1 // Copyright 2013 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
18 // A declInfo describes a package-level const, type, var, or func declaration.
19 type declInfo struct {
20 file *Scope // scope of file containing this declaration
21 lhs []*Var // lhs of n:1 variable declarations, or nil
22 vtyp ast.Expr // type, or nil (for const and var declarations only)
23 init ast.Expr // init/orig expression, or nil (for const and var declarations only)
24 inherited bool // if set, the init expression is inherited from a previous constant declaration
25 tdecl *ast.TypeSpec // type declaration, or nil
26 fdecl *ast.FuncDecl // func declaration, or nil
28 // The deps field tracks initialization expression dependencies.
29 deps map[Object]bool // lazily initialized
32 // hasInitializer reports whether the declared object has an initialization
33 // expression or function body.
34 func (d *declInfo) hasInitializer() bool {
35 return d.init != nil || d.fdecl != nil && d.fdecl.Body != nil
38 // addDep adds obj to the set of objects d's init expression depends on.
39 func (d *declInfo) addDep(obj Object) {
42 m = make(map[Object]bool)
48 // arityMatch checks that the lhs and rhs of a const or var decl
49 // have the appropriate number of names and init exprs. For const
50 // decls, init is the value spec providing the init exprs; for
51 // var decls, init is nil (the init exprs are in s in this case).
52 func (check *Checker) arityMatch(s, init *ast.ValueSpec) {
59 const code = _WrongAssignCount
61 case init == nil && r == 0:
62 // var decl w/o init expr
64 check.errorf(s, code, "missing type or init expr")
67 if l < len(s.Values) {
70 check.errorf(n, code, "extra init expr %s", n)
71 // TODO(gri) avoid declared but not used error here
73 // init exprs "inherited"
74 check.errorf(s, code, "extra init expr at %s", check.fset.Position(init.Pos()))
75 // TODO(gri) avoid declared but not used error here
77 case l > r && (init != nil || r != 1):
79 check.errorf(n, code, "missing init expr for %s", n)
83 func validatedImportPath(path string) (string, error) {
84 s, err := strconv.Unquote(path)
89 return "", fmt.Errorf("empty string")
91 const illegalChars = `!"#$%&'()*,:;<=>?[\]^{|}` + "`\uFFFD"
93 if !unicode.IsGraphic(r) || unicode.IsSpace(r) || strings.ContainsRune(illegalChars, r) {
94 return s, fmt.Errorf("invalid character %#U", r)
100 // declarePkgObj declares obj in the package scope, records its ident -> obj mapping,
101 // and updates check.objMap. The object must not be a function or method.
102 func (check *Checker) declarePkgObj(ident *ast.Ident, obj Object, d *declInfo) {
103 assert(ident.Name == obj.Name())
105 // spec: "A package-scope or file-scope identifier with name init
106 // may only be declared to be a function with this (func()) signature."
107 if ident.Name == "init" {
108 check.errorf(ident, _InvalidInitDecl, "cannot declare init - must be func")
112 // spec: "The main package must have package name main and declare
113 // a function main that takes no arguments and returns no value."
114 if ident.Name == "main" && check.pkg.name == "main" {
115 check.errorf(ident, _InvalidMainDecl, "cannot declare main - must be func")
119 check.declare(check.pkg.scope, ident, obj, token.NoPos)
120 check.objMap[obj] = d
121 obj.setOrder(uint32(len(check.objMap)))
124 // filename returns a filename suitable for debugging output.
125 func (check *Checker) filename(fileNo int) string {
126 file := check.files[fileNo]
127 if pos := file.Pos(); pos.IsValid() {
128 return check.fset.File(pos).Name()
130 return fmt.Sprintf("file[%d]", fileNo)
133 func (check *Checker) importPackage(pos token.Pos, path, dir string) *Package {
134 // If we already have a package for the given (path, dir)
135 // pair, use it instead of doing a full import.
136 // Checker.impMap only caches packages that are marked Complete
137 // or fake (dummy packages for failed imports). Incomplete but
138 // non-fake packages do require an import to complete them.
139 key := importKey{path, dir}
140 imp := check.impMap[key]
145 // no package yet => import it
146 if path == "C" && (check.conf.FakeImportC || check.conf.go115UsesCgo) {
147 imp = NewPackage("C", "C")
148 imp.fake = true // package scope is not populated
149 imp.cgo = check.conf.go115UsesCgo
153 if importer := check.conf.Importer; importer == nil {
154 err = fmt.Errorf("Config.Importer not installed")
155 } else if importerFrom, ok := importer.(ImporterFrom); ok {
156 imp, err = importerFrom.ImportFrom(path, dir, 0)
157 if imp == nil && err == nil {
158 err = fmt.Errorf("Config.Importer.ImportFrom(%s, %s, 0) returned nil but no error", path, dir)
161 imp, err = importer.Import(path)
162 if imp == nil && err == nil {
163 err = fmt.Errorf("Config.Importer.Import(%s) returned nil but no error", path)
166 // make sure we have a valid package name
167 // (errors here can only happen through manipulation of packages after creation)
168 if err == nil && imp != nil && (imp.name == "_" || imp.name == "") {
169 err = fmt.Errorf("invalid package name: %q", imp.name)
170 imp = nil // create fake package below
173 check.errorf(atPos(pos), _BrokenImport, "could not import %s (%s)", path, err)
175 // create a new fake package
176 // come up with a sensible package name (heuristic)
178 if i := len(name); i > 0 && name[i-1] == '/' {
181 if i := strings.LastIndex(name, "/"); i >= 0 {
184 imp = NewPackage(path, name)
186 // continue to use the package as best as we can
187 imp.fake = true // avoid follow-up lookup failures
191 // package should be complete or marked fake, but be cautious
192 if imp.complete || imp.fake {
193 check.impMap[key] = imp
194 check.pkgCnt[imp.name]++
198 // something went wrong (importer may have returned incomplete package without error)
202 // collectObjects collects all file and package objects and inserts them
203 // into their respective scopes. It also performs imports and associates
204 // methods with receiver base type names.
205 func (check *Checker) collectObjects() {
208 // pkgImports is the set of packages already imported by any package file seen
209 // so far. Used to avoid duplicate entries in pkg.imports. Allocate and populate
210 // it (pkg.imports may not be empty if we are checking test files incrementally).
211 // Note that pkgImports is keyed by package (and thus package path), not by an
212 // importKey value. Two different importKey values may map to the same package
213 // which is why we cannot use the check.impMap here.
214 var pkgImports = make(map[*Package]bool)
215 for _, imp := range pkg.imports {
216 pkgImports[imp] = true
219 type methodInfo struct {
221 ptr bool // true if pointer receiver
222 recv *ast.Ident // receiver type name
224 var methods []methodInfo // collected methods with valid receivers and non-blank _ names
225 var fileScopes []*Scope
226 for fileNo, file := range check.files {
227 // The package identifier denotes the current package,
228 // but there is no corresponding package object.
229 check.recordDef(file.Name, nil)
231 // Use the actual source file extent rather than *ast.File extent since the
232 // latter doesn't include comments which appear at the start or end of the file.
233 // Be conservative and use the *ast.File extent if we don't have a *token.File.
234 pos, end := file.Pos(), file.End()
235 if f := check.fset.File(file.Pos()); f != nil {
236 pos, end = token.Pos(f.Base()), token.Pos(f.Base()+f.Size())
238 fileScope := NewScope(check.pkg.scope, pos, end, check.filename(fileNo))
239 fileScopes = append(fileScopes, fileScope)
240 check.recordScope(file, fileScope)
242 // determine file directory, necessary to resolve imports
243 // FileName may be "" (typically for tests) in which case
244 // we get "." as the directory which is what we would want.
245 fileDir := dir(check.fset.Position(file.Name.Pos()).Filename)
247 check.walkDecls(file.Decls, func(d decl) {
248 switch d := d.(type) {
251 path, err := validatedImportPath(d.spec.Path.Value)
253 check.errorf(d.spec.Path, _BadImportPath, "invalid import path (%s)", err)
257 imp := check.importPackage(d.spec.Path.Pos(), path, fileDir)
262 // local name overrides imported package name
264 if d.spec.Name != nil {
265 name = d.spec.Name.Name
267 // match cmd/compile (not prescribed by spec)
268 check.errorf(d.spec.Name, _ImportCRenamed, `cannot rename import "C"`)
274 check.errorf(d.spec.Name, _InvalidInitDecl, "cannot import package as init - init must be a func")
278 // add package to list of explicit imports
279 // (this functionality is provided as a convenience
280 // for clients; it is not needed for type-checking)
281 if !pkgImports[imp] {
282 pkgImports[imp] = true
283 pkg.imports = append(pkg.imports, imp)
286 pkgName := NewPkgName(d.spec.Pos(), pkg, name, imp)
287 if d.spec.Name != nil {
288 // in a dot-import, the dot represents the package
289 check.recordDef(d.spec.Name, pkgName)
291 check.recordImplicit(d.spec, pkgName)
295 // match cmd/compile (not prescribed by spec)
299 // add import to file scope
300 check.imports = append(check.imports, pkgName)
303 if check.dotImportMap == nil {
304 check.dotImportMap = make(map[dotImportKey]*PkgName)
306 // merge imported scope with file scope
307 for _, obj := range imp.scope.elems {
308 // A package scope may contain non-exported objects,
309 // do not import them!
311 // declare dot-imported object
312 // (Do not use check.declare because it modifies the object
313 // via Object.setScopePos, which leads to a race condition;
314 // the object may be imported into more than one file scope
315 // concurrently. See issue #32154.)
316 if alt := fileScope.Insert(obj); alt != nil {
317 check.errorf(d.spec.Name, _DuplicateDecl, "%s redeclared in this block", obj.Name())
318 check.reportAltDecl(alt)
320 check.dotImportMap[dotImportKey{fileScope, obj}] = pkgName
325 // declare imported package object in file scope
326 // (no need to provide s.Name since we called check.recordDef earlier)
327 check.declare(fileScope, nil, pkgName, token.NoPos)
330 // declare all constants
331 for i, name := range d.spec.Names {
332 obj := NewConst(name.Pos(), pkg, name.Name, nil, constant.MakeInt64(int64(d.iota)))
339 d := &declInfo{file: fileScope, vtyp: d.typ, init: init, inherited: d.inherited}
340 check.declarePkgObj(name, obj, d)
344 lhs := make([]*Var, len(d.spec.Names))
345 // If there's exactly one rhs initializer, use
346 // the same declInfo d1 for all lhs variables
347 // so that each lhs variable depends on the same
348 // rhs initializer (n:1 var declaration).
350 if len(d.spec.Values) == 1 {
351 // The lhs elements are only set up after the for loop below,
352 // but that's ok because declareVar only collects the declInfo
353 // for a later phase.
354 d1 = &declInfo{file: fileScope, lhs: lhs, vtyp: d.spec.Type, init: d.spec.Values[0]}
357 // declare all variables
358 for i, name := range d.spec.Names {
359 obj := NewVar(name.Pos(), pkg, name.Name, nil)
364 // individual assignments
366 if i < len(d.spec.Values) {
367 init = d.spec.Values[i]
369 di = &declInfo{file: fileScope, vtyp: d.spec.Type, init: init}
372 check.declarePkgObj(name, obj, di)
375 obj := NewTypeName(d.spec.Name.Pos(), pkg, d.spec.Name.Name, nil)
376 check.declarePkgObj(d.spec.Name, obj, &declInfo{file: fileScope, tdecl: d.spec})
378 info := &declInfo{file: fileScope, fdecl: d.decl}
379 name := d.decl.Name.Name
380 obj := NewFunc(d.decl.Name.Pos(), pkg, name, nil)
381 if !d.decl.IsMethod() {
383 if d.decl.Recv != nil {
384 check.error(d.decl.Recv, _BadRecv, "method is missing receiver")
387 if name == "init" || (name == "main" && check.pkg.name == "main") {
388 code := _InvalidInitDecl
390 code = _InvalidMainDecl
392 if d.decl.Type.TParams != nil {
393 check.softErrorf(d.decl.Type.TParams, code, "func %s must have no type parameters", name)
395 if t := d.decl.Type; t.Params.NumFields() != 0 || t.Results != nil {
396 // TODO(rFindley) Should this be a hard error?
397 check.softErrorf(d.decl, code, "func %s must have no arguments and no return values", name)
401 // don't declare init functions in the package scope - they are invisible
402 obj.parent = pkg.scope
403 check.recordDef(d.decl.Name, obj)
404 // init functions must have a body
405 if d.decl.Body == nil {
406 // TODO(gri) make this error message consistent with the others above
407 check.softErrorf(obj, _MissingInitBody, "missing function body")
410 check.declare(pkg.scope, d.decl.Name, obj, token.NoPos)
415 // TODO(rFindley) earlier versions of this code checked that methods
416 // have no type parameters, but this is checked later
417 // when type checking the function type. Confirm that
418 // we don't need to check tparams here.
420 ptr, recv, _ := check.unpackRecv(d.decl.Recv.List[0].Type, false)
421 // (Methods with invalid receiver cannot be associated to a type, and
422 // methods with blank _ names are never found; no need to collect any
423 // of them. They will still be type-checked with all the other functions.)
424 if recv != nil && name != "_" {
425 methods = append(methods, methodInfo{obj, ptr, recv})
427 check.recordDef(d.decl.Name, obj)
429 // Methods are not package-level objects but we still track them in the
430 // object map so that we can handle them like regular functions (if the
431 // receiver is invalid); also we need their fdecl info when associating
432 // them with their receiver base type, below.
433 check.objMap[obj] = info
434 obj.setOrder(uint32(len(check.objMap)))
439 // verify that objects in package and file scopes have different names
440 for _, scope := range fileScopes {
441 for _, obj := range scope.elems {
442 if alt := pkg.scope.Lookup(obj.Name()); alt != nil {
443 if pkg, ok := obj.(*PkgName); ok {
444 check.errorf(alt, _DuplicateDecl, "%s already declared through import of %s", alt.Name(), pkg.Imported())
445 check.reportAltDecl(pkg)
447 check.errorf(alt, _DuplicateDecl, "%s already declared through dot-import of %s", alt.Name(), obj.Pkg())
448 // TODO(gri) dot-imported objects don't have a position; reportAltDecl won't print anything
449 check.reportAltDecl(obj)
455 // Now that we have all package scope objects and all methods,
456 // associate methods with receiver base type name where possible.
457 // Ignore methods that have an invalid receiver. They will be
458 // type-checked later, with regular functions.
460 return // nothing to do
462 check.methods = make(map[*TypeName][]*Func)
463 for i := range methods {
465 // Determine the receiver base type and associate m with it.
466 ptr, base := check.resolveBaseTypeName(m.ptr, m.recv)
468 m.obj.hasPtrRecv = ptr
469 check.methods[base] = append(check.methods[base], m.obj)
474 // unpackRecv unpacks a receiver type and returns its components: ptr indicates whether
475 // rtyp is a pointer receiver, rname is the receiver type name, and tparams are its
476 // type parameters, if any. The type parameters are only unpacked if unpackParams is
477 // set. If rname is nil, the receiver is unusable (i.e., the source has a bug which we
478 // cannot easily work around).
479 func (check *Checker) unpackRecv(rtyp ast.Expr, unpackParams bool) (ptr bool, rname *ast.Ident, tparams []*ast.Ident) {
480 L: // unpack receiver type
481 // This accepts invalid receivers such as ***T and does not
482 // work for other invalid receivers, but we don't care. The
483 // validity of receiver expressions is checked elsewhere.
485 switch t := rtyp.(type) {
496 // unpack type parameters, if any
497 if ptyp, _ := rtyp.(*ast.IndexExpr); ptyp != nil {
500 for _, arg := range unpackExpr(ptyp.Index) {
502 switch arg := arg.(type) {
506 // ignore - error already reported by parser
508 check.invalidAST(ptyp, "parameterized receiver contains nil parameters")
510 check.errorf(arg, _Todo, "receiver type parameter %s must be an identifier", arg)
513 par = &ast.Ident{NamePos: arg.Pos(), Name: "_"}
515 tparams = append(tparams, par)
520 // unpack receiver name
521 if name, _ := rtyp.(*ast.Ident); name != nil {
528 // resolveBaseTypeName returns the non-alias base type name for typ, and whether
529 // there was a pointer indirection to get to it. The base type name must be declared
530 // in package scope, and there can be at most one pointer indirection. If no such type
531 // name exists, the returned base is nil.
532 func (check *Checker) resolveBaseTypeName(seenPtr bool, name *ast.Ident) (ptr bool, base *TypeName) {
533 // Algorithm: Starting from a type expression, which may be a name,
534 // we follow that type through alias declarations until we reach a
535 // non-alias type name. If we encounter anything but pointer types or
536 // parentheses we're done. If we encounter more than one pointer type
539 var seen map[*TypeName]bool
540 var typ ast.Expr = name
544 // check if we have a pointer type
545 if pexpr, _ := typ.(*ast.StarExpr); pexpr != nil {
546 // if we've already seen a pointer, we're done
551 typ = unparen(pexpr.X) // continue with pointer base type
554 // typ must be a name
555 name, _ := typ.(*ast.Ident)
560 // name must denote an object found in the current package scope
561 // (note that dot-imported objects are not in the package scope!)
562 obj := check.pkg.scope.Lookup(name.Name)
567 // the object must be a type name...
568 tname, _ := obj.(*TypeName)
573 // ... which we have not seen before
578 // we're done if tdecl defined tname as a new type
579 // (rather than an alias)
580 tdecl := check.objMap[tname].tdecl // must exist for objects in package scope
581 if !tdecl.Assign.IsValid() {
585 // otherwise, continue resolving
588 seen = make(map[*TypeName]bool)
594 // packageObjects typechecks all package objects, but not function bodies.
595 func (check *Checker) packageObjects() {
596 // process package objects in source order for reproducible results
597 objList := make([]Object, len(check.objMap))
599 for obj := range check.objMap {
603 sort.Sort(inSourceOrder(objList))
605 // add new methods to already type-checked types (from a prior Checker.Files call)
606 for _, obj := range objList {
607 if obj, _ := obj.(*TypeName); obj != nil && obj.typ != nil {
608 check.collectMethods(obj)
612 // We process non-alias declarations first, in order to avoid situations where
613 // the type of an alias declaration is needed before it is available. In general
614 // this is still not enough, as it is possible to create sufficiently convoluted
615 // recursive type definitions that will cause a type alias to be needed before it
616 // is available (see issue #25838 for examples).
617 // As an aside, the cmd/compiler suffers from the same problem (#25838).
618 var aliasList []*TypeName
620 for _, obj := range objList {
621 // If we have a type alias, collect it for the 2nd phase.
622 if tname, _ := obj.(*TypeName); tname != nil && check.objMap[tname].tdecl.Assign.IsValid() {
623 aliasList = append(aliasList, tname)
627 check.objDecl(obj, nil)
630 for _, obj := range aliasList {
631 check.objDecl(obj, nil)
634 // At this point we may have a non-empty check.methods map; this means that not all
635 // entries were deleted at the end of typeDecl because the respective receiver base
636 // types were not found. In that case, an error was reported when declaring those
637 // methods. We can now safely discard this map.
641 // inSourceOrder implements the sort.Sort interface.
642 type inSourceOrder []Object
644 func (a inSourceOrder) Len() int { return len(a) }
645 func (a inSourceOrder) Less(i, j int) bool { return a[i].order() < a[j].order() }
646 func (a inSourceOrder) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
648 // unusedImports checks for unused imports.
649 func (check *Checker) unusedImports() {
650 // if function bodies are not checked, packages' uses are likely missing - don't check
651 if check.conf.IgnoreFuncBodies {
655 // spec: "It is illegal (...) to directly import a package without referring to
656 // any of its exported identifiers. To import a package solely for its side-effects
657 // (initialization), use the blank identifier as explicit package name."
659 for _, obj := range check.imports {
660 if !obj.used && obj.name != "_" {
661 check.errorUnusedPkg(obj)
666 func (check *Checker) errorUnusedPkg(obj *PkgName) {
667 // If the package was imported with a name other than the final
668 // import path element, show it explicitly in the error message.
669 // Note that this handles both renamed imports and imports of
670 // packages containing unconventional package declarations.
671 // Note that this uses / always, even on Windows, because Go import
672 // paths always use forward slashes.
673 path := obj.imported.path
675 if i := strings.LastIndex(elem, "/"); i >= 0 {
678 if obj.name == "" || obj.name == "." || obj.name == elem {
679 check.softErrorf(obj, _UnusedImport, "%q imported but not used", path)
681 check.softErrorf(obj, _UnusedImport, "%q imported but not used as %s", path, obj.name)
685 // dir makes a good-faith attempt to return the directory
686 // portion of path. If path is empty, the result is ".".
687 // (Per the go/build package dependency tests, we cannot import
688 // path/filepath and simply use filepath.Dir.)
689 func dir(path string) string {
690 if i := strings.LastIndexAny(path, `/\`); i > 0 {