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 inTParamList bool // set if inside a type parameter list
50 sig *Signature // function signature if inside a function; nil otherwise
51 isPanic map[*syntax.CallExpr]bool // set of panic call expressions (used for termination check)
52 hasLabel bool // set if a function makes use of labels (only ~1% of functions); unused outside functions
53 hasCallOrRecv bool // set if an expression contains a function call or channel receive operation
56 // lookup looks up name in the current context and returns the matching object, or nil.
57 func (ctxt *context) lookup(name string) Object {
58 _, obj := ctxt.scope.LookupParent(name, ctxt.pos)
62 // An importKey identifies an imported package by import path and source directory
63 // (directory containing the file containing the import). In practice, the directory
64 // may always be the same, or may not matter. Given an (import path, directory), an
65 // importer must always return the same package (but given two different import paths,
66 // an importer may still return the same package by mapping them to the same package
68 type importKey struct {
72 // A dotImportKey describes a dot-imported object in the given scope.
73 type dotImportKey struct {
78 // An action describes a (delayed) action.
80 f func() // action to be executed
81 desc *actionDesc // action description; may be nil, requires debug to be set
84 // If debug is set, describef sets a printf-formatted description for action a.
85 // Otherwise, it is a no-op.
86 func (a *action) describef(pos poser, format string, args ...interface{}) {
88 a.desc = &actionDesc{pos, format, args}
92 // An actionDesc provides information on an action.
93 // For debugging only.
94 type actionDesc struct {
100 // A Checker maintains the state of the type checker.
101 // It must be created with NewChecker.
102 type Checker struct {
103 // package information
104 // (initialized by NewChecker, valid for the life-time of checker)
106 ctxt *Context // context for de-duplicating instances
109 version version // accepted language version
110 nextID uint64 // unique Id for type parameters (first valid Id is 1)
111 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
112 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
114 // pkgPathMap maps package names to the set of distinct import paths we've
115 // seen for that name, anywhere in the import graph. It is used for
116 // disambiguating package names in error messages.
118 // pkgPathMap is allocated lazily, so that we don't pay the price of building
119 // it on the happy path. seenPkgMap tracks the packages that we've already
121 pkgPathMap map[string]map[string]bool
122 seenPkgMap map[*Package]bool
124 // information collected during type-checking of a set of package files
125 // (initialized by Files, valid only for the duration of check.Files;
126 // maps and lists are allocated on demand)
127 files []*syntax.File // list of package files
128 imports []*PkgName // list of imported packages
129 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
130 recvTParamMap map[*syntax.Name]*TypeParam // maps blank receiver type parameters to their type
131 mono monoGraph // graph for detecting non-monomorphizable instantiation loops
133 firstErr error // first error encountered
134 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
135 untyped map[syntax.Expr]exprInfo // map of expressions without final type
136 delayed []action // stack of delayed action segments; segments are processed in FIFO order
137 objPath []Object // path of object dependencies during type inference (for cycle reporting)
138 defTypes []*Named // defined types created during type checking, for final validation.
140 // context within which the current object is type-checked
141 // (valid only for the duration of type-checking a specific object)
145 indent int // indentation for tracing
148 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
149 func (check *Checker) addDeclDep(to Object) {
152 return // not in a package-level init expression
154 if _, found := check.objMap[to]; !found {
155 return // to is not a package-level object
160 func (check *Checker) rememberUntyped(e syntax.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
163 m = make(map[syntax.Expr]exprInfo)
166 m[e] = exprInfo{lhs, mode, typ, val}
169 // later pushes f on to the stack of actions that will be processed later;
170 // either at the end of the current statement, or in case of a local constant
171 // or variable declaration, before the constant or variable is in scope
172 // (so that f still sees the scope before any new declarations).
173 // later returns the pushed action so one can provide a description
174 // via action.describef for debugging, if desired.
175 func (check *Checker) later(f func()) *action {
176 i := len(check.delayed)
177 check.delayed = append(check.delayed, action{f: f})
178 return &check.delayed[i]
181 // push pushes obj onto the object path and returns its index in the path.
182 func (check *Checker) push(obj Object) int {
183 check.objPath = append(check.objPath, obj)
184 return len(check.objPath) - 1
187 // pop pops and returns the topmost object from the object path.
188 func (check *Checker) pop() Object {
189 i := len(check.objPath) - 1
190 obj := check.objPath[i]
191 check.objPath[i] = nil
192 check.objPath = check.objPath[:i]
196 // NewChecker returns a new Checker instance for a given package.
197 // Package files may be added incrementally via checker.Files.
198 func NewChecker(conf *Config, pkg *Package, info *Info) *Checker {
199 // make sure we have a configuration
204 // make sure we have an info struct
209 version, err := parseGoVersion(conf.GoVersion)
211 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
220 objMap: make(map[Object]*declInfo),
221 impMap: make(map[importKey]*Package),
225 // initFiles initializes the files-specific portion of checker.
226 // The provided files must all belong to the same package.
227 func (check *Checker) initFiles(files []*syntax.File) {
228 // start with a clean slate (check.Files may be called multiple times)
231 check.dotImportMap = nil
238 // determine package name and collect valid files
240 for _, file := range files {
241 switch name := file.PkgName.Value; pkg.name {
246 check.error(file.PkgName, "invalid package name _")
251 check.files = append(check.files, file)
254 check.errorf(file, "package %s; expected %s", name, pkg.name)
260 // A bailout panic is used for early termination.
261 type bailout struct{}
263 func (check *Checker) handleBailout(err *error) {
264 switch p := recover().(type) {
266 // normal return or early exit
267 *err = check.firstErr
274 // Files checks the provided files as part of the checker's package.
275 func (check *Checker) Files(files []*syntax.File) error { return check.checkFiles(files) }
277 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
279 func (check *Checker) checkFiles(files []*syntax.File) (err error) {
280 if check.conf.FakeImportC && check.conf.go115UsesCgo {
284 defer check.handleBailout(&err)
286 print := func(msg string) {
287 if check.conf.Trace {
293 print("== initFiles ==")
294 check.initFiles(files)
296 print("== collectObjects ==")
297 check.collectObjects()
299 print("== packageObjects ==")
300 check.packageObjects()
302 print("== processDelayed ==")
303 check.processDelayed(0) // incl. all functions
305 print("== expandDefTypes ==")
306 check.expandDefTypes()
308 print("== initOrder ==")
311 if !check.conf.DisableUnusedImportCheck {
312 print("== unusedImports ==")
313 check.unusedImports()
316 print("== recordUntyped ==")
317 check.recordUntyped()
319 if check.firstErr == nil {
320 // TODO(mdempsky): Ensure monomorph is safe when errors exist.
324 check.pkg.complete = true
326 // no longer needed - release memory
328 check.dotImportMap = nil
329 check.pkgPathMap = nil
330 check.seenPkgMap = nil
331 check.recvTParamMap = nil
335 // TODO(gri) There's more memory we should release at this point.
340 // processDelayed processes all delayed actions pushed after top.
341 func (check *Checker) processDelayed(top int) {
342 // If each delayed action pushes a new action, the
343 // stack will continue to grow during this loop.
344 // However, it is only processing functions (which
345 // are processed in a delayed fashion) that may
346 // add more actions (such as nested functions), so
347 // this is a sufficiently bounded process.
348 for i := top; i < len(check.delayed); i++ {
349 a := &check.delayed[i]
350 if check.conf.Trace && a.desc != nil {
352 check.trace(a.desc.pos.Pos(), "-- "+a.desc.format, a.desc.args...)
354 a.f() // may append to check.delayed
356 assert(top <= len(check.delayed)) // stack must not have shrunk
357 check.delayed = check.delayed[:top]
360 func (check *Checker) expandDefTypes() {
361 // Ensure that every defined type created in the course of type-checking has
362 // either non-*Named underlying, or is unresolved.
364 // This guarantees that we don't leak any types whose underlying is *Named,
365 // because any unresolved instances will lazily compute their underlying by
366 // substituting in the underlying of their origin. The origin must have
367 // either been imported or type-checked and expanded here, and in either case
368 // its underlying will be fully expanded.
369 for i := 0; i < len(check.defTypes); i++ {
370 n := check.defTypes[i]
371 switch n.underlying.(type) {
373 if n.resolver == nil {
374 panic("nil underlying")
377 n.under() // n.under may add entries to check.defTypes
383 func (check *Checker) record(x *operand) {
384 // convert x into a user-friendly set of values
385 // TODO(gri) this code can be simplified
387 var val constant.Value
399 assert(x.expr != nil && typ != nil)
402 // delay type and value recording until we know the type
403 // or until the end of type checking
404 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
406 check.recordTypeAndValue(x.expr, x.mode, typ, val)
410 func (check *Checker) recordUntyped() {
411 if !debug && check.Types == nil {
412 return // nothing to do
415 for x, info := range check.untyped {
416 if debug && isTyped(info.typ) {
417 check.dump("%v: %s (type %s) is typed", posFor(x), x, info.typ)
420 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
424 func (check *Checker) recordTypeAndValue(x syntax.Expr, mode operandMode, typ Type, val constant.Value) {
430 if mode == constant_ {
432 // We check allBasic(typ, IsConstType) here as constant expressions may be
433 // recorded as type parameters.
434 assert(typ == Typ[Invalid] || allBasic(typ, IsConstType))
436 if m := check.Types; m != nil {
437 m[x] = TypeAndValue{mode, typ, val}
441 func (check *Checker) recordBuiltinType(f syntax.Expr, sig *Signature) {
442 // f must be a (possibly parenthesized, possibly qualified)
443 // identifier denoting a built-in (including unsafe's non-constant
444 // functions Add and Slice): record the signature for f and possible
447 check.recordTypeAndValue(f, builtin, sig, nil)
448 switch p := f.(type) {
449 case *syntax.Name, *syntax.SelectorExpr:
451 case *syntax.ParenExpr:
459 func (check *Checker) recordCommaOkTypes(x syntax.Expr, a [2]Type) {
461 if a[0] == nil || a[1] == nil {
464 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
465 if m := check.Types; m != nil {
468 assert(tv.Type != nil) // should have been recorded already
471 NewVar(pos, check.pkg, "", a[0]),
472 NewVar(pos, check.pkg, "", a[1]),
475 // if x is a parenthesized expression (p.X), update p.X
476 p, _ := x.(*syntax.ParenExpr)
485 // recordInstance records instantiation information into check.Info, if the
486 // Instances map is non-nil. The given expr must be an ident, selector, or
487 // index (list) expr with ident or selector operand.
489 // TODO(rfindley): the expr parameter is fragile. See if we can access the
490 // instantiated identifier in some other way.
491 func (check *Checker) recordInstance(expr syntax.Expr, targs []Type, typ Type) {
492 ident := instantiatedIdent(expr)
495 if m := check.Instances; m != nil {
496 m[ident] = Instance{NewTypeList(targs), typ}
500 func instantiatedIdent(expr syntax.Expr) *syntax.Name {
501 var selOrIdent syntax.Expr
502 switch e := expr.(type) {
503 case *syntax.IndexExpr:
505 case *syntax.SelectorExpr, *syntax.Name:
508 switch x := selOrIdent.(type) {
511 case *syntax.SelectorExpr:
514 panic("instantiated ident not found")
517 func (check *Checker) recordDef(id *syntax.Name, obj Object) {
519 if m := check.Defs; m != nil {
524 func (check *Checker) recordUse(id *syntax.Name, obj Object) {
527 if m := check.Uses; m != nil {
532 func (check *Checker) recordImplicit(node syntax.Node, obj Object) {
535 if m := check.Implicits; m != nil {
540 func (check *Checker) recordSelection(x *syntax.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
541 assert(obj != nil && (recv == nil || len(index) > 0))
542 check.recordUse(x.Sel, obj)
543 if m := check.Selections; m != nil {
544 m[x] = &Selection{kind, recv, obj, index, indirect}
548 func (check *Checker) recordScope(node syntax.Node, scope *Scope) {
551 if m := check.Scopes; m != nil {