| // 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 and path, see check.typ, below. |
| // |
| func (check *Checker) ident(x *operand, e *ast.Ident, def *Named, path []*TypeName) { |
| x.mode = invalid |
| x.expr = e |
| |
| scope, obj := check.scope.LookupParent(e.Name, check.pos) |
| if obj == nil { |
| if e.Name == "_" { |
| check.errorf(e.Pos(), "cannot use _ as value or type") |
| } else { |
| check.errorf(e.Pos(), "undeclared name: %s", e.Name) |
| } |
| return |
| } |
| check.recordUse(e, obj) |
| |
| check.objDecl(obj, def, path) |
| typ := obj.Type() |
| 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.Pos(), "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.Pos(), "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 |
| // check for cycle |
| // (it's ok to iterate forward because each named type appears at most once in path) |
| for i, prev := range path { |
| if prev == obj { |
| check.errorf(obj.pos, "illegal cycle in declaration of %s", obj.name) |
| // print cycle |
| for _, obj := range path[i:] { |
| check.errorf(obj.Pos(), "\t%s refers to", obj.Name()) // secondary error, \t indented |
| } |
| check.errorf(obj.Pos(), "\t%s", obj.Name()) |
| // maintain x.mode == typexpr despite error |
| typ = Typ[Invalid] |
| break |
| } |
| } |
| |
| case *Var: |
| 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 |
| } |
| |
| // typExpr type-checks the type expression e and returns its type, or Typ[Invalid]. |
| // If def != nil, e is the type specification for the named 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. Path contains the path of named types |
| // referring to this type. |
| // |
| func (check *Checker) typExpr(e ast.Expr, def *Named, path []*TypeName) (T Type) { |
| if trace { |
| check.trace(e.Pos(), "%s", e) |
| check.indent++ |
| defer func() { |
| check.indent-- |
| check.trace(e.Pos(), "=> %s", T) |
| }() |
| } |
| |
| T = check.typExprInternal(e, def, path) |
| assert(isTyped(T)) |
| check.recordTypeAndValue(e, typexpr, T, nil) |
| |
| return |
| } |
| |
| func (check *Checker) typ(e ast.Expr) Type { |
| return check.typExpr(e, nil, nil) |
| } |
| |
| // 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") |
| 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.Pos(), "method is missing receiver") |
| recv = NewParam(0, nil, "", Typ[Invalid]) // ignore recv below |
| default: |
| // more than one receiver |
| check.error(recvList[len(recvList)-1].Pos(), "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.pos, "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 |
| } |
| |
| // typExprInternal drives type checking of types. |
| // Must only be called by typExpr. |
| // |
| func (check *Checker) typExprInternal(e ast.Expr, def *Named, path []*TypeName) Type { |
| switch e := e.(type) { |
| case *ast.BadExpr: |
| // ignore - error reported before |
| |
| case *ast.Ident: |
| var x operand |
| check.ident(&x, e, def, path) |
| |
| switch x.mode { |
| case typexpr: |
| typ := x.typ |
| def.setUnderlying(typ) |
| return typ |
| case invalid: |
| // ignore - error reported before |
| case novalue: |
| check.errorf(x.pos(), "%s used as type", &x) |
| default: |
| check.errorf(x.pos(), "%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.pos(), "%s used as type", &x) |
| default: |
| check.errorf(x.pos(), "%s is not a type", &x) |
| } |
| |
| case *ast.ParenExpr: |
| return check.typExpr(e.X, def, path) |
| |
| case *ast.ArrayType: |
| if e.Len != nil { |
| typ := new(Array) |
| def.setUnderlying(typ) |
| typ.len = check.arrayLength(e.Len) |
| typ.elem = check.typExpr(e.Elt, nil, path) |
| 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, path) |
| 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, path) |
| 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.delay(func() { |
| if !Comparable(typ.key) { |
| check.errorf(e.Key.Pos(), "invalid 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.Pos(), "unknown channel direction %d", e.Dir) |
| // ok to continue |
| } |
| |
| typ.dir = dir |
| typ.elem = check.typ(e.Value) |
| return typ |
| |
| default: |
| check.errorf(e.Pos(), "%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.pos(), "%s used as type", &x) |
| case typexpr: |
| return x.typ |
| case value: |
| if x.isNil() { |
| return nil |
| } |
| fallthrough |
| default: |
| check.errorf(x.pos(), "%s is not a type", &x) |
| } |
| return Typ[Invalid] |
| } |
| |
| 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.pos(), "array length %s must be constant", &x) |
| } |
| return 0 |
| } |
| if !x.isInteger() { |
| check.errorf(x.pos(), "array length %s must be integer", &x) |
| return 0 |
| } |
| n, ok := constant.Int64Val(x.val) |
| if !ok || n < 0 { |
| check.errorf(x.pos(), "invalid array length %s", &x) |
| return 0 |
| } |
| return n |
| } |
| |
| 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 { |
| variadic = true |
| } else { |
| check.invalidAST(field.Pos(), "... not permitted") |
| // 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.Pos(), "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.Pos(), "list contains both named and anonymous parameters") |
| // ok to continue |
| } |
| |
| // For a variadic function, change the last parameter's type from T to []T. |
| if variadic && len(params) > 0 { |
| last := params[len(params)-1] |
| last.typ = &Slice{elem: last.typ} |
| } |
| |
| return |
| } |
| |
| func (check *Checker) declareInSet(oset *objset, pos token.Pos, obj Object) bool { |
| if alt := oset.insert(obj); alt != nil { |
| check.errorf(pos, "%s redeclared", obj.Name()) |
| check.reportAltDecl(alt) |
| return false |
| } |
| return true |
| } |
| |
| func (check *Checker) interfaceType(iface *Interface, ityp *ast.InterfaceType, def *Named, path []*TypeName) { |
| // empty interface: common case |
| if ityp.Methods == nil { |
| return |
| } |
| |
| // The parser ensures that field tags are nil and we don't |
| // care if a constructed AST contains non-nil tags. |
| |
| // use named receiver type if available (for better error messages) |
| var recvTyp Type = iface |
| if def != nil { |
| recvTyp = def |
| } |
| |
| // Phase 1: Collect explicitly declared methods, the corresponding |
| // signature (AST) expressions, and the list of embedded |
| // type (AST) expressions. Do not resolve signatures or |
| // embedded types yet to avoid cycles referring to this |
| // interface. |
| |
| var ( |
| mset objset |
| signatures []ast.Expr // list of corresponding method signatures |
| embedded []ast.Expr // list of embedded types |
| ) |
| for _, f := range ityp.Methods.List { |
| if len(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] |
| pos := name.Pos() |
| // spec: "As with all method sets, in an interface type, |
| // each method must have a unique non-blank name." |
| if name.Name == "_" { |
| check.errorf(pos, "invalid method name _") |
| continue |
| } |
| // Don't type-check signature yet - use an |
| // empty signature now and update it later. |
| // Since we know the receiver, set it up now |
| // (required to avoid crash in ptrRecv; see |
| // e.g. test case for issue 6638). |
| // TODO(gri) Consider marking methods signatures |
| // as incomplete, for better error messages. See |
| // also the T4 and T5 tests in testdata/cycles2.src. |
| sig := new(Signature) |
| sig.recv = NewVar(pos, check.pkg, "", recvTyp) |
| m := NewFunc(pos, check.pkg, name.Name, sig) |
| if check.declareInSet(&mset, pos, m) { |
| iface.methods = append(iface.methods, m) |
| iface.allMethods = append(iface.allMethods, m) |
| signatures = append(signatures, f.Type) |
| check.recordDef(name, m) |
| } |
| } else { |
| // embedded type |
| embedded = append(embedded, f.Type) |
| } |
| } |
| |
| // Phase 2: Resolve embedded interfaces. Because an interface must not |
| // embed itself (directly or indirectly), each embedded interface |
| // can be fully resolved without depending on any method of this |
| // interface (if there is a cycle or another error, the embedded |
| // type resolves to an invalid type and is ignored). |
| // In particular, the list of methods for each embedded interface |
| // must be complete (it cannot depend on this interface), and so |
| // those methods can be added to the list of all methods of this |
| // interface. |
| |
| for _, e := range embedded { |
| pos := e.Pos() |
| typ := check.typExpr(e, nil, path) |
| // Determine underlying embedded (possibly incomplete) type |
| // by following its forward chain. |
| named, _ := typ.(*Named) |
| under := underlying(named) |
| embed, _ := under.(*Interface) |
| if embed == nil { |
| if typ != Typ[Invalid] { |
| check.errorf(pos, "%s is not an interface", typ) |
| } |
| continue |
| } |
| iface.embeddeds = append(iface.embeddeds, named) |
| // collect embedded methods |
| for _, m := range embed.allMethods { |
| if check.declareInSet(&mset, pos, m) { |
| iface.allMethods = append(iface.allMethods, m) |
| } |
| } |
| } |
| |
| // Phase 3: At this point all methods have been collected for this interface. |
| // It is now safe to type-check the signatures of all explicitly |
| // declared methods, even if they refer to this interface via a cycle |
| // and embed the methods of this interface in a parameter of interface |
| // type. |
| |
| for i, m := range iface.methods { |
| expr := signatures[i] |
| typ := check.typ(expr) |
| sig, _ := typ.(*Signature) |
| if sig == nil { |
| if typ != Typ[Invalid] { |
| check.invalidAST(expr.Pos(), "%s is not a method signature", typ) |
| } |
| continue // keep method with empty method signature |
| } |
| // update signature, but keep recv that was set up before |
| old := m.typ.(*Signature) |
| sig.recv = old.recv |
| *old = *sig // update signature (don't replace it!) |
| } |
| |
| // TODO(gri) The list of explicit methods is only sorted for now to |
| // produce the same Interface as NewInterface. We may be able to |
| // claim source order in the future. Revisit. |
| sort.Sort(byUniqueMethodName(iface.methods)) |
| |
| // TODO(gri) The list of embedded types is only sorted for now to |
| // produce the same Interface as NewInterface. We may be able to |
| // claim source order in the future. Revisit. |
| sort.Sort(byUniqueTypeName(iface.embeddeds)) |
| |
| sort.Sort(byUniqueMethodName(iface.allMethods)) |
| } |
| |
| // byUniqueTypeName named type lists can be sorted by their unique type names. |
| type byUniqueTypeName []*Named |
| |
| func (a byUniqueTypeName) Len() int { return len(a) } |
| func (a byUniqueTypeName) Less(i, j int) bool { return a[i].obj.Id() < a[j].obj.Id() } |
| func (a byUniqueTypeName) Swap(i, j int) { a[i], a[j] = a[j], a[i] } |
| |
| // 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.Pos(), "incorrect tag syntax: %q", t.Value) |
| } |
| return "" |
| } |
| |
| func (check *Checker) structType(styp *Struct, e *ast.StructType, path []*TypeName) { |
| 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 |
| // anonymous != nil indicates an anonymous field. |
| add := func(field *ast.Field, ident *ast.Ident, anonymous *TypeName, 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, anonymous != nil) |
| // 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) |
| } |
| if anonymous != nil { |
| check.recordUse(ident, anonymous) |
| } |
| } |
| |
| for _, f := range list.List { |
| typ = check.typExpr(f.Type, nil, path) |
| tag = check.tag(f.Tag) |
| if len(f.Names) > 0 { |
| // named fields |
| for _, name := range f.Names { |
| add(f, name, nil, name.Pos()) |
| } |
| } else { |
| // anonymous field |
| name := anonymousFieldIdent(f.Type) |
| pos := f.Type.Pos() |
| t, isPtr := deref(typ) |
| switch t := t.(type) { |
| case *Basic: |
| if t == Typ[Invalid] { |
| // error was reported before |
| continue |
| } |
| // unsafe.Pointer is treated like a regular pointer |
| if t.kind == UnsafePointer { |
| check.errorf(pos, "anonymous field type cannot be unsafe.Pointer") |
| continue |
| } |
| add(f, name, Universe.Lookup(t.name).(*TypeName), pos) |
| |
| case *Named: |
| // 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." |
| switch u := t.underlying.(type) { |
| case *Basic: |
| // unsafe.Pointer is treated like a regular pointer |
| if u.kind == UnsafePointer { |
| check.errorf(pos, "anonymous field type cannot be unsafe.Pointer") |
| continue |
| } |
| case *Pointer: |
| check.errorf(pos, "anonymous field type cannot be a pointer") |
| continue |
| case *Interface: |
| if isPtr { |
| check.errorf(pos, "anonymous field type cannot be a pointer to an interface") |
| continue |
| } |
| } |
| add(f, name, t.obj, pos) |
| |
| default: |
| check.invalidAST(pos, "anonymous field type %s must be named", typ) |
| } |
| } |
| } |
| |
| styp.fields = fields |
| styp.tags = tags |
| } |
| |
| func anonymousFieldIdent(e ast.Expr) *ast.Ident { |
| switch e := e.(type) { |
| case *ast.Ident: |
| return e |
| case *ast.StarExpr: |
| return anonymousFieldIdent(e.X) |
| case *ast.SelectorExpr: |
| return e.Sel |
| } |
| return nil // invalid anonymous field |
| } |
