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resolver.go
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resolver.go
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// 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.
package types
import (
"fmt"
"go/ast"
"go/constant"
"go/token"
"strconv"
"strings"
"unicode"
)
// A declInfo describes a package-level const, type, var, or func declaration.
type declInfo struct {
file *Scope // scope of file containing this declaration
lhs []*Var // lhs of n:1 variable declarations, or nil
typ ast.Expr // type, or nil
init ast.Expr // init/orig expression, or nil
fdecl *ast.FuncDecl // func declaration, or nil
alias bool // type alias declaration
// The deps field tracks initialization expression dependencies.
// As a special (overloaded) case, it also tracks dependencies of
// interface types on embedded interfaces (see ordering.go).
deps objSet // lazily initialized
}
// An objSet is simply a set of objects.
type objSet map[Object]bool
// hasInitializer reports whether the declared object has an initialization
// expression or function body.
func (d *declInfo) hasInitializer() bool {
return d.init != nil || d.fdecl != nil && d.fdecl.Body != nil
}
// addDep adds obj to the set of objects d's init expression depends on.
func (d *declInfo) addDep(obj Object) {
m := d.deps
if m == nil {
m = make(objSet)
d.deps = m
}
m[obj] = true
}
// arityMatch checks that the lhs and rhs of a const or var decl
// have the appropriate number of names and init exprs. For const
// decls, init is the value spec providing the init exprs; for
// var decls, init is nil (the init exprs are in s in this case).
func (check *Checker) arityMatch(s, init *ast.ValueSpec) {
l := len(s.Names)
r := len(s.Values)
if init != nil {
r = len(init.Values)
}
switch {
case init == nil && r == 0:
// var decl w/o init expr
if s.Type == nil {
check.errorf(s.Pos(), "missing type or init expr")
}
case l < r:
if l < len(s.Values) {
// init exprs from s
n := s.Values[l]
check.errorf(n.Pos(), "extra init expr %s", n)
// TODO(gri) avoid declared but not used error here
} else {
// init exprs "inherited"
check.errorf(s.Pos(), "extra init expr at %s", check.fset.Position(init.Pos()))
// TODO(gri) avoid declared but not used error here
}
case l > r && (init != nil || r != 1):
n := s.Names[r]
check.errorf(n.Pos(), "missing init expr for %s", n)
}
}
func validatedImportPath(path string) (string, error) {
s, err := strconv.Unquote(path)
if err != nil {
return "", err
}
if s == "" {
return "", fmt.Errorf("empty string")
}
const illegalChars = `!"#$%&'()*,:;<=>?[\]^{|}` + "`\uFFFD"
for _, r := range s {
if !unicode.IsGraphic(r) || unicode.IsSpace(r) || strings.ContainsRune(illegalChars, r) {
return s, fmt.Errorf("invalid character %#U", r)
}
}
return s, nil
}
// declarePkgObj declares obj in the package scope, records its ident -> obj mapping,
// and updates check.objMap. The object must not be a function or method.
func (check *Checker) declarePkgObj(ident *ast.Ident, obj Object, d *declInfo) {
assert(ident.Name == obj.Name())
// spec: "A package-scope or file-scope identifier with name init
// may only be declared to be a function with this (func()) signature."
if ident.Name == "init" {
check.errorf(ident.Pos(), "cannot declare init - must be func")
return
}
// spec: "The main package must have package name main and declare
// a function main that takes no arguments and returns no value."
if ident.Name == "main" && check.pkg.name == "main" {
check.errorf(ident.Pos(), "cannot declare main - must be func")
return
}
check.declare(check.pkg.scope, ident, obj, token.NoPos)
check.objMap[obj] = d
obj.setOrder(uint32(len(check.objMap)))
}
// filename returns a filename suitable for debugging output.
func (check *Checker) filename(fileNo int) string {
file := check.files[fileNo]
if pos := file.Pos(); pos.IsValid() {
return check.fset.File(pos).Name()
}
return fmt.Sprintf("file[%d]", fileNo)
}
func (check *Checker) importPackage(pos token.Pos, path, dir string) *Package {
// If we already have a package for the given (path, dir)
// pair, use it instead of doing a full import.
// Checker.impMap only caches packages that are marked Complete
// or fake (dummy packages for failed imports). Incomplete but
// non-fake packages do require an import to complete them.
key := importKey{path, dir}
imp := check.impMap[key]
if imp != nil {
return imp
}
// no package yet => import it
if path == "C" && check.conf.FakeImportC {
imp = NewPackage("C", "C")
imp.fake = true
} else {
// ordinary import
var err error
if importer := check.conf.Importer; importer == nil {
err = fmt.Errorf("Config.Importer not installed")
} else if importerFrom, ok := importer.(ImporterFrom); ok {
imp, err = importerFrom.ImportFrom(path, dir, 0)
if imp == nil && err == nil {
err = fmt.Errorf("Config.Importer.ImportFrom(%s, %s, 0) returned nil but no error", path, dir)
}
} else {
imp, err = importer.Import(path)
if imp == nil && err == nil {
err = fmt.Errorf("Config.Importer.Import(%s) returned nil but no error", path)
}
}
// make sure we have a valid package name
// (errors here can only happen through manipulation of packages after creation)
if err == nil && imp != nil && (imp.name == "_" || imp.name == "") {
err = fmt.Errorf("invalid package name: %q", imp.name)
imp = nil // create fake package below
}
if err != nil {
check.errorf(pos, "could not import %s (%s)", path, err)
if imp == nil {
// create a new fake package
// come up with a sensible package name (heuristic)
name := path
if i := len(name); i > 0 && name[i-1] == '/' {
name = name[:i-1]
}
if i := strings.LastIndex(name, "/"); i >= 0 {
name = name[i+1:]
}
imp = NewPackage(path, name)
}
// continue to use the package as best as we can
imp.fake = true // avoid follow-up lookup failures
}
}
// package should be complete or marked fake, but be cautious
if imp.complete || imp.fake {
check.impMap[key] = imp
return imp
}
// something went wrong (importer may have returned incomplete package without error)
return nil
}
// collectObjects collects all file and package objects and inserts them
// into their respective scopes. It also performs imports and associates
// methods with receiver base type names.
func (check *Checker) collectObjects() {
pkg := check.pkg
// pkgImports is the set of packages already imported by any package file seen
// so far. Used to avoid duplicate entries in pkg.imports. Allocate and populate
// it (pkg.imports may not be empty if we are checking test files incrementally).
// Note that pkgImports is keyed by package (and thus package path), not by an
// importKey value. Two different importKey values may map to the same package
// which is why we cannot use the check.impMap here.
var pkgImports = make(map[*Package]bool)
for _, imp := range pkg.imports {
pkgImports[imp] = true
}
for fileNo, file := range check.files {
// The package identifier denotes the current package,
// but there is no corresponding package object.
check.recordDef(file.Name, nil)
// Use the actual source file extent rather than *ast.File extent since the
// latter doesn't include comments which appear at the start or end of the file.
// Be conservative and use the *ast.File extent if we don't have a *token.File.
pos, end := file.Pos(), file.End()
if f := check.fset.File(file.Pos()); f != nil {
pos, end = token.Pos(f.Base()), token.Pos(f.Base()+f.Size())
}
fileScope := NewScope(check.pkg.scope, pos, end, check.filename(fileNo))
check.recordScope(file, fileScope)
// determine file directory, necessary to resolve imports
// FileName may be "" (typically for tests) in which case
// we get "." as the directory which is what we would want.
fileDir := dir(check.fset.Position(file.Name.Pos()).Filename)
for _, decl := range file.Decls {
switch d := decl.(type) {
case *ast.BadDecl:
// ignore
case *ast.GenDecl:
var last *ast.ValueSpec // last ValueSpec with type or init exprs seen
for iota, spec := range d.Specs {
switch s := spec.(type) {
case *ast.ImportSpec:
// import package
path, err := validatedImportPath(s.Path.Value)
if err != nil {
check.errorf(s.Path.Pos(), "invalid import path (%s)", err)
continue
}
imp := check.importPackage(s.Path.Pos(), path, fileDir)
if imp == nil {
continue
}
// add package to list of explicit imports
// (this functionality is provided as a convenience
// for clients; it is not needed for type-checking)
if !pkgImports[imp] {
pkgImports[imp] = true
pkg.imports = append(pkg.imports, imp)
}
// local name overrides imported package name
name := imp.name
if s.Name != nil {
name = s.Name.Name
if path == "C" {
// match cmd/compile (not prescribed by spec)
check.errorf(s.Name.Pos(), `cannot rename import "C"`)
continue
}
if name == "init" {
check.errorf(s.Name.Pos(), "cannot declare init - must be func")
continue
}
}
obj := NewPkgName(s.Pos(), pkg, name, imp)
if s.Name != nil {
// in a dot-import, the dot represents the package
check.recordDef(s.Name, obj)
} else {
check.recordImplicit(s, obj)
}
if path == "C" {
// match cmd/compile (not prescribed by spec)
obj.used = true
}
// add import to file scope
if name == "." {
// merge imported scope with file scope
for _, obj := range imp.scope.elems {
// A package scope may contain non-exported objects,
// do not import them!
if obj.Exported() {
// TODO(gri) When we import a package, we create
// a new local package object. We should do the
// same for each dot-imported object. That way
// they can have correct position information.
// (We must not modify their existing position
// information because the same package - found
// via Config.Packages - may be dot-imported in
// another package!)
check.declare(fileScope, nil, obj, token.NoPos)
}
}
// add position to set of dot-import positions for this file
// (this is only needed for "imported but not used" errors)
check.addUnusedDotImport(fileScope, imp, s.Pos())
} else {
// declare imported package object in file scope
check.declare(fileScope, nil, obj, token.NoPos)
}
case *ast.ValueSpec:
switch d.Tok {
case token.CONST:
// determine which initialization expressions to use
switch {
case s.Type != nil || len(s.Values) > 0:
last = s
case last == nil:
last = new(ast.ValueSpec) // make sure last exists
}
// declare all constants
for i, name := range s.Names {
obj := NewConst(name.Pos(), pkg, name.Name, nil, constant.MakeInt64(int64(iota)))
var init ast.Expr
if i < len(last.Values) {
init = last.Values[i]
}
d := &declInfo{file: fileScope, typ: last.Type, init: init}
check.declarePkgObj(name, obj, d)
}
check.arityMatch(s, last)
case token.VAR:
lhs := make([]*Var, len(s.Names))
// If there's exactly one rhs initializer, use
// the same declInfo d1 for all lhs variables
// so that each lhs variable depends on the same
// rhs initializer (n:1 var declaration).
var d1 *declInfo
if len(s.Values) == 1 {
// The lhs elements are only set up after the for loop below,
// but that's ok because declareVar only collects the declInfo
// for a later phase.
d1 = &declInfo{file: fileScope, lhs: lhs, typ: s.Type, init: s.Values[0]}
}
// declare all variables
for i, name := range s.Names {
obj := NewVar(name.Pos(), pkg, name.Name, nil)
lhs[i] = obj
d := d1
if d == nil {
// individual assignments
var init ast.Expr
if i < len(s.Values) {
init = s.Values[i]
}
d = &declInfo{file: fileScope, typ: s.Type, init: init}
}
check.declarePkgObj(name, obj, d)
}
check.arityMatch(s, nil)
default:
check.invalidAST(s.Pos(), "invalid token %s", d.Tok)
}
case *ast.TypeSpec:
obj := NewTypeName(s.Name.Pos(), pkg, s.Name.Name, nil)
check.declarePkgObj(s.Name, obj, &declInfo{file: fileScope, typ: s.Type, alias: s.Assign.IsValid()})
default:
check.invalidAST(s.Pos(), "unknown ast.Spec node %T", s)
}
}
case *ast.FuncDecl:
name := d.Name.Name
obj := NewFunc(d.Name.Pos(), pkg, name, nil)
if d.Recv == nil {
// regular function
if name == "init" {
// don't declare init functions in the package scope - they are invisible
obj.parent = pkg.scope
check.recordDef(d.Name, obj)
// init functions must have a body
if d.Body == nil {
check.softErrorf(obj.pos, "missing function body")
}
} else {
check.declare(pkg.scope, d.Name, obj, token.NoPos)
}
} else {
// method
check.recordDef(d.Name, obj)
// Associate method with receiver base type name, if possible.
// Ignore methods that have an invalid receiver, or a blank _
// receiver name. They will be type-checked later, with regular
// functions.
if list := d.Recv.List; len(list) > 0 {
typ := unparen(list[0].Type)
if ptr, _ := typ.(*ast.StarExpr); ptr != nil {
typ = unparen(ptr.X)
}
if base, _ := typ.(*ast.Ident); base != nil && base.Name != "_" {
check.assocMethod(base.Name, obj)
}
}
}
info := &declInfo{file: fileScope, fdecl: d}
check.objMap[obj] = info
obj.setOrder(uint32(len(check.objMap)))
default:
check.invalidAST(d.Pos(), "unknown ast.Decl node %T", d)
}
}
}
// verify that objects in package and file scopes have different names
for _, scope := range check.pkg.scope.children /* file scopes */ {
for _, obj := range scope.elems {
if alt := pkg.scope.Lookup(obj.Name()); alt != nil {
if pkg, ok := obj.(*PkgName); ok {
check.errorf(alt.Pos(), "%s already declared through import of %s", alt.Name(), pkg.Imported())
check.reportAltDecl(pkg)
} else {
check.errorf(alt.Pos(), "%s already declared through dot-import of %s", alt.Name(), obj.Pkg())
// TODO(gri) dot-imported objects don't have a position; reportAltDecl won't print anything
check.reportAltDecl(obj)
}
}
}
}
}
// packageObjects typechecks all package objects in objList, but not function bodies.
func (check *Checker) packageObjects(objList []Object) {
// add new methods to already type-checked types (from a prior Checker.Files call)
for _, obj := range objList {
if obj, _ := obj.(*TypeName); obj != nil && obj.typ != nil {
check.addMethodDecls(obj)
}
}
// pre-allocate space for type declaration paths so that the underlying array is reused
typePath := make([]*TypeName, 0, 8)
for _, obj := range objList {
check.objDecl(obj, nil, typePath)
}
// At this point we may have a non-empty check.methods map; this means that not all
// entries were deleted at the end of typeDecl because the respective receiver base
// types were not found. In that case, an error was reported when declaring those
// methods. We can now safely discard this map.
check.methods = nil
}
// functionBodies typechecks all function bodies.
func (check *Checker) functionBodies() {
for _, f := range check.funcs {
check.funcBody(f.decl, f.name, f.sig, f.body)
}
}
// unusedImports checks for unused imports.
func (check *Checker) unusedImports() {
// if function bodies are not checked, packages' uses are likely missing - don't check
if check.conf.IgnoreFuncBodies {
return
}
// spec: "It is illegal (...) to directly import a package without referring to
// any of its exported identifiers. To import a package solely for its side-effects
// (initialization), use the blank identifier as explicit package name."
// check use of regular imported packages
for _, scope := range check.pkg.scope.children /* file scopes */ {
for _, obj := range scope.elems {
if obj, ok := obj.(*PkgName); ok {
// Unused "blank imports" are automatically ignored
// since _ identifiers are not entered into scopes.
if !obj.used {
path := obj.imported.path
base := pkgName(path)
if obj.name == base {
check.softErrorf(obj.pos, "%q imported but not used", path)
} else {
check.softErrorf(obj.pos, "%q imported but not used as %s", path, obj.name)
}
}
}
}
}
// check use of dot-imported packages
for _, unusedDotImports := range check.unusedDotImports {
for pkg, pos := range unusedDotImports {
check.softErrorf(pos, "%q imported but not used", pkg.path)
}
}
}
// pkgName returns the package name (last element) of an import path.
func pkgName(path string) string {
if i := strings.LastIndex(path, "/"); i >= 0 {
path = path[i+1:]
}
return path
}
// dir makes a good-faith attempt to return the directory
// portion of path. If path is empty, the result is ".".
// (Per the go/build package dependency tests, we cannot import
// path/filepath and simply use filepath.Dir.)
func dir(path string) string {
if i := strings.LastIndexAny(path, `/\`); i > 0 {
return path[:i]
}
// i <= 0
return "."
}