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.
4 5 package types
6 7 import (
8 "cmp"
9 "fmt"
10 "go/ast"
11 "go/constant"
12 "go/token"
13 . "internal/types/errors"
14 "slices"
15 "strconv"
16 "strings"
17 "unicode"
18 )
19 20 // A declInfo describes a package-level const, type, var, or func declaration.
21 type declInfo struct {
22 file *Scope // scope of file containing this declaration
23 version goVersion // Go version of file containing this declaration
24 lhs []*Var // lhs of n:1 variable declarations, or nil
25 vtyp ast.Expr // type, or nil (for const and var declarations only)
26 init ast.Expr // init/orig expression, or nil (for const and var declarations only)
27 inherited bool // if set, the init expression is inherited from a previous constant declaration
28 tdecl *ast.TypeSpec // type declaration, or nil
29 fdecl *ast.FuncDecl // func declaration, or nil
30 31 // The deps field tracks initialization expression dependencies.
32 deps map[Object]bool // lazily initialized
33 }
34 35 // hasInitializer reports whether the declared object has an initialization
36 // expression or function body.
37 func (d *declInfo) hasInitializer() bool {
38 return d.init != nil || d.fdecl != nil && d.fdecl.Body != nil
39 }
40 41 // addDep adds obj to the set of objects d's init expression depends on.
42 func (d *declInfo) addDep(obj Object) {
43 m := d.deps
44 if m == nil {
45 m = make(map[Object]bool)
46 d.deps = m
47 }
48 m[obj] = true
49 }
50 51 // arityMatch checks that the lhs and rhs of a const or var decl
52 // have the appropriate number of names and init exprs. For const
53 // decls, init is the value spec providing the init exprs; for
54 // var decls, init is nil (the init exprs are in s in this case).
55 func (check *Checker) arityMatch(s, init *ast.ValueSpec) {
56 l := len(s.Names)
57 r := len(s.Values)
58 if init != nil {
59 r = len(init.Values)
60 }
61 62 const code = WrongAssignCount
63 switch {
64 case init == nil && r == 0:
65 // var decl w/o init expr
66 if s.Type == nil {
67 check.error(s, code, "missing type or init expr")
68 }
69 case l < r:
70 if l < len(s.Values) {
71 // init exprs from s
72 n := s.Values[l]
73 check.errorf(n, code, "extra init expr %s", n)
74 // TODO(gri) avoid declared and not used error here
75 } else {
76 // init exprs "inherited"
77 check.errorf(s, code, "extra init expr at %s", check.fset.Position(init.Pos()))
78 // TODO(gri) avoid declared and not used error here
79 }
80 case l > r && (init != nil || r != 1):
81 n := s.Names[r]
82 check.errorf(n, code, "missing init expr for %s", n)
83 }
84 }
85 86 func validatedImportPath(path string) (string, error) {
87 s, err := strconv.Unquote(path)
88 if err != nil {
89 return "", err
90 }
91 if s == "" {
92 return "", fmt.Errorf("empty string")
93 }
94 const illegalChars = `!"#$%&'()*,:;<=>?[\]^{|}` + "`\uFFFD"
95 for _, r := range s {
96 if !unicode.IsGraphic(r) || unicode.IsSpace(r) || strings.ContainsRune(illegalChars, r) {
97 return s, fmt.Errorf("invalid character %#U", r)
98 }
99 }
100 return s, nil
101 }
102 103 // declarePkgObj declares obj in the package scope, records its ident -> obj mapping,
104 // and updates check.objMap. The object must not be a function or method.
105 func (check *Checker) declarePkgObj(ident *ast.Ident, obj Object, d *declInfo) {
106 assert(ident.Name == obj.Name())
107 108 // spec: "A package-scope or file-scope identifier with name init
109 // may only be declared to be a function with this (func()) signature."
110 if ident.Name == "init" {
111 check.error(ident, InvalidInitDecl, "cannot declare init - must be func")
112 return
113 }
114 115 // spec: "The main package must have package name main and declare
116 // a function main that takes no arguments and returns no value."
117 if ident.Name == "main" && check.pkg.name == "main" {
118 check.error(ident, InvalidMainDecl, "cannot declare main - must be func")
119 return
120 }
121 122 check.declare(check.pkg.scope, ident, obj, nopos)
123 check.objMap[obj] = d
124 obj.setOrder(uint32(len(check.objMap)))
125 }
126 127 // filename returns a filename suitable for debugging output.
128 func (check *Checker) filename(fileNo int) string {
129 file := check.files[fileNo]
130 if pos := file.Pos(); pos.IsValid() {
131 return check.fset.File(pos).Name()
132 }
133 return fmt.Sprintf("file[%d]", fileNo)
134 }
135 136 func (check *Checker) importPackage(at positioner, path, dir string) *Package {
137 // If we already have a package for the given (path, dir)
138 // pair, use it instead of doing a full import.
139 // Checker.impMap only caches packages that are marked Complete
140 // or fake (dummy packages for failed imports). Incomplete but
141 // non-fake packages do require an import to complete them.
142 key := importKey{path, dir}
143 imp := check.impMap[key]
144 if imp != nil {
145 return imp
146 }
147 148 // no package yet => import it
149 if path == "C" && (check.conf.FakeImportC || check.conf.go115UsesCgo) {
150 if check.conf.FakeImportC && check.conf.go115UsesCgo {
151 check.error(at, BadImportPath, "cannot use FakeImportC and go115UsesCgo together")
152 }
153 imp = NewPackage("C", "C")
154 imp.fake = true // package scope is not populated
155 imp.cgo = check.conf.go115UsesCgo
156 } else {
157 // ordinary import
158 var err error
159 if importer := check.conf.Importer; importer == nil {
160 err = fmt.Errorf("Config.Importer not installed")
161 } else if importerFrom, ok := importer.(ImporterFrom); ok {
162 imp, err = importerFrom.ImportFrom(path, dir, 0)
163 if imp == nil && err == nil {
164 err = fmt.Errorf("Config.Importer.ImportFrom(%s, %s, 0) returned nil but no error", path, dir)
165 }
166 } else {
167 imp, err = importer.Import(path)
168 if imp == nil && err == nil {
169 err = fmt.Errorf("Config.Importer.Import(%s) returned nil but no error", path)
170 }
171 }
172 // make sure we have a valid package name
173 // (errors here can only happen through manipulation of packages after creation)
174 if err == nil && imp != nil && (imp.name == "_" || imp.name == "") {
175 err = fmt.Errorf("invalid package name: %q", imp.name)
176 imp = nil // create fake package below
177 }
178 if err != nil {
179 check.errorf(at, BrokenImport, "could not import %s (%s)", path, err)
180 if imp == nil {
181 // create a new fake package
182 // come up with a sensible package name (heuristic)
183 name := path
184 if i := len(name); i > 0 && name[i-1] == '/' {
185 name = name[:i-1]
186 }
187 if i := strings.LastIndex(name, "/"); i >= 0 {
188 name = name[i+1:]
189 }
190 imp = NewPackage(path, name)
191 }
192 // continue to use the package as best as we can
193 imp.fake = true // avoid follow-up lookup failures
194 }
195 }
196 197 // package should be complete or marked fake, but be cautious
198 if imp.complete || imp.fake {
199 check.impMap[key] = imp
200 // Once we've formatted an error message, keep the pkgPathMap
201 // up-to-date on subsequent imports. It is used for package
202 // qualification in error messages.
203 if check.pkgPathMap != nil {
204 check.markImports(imp)
205 }
206 return imp
207 }
208 209 // something went wrong (importer may have returned incomplete package without error)
210 return nil
211 }
212 213 // collectObjects collects all file and package objects and inserts them
214 // into their respective scopes. It also performs imports and associates
215 // methods with receiver base type names.
216 func (check *Checker) collectObjects() {
217 pkg := check.pkg
218 219 // pkgImports is the set of packages already imported by any package file seen
220 // so far. Used to avoid duplicate entries in pkg.imports. Allocate and populate
221 // it (pkg.imports may not be empty if we are checking test files incrementally).
222 // Note that pkgImports is keyed by package (and thus package path), not by an
223 // importKey value. Two different importKey values may map to the same package
224 // which is why we cannot use the check.impMap here.
225 var pkgImports = make(map[*Package]bool)
226 for _, imp := range pkg.imports {
227 pkgImports[imp] = true
228 }
229 230 type methodInfo struct {
231 obj *Func // method
232 ptr bool // true if pointer receiver
233 recv *ast.Ident // receiver type name
234 }
235 var methods []methodInfo // collected methods with valid receivers and non-blank _ names
236 237 fileScopes := make([]*Scope, len(check.files)) // fileScopes[i] corresponds to check.files[i]
238 for fileNo, file := range check.files {
239 check.version = asGoVersion(check.versions[file])
240 241 // The package identifier denotes the current package,
242 // but there is no corresponding package object.
243 check.recordDef(file.Name, nil)
244 245 // Use the actual source file extent rather than *ast.File extent since the
246 // latter doesn't include comments which appear at the start or end of the file.
247 // Be conservative and use the *ast.File extent if we don't have a *token.File.
248 pos, end := file.Pos(), file.End()
249 if f := check.fset.File(file.Pos()); f != nil {
250 pos, end = token.Pos(f.Base()), token.Pos(f.Base()+f.Size())
251 }
252 fileScope := NewScope(pkg.scope, pos, end, check.filename(fileNo))
253 fileScopes[fileNo] = fileScope
254 check.recordScope(file, fileScope)
255 256 // determine file directory, necessary to resolve imports
257 // FileName may be "" (typically for tests) in which case
258 // we get "." as the directory which is what we would want.
259 fileDir := dir(check.fset.Position(file.Name.Pos()).Filename)
260 261 check.walkDecls(file.Decls, func(d decl) {
262 switch d := d.(type) {
263 case importDecl:
264 // import package
265 if d.spec.Path.Value == "" {
266 return // error reported by parser
267 }
268 path, err := validatedImportPath(d.spec.Path.Value)
269 if err != nil {
270 check.errorf(d.spec.Path, BadImportPath, "invalid import path (%s)", err)
271 return
272 }
273 274 imp := check.importPackage(d.spec.Path, path, fileDir)
275 if imp == nil {
276 return
277 }
278 279 // local name overrides imported package name
280 name := imp.name
281 if d.spec.Name != nil {
282 name = d.spec.Name.Name
283 if path == "C" {
284 // match 1.17 cmd/compile (not prescribed by spec)
285 check.error(d.spec.Name, ImportCRenamed, `cannot rename import "C"`)
286 return
287 }
288 }
289 290 if name == "init" {
291 check.error(d.spec, InvalidInitDecl, "cannot import package as init - init must be a func")
292 return
293 }
294 295 // add package to list of explicit imports
296 // (this functionality is provided as a convenience
297 // for clients; it is not needed for type-checking)
298 if !pkgImports[imp] {
299 pkgImports[imp] = true
300 pkg.imports = append(pkg.imports, imp)
301 }
302 303 pkgName := NewPkgName(d.spec.Pos(), pkg, name, imp)
304 if d.spec.Name != nil {
305 // in a dot-import, the dot represents the package
306 check.recordDef(d.spec.Name, pkgName)
307 } else {
308 check.recordImplicit(d.spec, pkgName)
309 }
310 311 if imp.fake {
312 // match 1.17 cmd/compile (not prescribed by spec)
313 check.usedPkgNames[pkgName] = true
314 }
315 316 // add import to file scope
317 check.imports = append(check.imports, pkgName)
318 if name == "." {
319 // dot-import
320 if check.dotImportMap == nil {
321 check.dotImportMap = make(map[dotImportKey]*PkgName)
322 }
323 // merge imported scope with file scope
324 for name, obj := range imp.scope.elems {
325 // Note: Avoid eager resolve(name, obj) here, so we only
326 // resolve dot-imported objects as needed.
327 328 // A package scope may contain non-exported objects,
329 // do not import them!
330 if token.IsExported(name) {
331 // declare dot-imported object
332 // (Do not use check.declare because it modifies the object
333 // via Object.setScopePos, which leads to a race condition;
334 // the object may be imported into more than one file scope
335 // concurrently. See go.dev/issue/32154.)
336 if alt := fileScope.Lookup(name); alt != nil {
337 err := check.newError(DuplicateDecl)
338 err.addf(d.spec.Name, "%s redeclared in this block", alt.Name())
339 err.addAltDecl(alt)
340 err.report()
341 } else {
342 fileScope.insert(name, obj)
343 check.dotImportMap[dotImportKey{fileScope, name}] = pkgName
344 }
345 }
346 }
347 } else {
348 // declare imported package object in file scope
349 // (no need to provide s.Name since we called check.recordDef earlier)
350 check.declare(fileScope, nil, pkgName, nopos)
351 }
352 case constDecl:
353 // declare all constants
354 for i, name := range d.spec.Names {
355 obj := NewConst(name.Pos(), pkg, name.Name, nil, constant.MakeInt64(int64(d.iota)))
356 357 var init ast.Expr
358 if i < len(d.init) {
359 init = d.init[i]
360 }
361 362 d := &declInfo{file: fileScope, version: check.version, vtyp: d.typ, init: init, inherited: d.inherited}
363 check.declarePkgObj(name, obj, d)
364 }
365 366 case varDecl:
367 lhs := make([]*Var, len(d.spec.Names))
368 // If there's exactly one rhs initializer, use
369 // the same declInfo d1 for all lhs variables
370 // so that each lhs variable depends on the same
371 // rhs initializer (n:1 var declaration).
372 var d1 *declInfo
373 if len(d.spec.Values) == 1 {
374 // The lhs elements are only set up after the for loop below,
375 // but that's ok because declareVar only collects the declInfo
376 // for a later phase.
377 d1 = &declInfo{file: fileScope, version: check.version, lhs: lhs, vtyp: d.spec.Type, init: d.spec.Values[0]}
378 }
379 380 // declare all variables
381 for i, name := range d.spec.Names {
382 obj := newVar(PackageVar, name.Pos(), pkg, name.Name, nil)
383 lhs[i] = obj
384 385 di := d1
386 if di == nil {
387 // individual assignments
388 var init ast.Expr
389 if i < len(d.spec.Values) {
390 init = d.spec.Values[i]
391 }
392 di = &declInfo{file: fileScope, version: check.version, vtyp: d.spec.Type, init: init}
393 }
394 395 check.declarePkgObj(name, obj, di)
396 }
397 case typeDecl:
398 obj := NewTypeName(d.spec.Name.Pos(), pkg, d.spec.Name.Name, nil)
399 check.declarePkgObj(d.spec.Name, obj, &declInfo{file: fileScope, version: check.version, tdecl: d.spec})
400 case funcDecl:
401 name := d.decl.Name.Name
402 obj := NewFunc(d.decl.Name.Pos(), pkg, name, nil) // signature set later
403 hasTParamError := false // avoid duplicate type parameter errors
404 if d.decl.Recv.NumFields() == 0 {
405 // regular function
406 if d.decl.Recv != nil {
407 check.error(d.decl.Recv, BadRecv, "method has no receiver")
408 // treat as function
409 }
410 if name == "init" || (name == "main" && check.pkg.name == "main") {
411 code := InvalidInitDecl
412 if name == "main" {
413 code = InvalidMainDecl
414 }
415 if d.decl.Type.TypeParams.NumFields() != 0 {
416 check.softErrorf(d.decl.Type.TypeParams.List[0], code, "func %s must have no type parameters", name)
417 hasTParamError = true
418 }
419 if t := d.decl.Type; t.Params.NumFields() != 0 || t.Results != nil {
420 // TODO(rFindley) Should this be a hard error?
421 check.softErrorf(d.decl.Name, code, "func %s must have no arguments and no return values", name)
422 }
423 }
424 if name == "init" {
425 // don't declare init functions in the package scope - they are invisible
426 obj.parent = pkg.scope
427 check.recordDef(d.decl.Name, obj)
428 if d.decl.Body == nil {
429 check.softErrorf(obj, MissingInitBody, "func init must have a body")
430 }
431 } else {
432 check.declare(pkg.scope, d.decl.Name, obj, nopos)
433 }
434 } else {
435 // method
436 437 // TODO(rFindley) earlier versions of this code checked that methods
438 // have no type parameters, but this is checked later
439 // when type checking the function type. Confirm that
440 // we don't need to check tparams here.
441 442 ptr, base, _ := check.unpackRecv(d.decl.Recv.List[0].Type, false)
443 // (Methods with invalid receiver cannot be associated to a type, and
444 // methods with blank _ names are never found; no need to collect any
445 // of them. They will still be type-checked with all the other functions.)
446 if recv, _ := base.(*ast.Ident); recv != nil && name != "_" {
447 methods = append(methods, methodInfo{obj, ptr, recv})
448 }
449 check.recordDef(d.decl.Name, obj)
450 }
451 _ = d.decl.Type.TypeParams.NumFields() != 0 && !hasTParamError && check.verifyVersionf(d.decl.Type.TypeParams.List[0], go1_18, "type parameter")
452 info := &declInfo{file: fileScope, version: check.version, fdecl: d.decl}
453 // Methods are not package-level objects but we still track them in the
454 // object map so that we can handle them like regular functions (if the
455 // receiver is invalid); also we need their fdecl info when associating
456 // them with their receiver base type, below.
457 check.objMap[obj] = info
458 obj.setOrder(uint32(len(check.objMap)))
459 }
460 })
461 }
462 463 // verify that objects in package and file scopes have different names
464 for _, scope := range fileScopes {
465 for name, obj := range scope.elems {
466 if alt := pkg.scope.Lookup(name); alt != nil {
467 obj = resolve(name, obj)
468 err := check.newError(DuplicateDecl)
469 if pkg, ok := obj.(*PkgName); ok {
470 err.addf(alt, "%s already declared through import of %s", alt.Name(), pkg.Imported())
471 err.addAltDecl(pkg)
472 } else {
473 err.addf(alt, "%s already declared through dot-import of %s", alt.Name(), obj.Pkg())
474 // TODO(gri) dot-imported objects don't have a position; addAltDecl won't print anything
475 err.addAltDecl(obj)
476 }
477 err.report()
478 }
479 }
480 }
481 482 // Now that we have all package scope objects and all methods,
483 // associate methods with receiver base type name where possible.
484 // Ignore methods that have an invalid receiver. They will be
485 // type-checked later, with regular functions.
486 if methods == nil {
487 return
488 }
489 490 check.methods = make(map[*TypeName][]*Func)
491 for i := range methods {
492 m := &methods[i]
493 // Determine the receiver base type and associate m with it.
494 ptr, base := check.resolveBaseTypeName(m.ptr, m.recv)
495 if base != nil {
496 m.obj.hasPtrRecv_ = ptr
497 check.methods[base] = append(check.methods[base], m.obj)
498 }
499 }
500 }
501 502 // unpackRecv unpacks a receiver type expression and returns its components: ptr indicates
503 // whether rtyp is a pointer receiver, base is the receiver base type expression stripped
504 // of its type parameters (if any), and tparams are its type parameter names, if any. The
505 // type parameters are only unpacked if unpackParams is set. For instance, given the rtyp
506 //
507 // *T[A, _]
508 //
509 // ptr is true, base is T, and tparams is [A, _] (assuming unpackParams is set).
510 // Note that base may not be a *ast.Ident for erroneous programs.
511 func (check *Checker) unpackRecv(rtyp ast.Expr, unpackParams bool) (ptr bool, base ast.Expr, tparams []*ast.Ident) {
512 // unpack receiver type
513 base = ast.Unparen(rtyp)
514 if t, _ := base.(*ast.StarExpr); t != nil {
515 ptr = true
516 base = ast.Unparen(t.X)
517 }
518 519 // unpack type parameters, if any
520 switch base.(type) {
521 case *ast.IndexExpr, *ast.IndexListExpr:
522 ix := unpackIndexedExpr(base)
523 base = ix.x
524 if unpackParams {
525 for _, arg := range ix.indices {
526 var par *ast.Ident
527 switch arg := arg.(type) {
528 case *ast.Ident:
529 par = arg
530 case *ast.BadExpr:
531 // ignore - error already reported by parser
532 case nil:
533 check.error(ix.orig, InvalidSyntaxTree, "parameterized receiver contains nil parameters")
534 default:
535 check.errorf(arg, BadDecl, "receiver type parameter %s must be an identifier", arg)
536 }
537 if par == nil {
538 par = &ast.Ident{NamePos: arg.Pos(), Name: "_"}
539 }
540 tparams = append(tparams, par)
541 }
542 }
543 }
544 545 return
546 }
547 548 // resolveBaseTypeName returns the non-alias base type name for the given name, and whether
549 // there was a pointer indirection to get to it. The base type name must be declared
550 // in package scope, and there can be at most one pointer indirection. Traversals
551 // through generic alias types are not permitted. If no such type name exists, the
552 // returned base is nil.
553 func (check *Checker) resolveBaseTypeName(ptr bool, name *ast.Ident) (ptr_ bool, base *TypeName) {
554 // Algorithm: Starting from name, which is expected to denote a type,
555 // we follow that type through non-generic alias declarations until
556 // we reach a non-alias type name.
557 var seen map[*TypeName]bool
558 for name != nil {
559 // name must denote an object found in the current package scope
560 // (note that dot-imported objects are not in the package scope!)
561 obj := check.pkg.scope.Lookup(name.Name)
562 if obj == nil {
563 break
564 }
565 566 // the object must be a type name...
567 tname, _ := obj.(*TypeName)
568 if tname == nil {
569 break
570 }
571 572 // ... which we have not seen before
573 if seen[tname] {
574 break
575 }
576 577 // we're done if tdecl describes a defined type (not an alias)
578 tdecl := check.objMap[tname].tdecl // must exist for objects in package scope
579 if !tdecl.Assign.IsValid() {
580 return ptr, tname
581 }
582 583 // an alias must not be generic
584 // (importantly, we must not collect such methods - was https://go.dev/issue/70417)
585 if tdecl.TypeParams != nil {
586 break
587 }
588 589 // otherwise, remember this type name and continue resolving
590 if seen == nil {
591 seen = make(map[*TypeName]bool)
592 }
593 seen[tname] = true
594 595 // The go/parser keeps parentheses; strip them, if any.
596 typ := ast.Unparen(tdecl.Type)
597 598 // dereference a pointer type
599 if pexpr, _ := typ.(*ast.StarExpr); pexpr != nil {
600 // if we've already seen a pointer, we're done
601 if ptr {
602 break
603 }
604 ptr = true
605 typ = ast.Unparen(pexpr.X) // continue with pointer base type
606 }
607 608 // After dereferencing, typ must be a locally defined type name.
609 // Referring to other packages (qualified identifiers) or going
610 // through instantiated types (index expressions) is not permitted,
611 // so we can ignore those.
612 name, _ = typ.(*ast.Ident)
613 if name == nil {
614 break
615 }
616 }
617 618 // no base type found
619 return false, nil
620 }
621 622 // packageObjects typechecks all package objects, but not function bodies.
623 func (check *Checker) packageObjects() {
624 // process package objects in source order for reproducible results
625 objList := make([]Object, len(check.objMap))
626 i := 0
627 for obj := range check.objMap {
628 objList[i] = obj
629 i++
630 }
631 slices.SortFunc(objList, func(a, b Object) int {
632 return cmp.Compare(a.order(), b.order())
633 })
634 635 // add new methods to already type-checked types (from a prior Checker.Files call)
636 for _, obj := range objList {
637 if obj, _ := obj.(*TypeName); obj != nil && obj.typ != nil {
638 check.collectMethods(obj)
639 }
640 }
641 642 if false && check.conf._EnableAlias {
643 // With Alias nodes we can process declarations in any order.
644 //
645 // TODO(adonovan): unfortunately, Alias nodes
646 // (GODEBUG=gotypesalias=1) don't entirely resolve
647 // problems with cycles. For example, in
648 // GOROOT/test/typeparam/issue50259.go,
649 //
650 // type T[_ any] struct{}
651 // type A T[B]
652 // type B = T[A]
653 //
654 // TypeName A has Type Named during checking, but by
655 // the time the unified export data is written out,
656 // its Type is Invalid.
657 //
658 // Investigate and reenable this branch.
659 for _, obj := range objList {
660 check.objDecl(obj, nil)
661 }
662 } else {
663 // Without Alias nodes, we process non-alias type declarations first, followed by
664 // alias declarations, and then everything else. This appears to avoid most situations
665 // where the type of an alias is needed before it is available.
666 // There may still be cases where this is not good enough (see also go.dev/issue/25838).
667 // In those cases Checker.ident will report an error ("invalid use of type alias").
668 var aliasList []*TypeName
669 var othersList []Object // everything that's not a type
670 // phase 1: non-alias type declarations
671 for _, obj := range objList {
672 if tname, _ := obj.(*TypeName); tname != nil {
673 if check.objMap[tname].tdecl.Assign.IsValid() {
674 aliasList = append(aliasList, tname)
675 } else {
676 check.objDecl(obj, nil)
677 }
678 } else {
679 othersList = append(othersList, obj)
680 }
681 }
682 // phase 2: alias type declarations
683 for _, obj := range aliasList {
684 check.objDecl(obj, nil)
685 }
686 // phase 3: all other declarations
687 for _, obj := range othersList {
688 check.objDecl(obj, nil)
689 }
690 }
691 692 // At this point we may have a non-empty check.methods map; this means that not all
693 // entries were deleted at the end of typeDecl because the respective receiver base
694 // types were not found. In that case, an error was reported when declaring those
695 // methods. We can now safely discard this map.
696 check.methods = nil
697 }
698 699 // unusedImports checks for unused imports.
700 func (check *Checker) unusedImports() {
701 // If function bodies are not checked, packages' uses are likely missing - don't check.
702 if check.conf.IgnoreFuncBodies {
703 return
704 }
705 706 // spec: "It is illegal (...) to directly import a package without referring to
707 // any of its exported identifiers. To import a package solely for its side-effects
708 // (initialization), use the blank identifier as explicit package name."
709 710 for _, obj := range check.imports {
711 if obj.name != "_" && !check.usedPkgNames[obj] {
712 check.errorUnusedPkg(obj)
713 }
714 }
715 }
716 717 func (check *Checker) errorUnusedPkg(obj *PkgName) {
718 // If the package was imported with a name other than the final
719 // import path element, show it explicitly in the error message.
720 // Note that this handles both renamed imports and imports of
721 // packages containing unconventional package declarations.
722 // Note that this uses / always, even on Windows, because Go import
723 // paths always use forward slashes.
724 path := obj.imported.path
725 elem := path
726 if i := strings.LastIndex(elem, "/"); i >= 0 {
727 elem = elem[i+1:]
728 }
729 if obj.name == "" || obj.name == "." || obj.name == elem {
730 check.softErrorf(obj, UnusedImport, "%q imported and not used", path)
731 } else {
732 check.softErrorf(obj, UnusedImport, "%q imported as %s and not used", path, obj.name)
733 }
734 }
735 736 // dir makes a good-faith attempt to return the directory
737 // portion of path. If path is empty, the result is ".".
738 // (Per the go/build package dependency tests, we cannot import
739 // path/filepath and simply use filepath.Dir.)
740 func dir(path string) string {
741 if i := strings.LastIndexAny(path, `/\`); i > 0 {
742 return path[:i]
743 }
744 // i <= 0
745 return "."
746 }
747