1 // Copyright 2011 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.
5 // This file implements the Check function, which drives type-checking.
10 "cmd/compile/internal/syntax"
18 // debugging/development support
19 const debug = false // leave on during development
21 // If forceStrict is set, the type-checker enforces additional
22 // rules not specified by the Go 1 spec, but which will
23 // catch guaranteed run-time errors if the respective
24 // code is executed. In other words, programs passing in
25 // strict mode are Go 1 compliant, but not all Go 1 programs
26 // will pass in strict mode. The additional rules are:
28 // - A type assertion x.(T) where T is an interface type
29 // is invalid if any (statically known) method that exists
30 // for both x and T have different signatures.
32 const forceStrict = false
34 // exprInfo stores information about an untyped expression.
35 type exprInfo struct {
36 isLhs bool // expression is lhs operand of a shift with delayed type-check
39 val constant.Value // constant value; or nil (if not a constant)
42 // A context represents the context within which an object is type-checked.
44 decl *declInfo // package-level declaration whose init expression/function body is checked
45 scope *Scope // top-most scope for lookups
46 pos syntax.Pos // if valid, identifiers are looked up as if at position pos (used by Eval)
47 iota constant.Value // value of iota in a constant declaration; nil otherwise
48 errpos syntax.Pos // if valid, identifier position of a constant with inherited initializer
49 sig *Signature // function signature if inside a function; nil otherwise
50 isPanic map[*syntax.CallExpr]bool // set of panic call expressions (used for termination check)
51 hasLabel bool // set if a function makes use of labels (only ~1% of functions); unused outside functions
52 hasCallOrRecv bool // set if an expression contains a function call or channel receive operation
55 // lookup looks up name in the current context and returns the matching object, or nil.
56 func (ctxt *context) lookup(name string) Object {
57 _, obj := ctxt.scope.LookupParent(name, ctxt.pos)
61 // An importKey identifies an imported package by import path and source directory
62 // (directory containing the file containing the import). In practice, the directory
63 // may always be the same, or may not matter. Given an (import path, directory), an
64 // importer must always return the same package (but given two different import paths,
65 // an importer may still return the same package by mapping them to the same package
67 type importKey struct {
71 // A dotImportKey describes a dot-imported object in the given scope.
72 type dotImportKey struct {
77 // A Checker maintains the state of the type checker.
78 // It must be created with NewChecker.
80 // package information
81 // (initialized by NewChecker, valid for the life-time of checker)
85 version version // accepted language version
86 nextId uint64 // unique Id for type parameters (first valid Id is 1)
87 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
88 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
89 posMap map[*Interface][]syntax.Pos // maps interface types to lists of embedded interface positions
90 typMap map[string]*Named // maps an instantiated named type hash to a *Named type
91 pkgCnt map[string]int // counts number of imported packages with a given name (for better error messages)
93 // information collected during type-checking of a set of package files
94 // (initialized by Files, valid only for the duration of check.Files;
95 // maps and lists are allocated on demand)
96 files []*syntax.File // list of package files
97 imports []*PkgName // list of imported packages
98 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
100 firstErr error // first error encountered
101 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
102 untyped map[syntax.Expr]exprInfo // map of expressions without final type
103 delayed []func() // stack of delayed action segments; segments are processed in FIFO order
104 objPath []Object // path of object dependencies during type inference (for cycle reporting)
106 // context within which the current object is type-checked
107 // (valid only for the duration of type-checking a specific object)
111 indent int // indentation for tracing
114 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
115 func (check *Checker) addDeclDep(to Object) {
118 return // not in a package-level init expression
120 if _, found := check.objMap[to]; !found {
121 return // to is not a package-level object
126 func (check *Checker) rememberUntyped(e syntax.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
129 m = make(map[syntax.Expr]exprInfo)
132 m[e] = exprInfo{lhs, mode, typ, val}
135 // later pushes f on to the stack of actions that will be processed later;
136 // either at the end of the current statement, or in case of a local constant
137 // or variable declaration, before the constant or variable is in scope
138 // (so that f still sees the scope before any new declarations).
139 func (check *Checker) later(f func()) {
140 check.delayed = append(check.delayed, f)
143 // push pushes obj onto the object path and returns its index in the path.
144 func (check *Checker) push(obj Object) int {
145 check.objPath = append(check.objPath, obj)
146 return len(check.objPath) - 1
149 // pop pops and returns the topmost object from the object path.
150 func (check *Checker) pop() Object {
151 i := len(check.objPath) - 1
152 obj := check.objPath[i]
153 check.objPath[i] = nil
154 check.objPath = check.objPath[:i]
158 // NewChecker returns a new Checker instance for a given package.
159 // Package files may be added incrementally via checker.Files.
160 func NewChecker(conf *Config, pkg *Package, info *Info) *Checker {
161 // make sure we have a configuration
166 // make sure we have an info struct
171 version, err := parseGoVersion(conf.GoVersion)
173 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
182 objMap: make(map[Object]*declInfo),
183 impMap: make(map[importKey]*Package),
184 posMap: make(map[*Interface][]syntax.Pos),
185 typMap: make(map[string]*Named),
186 pkgCnt: make(map[string]int),
190 // initFiles initializes the files-specific portion of checker.
191 // The provided files must all belong to the same package.
192 func (check *Checker) initFiles(files []*syntax.File) {
193 // start with a clean slate (check.Files may be called multiple times)
196 check.dotImportMap = nil
203 // determine package name and collect valid files
205 for _, file := range files {
206 switch name := file.PkgName.Value; pkg.name {
211 check.error(file.PkgName, "invalid package name _")
216 check.files = append(check.files, file)
219 check.errorf(file, "package %s; expected %s", name, pkg.name)
225 // A bailout panic is used for early termination.
226 type bailout struct{}
228 func (check *Checker) handleBailout(err *error) {
229 switch p := recover().(type) {
231 // normal return or early exit
232 *err = check.firstErr
239 // Files checks the provided files as part of the checker's package.
240 func (check *Checker) Files(files []*syntax.File) error { return check.checkFiles(files) }
242 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
244 func (check *Checker) checkFiles(files []*syntax.File) (err error) {
245 if check.conf.FakeImportC && check.conf.go115UsesCgo {
249 defer check.handleBailout(&err)
251 print := func(msg string) {
252 if check.conf.Trace {
257 print("== initFiles ==")
258 check.initFiles(files)
260 print("== collectObjects ==")
261 check.collectObjects()
263 print("== packageObjects ==")
264 check.packageObjects()
266 print("== processDelayed ==")
267 check.processDelayed(0) // incl. all functions
269 print("== initOrder ==")
272 if !check.conf.DisableUnusedImportCheck {
273 print("== unusedImports ==")
274 check.unusedImports()
276 // no longer needed - release memory
278 check.dotImportMap = nil
280 print("== recordUntyped ==")
281 check.recordUntyped()
283 if check.Info != nil {
284 print("== sanitizeInfo ==")
285 sanitizeInfo(check.Info)
288 check.pkg.complete = true
290 // TODO(gri) There's more memory we should release at this point.
295 // processDelayed processes all delayed actions pushed after top.
296 func (check *Checker) processDelayed(top int) {
297 // If each delayed action pushes a new action, the
298 // stack will continue to grow during this loop.
299 // However, it is only processing functions (which
300 // are processed in a delayed fashion) that may
301 // add more actions (such as nested functions), so
302 // this is a sufficiently bounded process.
303 for i := top; i < len(check.delayed); i++ {
304 check.delayed[i]() // may append to check.delayed
306 assert(top <= len(check.delayed)) // stack must not have shrunk
307 check.delayed = check.delayed[:top]
310 func (check *Checker) record(x *operand) {
311 // convert x into a user-friendly set of values
312 // TODO(gri) this code can be simplified
314 var val constant.Value
326 assert(x.expr != nil && typ != nil)
329 // delay type and value recording until we know the type
330 // or until the end of type checking
331 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
333 check.recordTypeAndValue(x.expr, x.mode, typ, val)
337 func (check *Checker) recordUntyped() {
338 if !debug && check.Types == nil {
339 return // nothing to do
342 for x, info := range check.untyped {
343 if debug && isTyped(info.typ) {
344 check.dump("%v: %s (type %s) is typed", posFor(x), x, info.typ)
347 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
351 func (check *Checker) recordTypeAndValue(x syntax.Expr, mode operandMode, typ Type, val constant.Value) {
357 if mode == constant_ {
359 // We check is(typ, IsConstType) here as constant expressions may be
360 // recorded as type parameters.
361 assert(typ == Typ[Invalid] || is(typ, IsConstType))
363 if m := check.Types; m != nil {
364 m[x] = TypeAndValue{mode, typ, val}
368 func (check *Checker) recordBuiltinType(f syntax.Expr, sig *Signature) {
369 // f must be a (possibly parenthesized) identifier denoting a built-in
370 // (built-ins in package unsafe always produce a constant result and
371 // we don't record their signatures, so we don't see qualified idents
372 // here): record the signature for f and possible children.
374 check.recordTypeAndValue(f, builtin, sig, nil)
375 switch p := f.(type) {
378 case *syntax.ParenExpr:
386 func (check *Checker) recordCommaOkTypes(x syntax.Expr, a [2]Type) {
388 if a[0] == nil || a[1] == nil {
391 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
392 if m := check.Types; m != nil {
395 assert(tv.Type != nil) // should have been recorded already
398 NewVar(pos, check.pkg, "", a[0]),
399 NewVar(pos, check.pkg, "", a[1]),
402 // if x is a parenthesized expression (p.X), update p.X
403 p, _ := x.(*syntax.ParenExpr)
412 func (check *Checker) recordInferred(call syntax.Expr, targs []Type, sig *Signature) {
415 if m := check.Inferred; m != nil {
416 m[call] = Inferred{targs, sig}
420 func (check *Checker) recordDef(id *syntax.Name, obj Object) {
422 if m := check.Defs; m != nil {
427 func (check *Checker) recordUse(id *syntax.Name, obj Object) {
430 if m := check.Uses; m != nil {
435 func (check *Checker) recordImplicit(node syntax.Node, obj Object) {
438 if m := check.Implicits; m != nil {
443 func (check *Checker) recordSelection(x *syntax.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
444 assert(obj != nil && (recv == nil || len(index) > 0))
445 check.recordUse(x.Sel, obj)
446 if m := check.Selections; m != nil {
447 m[x] = &Selection{kind, recv, obj, index, indirect}
451 func (check *Checker) recordScope(node syntax.Node, scope *Scope) {
454 if m := check.Scopes; m != nil {