| for _, m := range typ.allMethods { |
| addMethod(pos, m, false) // use embedding position pos rather than m.pos |
| } |
| } |
| |
| if methods != nil { |
| sort.Sort(byUniqueMethodName(methods)) |
| ityp.allMethods = methods |
| } |
| } |
| |
| // byUniqueTypeName named type lists can be sorted by their unique type names. |
| type byUniqueTypeName []Type |
| |
| func (a byUniqueTypeName) Len() int { return len(a) } |
| func (a byUniqueTypeName) Less(i, j int) bool { return sortName(a[i]) < sortName(a[j]) } |
| func (a byUniqueTypeName) Swap(i, j int) { a[i], a[j] = a[j], a[i] } |
| |
| func sortName(t Type) string { |
| if named, _ := t.(*Named); named != nil { |
| return named.obj.Id() |
| } |
| return "" |
| } |
| |
| // byUniqueMethodName method lists can be sorted by their unique method names. |
| type byUniqueMethodName []*Func |
| |
| func (a byUniqueMethodName) Len() int { return len(a) } |
| func (a byUniqueMethodName) Less(i, j int) bool { return a[i].Id() < a[j].Id() } |
| func (a byUniqueMethodName) Swap(i, j int) { a[i], a[j] = a[j], a[i] } |
| |
| func (check *Checker) tag(t *ast.BasicLit) string { |
| if t != nil { |
| if t.Kind == token.STRING { |
| if val, err := strconv.Unquote(t.Value); err == nil { |
| return val |
| } |
| } |
| check.invalidAST(t, "incorrect tag syntax: %q", t.Value) |
| } |
| return "" |
| } |
| |
| func (check *Checker) structType(styp *Struct, e *ast.StructType) { |
| list := e.Fields |
| if list == nil { |
| return |
| } |
| |
| // struct fields and tags |
| var fields []*Var |
| var tags []string |
| |
| // for double-declaration checks |
| var fset objset |
| |
| // current field typ and tag |
| var typ Type |
| var tag string |
| add := func(ident *ast.Ident, embedded bool, pos token.Pos) { |
| if tag != "" && tags == nil { |
| tags = make([]string, len(fields)) |
| } |
| if tags != nil { |
| tags = append(tags, tag) |
| } |
| |
| name := ident.Name |
| fld := NewField(pos, check.pkg, name, typ, embedded) |
| // spec: "Within a struct, non-blank field names must be unique." |
| if name == "_" || check.declareInSet(&fset, pos, fld) { |
| fields = append(fields, fld) |
| check.recordDef(ident, fld) |
| } |
| } |
| |
| // addInvalid adds an embedded field of invalid type to the struct for |
| // fields with errors; this keeps the number of struct fields in sync |
| // with the source as long as the fields are _ or have different names |
| // (issue #25627). |
| addInvalid := func(ident *ast.Ident, pos token.Pos) { |
| typ = Typ[Invalid] |
| tag = "" |
| add(ident, true, pos) |
| } |
| |
| for _, f := range list.List { |
| typ = check.typ(f.Type) |
| tag = check.tag(f.Tag) |
| if len(f.Names) > 0 { |
| // named fields |
| for _, name := range f.Names { |
| add(name, false, name.Pos()) |
| } |
| } else { |
| // embedded field |
| // spec: "An embedded type must be specified as a type name T or as a pointer |
| // to a non-interface type name *T, and T itself may not be a pointer type." |
| pos := f.Type.Pos() |
| name := embeddedFieldIdent(f.Type) |
| if name == nil { |
| check.invalidAST(f.Type, "embedded field type %s has no name", f.Type) |
| name = ast.NewIdent("_") |
| name.NamePos = pos |
| addInvalid(name, pos) |
| continue |
| } |
| t, isPtr := deref(typ) |
| // Because we have a name, typ must be of the form T or *T, where T is the name |
| // of a (named or alias) type, and t (= deref(typ)) must be the type of T. |
| switch t := t.Underlying().(type) { |
| case *Basic: |
| if t == Typ[Invalid] { |
| // error was reported before |
| addInvalid(name, pos) |
| continue |
| } |
| |
| // unsafe.Pointer is treated like a regular pointer |
| if t.kind == UnsafePointer { |
| check.errorf(f.Type, _InvalidPtrEmbed, "embedded field type cannot be unsafe.Pointer") |
| addInvalid(name, pos) |
| continue |
| } |
| |
| case *Pointer: |
| check.errorf(f.Type, _InvalidPtrEmbed, "embedded field type cannot be a pointer") |
| addInvalid(name, pos) |
| continue |
| |
| case *Interface: |
| if isPtr { |
| check.errorf(f.Type, _InvalidPtrEmbed, "embedded field type cannot be a pointer to an interface") |
| addInvalid(name, pos) |
| continue |
| } |
| } |
| add(name, true, pos) |
| } |
| } |
| |
| styp.fields = fields |
| styp.tags = tags |
| } |
| |
| func embeddedFieldIdent(e ast.Expr) *ast.Ident { |
| switch e := e.(type) { |
| case *ast.Ident: |
| return e |
| case *ast.StarExpr: |
| // *T is valid, but **T is not |
| if _, ok := e.X.(*ast.StarExpr); !ok { |
| return embeddedFieldIdent(e.X) |
| } |
| case *ast.SelectorExpr: |
| return e.Sel |
| } |
| return nil // invalid embedded field |
| } |
