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 ...interface{}) {
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
122 // pkgPathMap maps package names to the set of distinct import paths we've
123 // seen for that name, anywhere in the import graph. It is used for
124 // disambiguating package names in error messages.
126 // pkgPathMap is allocated lazily, so that we don't pay the price of building
127 // it on the happy path. seenPkgMap tracks the packages that we've already
129 pkgPathMap map[string]map[string]bool
130 seenPkgMap map[*Package]bool
132 // information collected during type-checking of a set of package files
133 // (initialized by Files, valid only for the duration of check.Files;
134 // maps and lists are allocated on demand)
135 files []*ast.File // package files
136 imports []*PkgName // list of imported packages
137 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
138 recvTParamMap map[*ast.Ident]*TypeParam // maps blank receiver type parameters to their type
139 mono monoGraph // graph for detecting non-monomorphizable instantiation loops
141 firstErr error // first error encountered
142 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
143 untyped map[ast.Expr]exprInfo // map of expressions without final type
144 delayed []action // stack of delayed action segments; segments are processed in FIFO order
145 objPath []Object // path of object dependencies during type inference (for cycle reporting)
146 defTypes []*Named // defined types created during type checking, for final validation.
148 // environment within which the current object is type-checked (valid only
149 // for the duration of type-checking a specific object)
153 indent int // indentation for tracing
156 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
157 func (check *Checker) addDeclDep(to Object) {
160 return // not in a package-level init expression
162 if _, found := check.objMap[to]; !found {
163 return // to is not a package-level object
168 func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
171 m = make(map[ast.Expr]exprInfo)
174 m[e] = exprInfo{lhs, mode, typ, val}
177 // later pushes f on to the stack of actions that will be processed later;
178 // either at the end of the current statement, or in case of a local constant
179 // or variable declaration, before the constant or variable is in scope
180 // (so that f still sees the scope before any new declarations).
181 // later returns the pushed action so one can provide a description
182 // via action.describef for debugging, if desired.
183 func (check *Checker) later(f func()) *action {
184 i := len(check.delayed)
185 check.delayed = append(check.delayed, action{f: f})
186 return &check.delayed[i]
189 // push pushes obj onto the object path and returns its index in the path.
190 func (check *Checker) push(obj Object) int {
191 check.objPath = append(check.objPath, obj)
192 return len(check.objPath) - 1
195 // pop pops and returns the topmost object from the object path.
196 func (check *Checker) pop() Object {
197 i := len(check.objPath) - 1
198 obj := check.objPath[i]
199 check.objPath[i] = nil
200 check.objPath = check.objPath[:i]
204 // NewChecker returns a new Checker instance for a given package.
205 // Package files may be added incrementally via checker.Files.
206 func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {
207 // make sure we have a configuration
212 // make sure we have an info struct
217 version, err := parseGoVersion(conf.GoVersion)
219 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
229 objMap: make(map[Object]*declInfo),
230 impMap: make(map[importKey]*Package),
234 // initFiles initializes the files-specific portion of checker.
235 // The provided files must all belong to the same package.
236 func (check *Checker) initFiles(files []*ast.File) {
237 // start with a clean slate (check.Files may be called multiple times)
240 check.dotImportMap = nil
247 // determine package name and collect valid files
249 for _, file := range files {
250 switch name := file.Name.Name; pkg.name {
255 check.errorf(file.Name, _BlankPkgName, "invalid package name _")
260 check.files = append(check.files, file)
263 check.errorf(atPos(file.Package), _MismatchedPkgName, "package %s; expected %s", name, pkg.name)
269 // A bailout panic is used for early termination.
270 type bailout struct{}
272 func (check *Checker) handleBailout(err *error) {
273 switch p := recover().(type) {
275 // normal return or early exit
276 *err = check.firstErr
283 // Files checks the provided files as part of the checker's package.
284 func (check *Checker) Files(files []*ast.File) error { return check.checkFiles(files) }
286 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
288 func (check *Checker) checkFiles(files []*ast.File) (err error) {
289 if check.conf.FakeImportC && check.conf.go115UsesCgo {
293 defer check.handleBailout(&err)
295 check.initFiles(files)
297 check.collectObjects()
299 check.packageObjects()
301 check.processDelayed(0) // incl. all functions
303 check.expandDefTypes()
307 if !check.conf.DisableUnusedImportCheck {
308 check.unusedImports()
311 check.recordUntyped()
313 if check.firstErr == nil {
314 // TODO(mdempsky): Ensure monomorph is safe when errors exist.
318 check.pkg.complete = true
320 // no longer needed - release memory
322 check.dotImportMap = nil
323 check.pkgPathMap = nil
324 check.seenPkgMap = nil
325 check.recvTParamMap = nil
329 // TODO(rFindley) There's more memory we should release at this point.
334 // processDelayed processes all delayed actions pushed after top.
335 func (check *Checker) processDelayed(top int) {
336 // If each delayed action pushes a new action, the
337 // stack will continue to grow during this loop.
338 // However, it is only processing functions (which
339 // are processed in a delayed fashion) that may
340 // add more actions (such as nested functions), so
341 // this is a sufficiently bounded process.
342 for i := top; i < len(check.delayed); i++ {
343 a := &check.delayed[i]
344 if trace && a.desc != nil {
346 check.trace(a.desc.pos.Pos(), "-- "+a.desc.format, a.desc.args...)
348 a.f() // may append to check.delayed
350 assert(top <= len(check.delayed)) // stack must not have shrunk
351 check.delayed = check.delayed[:top]
354 func (check *Checker) expandDefTypes() {
355 // Ensure that every defined type created in the course of type-checking has
356 // either non-*Named underlying, or is unresolved.
358 // This guarantees that we don't leak any types whose underlying is *Named,
359 // because any unresolved instances will lazily compute their underlying by
360 // substituting in the underlying of their origin. The origin must have
361 // either been imported or type-checked and expanded here, and in either case
362 // its underlying will be fully expanded.
363 for i := 0; i < len(check.defTypes); i++ {
364 n := check.defTypes[i]
365 switch n.underlying.(type) {
367 if n.resolver == nil {
368 panic("nil underlying")
371 n.under() // n.under may add entries to check.defTypes
377 func (check *Checker) record(x *operand) {
378 // convert x into a user-friendly set of values
379 // TODO(gri) this code can be simplified
381 var val constant.Value
393 assert(x.expr != nil && typ != nil)
396 // delay type and value recording until we know the type
397 // or until the end of type checking
398 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
400 check.recordTypeAndValue(x.expr, x.mode, typ, val)
404 func (check *Checker) recordUntyped() {
405 if !debug && check.Types == nil {
406 return // nothing to do
409 for x, info := range check.untyped {
410 if debug && isTyped(info.typ) {
411 check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ)
414 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
418 func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
424 if mode == constant_ {
426 // We check allBasic(typ, IsConstType) here as constant expressions may be
427 // recorded as type parameters.
428 assert(typ == Typ[Invalid] || allBasic(typ, IsConstType))
430 if m := check.Types; m != nil {
431 m[x] = TypeAndValue{mode, typ, val}
435 func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
436 // f must be a (possibly parenthesized, possibly qualified)
437 // identifier denoting a built-in (including unsafe's non-constant
438 // functions Add and Slice): record the signature for f and possible
441 check.recordTypeAndValue(f, builtin, sig, nil)
442 switch p := f.(type) {
443 case *ast.Ident, *ast.SelectorExpr:
453 func (check *Checker) recordCommaOkTypes(x ast.Expr, a [2]Type) {
455 if a[0] == nil || a[1] == nil {
458 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
459 if m := check.Types; m != nil {
462 assert(tv.Type != nil) // should have been recorded already
465 NewVar(pos, check.pkg, "", a[0]),
466 NewVar(pos, check.pkg, "", a[1]),
469 // if x is a parenthesized expression (p.X), update p.X
470 p, _ := x.(*ast.ParenExpr)
479 // recordInstance records instantiation information into check.Info, if the
480 // Instances map is non-nil. The given expr must be an ident, selector, or
481 // index (list) expr with ident or selector operand.
483 // TODO(rfindley): the expr parameter is fragile. See if we can access the
484 // instantiated identifier in some other way.
485 func (check *Checker) recordInstance(expr ast.Expr, targs []Type, typ Type) {
486 ident := instantiatedIdent(expr)
489 if m := check.Instances; m != nil {
490 m[ident] = Instance{NewTypeList(targs), typ}
494 func instantiatedIdent(expr ast.Expr) *ast.Ident {
495 var selOrIdent ast.Expr
496 switch e := expr.(type) {
499 case *ast.IndexListExpr:
501 case *ast.SelectorExpr, *ast.Ident:
504 switch x := selOrIdent.(type) {
507 case *ast.SelectorExpr:
510 panic("instantiated ident not found")
513 func (check *Checker) recordDef(id *ast.Ident, obj Object) {
515 if m := check.Defs; m != nil {
520 func (check *Checker) recordUse(id *ast.Ident, obj Object) {
523 if m := check.Uses; m != nil {
528 func (check *Checker) recordImplicit(node ast.Node, obj Object) {
531 if m := check.Implicits; m != nil {
536 func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
537 assert(obj != nil && (recv == nil || len(index) > 0))
538 check.recordUse(x.Sel, obj)
539 if m := check.Selections; m != nil {
540 m[x] = &Selection{kind, recv, obj, index, indirect}
544 func (check *Checker) recordScope(node ast.Node, scope *Scope) {
547 if m := check.Scopes; m != nil {