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 // If forceStrict is set, the type-checker enforces additional
28 // rules not specified by the Go 1 spec, but which will
29 // catch guaranteed run-time errors if the respective
30 // code is executed. In other words, programs passing in
31 // strict mode are Go 1 compliant, but not all Go 1 programs
32 // will pass in strict mode. The additional rules are:
34 // - A type assertion x.(T) where T is an interface type
35 // is invalid if any (statically known) method that exists
36 // for both x and T have different signatures.
38 const forceStrict = false
40 // exprInfo stores information about an untyped expression.
41 type exprInfo struct {
42 isLhs bool // expression is lhs operand of a shift with delayed type-check
45 val constant.Value // constant value; or nil (if not a constant)
48 // An environment represents the environment within which an object is
50 type environment struct {
51 decl *declInfo // package-level declaration whose init expression/function body is checked
52 scope *Scope // top-most scope for lookups
53 pos token.Pos // if valid, identifiers are looked up as if at position pos (used by Eval)
54 iota constant.Value // value of iota in a constant declaration; nil otherwise
55 errpos positioner // if set, identifier position of a constant with inherited initializer
56 inTParamList bool // set if inside a type parameter list
57 sig *Signature // function signature if inside a function; nil otherwise
58 isPanic map[*ast.CallExpr]bool // set of panic call expressions (used for termination check)
59 hasLabel bool // set if a function makes use of labels (only ~1% of functions); unused outside functions
60 hasCallOrRecv bool // set if an expression contains a function call or channel receive operation
63 // lookup looks up name in the current environment and returns the matching object, or nil.
64 func (env *environment) lookup(name string) Object {
65 _, obj := env.scope.LookupParent(name, env.pos)
69 // An importKey identifies an imported package by import path and source directory
70 // (directory containing the file containing the import). In practice, the directory
71 // may always be the same, or may not matter. Given an (import path, directory), an
72 // importer must always return the same package (but given two different import paths,
73 // an importer may still return the same package by mapping them to the same package
75 type importKey struct {
79 // A dotImportKey describes a dot-imported object in the given scope.
80 type dotImportKey struct {
85 // An action describes a (delayed) action.
87 f func() // action to be executed
88 desc *actionDesc // action description; may be nil, requires debug to be set
91 // If debug is set, describef sets a printf-formatted description for action a.
92 // Otherwise, it is a no-op.
93 func (a *action) describef(pos positioner, format string, args ...any) {
95 a.desc = &actionDesc{pos, format, args}
99 // An actionDesc provides information on an action.
100 // For debugging only.
101 type actionDesc struct {
107 // A Checker maintains the state of the type checker.
108 // It must be created with NewChecker.
109 type Checker struct {
110 // package information
111 // (initialized by NewChecker, valid for the life-time of checker)
113 ctxt *Context // context for de-duplicating instances
117 version version // accepted language version
118 nextID uint64 // unique Id for type parameters (first valid Id is 1)
119 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
120 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
121 infoMap map[*Named]typeInfo // maps named types to their associated type info (for cycle detection)
123 // pkgPathMap maps package names to the set of distinct import paths we've
124 // seen for that name, anywhere in the import graph. It is used for
125 // disambiguating package names in error messages.
127 // pkgPathMap is allocated lazily, so that we don't pay the price of building
128 // it on the happy path. seenPkgMap tracks the packages that we've already
130 pkgPathMap map[string]map[string]bool
131 seenPkgMap map[*Package]bool
133 // information collected during type-checking of a set of package files
134 // (initialized by Files, valid only for the duration of check.Files;
135 // maps and lists are allocated on demand)
136 files []*ast.File // package files
137 imports []*PkgName // list of imported packages
138 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
139 recvTParamMap map[*ast.Ident]*TypeParam // maps blank receiver type parameters to their type
140 brokenAliases map[*TypeName]bool // set of aliases with broken (not yet determined) types
141 unionTypeSets map[*Union]*_TypeSet // computed type sets for union types
142 mono monoGraph // graph for detecting non-monomorphizable instantiation loops
144 firstErr error // first error encountered
145 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
146 untyped map[ast.Expr]exprInfo // map of expressions without final type
147 delayed []action // stack of delayed action segments; segments are processed in FIFO order
148 objPath []Object // path of object dependencies during type inference (for cycle reporting)
149 defTypes []*Named // defined types created during type checking, for final validation.
151 // environment within which the current object is type-checked (valid only
152 // for the duration of type-checking a specific object)
156 indent int // indentation for tracing
159 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
160 func (check *Checker) addDeclDep(to Object) {
163 return // not in a package-level init expression
165 if _, found := check.objMap[to]; !found {
166 return // to is not a package-level object
171 // brokenAlias records that alias doesn't have a determined type yet.
172 // It also sets alias.typ to Typ[Invalid].
173 func (check *Checker) brokenAlias(alias *TypeName) {
174 if check.brokenAliases == nil {
175 check.brokenAliases = make(map[*TypeName]bool)
177 check.brokenAliases[alias] = true
178 alias.typ = Typ[Invalid]
181 // validAlias records that alias has the valid type typ (possibly Typ[Invalid]).
182 func (check *Checker) validAlias(alias *TypeName, typ Type) {
183 delete(check.brokenAliases, alias)
187 // isBrokenAlias reports whether alias doesn't have a determined type yet.
188 func (check *Checker) isBrokenAlias(alias *TypeName) bool {
189 return alias.typ == Typ[Invalid] && check.brokenAliases[alias]
192 func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
195 m = make(map[ast.Expr]exprInfo)
198 m[e] = exprInfo{lhs, mode, typ, val}
201 // later pushes f on to the stack of actions that will be processed later;
202 // either at the end of the current statement, or in case of a local constant
203 // or variable declaration, before the constant or variable is in scope
204 // (so that f still sees the scope before any new declarations).
205 // later returns the pushed action so one can provide a description
206 // via action.describef for debugging, if desired.
207 func (check *Checker) later(f func()) *action {
208 i := len(check.delayed)
209 check.delayed = append(check.delayed, action{f: f})
210 return &check.delayed[i]
213 // push pushes obj onto the object path and returns its index in the path.
214 func (check *Checker) push(obj Object) int {
215 check.objPath = append(check.objPath, obj)
216 return len(check.objPath) - 1
219 // pop pops and returns the topmost object from the object path.
220 func (check *Checker) pop() Object {
221 i := len(check.objPath) - 1
222 obj := check.objPath[i]
223 check.objPath[i] = nil
224 check.objPath = check.objPath[:i]
228 // NewChecker returns a new Checker instance for a given package.
229 // Package files may be added incrementally via checker.Files.
230 func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {
231 // make sure we have a configuration
236 // make sure we have an info struct
241 version, err := parseGoVersion(conf.GoVersion)
243 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
253 objMap: make(map[Object]*declInfo),
254 impMap: make(map[importKey]*Package),
255 infoMap: make(map[*Named]typeInfo),
259 // initFiles initializes the files-specific portion of checker.
260 // The provided files must all belong to the same package.
261 func (check *Checker) initFiles(files []*ast.File) {
262 // start with a clean slate (check.Files may be called multiple times)
265 check.dotImportMap = nil
272 // determine package name and collect valid files
274 for _, file := range files {
275 switch name := file.Name.Name; pkg.name {
280 check.errorf(file.Name, _BlankPkgName, "invalid package name _")
285 check.files = append(check.files, file)
288 check.errorf(atPos(file.Package), _MismatchedPkgName, "package %s; expected %s", name, pkg.name)
294 // A bailout panic is used for early termination.
295 type bailout struct{}
297 func (check *Checker) handleBailout(err *error) {
298 switch p := recover().(type) {
300 // normal return or early exit
301 *err = check.firstErr
308 // Files checks the provided files as part of the checker's package.
309 func (check *Checker) Files(files []*ast.File) error { return check.checkFiles(files) }
311 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
313 func (check *Checker) checkFiles(files []*ast.File) (err error) {
314 if check.conf.FakeImportC && check.conf.go115UsesCgo {
318 defer check.handleBailout(&err)
320 check.initFiles(files)
322 check.collectObjects()
324 check.packageObjects()
326 check.processDelayed(0) // incl. all functions
328 check.expandDefTypes()
332 if !check.conf.DisableUnusedImportCheck {
333 check.unusedImports()
336 check.recordUntyped()
338 if check.firstErr == nil {
339 // TODO(mdempsky): Ensure monomorph is safe when errors exist.
343 check.pkg.complete = true
345 // no longer needed - release memory
347 check.dotImportMap = nil
348 check.pkgPathMap = nil
349 check.seenPkgMap = nil
350 check.recvTParamMap = nil
351 check.brokenAliases = nil
352 check.unionTypeSets = nil
356 // TODO(rFindley) There's more memory we should release at this point.
361 // processDelayed processes all delayed actions pushed after top.
362 func (check *Checker) processDelayed(top int) {
363 // If each delayed action pushes a new action, the
364 // stack will continue to grow during this loop.
365 // However, it is only processing functions (which
366 // are processed in a delayed fashion) that may
367 // add more actions (such as nested functions), so
368 // this is a sufficiently bounded process.
369 for i := top; i < len(check.delayed); i++ {
370 a := &check.delayed[i]
371 if trace && a.desc != nil {
373 check.trace(a.desc.pos.Pos(), "-- "+a.desc.format, a.desc.args...)
375 a.f() // may append to check.delayed
377 assert(top <= len(check.delayed)) // stack must not have shrunk
378 check.delayed = check.delayed[:top]
381 func (check *Checker) expandDefTypes() {
382 // Ensure that every defined type created in the course of type-checking has
383 // either non-*Named underlying, or is unresolved.
385 // This guarantees that we don't leak any types whose underlying is *Named,
386 // because any unresolved instances will lazily compute their underlying by
387 // substituting in the underlying of their origin. The origin must have
388 // either been imported or type-checked and expanded here, and in either case
389 // its underlying will be fully expanded.
390 for i := 0; i < len(check.defTypes); i++ {
391 n := check.defTypes[i]
392 switch n.underlying.(type) {
394 if n.resolver == nil {
395 panic("nil underlying")
398 n.under() // n.under may add entries to check.defTypes
404 func (check *Checker) record(x *operand) {
405 // convert x into a user-friendly set of values
406 // TODO(gri) this code can be simplified
408 var val constant.Value
420 assert(x.expr != nil && typ != nil)
423 // delay type and value recording until we know the type
424 // or until the end of type checking
425 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
427 check.recordTypeAndValue(x.expr, x.mode, typ, val)
431 func (check *Checker) recordUntyped() {
432 if !debug && check.Types == nil {
433 return // nothing to do
436 for x, info := range check.untyped {
437 if debug && isTyped(info.typ) {
438 check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ)
441 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
445 func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
451 if mode == constant_ {
453 // We check allBasic(typ, IsConstType) here as constant expressions may be
454 // recorded as type parameters.
455 assert(typ == Typ[Invalid] || allBasic(typ, IsConstType))
457 if m := check.Types; m != nil {
458 m[x] = TypeAndValue{mode, typ, val}
462 func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
463 // f must be a (possibly parenthesized, possibly qualified)
464 // identifier denoting a built-in (including unsafe's non-constant
465 // functions Add and Slice): record the signature for f and possible
468 check.recordTypeAndValue(f, builtin, sig, nil)
469 switch p := f.(type) {
470 case *ast.Ident, *ast.SelectorExpr:
480 func (check *Checker) recordCommaOkTypes(x ast.Expr, a [2]Type) {
482 if a[0] == nil || a[1] == nil {
485 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
486 if m := check.Types; m != nil {
489 assert(tv.Type != nil) // should have been recorded already
492 NewVar(pos, check.pkg, "", a[0]),
493 NewVar(pos, check.pkg, "", a[1]),
496 // if x is a parenthesized expression (p.X), update p.X
497 p, _ := x.(*ast.ParenExpr)
506 // recordInstance records instantiation information into check.Info, if the
507 // Instances map is non-nil. The given expr must be an ident, selector, or
508 // index (list) expr with ident or selector operand.
510 // TODO(rfindley): the expr parameter is fragile. See if we can access the
511 // instantiated identifier in some other way.
512 func (check *Checker) recordInstance(expr ast.Expr, targs []Type, typ Type) {
513 ident := instantiatedIdent(expr)
516 if m := check.Instances; m != nil {
517 m[ident] = Instance{newTypeList(targs), typ}
521 func instantiatedIdent(expr ast.Expr) *ast.Ident {
522 var selOrIdent ast.Expr
523 switch e := expr.(type) {
526 case *ast.IndexListExpr:
528 case *ast.SelectorExpr, *ast.Ident:
531 switch x := selOrIdent.(type) {
534 case *ast.SelectorExpr:
537 panic("instantiated ident not found")
540 func (check *Checker) recordDef(id *ast.Ident, obj Object) {
542 if m := check.Defs; m != nil {
547 func (check *Checker) recordUse(id *ast.Ident, obj Object) {
550 if m := check.Uses; m != nil {
555 func (check *Checker) recordImplicit(node ast.Node, obj Object) {
558 if m := check.Implicits; m != nil {
563 func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
564 assert(obj != nil && (recv == nil || len(index) > 0))
565 check.recordUse(x.Sel, obj)
566 if m := check.Selections; m != nil {
567 m[x] = &Selection{kind, recv, obj, index, indirect}
571 func (check *Checker) recordScope(node ast.Node, scope *Scope) {
574 if m := check.Scopes; m != nil {