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 typ ast.Expr // type, or nil
23 init ast.Expr // init/orig expression, or nil
24 inherited bool // if set, the init expression is inherited from a previous constant declaration
25 fdecl *ast.FuncDecl // func declaration, or nil
26 alias bool // type alias declaration
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 var methods []*Func // list of methods with non-blank _ names
220 for fileNo, file := range check.files {
221 // The package identifier denotes the current package,
222 // but there is no corresponding package object.
223 check.recordDef(file.Name, nil)
225 // Use the actual source file extent rather than *ast.File extent since the
226 // latter doesn't include comments which appear at the start or end of the file.
227 // Be conservative and use the *ast.File extent if we don't have a *token.File.
228 pos, end := file.Pos(), file.End()
229 if f := check.fset.File(file.Pos()); f != nil {
230 pos, end = token.Pos(f.Base()), token.Pos(f.Base()+f.Size())
232 fileScope := NewScope(check.pkg.scope, pos, end, check.filename(fileNo))
233 check.recordScope(file, fileScope)
235 // determine file directory, necessary to resolve imports
236 // FileName may be "" (typically for tests) in which case
237 // we get "." as the directory which is what we would want.
238 fileDir := dir(check.fset.Position(file.Name.Pos()).Filename)
240 check.walkDecls(file.Decls, func(d decl) {
241 switch d := d.(type) {
244 path, err := validatedImportPath(d.spec.Path.Value)
246 check.errorf(d.spec.Path, _BadImportPath, "invalid import path (%s)", err)
250 imp := check.importPackage(d.spec.Path.Pos(), path, fileDir)
255 // add package to list of explicit imports
256 // (this functionality is provided as a convenience
257 // for clients; it is not needed for type-checking)
258 if !pkgImports[imp] {
259 pkgImports[imp] = true
260 pkg.imports = append(pkg.imports, imp)
263 // local name overrides imported package name
265 if d.spec.Name != nil {
266 name = d.spec.Name.Name
268 // match cmd/compile (not prescribed by spec)
269 check.errorf(d.spec.Name, _ImportCRenamed, `cannot rename import "C"`)
273 check.errorf(d.spec.Name, _InvalidInitDecl, "cannot declare init - must be func")
278 obj := NewPkgName(d.spec.Pos(), pkg, name, imp)
279 if d.spec.Name != nil {
280 // in a dot-import, the dot represents the package
281 check.recordDef(d.spec.Name, obj)
283 check.recordImplicit(d.spec, obj)
287 // match cmd/compile (not prescribed by spec)
291 // add import to file scope
293 // merge imported scope with file scope
294 for _, obj := range imp.scope.elems {
295 // A package scope may contain non-exported objects,
296 // do not import them!
298 // declare dot-imported object
299 // (Do not use check.declare because it modifies the object
300 // via Object.setScopePos, which leads to a race condition;
301 // the object may be imported into more than one file scope
302 // concurrently. See issue #32154.)
303 if alt := fileScope.Insert(obj); alt != nil {
304 check.errorf(d.spec.Name, _DuplicateDecl, "%s redeclared in this block", obj.Name())
305 check.reportAltDecl(alt)
309 // add position to set of dot-import positions for this file
310 // (this is only needed for "imported but not used" errors)
311 check.addUnusedDotImport(fileScope, imp, d.spec)
313 // declare imported package object in file scope
314 // (no need to provide s.Name since we called check.recordDef earlier)
315 check.declare(fileScope, nil, obj, token.NoPos)
318 // declare all constants
319 for i, name := range d.spec.Names {
320 obj := NewConst(name.Pos(), pkg, name.Name, nil, constant.MakeInt64(int64(d.iota)))
327 d := &declInfo{file: fileScope, typ: d.typ, init: init, inherited: d.inherited}
328 check.declarePkgObj(name, obj, d)
332 lhs := make([]*Var, len(d.spec.Names))
333 // If there's exactly one rhs initializer, use
334 // the same declInfo d1 for all lhs variables
335 // so that each lhs variable depends on the same
336 // rhs initializer (n:1 var declaration).
338 if len(d.spec.Values) == 1 {
339 // The lhs elements are only set up after the for loop below,
340 // but that's ok because declareVar only collects the declInfo
341 // for a later phase.
342 d1 = &declInfo{file: fileScope, lhs: lhs, typ: d.spec.Type, init: d.spec.Values[0]}
345 // declare all variables
346 for i, name := range d.spec.Names {
347 obj := NewVar(name.Pos(), pkg, name.Name, nil)
352 // individual assignments
354 if i < len(d.spec.Values) {
355 init = d.spec.Values[i]
357 di = &declInfo{file: fileScope, typ: d.spec.Type, init: init}
360 check.declarePkgObj(name, obj, di)
363 obj := NewTypeName(d.spec.Name.Pos(), pkg, d.spec.Name.Name, nil)
364 check.declarePkgObj(d.spec.Name, obj, &declInfo{file: fileScope, typ: d.spec.Type, alias: d.spec.Assign.IsValid()})
366 info := &declInfo{file: fileScope, fdecl: d.decl}
367 name := d.decl.Name.Name
368 obj := NewFunc(d.decl.Name.Pos(), pkg, name, nil)
369 if d.decl.Recv == nil {
372 // don't declare init functions in the package scope - they are invisible
373 obj.parent = pkg.scope
374 check.recordDef(d.decl.Name, obj)
375 // init functions must have a body
376 if d.decl.Body == nil {
377 check.softErrorf(obj, _MissingInitBody, "missing function body")
380 check.declare(pkg.scope, d.decl.Name, obj, token.NoPos)
384 // (Methods with blank _ names are never found; no need to collect
385 // them for later type association. They will still be type-checked
386 // with all the other functions.)
388 methods = append(methods, obj)
390 check.recordDef(d.decl.Name, obj)
392 // Methods are not package-level objects but we still track them in the
393 // object map so that we can handle them like regular functions (if the
394 // receiver is invalid); also we need their fdecl info when associating
395 // them with their receiver base type, below.
396 check.objMap[obj] = info
397 obj.setOrder(uint32(len(check.objMap)))
402 // verify that objects in package and file scopes have different names
403 for _, scope := range check.pkg.scope.children /* file scopes */ {
404 for _, obj := range scope.elems {
405 if alt := pkg.scope.Lookup(obj.Name()); alt != nil {
406 if pkg, ok := obj.(*PkgName); ok {
407 check.errorf(alt, _DuplicateDecl, "%s already declared through import of %s", alt.Name(), pkg.Imported())
408 check.reportAltDecl(pkg)
410 check.errorf(alt, _DuplicateDecl, "%s already declared through dot-import of %s", alt.Name(), obj.Pkg())
411 // TODO(gri) dot-imported objects don't have a position; reportAltDecl won't print anything
412 check.reportAltDecl(obj)
418 // Now that we have all package scope objects and all methods,
419 // associate methods with receiver base type name where possible.
420 // Ignore methods that have an invalid receiver. They will be
421 // type-checked later, with regular functions.
423 return // nothing to do
425 check.methods = make(map[*TypeName][]*Func)
426 for _, f := range methods {
427 fdecl := check.objMap[f].fdecl
428 if list := fdecl.Recv.List; len(list) > 0 {
430 // Determine the receiver base type and associate f with it.
431 ptr, base := check.resolveBaseTypeName(list[0].Type)
434 check.methods[base] = append(check.methods[base], f)
440 // resolveBaseTypeName returns the non-alias base type name for typ, and whether
441 // there was a pointer indirection to get to it. The base type name must be declared
442 // in package scope, and there can be at most one pointer indirection. If no such type
443 // name exists, the returned base is nil.
444 func (check *Checker) resolveBaseTypeName(typ ast.Expr) (ptr bool, base *TypeName) {
445 // Algorithm: Starting from a type expression, which may be a name,
446 // we follow that type through alias declarations until we reach a
447 // non-alias type name. If we encounter anything but pointer types or
448 // parentheses we're done. If we encounter more than one pointer type
450 var seen map[*TypeName]bool
454 // check if we have a pointer type
455 if pexpr, _ := typ.(*ast.StarExpr); pexpr != nil {
456 // if we've already seen a pointer, we're done
461 typ = unparen(pexpr.X) // continue with pointer base type
464 // typ must be a name
465 name, _ := typ.(*ast.Ident)
470 // name must denote an object found in the current package scope
471 // (note that dot-imported objects are not in the package scope!)
472 obj := check.pkg.scope.Lookup(name.Name)
477 // the object must be a type name...
478 tname, _ := obj.(*TypeName)
483 // ... which we have not seen before
488 // we're done if tdecl defined tname as a new type
489 // (rather than an alias)
490 tdecl := check.objMap[tname] // must exist for objects in package scope
495 // otherwise, continue resolving
498 seen = make(map[*TypeName]bool)
504 // packageObjects typechecks all package objects, but not function bodies.
505 func (check *Checker) packageObjects() {
506 // process package objects in source order for reproducible results
507 objList := make([]Object, len(check.objMap))
509 for obj := range check.objMap {
513 sort.Sort(inSourceOrder(objList))
515 // add new methods to already type-checked types (from a prior Checker.Files call)
516 for _, obj := range objList {
517 if obj, _ := obj.(*TypeName); obj != nil && obj.typ != nil {
518 check.addMethodDecls(obj)
522 // We process non-alias declarations first, in order to avoid situations where
523 // the type of an alias declaration is needed before it is available. In general
524 // this is still not enough, as it is possible to create sufficiently convoluted
525 // recursive type definitions that will cause a type alias to be needed before it
526 // is available (see issue #25838 for examples).
527 // As an aside, the cmd/compiler suffers from the same problem (#25838).
528 var aliasList []*TypeName
530 for _, obj := range objList {
531 // If we have a type alias, collect it for the 2nd phase.
532 if tname, _ := obj.(*TypeName); tname != nil && check.objMap[tname].alias {
533 aliasList = append(aliasList, tname)
537 check.objDecl(obj, nil)
540 for _, obj := range aliasList {
541 check.objDecl(obj, nil)
544 // At this point we may have a non-empty check.methods map; this means that not all
545 // entries were deleted at the end of typeDecl because the respective receiver base
546 // types were not found. In that case, an error was reported when declaring those
547 // methods. We can now safely discard this map.
551 // inSourceOrder implements the sort.Sort interface.
552 type inSourceOrder []Object
554 func (a inSourceOrder) Len() int { return len(a) }
555 func (a inSourceOrder) Less(i, j int) bool { return a[i].order() < a[j].order() }
556 func (a inSourceOrder) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
558 // unusedImports checks for unused imports.
559 func (check *Checker) unusedImports() {
560 // if function bodies are not checked, packages' uses are likely missing - don't check
561 if check.conf.IgnoreFuncBodies {
565 // spec: "It is illegal (...) to directly import a package without referring to
566 // any of its exported identifiers. To import a package solely for its side-effects
567 // (initialization), use the blank identifier as explicit package name."
569 // check use of regular imported packages
570 for _, scope := range check.pkg.scope.children /* file scopes */ {
571 for _, obj := range scope.elems {
572 if obj, ok := obj.(*PkgName); ok {
573 // Unused "blank imports" are automatically ignored
574 // since _ identifiers are not entered into scopes.
576 path := obj.imported.path
577 base := pkgName(path)
578 if obj.name == base {
579 check.softErrorf(obj, _UnusedImport, "%q imported but not used", path)
581 check.softErrorf(obj, _UnusedImport, "%q imported but not used as %s", path, obj.name)
588 // check use of dot-imported packages
589 for _, unusedDotImports := range check.unusedDotImports {
590 for pkg, pos := range unusedDotImports {
591 check.softErrorf(pos, _UnusedImport, "%q imported but not used", pkg.path)
596 // pkgName returns the package name (last element) of an import path.
597 func pkgName(path string) string {
598 if i := strings.LastIndex(path, "/"); i >= 0 {
604 // dir makes a good-faith attempt to return the directory
605 // portion of path. If path is empty, the result is ".".
606 // (Per the go/build package dependency tests, we cannot import
607 // path/filepath and simply use filepath.Dir.)
608 func dir(path string) string {
609 if i := strings.LastIndexAny(path, `/\`); i > 0 {