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.
17 // debugging/development support
19 debug = false // leave on during development
20 trace = false // turn on for detailed type resolution traces
22 // TODO(rfindley): add compiler error message handling from types2, guarded
23 // behind this flag, so that we can keep the code in sync.
24 compilerErrorMessages = false // match compiler error messages
27 // exprInfo stores information about an untyped expression.
28 type exprInfo struct {
29 isLhs bool // expression is lhs operand of a shift with delayed type-check
32 val constant.Value // constant value; or nil (if not a constant)
35 // An environment represents the environment within which an object is
37 type environment struct {
38 decl *declInfo // package-level declaration whose init expression/function body is checked
39 scope *Scope // top-most scope for lookups
40 pos token.Pos // if valid, identifiers are looked up as if at position pos (used by Eval)
41 iota constant.Value // value of iota in a constant declaration; nil otherwise
42 errpos positioner // if set, identifier position of a constant with inherited initializer
43 inTParamList bool // set if inside a type parameter list
44 sig *Signature // function signature if inside a function; nil otherwise
45 isPanic map[*ast.CallExpr]bool // set of panic call expressions (used for termination check)
46 hasLabel bool // set if a function makes use of labels (only ~1% of functions); unused outside functions
47 hasCallOrRecv bool // set if an expression contains a function call or channel receive operation
50 // lookup looks up name in the current environment and returns the matching object, or nil.
51 func (env *environment) lookup(name string) Object {
52 _, obj := env.scope.LookupParent(name, env.pos)
56 // An importKey identifies an imported package by import path and source directory
57 // (directory containing the file containing the import). In practice, the directory
58 // may always be the same, or may not matter. Given an (import path, directory), an
59 // importer must always return the same package (but given two different import paths,
60 // an importer may still return the same package by mapping them to the same package
62 type importKey struct {
66 // A dotImportKey describes a dot-imported object in the given scope.
67 type dotImportKey struct {
72 // An action describes a (delayed) action.
74 f func() // action to be executed
75 desc *actionDesc // action description; may be nil, requires debug to be set
78 // If debug is set, describef sets a printf-formatted description for action a.
79 // Otherwise, it is a no-op.
80 func (a *action) describef(pos positioner, format string, args ...any) {
82 a.desc = &actionDesc{pos, format, args}
86 // An actionDesc provides information on an action.
87 // For debugging only.
88 type actionDesc struct {
94 // A Checker maintains the state of the type checker.
95 // It must be created with NewChecker.
97 // package information
98 // (initialized by NewChecker, valid for the life-time of checker)
100 ctxt *Context // context for de-duplicating instances
104 version version // accepted language version
105 nextID uint64 // unique Id for type parameters (first valid Id is 1)
106 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
107 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
108 infoMap map[*Named]typeInfo // maps named types to their associated type info (for cycle detection)
110 // pkgPathMap maps package names to the set of distinct import paths we've
111 // seen for that name, anywhere in the import graph. It is used for
112 // disambiguating package names in error messages.
114 // pkgPathMap is allocated lazily, so that we don't pay the price of building
115 // it on the happy path. seenPkgMap tracks the packages that we've already
117 pkgPathMap map[string]map[string]bool
118 seenPkgMap map[*Package]bool
120 // information collected during type-checking of a set of package files
121 // (initialized by Files, valid only for the duration of check.Files;
122 // maps and lists are allocated on demand)
123 files []*ast.File // package files
124 imports []*PkgName // list of imported packages
125 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
126 recvTParamMap map[*ast.Ident]*TypeParam // maps blank receiver type parameters to their type
127 brokenAliases map[*TypeName]bool // set of aliases with broken (not yet determined) types
128 unionTypeSets map[*Union]*_TypeSet // computed type sets for union types
129 mono monoGraph // graph for detecting non-monomorphizable instantiation loops
131 firstErr error // first error encountered
132 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
133 untyped map[ast.Expr]exprInfo // map of expressions without final type
134 delayed []action // stack of delayed action segments; segments are processed in FIFO order
135 objPath []Object // path of object dependencies during type inference (for cycle reporting)
136 defTypes []*Named // defined types created during type checking, for final validation.
138 // environment within which the current object is type-checked (valid only
139 // for the duration of type-checking a specific object)
143 indent int // indentation for tracing
146 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
147 func (check *Checker) addDeclDep(to Object) {
150 return // not in a package-level init expression
152 if _, found := check.objMap[to]; !found {
153 return // to is not a package-level object
158 // brokenAlias records that alias doesn't have a determined type yet.
159 // It also sets alias.typ to Typ[Invalid].
160 func (check *Checker) brokenAlias(alias *TypeName) {
161 if check.brokenAliases == nil {
162 check.brokenAliases = make(map[*TypeName]bool)
164 check.brokenAliases[alias] = true
165 alias.typ = Typ[Invalid]
168 // validAlias records that alias has the valid type typ (possibly Typ[Invalid]).
169 func (check *Checker) validAlias(alias *TypeName, typ Type) {
170 delete(check.brokenAliases, alias)
174 // isBrokenAlias reports whether alias doesn't have a determined type yet.
175 func (check *Checker) isBrokenAlias(alias *TypeName) bool {
176 return alias.typ == Typ[Invalid] && check.brokenAliases[alias]
179 func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
182 m = make(map[ast.Expr]exprInfo)
185 m[e] = exprInfo{lhs, mode, typ, val}
188 // later pushes f on to the stack of actions that will be processed later;
189 // either at the end of the current statement, or in case of a local constant
190 // or variable declaration, before the constant or variable is in scope
191 // (so that f still sees the scope before any new declarations).
192 // later returns the pushed action so one can provide a description
193 // via action.describef for debugging, if desired.
194 func (check *Checker) later(f func()) *action {
195 i := len(check.delayed)
196 check.delayed = append(check.delayed, action{f: f})
197 return &check.delayed[i]
200 // push pushes obj onto the object path and returns its index in the path.
201 func (check *Checker) push(obj Object) int {
202 check.objPath = append(check.objPath, obj)
203 return len(check.objPath) - 1
206 // pop pops and returns the topmost object from the object path.
207 func (check *Checker) pop() Object {
208 i := len(check.objPath) - 1
209 obj := check.objPath[i]
210 check.objPath[i] = nil
211 check.objPath = check.objPath[:i]
215 // NewChecker returns a new Checker instance for a given package.
216 // Package files may be added incrementally via checker.Files.
217 func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {
218 // make sure we have a configuration
223 // make sure we have an info struct
228 version, err := parseGoVersion(conf.GoVersion)
230 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
240 objMap: make(map[Object]*declInfo),
241 impMap: make(map[importKey]*Package),
242 infoMap: make(map[*Named]typeInfo),
246 // initFiles initializes the files-specific portion of checker.
247 // The provided files must all belong to the same package.
248 func (check *Checker) initFiles(files []*ast.File) {
249 // start with a clean slate (check.Files may be called multiple times)
252 check.dotImportMap = nil
259 // determine package name and collect valid files
261 for _, file := range files {
262 switch name := file.Name.Name; pkg.name {
267 check.errorf(file.Name, _BlankPkgName, "invalid package name _")
272 check.files = append(check.files, file)
275 check.errorf(atPos(file.Package), _MismatchedPkgName, "package %s; expected %s", name, pkg.name)
281 // A bailout panic is used for early termination.
282 type bailout struct{}
284 func (check *Checker) handleBailout(err *error) {
285 switch p := recover().(type) {
287 // normal return or early exit
288 *err = check.firstErr
295 // Files checks the provided files as part of the checker's package.
296 func (check *Checker) Files(files []*ast.File) error { return check.checkFiles(files) }
298 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
300 func (check *Checker) checkFiles(files []*ast.File) (err error) {
301 if check.conf.FakeImportC && check.conf.go115UsesCgo {
305 defer check.handleBailout(&err)
307 check.initFiles(files)
309 check.collectObjects()
311 check.packageObjects()
313 check.processDelayed(0) // incl. all functions
315 check.expandDefTypes()
319 if !check.conf.DisableUnusedImportCheck {
320 check.unusedImports()
323 check.recordUntyped()
325 if check.firstErr == nil {
326 // TODO(mdempsky): Ensure monomorph is safe when errors exist.
330 check.pkg.complete = true
332 // no longer needed - release memory
334 check.dotImportMap = nil
335 check.pkgPathMap = nil
336 check.seenPkgMap = nil
337 check.recvTParamMap = nil
338 check.brokenAliases = nil
339 check.unionTypeSets = nil
343 // TODO(rFindley) There's more memory we should release at this point.
348 // processDelayed processes all delayed actions pushed after top.
349 func (check *Checker) processDelayed(top int) {
350 // If each delayed action pushes a new action, the
351 // stack will continue to grow during this loop.
352 // However, it is only processing functions (which
353 // are processed in a delayed fashion) that may
354 // add more actions (such as nested functions), so
355 // this is a sufficiently bounded process.
356 for i := top; i < len(check.delayed); i++ {
357 a := &check.delayed[i]
358 if trace && a.desc != nil {
360 check.trace(a.desc.pos.Pos(), "-- "+a.desc.format, a.desc.args...)
362 a.f() // may append to check.delayed
364 assert(top <= len(check.delayed)) // stack must not have shrunk
365 check.delayed = check.delayed[:top]
368 func (check *Checker) expandDefTypes() {
369 // Ensure that every defined type created in the course of type-checking has
370 // either non-*Named underlying, or is unresolved.
372 // This guarantees that we don't leak any types whose underlying is *Named,
373 // because any unresolved instances will lazily compute their underlying by
374 // substituting in the underlying of their origin. The origin must have
375 // either been imported or type-checked and expanded here, and in either case
376 // its underlying will be fully expanded.
377 for i := 0; i < len(check.defTypes); i++ {
378 n := check.defTypes[i]
379 switch n.underlying.(type) {
381 if n.resolver == nil {
382 panic("nil underlying")
385 n.under() // n.under may add entries to check.defTypes
391 func (check *Checker) record(x *operand) {
392 // convert x into a user-friendly set of values
393 // TODO(gri) this code can be simplified
395 var val constant.Value
407 assert(x.expr != nil && typ != nil)
410 // delay type and value recording until we know the type
411 // or until the end of type checking
412 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
414 check.recordTypeAndValue(x.expr, x.mode, typ, val)
418 func (check *Checker) recordUntyped() {
419 if !debug && check.Types == nil {
420 return // nothing to do
423 for x, info := range check.untyped {
424 if debug && isTyped(info.typ) {
425 check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ)
428 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
432 func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
438 if mode == constant_ {
440 // We check allBasic(typ, IsConstType) here as constant expressions may be
441 // recorded as type parameters.
442 assert(typ == Typ[Invalid] || allBasic(typ, IsConstType))
444 if m := check.Types; m != nil {
445 m[x] = TypeAndValue{mode, typ, val}
449 func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
450 // f must be a (possibly parenthesized, possibly qualified)
451 // identifier denoting a built-in (including unsafe's non-constant
452 // functions Add and Slice): record the signature for f and possible
455 check.recordTypeAndValue(f, builtin, sig, nil)
456 switch p := f.(type) {
457 case *ast.Ident, *ast.SelectorExpr:
467 func (check *Checker) recordCommaOkTypes(x ast.Expr, a [2]Type) {
469 if a[0] == nil || a[1] == nil {
472 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
473 if m := check.Types; m != nil {
476 assert(tv.Type != nil) // should have been recorded already
479 NewVar(pos, check.pkg, "", a[0]),
480 NewVar(pos, check.pkg, "", a[1]),
483 // if x is a parenthesized expression (p.X), update p.X
484 p, _ := x.(*ast.ParenExpr)
493 // recordInstance records instantiation information into check.Info, if the
494 // Instances map is non-nil. The given expr must be an ident, selector, or
495 // index (list) expr with ident or selector operand.
497 // TODO(rfindley): the expr parameter is fragile. See if we can access the
498 // instantiated identifier in some other way.
499 func (check *Checker) recordInstance(expr ast.Expr, targs []Type, typ Type) {
500 ident := instantiatedIdent(expr)
503 if m := check.Instances; m != nil {
504 m[ident] = Instance{newTypeList(targs), typ}
508 func instantiatedIdent(expr ast.Expr) *ast.Ident {
509 var selOrIdent ast.Expr
510 switch e := expr.(type) {
513 case *ast.IndexListExpr:
515 case *ast.SelectorExpr, *ast.Ident:
518 switch x := selOrIdent.(type) {
521 case *ast.SelectorExpr:
524 panic("instantiated ident not found")
527 func (check *Checker) recordDef(id *ast.Ident, obj Object) {
529 if m := check.Defs; m != nil {
534 func (check *Checker) recordUse(id *ast.Ident, obj Object) {
537 if m := check.Uses; m != nil {
542 func (check *Checker) recordImplicit(node ast.Node, obj Object) {
545 if m := check.Implicits; m != nil {
550 func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
551 assert(obj != nil && (recv == nil || len(index) > 0))
552 check.recordUse(x.Sel, obj)
553 if m := check.Selections; m != nil {
554 m[x] = &Selection{kind, recv, obj, index, indirect}
558 func (check *Checker) recordScope(node ast.Node, scope *Scope) {
561 if m := check.Scopes; m != nil {