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.
16 . "internal/types/errors"
19 // nopos indicates an unknown position
22 // debugging/development support
23 const debug = false // leave on during development
25 // exprInfo stores information about an untyped expression.
26 type exprInfo struct {
27 isLhs bool // expression is lhs operand of a shift with delayed type-check
30 val constant.Value // constant value; or nil (if not a constant)
33 // An environment represents the environment within which an object is
35 type environment struct {
36 decl *declInfo // package-level declaration whose init expression/function body is checked
37 scope *Scope // top-most scope for lookups
38 pos token.Pos // if valid, identifiers are looked up as if at position pos (used by Eval)
39 iota constant.Value // value of iota in a constant declaration; nil otherwise
40 errpos positioner // if set, identifier position of a constant with inherited initializer
41 inTParamList bool // set if inside a type parameter list
42 sig *Signature // function signature if inside a function; nil otherwise
43 isPanic map[*ast.CallExpr]bool // set of panic call expressions (used for termination check)
44 hasLabel bool // set if a function makes use of labels (only ~1% of functions); unused outside functions
45 hasCallOrRecv bool // set if an expression contains a function call or channel receive operation
48 // lookup looks up name in the current environment and returns the matching object, or nil.
49 func (env *environment) lookup(name string) Object {
50 _, obj := env.scope.LookupParent(name, env.pos)
54 // An importKey identifies an imported package by import path and source directory
55 // (directory containing the file containing the import). In practice, the directory
56 // may always be the same, or may not matter. Given an (import path, directory), an
57 // importer must always return the same package (but given two different import paths,
58 // an importer may still return the same package by mapping them to the same package
60 type importKey struct {
64 // A dotImportKey describes a dot-imported object in the given scope.
65 type dotImportKey struct {
70 // An action describes a (delayed) action.
72 f func() // action to be executed
73 desc *actionDesc // action description; may be nil, requires debug to be set
76 // If debug is set, describef sets a printf-formatted description for action a.
77 // Otherwise, it is a no-op.
78 func (a *action) describef(pos positioner, format string, args ...any) {
80 a.desc = &actionDesc{pos, format, args}
84 // An actionDesc provides information on an action.
85 // For debugging only.
86 type actionDesc struct {
92 // A Checker maintains the state of the type checker.
93 // It must be created with [NewChecker].
95 // package information
96 // (initialized by NewChecker, valid for the life-time of checker)
98 ctxt *Context // context for de-duplicating instances
102 version version // accepted language version
103 posVers map[token.Pos]version // maps file start positions to versions (may be nil)
104 nextID uint64 // unique Id for type parameters (first valid Id is 1)
105 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
106 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
107 valids instanceLookup // valid *Named (incl. instantiated) types per the validType check
109 // pkgPathMap maps package names to the set of distinct import paths we've
110 // seen for that name, anywhere in the import graph. It is used for
111 // disambiguating package names in error messages.
113 // pkgPathMap is allocated lazily, so that we don't pay the price of building
114 // it on the happy path. seenPkgMap tracks the packages that we've already
116 pkgPathMap map[string]map[string]bool
117 seenPkgMap map[*Package]bool
119 // information collected during type-checking of a set of package files
120 // (initialized by Files, valid only for the duration of check.Files;
121 // maps and lists are allocated on demand)
122 files []*ast.File // package files
123 imports []*PkgName // list of imported packages
124 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
125 recvTParamMap map[*ast.Ident]*TypeParam // maps blank receiver type parameters to their type
126 brokenAliases map[*TypeName]bool // set of aliases with broken (not yet determined) types
127 unionTypeSets map[*Union]*_TypeSet // computed type sets for union types
128 mono monoGraph // graph for detecting non-monomorphizable instantiation loops
130 firstErr error // first error encountered
131 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
132 untyped map[ast.Expr]exprInfo // map of expressions without final type
133 delayed []action // stack of delayed action segments; segments are processed in FIFO order
134 objPath []Object // path of object dependencies during type inference (for cycle reporting)
135 cleaners []cleaner // list of types that may need a final cleanup at the end of type-checking
137 // environment within which the current object is type-checked (valid only
138 // for the duration of type-checking a specific object)
142 indent int // indentation for tracing
145 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
146 func (check *Checker) addDeclDep(to Object) {
149 return // not in a package-level init expression
151 if _, found := check.objMap[to]; !found {
152 return // to is not a package-level object
157 // Note: The following three alias-related functions are only used
158 // when _Alias types are not enabled.
160 // brokenAlias records that alias doesn't have a determined type yet.
161 // It also sets alias.typ to Typ[Invalid].
162 // Not used if check.conf._EnableAlias is set.
163 func (check *Checker) brokenAlias(alias *TypeName) {
164 assert(!check.conf._EnableAlias)
165 if check.brokenAliases == nil {
166 check.brokenAliases = make(map[*TypeName]bool)
168 check.brokenAliases[alias] = true
169 alias.typ = Typ[Invalid]
172 // validAlias records that alias has the valid type typ (possibly Typ[Invalid]).
173 func (check *Checker) validAlias(alias *TypeName, typ Type) {
174 assert(!check.conf._EnableAlias)
175 delete(check.brokenAliases, alias)
179 // isBrokenAlias reports whether alias doesn't have a determined type yet.
180 func (check *Checker) isBrokenAlias(alias *TypeName) bool {
181 assert(!check.conf._EnableAlias)
182 return check.brokenAliases[alias]
185 func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
188 m = make(map[ast.Expr]exprInfo)
191 m[e] = exprInfo{lhs, mode, typ, val}
194 // later pushes f on to the stack of actions that will be processed later;
195 // either at the end of the current statement, or in case of a local constant
196 // or variable declaration, before the constant or variable is in scope
197 // (so that f still sees the scope before any new declarations).
198 // later returns the pushed action so one can provide a description
199 // via action.describef for debugging, if desired.
200 func (check *Checker) later(f func()) *action {
201 i := len(check.delayed)
202 check.delayed = append(check.delayed, action{f: f})
203 return &check.delayed[i]
206 // push pushes obj onto the object path and returns its index in the path.
207 func (check *Checker) push(obj Object) int {
208 check.objPath = append(check.objPath, obj)
209 return len(check.objPath) - 1
212 // pop pops and returns the topmost object from the object path.
213 func (check *Checker) pop() Object {
214 i := len(check.objPath) - 1
215 obj := check.objPath[i]
216 check.objPath[i] = nil
217 check.objPath = check.objPath[:i]
221 type cleaner interface {
225 // needsCleanup records objects/types that implement the cleanup method
226 // which will be called at the end of type-checking.
227 func (check *Checker) needsCleanup(c cleaner) {
228 check.cleaners = append(check.cleaners, c)
231 // NewChecker returns a new [Checker] instance for a given package.
232 // [Package] files may be added incrementally via checker.Files.
233 func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {
234 // make sure we have a configuration
239 // make sure we have an info struct
244 // Note: clients may call NewChecker with the Unsafe package, which is
245 // globally shared and must not be mutated. Therefore NewChecker must not
248 // (previously, pkg.goVersion was mutated here: go.dev/issue/61212)
256 objMap: make(map[Object]*declInfo),
257 impMap: make(map[importKey]*Package),
261 // initFiles initializes the files-specific portion of checker.
262 // The provided files must all belong to the same package.
263 func (check *Checker) initFiles(files []*ast.File) {
264 // start with a clean slate (check.Files may be called multiple times)
267 check.dotImportMap = nil
276 // determine package name and collect valid files
278 for _, file := range files {
279 switch name := file.Name.Name; pkg.name {
284 check.error(file.Name, BlankPkgName, "invalid package name _")
289 check.files = append(check.files, file)
292 check.errorf(atPos(file.Package), MismatchedPkgName, "package %s; expected %s", name, pkg.name)
297 // collect file versions
298 for _, file := range check.files {
299 check.recordFileVersion(file, check.conf.GoVersion) // record package version (possibly zero version)
300 if v, _ := parseGoVersion(file.GoVersion); v.major > 0 {
301 if v.equal(check.version) {
304 // Go 1.21 introduced the feature of setting the go.mod
305 // go line to an early version of Go and allowing //go:build lines
306 // to “upgrade” the Go version in a given file.
307 // We can do that backwards compatibly.
308 // Go 1.21 also introduced the feature of allowing //go:build lines
309 // to “downgrade” the Go version in a given file.
310 // That can't be done compatibly in general, since before the
311 // build lines were ignored and code got the module's Go version.
312 // To work around this, downgrades are only allowed when the
313 // module's Go version is Go 1.21 or later.
314 // If there is no check.version, then we don't really know what Go version to apply.
315 // Legacy tools may do this, and they historically have accepted everything.
316 // Preserve that behavior by ignoring //go:build constraints entirely in that case.
317 if (v.before(check.version) && check.version.before(go1_21)) || check.version.equal(go0_0) {
320 if check.posVers == nil {
321 check.posVers = make(map[token.Pos]version)
323 check.posVers[file.FileStart] = v
324 check.recordFileVersion(file, file.GoVersion) // overwrite package version
329 // A bailout panic is used for early termination.
330 type bailout struct{}
332 func (check *Checker) handleBailout(err *error) {
333 switch p := recover().(type) {
335 // normal return or early exit
336 *err = check.firstErr
343 // Files checks the provided files as part of the checker's package.
344 func (check *Checker) Files(files []*ast.File) error { return check.checkFiles(files) }
346 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
348 func (check *Checker) checkFiles(files []*ast.File) (err error) {
349 if check.pkg == Unsafe {
350 // Defensive handling for Unsafe, which cannot be type checked, and must
351 // not be mutated. See https://go.dev/issue/61212 for an example of where
352 // Unsafe is passed to NewChecker.
356 // Note: parseGoVersion and the subsequent checks should happen once,
357 // when we create a new Checker, not for each batch of files.
358 // We can't change it at this point because NewChecker doesn't
360 check.version, err = parseGoVersion(check.conf.GoVersion)
364 if check.version.after(version{1, goversion.Version}) {
365 return fmt.Errorf("package requires newer Go version %v", check.version)
367 if check.conf.FakeImportC && check.conf.go115UsesCgo {
371 defer check.handleBailout(&err)
373 print := func(msg string) {
374 if check.conf._Trace {
380 print("== initFiles ==")
381 check.initFiles(files)
383 print("== collectObjects ==")
384 check.collectObjects()
386 print("== packageObjects ==")
387 check.packageObjects()
389 print("== processDelayed ==")
390 check.processDelayed(0) // incl. all functions
392 print("== cleanup ==")
395 print("== initOrder ==")
398 if !check.conf.DisableUnusedImportCheck {
399 print("== unusedImports ==")
400 check.unusedImports()
403 print("== recordUntyped ==")
404 check.recordUntyped()
406 if check.firstErr == nil {
407 // TODO(mdempsky): Ensure monomorph is safe when errors exist.
411 check.pkg.goVersion = check.conf.GoVersion
412 check.pkg.complete = true
414 // no longer needed - release memory
416 check.dotImportMap = nil
417 check.pkgPathMap = nil
418 check.seenPkgMap = nil
419 check.recvTParamMap = nil
420 check.brokenAliases = nil
421 check.unionTypeSets = nil
424 // TODO(rFindley) There's more memory we should release at this point.
429 // processDelayed processes all delayed actions pushed after top.
430 func (check *Checker) processDelayed(top int) {
431 // If each delayed action pushes a new action, the
432 // stack will continue to grow during this loop.
433 // However, it is only processing functions (which
434 // are processed in a delayed fashion) that may
435 // add more actions (such as nested functions), so
436 // this is a sufficiently bounded process.
437 for i := top; i < len(check.delayed); i++ {
438 a := &check.delayed[i]
439 if check.conf._Trace {
441 check.trace(a.desc.pos.Pos(), "-- "+a.desc.format, a.desc.args...)
443 check.trace(nopos, "-- delayed %p", a.f)
446 a.f() // may append to check.delayed
447 if check.conf._Trace {
451 assert(top <= len(check.delayed)) // stack must not have shrunk
452 check.delayed = check.delayed[:top]
455 // cleanup runs cleanup for all collected cleaners.
456 func (check *Checker) cleanup() {
457 // Don't use a range clause since Named.cleanup may add more cleaners.
458 for i := 0; i < len(check.cleaners); i++ {
459 check.cleaners[i].cleanup()
464 func (check *Checker) record(x *operand) {
465 // convert x into a user-friendly set of values
466 // TODO(gri) this code can be simplified
468 var val constant.Value
480 assert(x.expr != nil && typ != nil)
483 // delay type and value recording until we know the type
484 // or until the end of type checking
485 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
487 check.recordTypeAndValue(x.expr, x.mode, typ, val)
491 func (check *Checker) recordUntyped() {
492 if !debug && check.Types == nil {
493 return // nothing to do
496 for x, info := range check.untyped {
497 if debug && isTyped(info.typ) {
498 check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ)
501 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
505 func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
511 if mode == constant_ {
513 // We check allBasic(typ, IsConstType) here as constant expressions may be
514 // recorded as type parameters.
515 assert(!isValid(typ) || allBasic(typ, IsConstType))
517 if m := check.Types; m != nil {
518 m[x] = TypeAndValue{mode, typ, val}
522 func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
523 // f must be a (possibly parenthesized, possibly qualified)
524 // identifier denoting a built-in (including unsafe's non-constant
525 // functions Add and Slice): record the signature for f and possible
528 check.recordTypeAndValue(f, builtin, sig, nil)
529 switch p := f.(type) {
530 case *ast.Ident, *ast.SelectorExpr:
540 // recordCommaOkTypes updates recorded types to reflect that x is used in a commaOk context
541 // (and therefore has tuple type).
542 func (check *Checker) recordCommaOkTypes(x ast.Expr, a []*operand) {
545 if a[0].mode == invalid {
548 t0, t1 := a[0].typ, a[1].typ
549 assert(isTyped(t0) && isTyped(t1) && (isBoolean(t1) || t1 == universeError))
550 if m := check.Types; m != nil {
553 assert(tv.Type != nil) // should have been recorded already
556 NewVar(pos, check.pkg, "", t0),
557 NewVar(pos, check.pkg, "", t1),
560 // if x is a parenthesized expression (p.X), update p.X
561 p, _ := x.(*ast.ParenExpr)
570 // recordInstance records instantiation information into check.Info, if the
571 // Instances map is non-nil. The given expr must be an ident, selector, or
572 // index (list) expr with ident or selector operand.
574 // TODO(rfindley): the expr parameter is fragile. See if we can access the
575 // instantiated identifier in some other way.
576 func (check *Checker) recordInstance(expr ast.Expr, targs []Type, typ Type) {
577 ident := instantiatedIdent(expr)
580 if m := check.Instances; m != nil {
581 m[ident] = Instance{newTypeList(targs), typ}
585 func instantiatedIdent(expr ast.Expr) *ast.Ident {
586 var selOrIdent ast.Expr
587 switch e := expr.(type) {
590 case *ast.IndexListExpr:
592 case *ast.SelectorExpr, *ast.Ident:
595 switch x := selOrIdent.(type) {
598 case *ast.SelectorExpr:
601 panic("instantiated ident not found")
604 func (check *Checker) recordDef(id *ast.Ident, obj Object) {
606 if m := check.Defs; m != nil {
611 func (check *Checker) recordUse(id *ast.Ident, obj Object) {
614 if m := check.Uses; m != nil {
619 func (check *Checker) recordImplicit(node ast.Node, obj Object) {
622 if m := check.Implicits; m != nil {
627 func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
628 assert(obj != nil && (recv == nil || len(index) > 0))
629 check.recordUse(x.Sel, obj)
630 if m := check.Selections; m != nil {
631 m[x] = &Selection{kind, recv, obj, index, indirect}
635 func (check *Checker) recordScope(node ast.Node, scope *Scope) {
638 if m := check.Scopes; m != nil {
643 func (check *Checker) recordFileVersion(file *ast.File, version string) {
644 if m := check.FileVersions; m != nil {