golang check 代码
文件路径：/src/cmd/compile/internal/types2/check.go
/ Copyright 2011 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.
/ This file implements the Check function, which drives type-checking.
package types2
import (
"cmd/compile/internal/syntax"
"errors"
"fmt"
"go/constant"
)
var nopos syntax.Pos
/ debugging/development support
const debug = false / leave on during development
/ exprInfo stores information about an untyped expression.
type exprInfo struct {
isLhs bool / expression is lhs operand of a shift with delayed type-check
mode operandMode
typ *Basic
val constant.Value / constant value; or nil (if not a constant)
}
/ An environment represents the environment within which an object is
/ type-checked.
type environment struct {
decl *declInfo / package-level declaration whose init expression/function body is checked
scope *Scope / top-most scope for lookups
pos syntax.Pos / if valid, identifiers are looked up as if at position pos (used by Eval)
iota constant.Value / value of iota in a constant declaration; nil otherwise
errpos syntax.Pos / if valid, identifier position of a constant with inherited initializer
inTParamList bool / set if inside a type parameter list
sig *Signature / function signature if inside a function; nil otherwise
isPanic map[*syntax.CallExpr]bool / set of panic call expressions (used for termination check)
hasLabel bool / set if a function makes use of labels (only ~1% of functions); unused outside functions
hasCallOrRecv bool / set if an expression contains a function call or channel receive operation
}
/ lookup looks up name in the current environment and returns the matching object, or nil.
func (env *environment) lookup(name string) Object {
_, obj := env.scope.LookupParent(name, env.pos)
return obj
}
/ An importKey identifies an imported package by import path and source directory
/ (directory containing the file containing the import). In practice, the directory
/ may always be the same, or may not matter. Given an (import path, directory), an
/ importer must always return the same package (but given two different import paths,
/ an importer may still return the same package by mapping them to the same package
/ paths).
type importKey struct {
path, dir string
}
/ A dotImportKey describes a dot-imported object in the given scope.
type dotImportKey struct {
scope *Scope
name string
}
/ An action describes a (delayed) action.
type action struct {
f func() / action to be executed
desc *actionDesc / action description; may be nil, requires debug to be set
}
/ If debug is set, describef sets a printf-formatted description for action a.
/ Otherwise, it is a no-op.
func (a *action) describef(pos poser, format string, args ...interface{}) {
if debug {
a.desc = &actionDesc{pos, format, args}
}
}
/ An actionDesc provides information on an action.
/ For debugging only.
type actionDesc struct {
pos poser
format string
args []interface{}
}
/ A Checker maintains the state of the type checker.
/ It must be created with NewChecker.
type Checker struct {
/ package information
/ (initialized by NewChecker, valid for the life-time of checker)
conf *Config
ctxt *Context / context for de-duplicating instances
pkg *Package
*Info
version version / accepted language version
nextID uint64 / unique Id for type parameters (first valid Id is 1)
objMap map[Object]*declInfo / maps package-level objects and (non-interface) methods to declaration info
impMap map[importKey]*Package / maps (import path, source directory) to (complete or fake) package
valids instanceLookup / valid *Named (incl. instantiated) types per the validType check
/ pkgPathMap maps package names to the set of distinct import paths we've
/ seen for that name, anywhere in the import graph. It is used for
/ disambiguating package names in error messages.
/
/ pkgPathMap is allocated lazily, so that we don't pay the price of building
/ it on the happy path. seenPkgMap tracks the packages that we've already
/ walked.
pkgPathMap map[string]map[string]bool
seenPkgMap map[*Package]bool
/ information collected during type-checking of a set of package files
/ (initialized by Files, valid only for the duration of check.Files;
/ maps and lists are allocated on demand)
files []*syntax.File / list of package files
imports []*PkgName / list of imported packages
dotImportMap map[dotImportKey]*PkgName / maps dot-imported objects to the package they were dot-imported through
recvTParamMap map[*syntax.Name]*TypeParam / maps blank receiver type parameters to their type
brokenAliases map[*TypeName]bool / set of aliases with broken (not yet determined) types
unionTypeSets map[*Union]*_TypeSet / computed type sets for union types
mono monoGraph / graph for detecting non-monomorphizable instantiation loops
firstErr error / first error encountered
methods map[*TypeName][]*Func / maps package scope type names to associated non-blank (non-interface) methods
untyped map[syntax.Expr]exprInfo / map of expressions without final type
delayed []action / stack of delayed action segments; segments are processed in FIFO order
objPath []Object / path of object dependencies during type inference (for cycle reporting)
cleaners []cleaner / list of types that may need a final cleanup at the end of type-checking
/ environment within which the current object is type-checked (valid only
/ for the duration of type-checking a specific object)
environment
/ debugging
indent int / indentation for tracing
}
/ addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
func (check *Checker) addDeclDep(to Object) {
from := check.decl
if from == nil {
return / not in a package-level init expression
}
if _, found := check.objMap[to]; !found {
return / to is not a package-level object
}
from.addDep(to)
}
/ brokenAlias records that alias doesn't have a determined type yet.
/ It also sets alias.typ to Typ[Invalid].
func (check *Checker) brokenAlias(alias *TypeName) {
if check.brokenAliases == nil {
check.brokenAliases = make(map[*TypeName]bool)
}
check.brokenAliases[alias] = true
alias.typ = Typ[Invalid]
}
/ validAlias records that alias has the valid type typ (possibly Typ[Invalid]).
func (check *Checker) validAlias(alias *TypeName, typ Type) {
delete(check.brokenAliases, alias)
alias.typ = typ
}
/ isBrokenAlias reports whether alias doesn't have a determined type yet.
func (check *Checker) isBrokenAlias(alias *TypeName) bool {
return alias.typ == Typ[Invalid] && check.brokenAliases[alias]
}
func (check *Checker) rememberUntyped(e syntax.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
m := check.untyped
if m == nil {
m = make(map[syntax.Expr]exprInfo)
check.untyped = m
}
m[e] = exprInfo{lhs, mode, typ, val}
}
/ later pushes f on to the stack of actions that will be processed later;
/ either at the end of the current statement, or in case of a local constant
/ or variable declaration, before the constant or variable is in scope
/ (so that f still sees the scope before any new declarations).
/ later returns the pushed action so one can provide a description
/ via action.describef for debugging, if desired.
func (check *Checker) later(f func()) *action {
i := len(check.delayed)
check.delayed = append(check.delayed, action{f: f})
return &check.delayed[i]
}
/ push pushes obj onto the object path and returns its index in the path.
func (check *Checker) push(obj Object) int {
check.objPath = append(check.objPath, obj)
return len(check.objPath) - 1
}
/ pop pops and returns the topmost object from the object path.
func (check *Checker) pop() Object {
i := len(check.objPath) - 1
obj := check.objPath[i]
check.objPath[i] = nil
check.objPath = check.objPath[:i]
return obj
}
type cleaner interface {
cleanup()
}
/ needsCleanup records objects/types that implement the cleanup method
/ which will be called at the end of type-checking.
func (check *Checker) needsCleanup(c cleaner) {
check.cleaners = append(check.cleaners, c)
}
/ NewChecker returns a new Checker instance for a given package.
/ Package files may be added incrementally via checker.Files.
func NewChecker(conf *Config, pkg *Package, info *Info) *Checker {
/ make sure we have a configuration
if conf == nil {
conf = new(Config)
}
/ make sure we have an info struct
if info == nil {
info = new(Info)
}
version, err := parseGoVersion(conf.GoVersion)
if err != nil {
panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
}
return &Checker{
conf: conf,
ctxt: conf.Context,
pkg: pkg,
Info: info,
version: version,
objMap: make(map[Object]*declInfo),
impMap: make(map[importKey]*Package),
}
}
/ initFiles initializes the files-specific portion of checker.
/ The provided files must all belong to the same package.
func (check *Checker) initFiles(files []*syntax.File) {
/ start with a clean slate (check.Files may be called multiple times)
check.files = nil
check.imports = nil
check.dotImportMap = nil
check.firstErr = nil
check.methods = nil
check.untyped = nil
check.delayed = nil
check.objPath = nil
check.cleaners = nil
/ determine package name and collect valid files
pkg := check.pkg
for _, file := range files {
switch name := file.PkgName.Value; pkg.name {
case "":
if name != "_" {
pkg.name = name
} else {
check.error(file.PkgName, "invalid package name _")
}
fallthrough
case name:
check.files = append(check.files, file)
default:
check.errorf(file, "package %s; expected %s", name, pkg.name)
/ ignore this file
}
}
}
/ A bailout panic is used for early termination.
type bailout struct{}
func (check *Checker) handleBailout(err *error) {
switch p := recover().(type) {
case nil, bailout:
/ normal return or early exit
*err = check.firstErr
default:
/ re-panic
panic(p)
}
}
/ Files checks the provided files as part of the checker's package.
func (check *Checker) Files(files []*syntax.File) error { return check.checkFiles(files) }
var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
func (check *Checker) checkFiles(files []*syntax.File) (err error) {
if check.conf.FakeImportC && check.conf.go115UsesCgo {
return errBadCgo
}
defer check.handleBailout(&err)
print := func(msg string) {
if check.conf.Trace {
fmt.Println()
fmt.Println(msg)
}
}
print("== initFiles ==")
check.initFiles(files)
print("== collectObjects ==")
check.collectObjects()
print("== packageObjects ==")
check.packageObjects()
print("== processDelayed ==")
check.processDelayed(0) / incl. all functions
print("== cleanup ==")
check.cleanup()
print("== initOrder ==")
check.initOrder()
if !check.conf.DisableUnusedImportCheck {
print("== unusedImports ==")
check.unusedImports()
}
print("== recordUntyped ==")
check.recordUntyped()
if check.firstErr == nil {
/ TODO(mdempsky): Ensure monomorph is safe when errors exist.
check.monomorph()
}
check.pkg.complete = true
/ no longer needed - release memory
check.imports = nil
check.dotImportMap = nil
check.pkgPathMap = nil
check.seenPkgMap = nil
check.recvTParamMap = nil
check.brokenAliases = nil
check.unionTypeSets = nil
check.ctxt = nil
/ TODO(gri) There's more memory we should release at this point.
return
}
/ processDelayed processes all delayed actions pushed after top.
func (check *Checker) processDelayed(top int) {
/ If each delayed action pushes a new action, the
/ stack will continue to grow during this loop.
/ However, it is only processing functions (which
/ are processed in a delayed fashion) that may
/ add more actions (such as nested functions), so
/ this is a sufficiently bounded process.
for i := top; i < len(check.delayed); i++ {
a := &check.delayed[i]
if check.conf.Trace {
if a.desc != nil {
check.trace(a.desc.pos.Pos(), "-- "+a.desc.format, a.desc.args...)
} else {
check.trace(nopos, "-- delayed %p", a.f)
}
}
a.f() / may append to check.delayed
if check.conf.Trace {
fmt.Println()
}
}
assert(top <= len(check.delayed)) / stack must not have shrunk
check.delayed = check.delayed[:top]
}
/ cleanup runs cleanup for all collected cleaners.
func (check *Checker) cleanup() {
/ Don't use a range clause since Named.cleanup may add more cleaners.
for i := 0; i < len(check.cleaners); i++ {
check.cleaners[i].cleanup()
}
check.cleaners = nil
}
func (check *Checker) record(x *operand) {
/ convert x into a user-friendly set of values
/ TODO(gri) this code can be simplified
var typ Type
var val constant.Value
switch x.mode {
case invalid:
typ = Typ[Invalid]
case novalue:
typ = (*Tuple)(nil)
case constant_:
typ = x.typ
val = x.val
default:
typ = x.typ
}
assert(x.expr != nil && typ != nil)
if isUntyped(typ) {
/ delay type and value recording until we know the type
/ or until the end of type checking
check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
} else {
check.recordTypeAndValue(x.expr, x.mode, typ, val)
}
}
func (check *Checker) recordUntyped() {
if !debug && check.Types == nil {
return / nothing to do
}
for x, info := range check.untyped {
if debug && isTyped(info.typ) {
check.dump("%v: %s (type %s) is typed", posFor(x), x, info.typ)
unreachable()
}
check.recordTypeAndValue(x, info.mode, info.typ, info.val)
}
}
func (check *Checker) recordTypeAndValue(x syntax.Expr, mode operandMode, typ Type, val constant.Value) {
assert(x != nil)
assert(typ != nil)
if mode == invalid {
return / omit
}
if mode == constant_ {
assert(val != nil)
/ We check allBasic(typ, IsConstType) here as constant expressions may be
/ recorded as type parameters.
assert(typ == Typ[Invalid] || allBasic(typ, IsConstType))
}
if m := check.Types; m != nil {
m[x] = TypeAndValue{mode, typ, val}
}
}
func (check *Checker) recordBuiltinType(f syntax.Expr, sig *Signature) {
/ f must be a (possibly parenthesized, possibly qualified)
/ identifier denoting a built-in (including unsafe's non-constant
/ functions Add and Slice): record the signature for f and possible
/ children.
for {
check.recordTypeAndValue(f, builtin, sig, nil)
switch p := f.(type) {
case *syntax.Name, *syntax.SelectorExpr:
return / we're done
case *syntax.ParenExpr:
f = p.X
default:
unreachable()
}
}
}
func (check *Checker) recordCommaOkTypes(x syntax.Expr, a [2]Type) {
assert(x != nil)
if a[0] == nil || a[1] == nil {
return
}
assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
if m := check.Types; m != nil {
for {
tv := m[x]
assert(tv.Type != nil) / should have been recorded already
pos := x.Pos()
tv.Type = NewTuple(
NewVar(pos, check.pkg, "", a[0]),
NewVar(pos, check.pkg, "", a[1]),
)
m[x] = tv
/ if x is a parenthesized expression (p.X), update p.X
p, _ := x.(*syntax.ParenExpr)
if p == nil {
break
}
x = p.X
}
}
}
/ recordInstance records instantiation information into check.Info, if the
/ Instances map is non-nil. The given expr must be an ident, selector, or
/ index (list) expr with ident or selector operand.
/
/ TODO(rfindley): the expr parameter is fragile. See if we can access the
/ instantiated identifier in some other way.
func (check *Checker) recordInstance(expr syntax.Expr, targs []Type, typ Type) {
ident := instantiatedIdent(expr)
assert(ident != nil)
assert(typ != nil)
if m := check.Instances; m != nil {
m[ident] = Instance{newTypeList(targs), typ}
}
}
func instantiatedIdent(expr syntax.Expr) *syntax.Name {
var selOrIdent syntax.Expr
switch e := expr.(type) {
case *syntax.IndexExpr:
selOrIdent = e.X
case *syntax.SelectorExpr, *syntax.Name:
selOrIdent = e
}
switch x := selOrIdent.(type) {
case *syntax.Name:
return x
case *syntax.SelectorExpr:
return x.Sel
}
panic("instantiated ident not found")
}
func (check *Checker) recordDef(id *syntax.Name, obj Object) {
assert(id != nil)
if m := check.Defs; m != nil {
m[id] = obj
}
}
func (check *Checker) recordUse(id *syntax.Name, obj Object) {
assert(id != nil)
assert(obj != nil)
if m := check.Uses; m != nil {
m[id] = obj
}
}
func (check *Checker) recordImplicit(node syntax.Node, obj Object) {
assert(node != nil)
assert(obj != nil)
if m := check.Implicits; m != nil {
m[node] = obj
}
}
func (check *Checker) recordSelection(x *syntax.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
assert(obj != nil && (recv == nil || len(index) > 0))
check.recordUse(x.Sel, obj)
if m := check.Selections; m != nil {
m[x] = &Selection{kind, recv, obj, index, indirect}
}
}
func (check *Checker) recordScope(node syntax.Node, scope *Scope) {
assert(node != nil)
assert(scope != nil)
if m := check.Scopes; m != nil {
m[node] = scope
}
}