go resolver 源码
golang resolver 代码
文件路径：/src/go/types/resolver.go
// 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/internal/typeparams"
"go/token"
"sort"
"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
vtyp ast.Expr // type, or nil (for const and var declarations only)
init ast.Expr // init/orig expression, or nil (for const and var declarations only)
inherited bool // if set, the init expression is inherited from a previous constant declaration
tdecl *ast.TypeSpec // type declaration, or nil
fdecl *ast.FuncDecl // func declaration, or nil
// The deps field tracks initialization expression dependencies.
deps map[Object]bool // lazily initialized
}
// 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(map[Object]bool)
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)
}
const code = _WrongAssignCount
switch {
case init == nil && r == 0:
// var decl w/o init expr
if s.Type == nil {
check.errorf(s, code, "missing type or init expr")
}
case l < r:
if l < len(s.Values) {
// init exprs from s
n := s.Values[l]
check.errorf(n, code, "extra init expr %s", n)
// TODO(gri) avoid declared but not used error here
} else {
// init exprs "inherited"
check.errorf(s, code, "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, code, "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, _InvalidInitDecl, "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, _InvalidMainDecl, "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(at positioner, 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 || check.conf.go115UsesCgo) {
imp = NewPackage("C", "C")
imp.fake = true // package scope is not populated
imp.cgo = check.conf.go115UsesCgo
} 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(at, _BrokenImport, "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
// Once we've formatted an error message, keep the pkgPathMap
// up-to-date on subsequent imports. It is used for package
// qualification in error messages.
if check.pkgPathMap != nil {
check.markImports(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
}
type methodInfo struct {
obj *Func // method
ptr bool // true if pointer receiver
recv *ast.Ident // receiver type name
}
var methods []methodInfo // collected methods with valid receivers and non-blank _ names
var fileScopes []*Scope
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))
fileScopes = append(fileScopes, fileScope)
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)
check.walkDecls(file.Decls, func(d decl) {
switch d := d.(type) {
case importDecl:
// import package
path, err := validatedImportPath(d.spec.Path.Value)
if err != nil {
check.errorf(d.spec.Path, _BadImportPath, "invalid import path (%s)", err)
return
}
imp := check.importPackage(d.spec.Path, path, fileDir)
if imp == nil {
return
}
// local name overrides imported package name
name := imp.name
if d.spec.Name != nil {
name = d.spec.Name.Name
if path == "C" {
// match 1.17 cmd/compile (not prescribed by spec)
check.errorf(d.spec.Name, _ImportCRenamed, `cannot rename import "C"`)
return
}
}
if name == "init" {
check.errorf(d.spec, _InvalidInitDecl, "cannot import package as init - init must be a func")
return
}
// 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)
}
pkgName := NewPkgName(d.spec.Pos(), pkg, name, imp)
if d.spec.Name != nil {
// in a dot-import, the dot represents the package
check.recordDef(d.spec.Name, pkgName)
} else {
check.recordImplicit(d.spec, pkgName)
}
if imp.fake {
// match 1.17 cmd/compile (not prescribed by spec)
pkgName.used = true
}
// add import to file scope
check.imports = append(check.imports, pkgName)
if name == "." {
// dot-import
if check.dotImportMap == nil {
check.dotImportMap = make(map[dotImportKey]*PkgName)
}
// merge imported scope with file scope
for name, obj := range imp.scope.elems {
// Note: Avoid eager resolve(name, obj) here, so we only
// resolve dot-imported objects as needed.
// A package scope may contain non-exported objects,
// do not import them!
if token.IsExported(name) {
// declare dot-imported object
// (Do not use check.declare because it modifies the object
// via Object.setScopePos, which leads to a race condition;
// the object may be imported into more than one file scope
// concurrently. See issue #32154.)
if alt := fileScope.Lookup(name); alt != nil {
check.errorf(d.spec.Name, _DuplicateDecl, "%s redeclared in this block", alt.Name())
check.reportAltDecl(alt)
} else {
fileScope.insert(name, obj)
check.dotImportMap[dotImportKey{fileScope, name}] = pkgName
}
}
}
} else {
// declare imported package object in file scope
// (no need to provide s.Name since we called check.recordDef earlier)
check.declare(fileScope, nil, pkgName, token.NoPos)
}
case constDecl:
// declare all constants
for i, name := range d.spec.Names {
obj := NewConst(name.Pos(), pkg, name.Name, nil, constant.MakeInt64(int64(d.iota)))
var init ast.Expr
if i < len(d.init) {
init = d.init[i]
}
d := &declInfo{file: fileScope, vtyp: d.typ, init: init, inherited: d.inherited}
check.declarePkgObj(name, obj, d)
}
case varDecl:
lhs := make([]*Var, len(d.spec.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(d.spec.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, vtyp: d.spec.Type, init: d.spec.Values[0]}
}
// declare all variables
for i, name := range d.spec.Names {
obj := NewVar(name.Pos(), pkg, name.Name, nil)
lhs[i] = obj
di := d1
if di == nil {
// individual assignments
var init ast.Expr
if i < len(d.spec.Values) {
init = d.spec.Values[i]
}
di = &declInfo{file: fileScope, vtyp: d.spec.Type, init: init}
}
check.declarePkgObj(name, obj, di)
}
case typeDecl:
if d.spec.TypeParams.NumFields() != 0 && !check.allowVersion(pkg, 1, 18) {
check.softErrorf(d.spec.TypeParams.List[0], _UnsupportedFeature, "type parameters require go1.18 or later")
}
obj := NewTypeName(d.spec.Name.Pos(), pkg, d.spec.Name.Name, nil)
check.declarePkgObj(d.spec.Name, obj, &declInfo{file: fileScope, tdecl: d.spec})
case funcDecl:
name := d.decl.Name.Name
obj := NewFunc(d.decl.Name.Pos(), pkg, name, nil)
hasTParamError := false // avoid duplicate type parameter errors
if d.decl.Recv.NumFields() == 0 {
// regular function
if d.decl.Recv != nil {
check.error(d.decl.Recv, _BadRecv, "method is missing receiver")
// treat as function
}
if name == "init" || (name == "main" && check.pkg.name == "main") {
code := _InvalidInitDecl
if name == "main" {
code = _InvalidMainDecl
}
if d.decl.Type.TypeParams.NumFields() != 0 {
check.softErrorf(d.decl.Type.TypeParams.List[0], code, "func %s must have no type parameters", name)
hasTParamError = true
}
if t := d.decl.Type; t.Params.NumFields() != 0 || t.Results != nil {
// TODO(rFindley) Should this be a hard error?
check.softErrorf(d.decl, code, "func %s must have no arguments and no return values", name)
}
}
if name == "init" {
// don't declare init functions in the package scope - they are invisible
obj.parent = pkg.scope
check.recordDef(d.decl.Name, obj)
// init functions must have a body
if d.decl.Body == nil {
// TODO(gri) make this error message consistent with the others above
check.softErrorf(obj, _MissingInitBody, "missing function body")
}
} else {
check.declare(pkg.scope, d.decl.Name, obj, token.NoPos)
}
} else {
// method
// TODO(rFindley) earlier versions of this code checked that methods
// have no type parameters, but this is checked later
// when type checking the function type. Confirm that
// we don't need to check tparams here.
ptr, recv, _ := check.unpackRecv(d.decl.Recv.List[0].Type, false)
// (Methods with invalid receiver cannot be associated to a type, and
// methods with blank _ names are never found; no need to collect any
// of them. They will still be type-checked with all the other functions.)
if recv != nil && name != "_" {
methods = append(methods, methodInfo{obj, ptr, recv})
}
check.recordDef(d.decl.Name, obj)
}
if d.decl.Type.TypeParams.NumFields() != 0 && !check.allowVersion(pkg, 1, 18) && !hasTParamError {
check.softErrorf(d.decl.Type.TypeParams.List[0], _UnsupportedFeature, "type parameters require go1.18 or later")
}
info := &declInfo{file: fileScope, fdecl: d.decl}
// Methods are not package-level objects but we still track them in the
// object map so that we can handle them like regular functions (if the
// receiver is invalid); also we need their fdecl info when associating
// them with their receiver base type, below.
check.objMap[obj] = info
obj.setOrder(uint32(len(check.objMap)))
}
})
}
// verify that objects in package and file scopes have different names
for _, scope := range fileScopes {
for name, obj := range scope.elems {
if alt := pkg.scope.Lookup(name); alt != nil {
obj = resolve(name, obj)
if pkg, ok := obj.(*PkgName); ok {
check.errorf(alt, _DuplicateDecl, "%s already declared through import of %s", alt.Name(), pkg.Imported())
check.reportAltDecl(pkg)
} else {
check.errorf(alt, _DuplicateDecl, "%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)
}
}
}
}
// Now that we have all package scope objects and all methods,
// associate methods with receiver base type name where possible.
// Ignore methods that have an invalid receiver. They will be
// type-checked later, with regular functions.
if methods == nil {
return // nothing to do
}
check.methods = make(map[*TypeName][]*Func)
for i := range methods {
m := &methods[i]
// Determine the receiver base type and associate m with it.
ptr, base := check.resolveBaseTypeName(m.ptr, m.recv)
if base != nil {
m.obj.hasPtrRecv_ = ptr
check.methods[base] = append(check.methods[base], m.obj)
}
}
}
// unpackRecv unpacks a receiver type and returns its components: ptr indicates whether
// rtyp is a pointer receiver, rname is the receiver type name, and tparams are its
// type parameters, if any. The type parameters are only unpacked if unpackParams is
// set. If rname is nil, the receiver is unusable (i.e., the source has a bug which we
// cannot easily work around).
func (check *Checker) unpackRecv(rtyp ast.Expr, unpackParams bool) (ptr bool, rname *ast.Ident, tparams []*ast.Ident) {
L: // unpack receiver type
// This accepts invalid receivers such as ***T and does not
// work for other invalid receivers, but we don't care. The
// validity of receiver expressions is checked elsewhere.
for {
switch t := rtyp.(type) {
case *ast.ParenExpr:
rtyp = t.X
case *ast.StarExpr:
ptr = true
rtyp = t.X
default:
break L
}
}
// unpack type parameters, if any
switch rtyp.(type) {
case *ast.IndexExpr, *ast.IndexListExpr:
ix := typeparams.UnpackIndexExpr(rtyp)
rtyp = ix.X
if unpackParams {
for _, arg := range ix.Indices {
var par *ast.Ident
switch arg := arg.(type) {
case *ast.Ident:
par = arg
case *ast.BadExpr:
// ignore - error already reported by parser
case nil:
check.invalidAST(ix.Orig, "parameterized receiver contains nil parameters")
default:
check.errorf(arg, _BadDecl, "receiver type parameter %s must be an identifier", arg)
}
if par == nil {
par = &ast.Ident{NamePos: arg.Pos(), Name: "_"}
}
tparams = append(tparams, par)
}
}
}
// unpack receiver name
if name, _ := rtyp.(*ast.Ident); name != nil {
rname = name
}
return
}
// resolveBaseTypeName returns the non-alias base type name for typ, and whether
// there was a pointer indirection to get to it. The base type name must be declared
// in package scope, and there can be at most one pointer indirection. If no such type
// name exists, the returned base is nil.
func (check *Checker) resolveBaseTypeName(seenPtr bool, name *ast.Ident) (ptr bool, base *TypeName) {
// Algorithm: Starting from a type expression, which may be a name,
// we follow that type through alias declarations until we reach a
// non-alias type name. If we encounter anything but pointer types or
// parentheses we're done. If we encounter more than one pointer type
// we're done.
ptr = seenPtr
var seen map[*TypeName]bool
var typ ast.Expr = name
for {
typ = unparen(typ)
// check if we have a pointer type
if pexpr, _ := typ.(*ast.StarExpr); pexpr != nil {
// if we've already seen a pointer, we're done
if ptr {
return false, nil
}
ptr = true
typ = unparen(pexpr.X) // continue with pointer base type
}
// typ must be a name
name, _ := typ.(*ast.Ident)
if name == nil {
return false, nil
}
// name must denote an object found in the current package scope
// (note that dot-imported objects are not in the package scope!)
obj := check.pkg.scope.Lookup(name.Name)
if obj == nil {
return false, nil
}
// the object must be a type name...
tname, _ := obj.(*TypeName)
if tname == nil {
return false, nil
}
// ... which we have not seen before
if seen[tname] {
return false, nil
}
// we're done if tdecl defined tname as a new type
// (rather than an alias)
tdecl := check.objMap[tname].tdecl // must exist for objects in package scope
if !tdecl.Assign.IsValid() {
return ptr, tname
}
// otherwise, continue resolving
typ = tdecl.Type
if seen == nil {
seen = make(map[*TypeName]bool)
}
seen[tname] = true
}
}
// packageObjects typechecks all package objects, but not function bodies.
func (check *Checker) packageObjects() {
// process package objects in source order for reproducible results
objList := make([]Object, len(check.objMap))
i := 0
for obj := range check.objMap {
objList[i] = obj
i++
}
sort.Sort(inSourceOrder(objList))
// 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.collectMethods(obj)
}
}
// We process non-alias type declarations first, followed by alias declarations,
// and then everything else. This appears to avoid most situations where the type
// of an alias is needed before it is available.
// There may still be cases where this is not good enough (see also issue #25838).
// In those cases Checker.ident will report an error ("invalid use of type alias").
var aliasList []*TypeName
var othersList []Object // everything that's not a type
// phase 1: non-alias type declarations
for _, obj := range objList {
if tname, _ := obj.(*TypeName); tname != nil {
if check.objMap[tname].tdecl.Assign.IsValid() {
aliasList = append(aliasList, tname)
} else {
check.objDecl(obj, nil)
}
} else {
othersList = append(othersList, obj)
}
}
// phase 2: alias type declarations
for _, obj := range aliasList {
check.objDecl(obj, nil)
}
// phase 3: all other declarations
for _, obj := range othersList {
check.objDecl(obj, nil)
}
// 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
}
// inSourceOrder implements the sort.Sort interface.
type inSourceOrder []Object
func (a inSourceOrder) Len() int { return len(a) }
func (a inSourceOrder) Less(i, j int) bool { return a[i].order() < a[j].order() }
func (a inSourceOrder) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
// 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."
for _, obj := range check.imports {
if !obj.used && obj.name != "_" {
check.errorUnusedPkg(obj)
}
}
}
func (check *Checker) errorUnusedPkg(obj *PkgName) {
// If the package was imported with a name other than the final
// import path element, show it explicitly in the error message.
// Note that this handles both renamed imports and imports of
// packages containing unconventional package declarations.
// Note that this uses / always, even on Windows, because Go import
// paths always use forward slashes.
path := obj.imported.path
elem := path
if i := strings.LastIndex(elem, "/"); i >= 0 {
elem = elem[i+1:]
}
if obj.name == "" || obj.name == "." || obj.name == elem {
check.softErrorf(obj, _UnusedImport, "%q imported but not used", path)
} else {
check.softErrorf(obj, _UnusedImport, "%q imported but not used as %s", path, obj.name)
}
}
// 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 "."
}
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