"go/constant"
"go/internal/typeparams"
"go/token"
- "sort"
- "strconv"
"strings"
)
return typ
}
-// isubst returns an x with identifiers substituted per the substitution map smap.
-// isubst only handles the case of (valid) method receiver type expressions correctly.
-func isubst(x ast.Expr, smap map[*ast.Ident]*ast.Ident) ast.Expr {
- switch n := x.(type) {
- case *ast.Ident:
- if alt := smap[n]; alt != nil {
- return alt
- }
- case *ast.StarExpr:
- X := isubst(n.X, smap)
- if X != n.X {
- new := *n
- new.X = X
- return &new
- }
- case *ast.IndexExpr:
- elems := typeparams.UnpackExpr(n.Index)
- var newElems []ast.Expr
- for i, elem := range elems {
- new := isubst(elem, smap)
- if new != elem {
- if newElems == nil {
- newElems = make([]ast.Expr, len(elems))
- copy(newElems, elems)
- }
- newElems[i] = new
- }
- }
- if newElems != nil {
- index := typeparams.PackExpr(newElems)
- new := *n
- new.Index = index
- return &new
- }
- case *ast.ParenExpr:
- return isubst(n.X, smap) // no need to keep parentheses
- default:
- // Other receiver type expressions are invalid.
- // It's fine to ignore those here as they will
- // be checked elsewhere.
- }
- return x
-}
-
-// funcType type-checks a function or method type.
-func (check *Checker) funcType(sig *Signature, recvPar *ast.FieldList, ftyp *ast.FuncType) {
- check.openScope(ftyp, "function")
- check.scope.isFunc = true
- check.recordScope(ftyp, check.scope)
- sig.scope = check.scope
- defer check.closeScope()
-
- var recvTyp ast.Expr // rewritten receiver type; valid if != nil
- if recvPar != nil && len(recvPar.List) > 0 {
- // collect generic receiver type parameters, if any
- // - a receiver type parameter is like any other type parameter, except that it is declared implicitly
- // - the receiver specification acts as local declaration for its type parameters, which may be blank
- _, rname, rparams := check.unpackRecv(recvPar.List[0].Type, true)
- if len(rparams) > 0 {
- // Blank identifiers don't get declared and regular type-checking of the instantiated
- // parameterized receiver type expression fails in Checker.collectParams of receiver.
- // Identify blank type parameters and substitute each with a unique new identifier named
- // "n_" (where n is the parameter index) and which cannot conflict with any user-defined
- // name.
- var smap map[*ast.Ident]*ast.Ident // substitution map from "_" to "n_" identifiers
- for i, p := range rparams {
- if p.Name == "_" {
- new := *p
- new.Name = fmt.Sprintf("%d_", i)
- rparams[i] = &new // use n_ identifier instead of _ so it can be looked up
- if smap == nil {
- smap = make(map[*ast.Ident]*ast.Ident)
- }
- smap[p] = &new
- }
- }
- if smap != nil {
- // blank identifiers were found => use rewritten receiver type
- recvTyp = isubst(recvPar.List[0].Type, smap)
- }
- sig.rparams = check.declareTypeParams(nil, rparams)
- // determine receiver type to get its type parameters
- // and the respective type parameter bounds
- var recvTParams []*TypeName
- if rname != nil {
- // recv should be a Named type (otherwise an error is reported elsewhere)
- // Also: Don't report an error via genericType since it will be reported
- // again when we type-check the signature.
- // TODO(gri) maybe the receiver should be marked as invalid instead?
- if recv := asNamed(check.genericType(rname, false)); recv != nil {
- recvTParams = recv.tparams
- }
- }
- // provide type parameter bounds
- // - only do this if we have the right number (otherwise an error is reported elsewhere)
- if len(sig.rparams) == len(recvTParams) {
- // We have a list of *TypeNames but we need a list of Types.
- list := make([]Type, len(sig.rparams))
- for i, t := range sig.rparams {
- list[i] = t.typ
- }
- smap := makeSubstMap(recvTParams, list)
- for i, tname := range sig.rparams {
- bound := recvTParams[i].typ.(*_TypeParam).bound
- // bound is (possibly) parameterized in the context of the
- // receiver type declaration. Substitute parameters for the
- // current context.
- // TODO(gri) should we assume now that bounds always exist?
- // (no bound == empty interface)
- if bound != nil {
- bound = check.subst(tname.pos, bound, smap)
- tname.typ.(*_TypeParam).bound = bound
- }
- }
- }
- }
- }
-
- if tparams := typeparams.Get(ftyp); tparams != nil {
- sig.tparams = check.collectTypeParams(tparams)
- // Always type-check method type parameters but complain that they are not allowed.
- // (A separate check is needed when type-checking interface method signatures because
- // they don't have a receiver specification.)
- if recvPar != nil {
- check.errorf(tparams, _Todo, "methods cannot have type parameters")
- }
- }
-
- // Value (non-type) parameters' scope starts in the function body. Use a temporary scope for their
- // declarations and then squash that scope into the parent scope (and report any redeclarations at
- // that time).
- scope := NewScope(check.scope, token.NoPos, token.NoPos, "function body (temp. scope)")
- recvList, _ := check.collectParams(scope, recvPar, recvTyp, false) // use rewritten receiver type, if any
- params, variadic := check.collectParams(scope, ftyp.Params, nil, true)
- results, _ := check.collectParams(scope, ftyp.Results, nil, false)
- scope.squash(func(obj, alt Object) {
- check.errorf(obj, _DuplicateDecl, "%s redeclared in this block", obj.Name())
- check.reportAltDecl(alt)
- })
-
- 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:
- // error reported by resolver
- 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]
- }
-
- // TODO(gri) We should delay rtyp expansion to when we actually need the
- // receiver; thus all checks here should be delayed to later.
- rtyp, _ := deref(recv.typ)
- rtyp = expand(rtyp)
-
- // 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 := rtyp; t != Typ[Invalid] {
- var err string
- if T := asNamed(t); 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 {
- switch u := optype(T).(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.params = NewTuple(params...)
- sig.results = NewTuple(results...)
- sig.variadic = variadic
-}
-
// goTypeName returns the Go type name for typ and
// removes any occurrences of "types." from that name.
func goTypeName(typ Type) string {
}
return res
}
-
-// collectParams declares the parameters of list in scope and returns the corresponding
-// variable list. If type0 != nil, it is used instead of the first type in list.
-func (check *Checker) collectParams(scope *Scope, list *ast.FieldList, type0 ast.Expr, variadicOk bool) (params []*Var, variadic bool) {
- if list == nil {
- return
- }
-
- var named, anonymous bool
- for i, field := range list.List {
- ftype := field.Type
- if i == 0 && type0 != nil {
- ftype = type0
- }
- 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.varType(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) {
- var tlist *ast.Ident // "type" name of first entry in a type list declaration
- var types []ast.Expr
- for _, f := range iface.Methods.List {
- if len(f.Names) > 0 {
- // We have a method with name f.Names[0], or a type
- // of a type list (name.Name == "type").
- // (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
- }
-
- if name.Name == "type" {
- // Always collect all type list entries, even from
- // different type lists, under the assumption that
- // the author intended to include all types.
- types = append(types, f.Type)
- if tlist != nil && tlist != name {
- check.errorf(name, _Todo, "cannot have multiple type lists in an interface")
- }
- tlist = name
- continue
- }
-
- 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
- }
-
- // Always type-check method type parameters but complain if they are not enabled.
- // (This extra check is needed here because interface method signatures don't have
- // a receiver specification.)
- if sig.tparams != nil {
- var at positioner = f.Type
- if tparams := typeparams.Get(f.Type); tparams != nil {
- at = tparams
- }
- check.errorf(at, _Todo, "methods cannot have type parameters")
- }
-
- // 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 type. completeInterface will
- // eventually verify that we have an interface.
- ityp.embeddeds = append(ityp.embeddeds, check.typ(f.Type))
- check.posMap[ityp] = append(check.posMap[ityp], f.Type.Pos())
- }
- }
-
- // type constraints
- ityp.types = _NewSum(check.collectTypeConstraints(iface.Pos(), types))
-
- if len(ityp.methods) == 0 && ityp.types == nil && len(ityp.embeddeds) == 0 {
- // empty interface
- ityp.allMethods = markComplete
- return
- }
-
- // sort for API stability
- sortMethods(ityp.methods)
- sortTypes(ityp.embeddeds)
-
- check.later(func() { check.completeInterface(iface.Pos(), ityp) })
-}
-
-func (check *Checker) completeInterface(pos token.Pos, 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 {
- // Types don't generally have position information.
- // If we don't have a valid pos provided, try to use
- // one close enough.
- if !pos.IsValid() && len(ityp.methods) > 0 {
- pos = ityp.methods[0].pos
- }
-
- check.trace(pos, "complete %s", ityp)
- check.indent++
- defer func() {
- check.indent--
- check.trace(pos, "=> %s (methods = %v, types = %v)", ityp, ityp.allMethods, ityp.allTypes)
- }()
- }
-
- // 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:
- // We have a duplicate method name in an embedded (not explicitly declared) method.
- // Check method signatures after all types are computed (issue #33656).
- // If we're pre-go1.14 (overlapping embeddings are not permitted), report that
- // error here as well (even though we could do it eagerly) because it's the same
- // error message.
- check.later(func() {
- if !check.allowVersion(m.pkg, 1, 14) || !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)
- }
-
- // collect types
- allTypes := ityp.types
-
- posList := check.posMap[ityp]
- for i, typ := range ityp.embeddeds {
- pos := posList[i] // embedding position
- utyp := under(typ)
- etyp := asInterface(utyp)
- if etyp == nil {
- if utyp != Typ[Invalid] {
- var format string
- if _, ok := utyp.(*_TypeParam); ok {
- format = "%s is a type parameter, not an interface"
- } else {
- format = "%s is not an interface"
- }
- // TODO: correct error code.
- check.errorf(atPos(pos), _InvalidIfaceEmbed, format, typ)
- }
- continue
- }
- check.completeInterface(pos, etyp)
- for _, m := range etyp.allMethods {
- addMethod(pos, m, false) // use embedding position pos rather than m.pos
- }
- allTypes = intersect(allTypes, etyp.allTypes)
- }
-
- if methods != nil {
- sort.Sort(byUniqueMethodName(methods))
- ityp.allMethods = methods
- }
- ityp.allTypes = allTypes
-}
-
-// intersect computes the intersection of the types x and y.
-// Note: A incomming nil type stands for the top type. A top
-// type result is returned as nil.
-func intersect(x, y Type) (r Type) {
- defer func() {
- if r == theTop {
- r = nil
- }
- }()
-
- switch {
- case x == theBottom || y == theBottom:
- return theBottom
- case x == nil || x == theTop:
- return y
- case y == nil || x == theTop:
- return x
- }
-
- xtypes := unpackType(x)
- ytypes := unpackType(y)
- // Compute the list rtypes which includes only
- // types that are in both xtypes and ytypes.
- // Quadratic algorithm, but good enough for now.
- // TODO(gri) fix this
- var rtypes []Type
- for _, x := range xtypes {
- if includes(ytypes, x) {
- rtypes = append(rtypes, x)
- }
- }
-
- if rtypes == nil {
- return theBottom
- }
- return _NewSum(rtypes)
-}
-
-func sortTypes(list []Type) {
- sort.Stable(byUniqueTypeName(list))
-}
-
-// 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 := asNamed(t); named != nil {
- return named.obj.Id()
- }
- return ""
-}
-
-func sortMethods(list []*Func) {
- sort.Sort(byUniqueMethodName(list))
-}
-
-func assertSortedMethods(list []*Func) {
- if !debug {
- panic("internal error: assertSortedMethods called outside debug mode")
- }
- if !sort.IsSorted(byUniqueMethodName(list)) {
- panic("internal error: methods not sorted")
- }
-}
-
-// 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.varType(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 {
- // TODO(rFindley): using invalidAST here causes test failures (all
- // errors should have codes). Clean this up.
- check.errorf(f.Type, _Todo, "invalid AST: embedded field type %s has no name", f.Type)
- name = ast.NewIdent("_")
- name.NamePos = pos
- addInvalid(name, pos)
- continue
- }
- add(name, true, pos)
-
- // 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.
- // We must delay this check to the end because we don't want to instantiate
- // (via under(t)) a possibly incomplete type.
-
- // for use in the closure below
- embeddedTyp := typ
- embeddedPos := f.Type
-
- check.later(func() {
- t, isPtr := deref(embeddedTyp)
- switch t := optype(t).(type) {
- case *Basic:
- if t == Typ[Invalid] {
- // error was reported before
- return
- }
- // unsafe.Pointer is treated like a regular pointer
- if t.kind == UnsafePointer {
- check.errorf(embeddedPos, _InvalidPtrEmbed, "embedded field type cannot be unsafe.Pointer")
- }
- case *Pointer:
- check.errorf(embeddedPos, _InvalidPtrEmbed, "embedded field type cannot be a pointer")
- case *Interface:
- if isPtr {
- check.errorf(embeddedPos, _InvalidPtrEmbed, "embedded field type cannot be a pointer to an interface")
- }
- }
- })
- }
- }
-
- 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
- case *ast.IndexExpr:
- return embeddedFieldIdent(e.X)
- }
- return nil // invalid embedded field
-}
-
-func (check *Checker) collectTypeConstraints(pos token.Pos, types []ast.Expr) []Type {
- list := make([]Type, 0, len(types)) // assume all types are correct
- for _, texpr := range types {
- if texpr == nil {
- check.invalidAST(atPos(pos), "missing type constraint")
- continue
- }
- list = append(list, check.varType(texpr))
- }
-
- // Ensure that each type is only present once in the type list. Types may be
- // interfaces, which may not be complete yet. It's ok to do this check at the
- // end because it's not a requirement for correctness of the code.
- // Note: This is a quadratic algorithm, but type lists tend to be short.
- check.later(func() {
- for i, t := range list {
- if t := asInterface(t); t != nil {
- check.completeInterface(types[i].Pos(), t)
- }
- if includes(list[:i], t) {
- check.softErrorf(types[i], _Todo, "duplicate type %s in type list", t)
- }
- }
- })
-
- return list
-}
-
-// includes reports whether typ is in list.
-func includes(list []Type, typ Type) bool {
- for _, e := range list {
- if Identical(typ, e) {
- return true
- }
- }
- return false
-}