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// 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 types
import (
"go/ast"
"go/constant"
"go/token"
)
// debugging/development support
const (
debug = false // leave on during development
trace = false // turn on for detailed type resolution traces
)
// If Strict is set, the type-checker enforces additional
// rules not specified by the Go 1 spec, but which will
// catch guaranteed run-time errors if the respective
// code is executed. In other words, programs passing in
// Strict mode are Go 1 compliant, but not all Go 1 programs
// will pass in Strict mode. The additional rules are:
//
// - A type assertion x.(T) where T is an interface type
// is invalid if any (statically known) method that exists
// for both x and T have different signatures.
//
const strict = false
// 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)
}
// funcInfo stores the information required for type-checking a function.
type funcInfo struct {
name string // for debugging/tracing only
decl *declInfo // for cycle detection
sig *Signature
body *ast.BlockStmt
}
// A context represents the context within which an object is type-checked.
type context struct {
decl *declInfo // package-level declaration whose init expression/function body is checked
scope *Scope // top-most scope for lookups
iota constant.Value // value of iota in a constant declaration; nil otherwise
sig *Signature // function signature if inside a function; nil otherwise
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
}
// 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 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
fset *token.FileSet
pkg *Package
*Info
objMap map[Object]*declInfo // maps package-level object to declaration info
impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
// 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 []*ast.File // package files
unusedDotImports map[*Scope]map[*Package]token.Pos // positions of unused dot-imported packages for each file scope
firstErr error // first error encountered
methods map[string][]*Func // maps type names to associated methods
untyped map[ast.Expr]exprInfo // map of expressions without final type
funcs []funcInfo // list of functions to type-check
delayed []func() // delayed checks requiring fully setup types
// context within which the current object is type-checked
// (valid only for the duration of type-checking a specific object)
context
pos token.Pos // if valid, identifiers are looked up as if at position pos (used by Eval)
// debugging
indent int // indentation for tracing
}
// addUnusedImport adds the position of a dot-imported package
// pkg to the map of dot imports for the given file scope.
func (check *Checker) addUnusedDotImport(scope *Scope, pkg *Package, pos token.Pos) {
mm := check.unusedDotImports
if mm == nil {
mm = make(map[*Scope]map[*Package]token.Pos)
check.unusedDotImports = mm
}
m := mm[scope]
if m == nil {
m = make(map[*Package]token.Pos)
mm[scope] = m
}
m[pkg] = pos
}
// 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)
}
func (check *Checker) assocMethod(tname string, meth *Func) {
m := check.methods
if m == nil {
m = make(map[string][]*Func)
check.methods = m
}
m[tname] = append(m[tname], meth)
}
func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
m := check.untyped
if m == nil {
m = make(map[ast.Expr]exprInfo)
check.untyped = m
}
m[e] = exprInfo{lhs, mode, typ, val}
}
func (check *Checker) later(name string, decl *declInfo, sig *Signature, body *ast.BlockStmt) {
check.funcs = append(check.funcs, funcInfo{name, decl, sig, body})
}
func (check *Checker) delay(f func()) {
check.delayed = append(check.delayed, f)
}
// NewChecker returns a new Checker instance for a given package.
// Package files may be added incrementally via checker.Files.
func NewChecker(conf *Config, fset *token.FileSet, 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)
}
return &Checker{
conf: conf,
fset: fset,
pkg: pkg,
Info: info,
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 []*ast.File) {
// start with a clean slate (check.Files may be called multiple times)
check.files = nil
check.unusedDotImports = nil
check.firstErr = nil
check.methods = nil
check.untyped = nil
check.funcs = nil
check.delayed = nil
// determine package name and collect valid files
pkg := check.pkg
for _, file := range files {
switch name := file.Name.Name; pkg.name {
case "":
if name != "_" {
pkg.name = name
} else {
check.errorf(file.Name.Pos(), "invalid package name _")
}
fallthrough
case name:
check.files = append(check.files, file)
default:
check.errorf(file.Package, "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 []*ast.File) error { return check.checkFiles(files) }
func (check *Checker) checkFiles(files []*ast.File) (err error) {
defer check.handleBailout(&err)
check.initFiles(files)
check.collectObjects()
check.packageObjects(check.resolveOrder())
check.functionBodies()
check.initOrder()
if !check.conf.DisableUnusedImportCheck {
check.unusedImports()
}
// perform delayed checks
for _, f := range check.delayed {
f()
}
check.recordUntyped()
check.pkg.complete = true
return
}
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("%s: %s (type %s) is typed", x.Pos(), x, info.typ)
unreachable()
}
check.recordTypeAndValue(x, info.mode, info.typ, info.val)
}
}
func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
assert(x != nil)
assert(typ != nil)
if mode == invalid {
return // omit
}
assert(typ != nil)
if mode == constant_ {
assert(val != nil)
assert(typ == Typ[Invalid] || isConstType(typ))
}
if m := check.Types; m != nil {
m[x] = TypeAndValue{mode, typ, val}
}
}
func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
// f must be a (possibly parenthesized) identifier denoting a built-in
// (built-ins in package unsafe always produce a constant result and
// we don't record their signatures, so we don't see qualified idents
// here): record the signature for f and possible children.
for {
check.recordTypeAndValue(f, builtin, sig, nil)
switch p := f.(type) {
case *ast.Ident:
return // we're done
case *ast.ParenExpr:
f = p.X
default:
unreachable()
}
}
}
func (check *Checker) recordCommaOkTypes(x ast.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]))
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.(*ast.ParenExpr)
if p == nil {
break
}
x = p.X
}
}
}
func (check *Checker) recordDef(id *ast.Ident, obj Object) {
assert(id != nil)
if m := check.Defs; m != nil {
m[id] = obj
}
}
func (check *Checker) recordUse(id *ast.Ident, obj Object) {
assert(id != nil)
assert(obj != nil)
if m := check.Uses; m != nil {
m[id] = obj
}
}
func (check *Checker) recordImplicit(node ast.Node, obj Object) {
assert(node != nil)
assert(obj != nil)
if m := check.Implicits; m != nil {
m[node] = obj
}
}
func (check *Checker) recordSelection(x *ast.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 ast.Node, scope *Scope) {
assert(node != nil)
assert(scope != nil)
if m := check.Scopes; m != nil {
m[node] = scope
}
}