2 // Copyright 2011 The Go Authors. All rights reserved.
3 // Use of this source code is governed by a BSD-style
4 // license that can be found in the LICENSE file.
6 // This file implements the Check function, which drives type-checking.
11 "cmd/compile/internal/syntax"
19 // debugging/development support
20 const debug = true // leave on during development
22 // If forceStrict is set, the type-checker enforces additional
23 // rules not specified by the Go 1 spec, but which will
24 // catch guaranteed run-time errors if the respective
25 // code is executed. In other words, programs passing in
26 // strict mode are Go 1 compliant, but not all Go 1 programs
27 // will pass in strict mode. The additional rules are:
29 // - A type assertion x.(T) where T is an interface type
30 // is invalid if any (statically known) method that exists
31 // for both x and T have different signatures.
33 const forceStrict = false
35 // If methodTypeParamsOk is set, type parameters are
36 // permitted in method declarations (in interfaces, too).
37 // Generalization and experimental feature.
38 const methodTypeParamsOk = true
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 // A context represents the context within which an object is type-checked.
50 decl *declInfo // package-level declaration whose init expression/function body is checked
51 scope *Scope // top-most scope for lookups
52 pos syntax.Pos // if valid, identifiers are looked up as if at position pos (used by Eval)
53 iota constant.Value // value of iota in a constant declaration; nil otherwise
54 errpos syntax.Pos // if valid, identifier position of a constant with inherited initializer
55 sig *Signature // function signature if inside a function; nil otherwise
56 isPanic map[*syntax.CallExpr]bool // set of panic call expressions (used for termination check)
57 hasLabel bool // set if a function makes use of labels (only ~1% of functions); unused outside functions
58 hasCallOrRecv bool // set if an expression contains a function call or channel receive operation
61 // lookup looks up name in the current context and returns the matching object, or nil.
62 func (ctxt *context) lookup(name string) Object {
63 _, obj := ctxt.scope.LookupParent(name, ctxt.pos)
67 // An importKey identifies an imported package by import path and source directory
68 // (directory containing the file containing the import). In practice, the directory
69 // may always be the same, or may not matter. Given an (import path, directory), an
70 // importer must always return the same package (but given two different import paths,
71 // an importer may still return the same package by mapping them to the same package
73 type importKey struct {
77 // A Checker maintains the state of the type checker.
78 // It must be created with NewChecker.
80 // package information
81 // (initialized by NewChecker, valid for the life-time of checker)
85 nextId uint64 // unique Id for type parameters (first valid Id is 1)
86 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
87 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
88 posMap map[*Interface][]syntax.Pos // maps interface types to lists of embedded interface positions
89 typMap map[string]*Named // maps an instantiated named type hash to a *Named type
90 pkgCnt map[string]int // counts number of imported packages with a given name (for better error messages)
92 // information collected during type-checking of a set of package files
93 // (initialized by Files, valid only for the duration of check.Files;
94 // maps and lists are allocated on demand)
95 files []*syntax.File // package files
96 unusedDotImports map[*Scope]map[*Package]syntax.Pos // positions of unused dot-imported packages for each file scope
98 firstErr error // first error encountered
99 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
100 untyped map[syntax.Expr]exprInfo // map of expressions without final type
101 delayed []func() // stack of delayed action segments; segments are processed in FIFO order
102 finals []func() // list of final actions; processed at the end of type-checking the current set of files
103 objPath []Object // path of object dependencies during type inference (for cycle reporting)
105 // context within which the current object is type-checked
106 // (valid only for the duration of type-checking a specific object)
110 indent int // indentation for tracing
113 // addUnusedImport adds the position of a dot-imported package
114 // pkg to the map of dot imports for the given file scope.
115 func (check *Checker) addUnusedDotImport(scope *Scope, pkg *Package, pos syntax.Pos) {
116 mm := check.unusedDotImports
118 mm = make(map[*Scope]map[*Package]syntax.Pos)
119 check.unusedDotImports = mm
123 m = make(map[*Package]syntax.Pos)
129 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
130 func (check *Checker) addDeclDep(to Object) {
133 return // not in a package-level init expression
135 if _, found := check.objMap[to]; !found {
136 return // to is not a package-level object
141 func (check *Checker) rememberUntyped(e syntax.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
144 m = make(map[syntax.Expr]exprInfo)
147 m[e] = exprInfo{lhs, mode, typ, val}
150 // later pushes f on to the stack of actions that will be processed later;
151 // either at the end of the current statement, or in case of a local constant
152 // or variable declaration, before the constant or variable is in scope
153 // (so that f still sees the scope before any new declarations).
154 func (check *Checker) later(f func()) {
155 check.delayed = append(check.delayed, f)
158 // atEnd adds f to the list of actions processed at the end
159 // of type-checking, before initialization order computation.
160 // Actions added by atEnd are processed after any actions
162 func (check *Checker) atEnd(f func()) {
163 check.finals = append(check.finals, f)
166 // push pushes obj onto the object path and returns its index in the path.
167 func (check *Checker) push(obj Object) int {
168 check.objPath = append(check.objPath, obj)
169 return len(check.objPath) - 1
172 // pop pops and returns the topmost object from the object path.
173 func (check *Checker) pop() Object {
174 i := len(check.objPath) - 1
175 obj := check.objPath[i]
176 check.objPath[i] = nil
177 check.objPath = check.objPath[:i]
181 // NewChecker returns a new Checker instance for a given package.
182 // Package files may be added incrementally via checker.Files.
183 func NewChecker(conf *Config, pkg *Package, info *Info) *Checker {
184 // make sure we have a configuration
189 // make sure we have an info struct
199 objMap: make(map[Object]*declInfo),
200 impMap: make(map[importKey]*Package),
201 posMap: make(map[*Interface][]syntax.Pos),
202 typMap: make(map[string]*Named),
203 pkgCnt: make(map[string]int),
207 // initFiles initializes the files-specific portion of checker.
208 // The provided files must all belong to the same package.
209 func (check *Checker) initFiles(files []*syntax.File) {
210 // start with a clean slate (check.Files may be called multiple times)
212 check.unusedDotImports = nil
220 // determine package name and collect valid files
222 for _, file := range files {
223 switch name := file.PkgName.Value; pkg.name {
228 check.errorf(file.PkgName, "invalid package name _")
233 check.files = append(check.files, file)
236 check.errorf(file, "package %s; expected %s", name, pkg.name)
242 // A bailout panic is used for early termination.
243 type bailout struct{}
245 func (check *Checker) handleBailout(err *error) {
246 switch p := recover().(type) {
248 // normal return or early exit
249 *err = check.firstErr
256 // Files checks the provided files as part of the checker's package.
257 func (check *Checker) Files(files []*syntax.File) error { return check.checkFiles(files) }
259 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
261 func (check *Checker) checkFiles(files []*syntax.File) (err error) {
262 if check.conf.FakeImportC && check.conf.go115UsesCgo {
266 defer check.handleBailout(&err)
268 print := func(msg string) {
269 if check.conf.Trace {
274 print("== initFiles ==")
275 check.initFiles(files)
277 print("== collectObjects ==")
278 check.collectObjects()
280 print("== packageObjects ==")
281 check.packageObjects()
283 print("== processDelayed ==")
284 check.processDelayed(0) // incl. all functions
285 check.processFinals()
287 print("== initOrder ==")
290 if !check.conf.DisableUnusedImportCheck {
291 print("== unusedImports ==")
292 check.unusedImports()
295 print("== recordUntyped ==")
296 check.recordUntyped()
298 if check.Info != nil {
299 print("== sanitizeInfo ==")
300 sanitizeInfo(check.Info)
303 check.pkg.complete = true
307 // processDelayed processes all delayed actions pushed after top.
308 func (check *Checker) processDelayed(top int) {
309 // If each delayed action pushes a new action, the
310 // stack will continue to grow during this loop.
311 // However, it is only processing functions (which
312 // are processed in a delayed fashion) that may
313 // add more actions (such as nested functions), so
314 // this is a sufficiently bounded process.
315 for i := top; i < len(check.delayed); i++ {
316 check.delayed[i]() // may append to check.delayed
318 assert(top <= len(check.delayed)) // stack must not have shrunk
319 check.delayed = check.delayed[:top]
322 func (check *Checker) processFinals() {
323 n := len(check.finals)
324 for _, f := range check.finals {
325 f() // must not append to check.finals
327 if len(check.finals) != n {
328 panic("internal error: final action list grew")
332 func (check *Checker) recordUntyped() {
333 if !debug && check.Types == nil {
334 return // nothing to do
337 for x, info := range check.untyped {
338 if debug && isTyped(info.typ) {
339 check.dump("%v: %s (type %s) is typed", posFor(x), x, info.typ)
342 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
346 func (check *Checker) recordTypeAndValue(x syntax.Expr, mode operandMode, typ Type, val constant.Value) {
352 if mode == constant_ {
354 assert(typ == Typ[Invalid] || isConstType(typ))
356 if m := check.Types; m != nil {
357 m[x] = TypeAndValue{mode, typ, val}
361 func (check *Checker) recordBuiltinType(f syntax.Expr, sig *Signature) {
362 // f must be a (possibly parenthesized) identifier denoting a built-in
363 // (built-ins in package unsafe always produce a constant result and
364 // we don't record their signatures, so we don't see qualified idents
365 // here): record the signature for f and possible children.
367 check.recordTypeAndValue(f, builtin, sig, nil)
368 switch p := f.(type) {
371 case *syntax.ParenExpr:
379 func (check *Checker) recordCommaOkTypes(x syntax.Expr, a [2]Type) {
381 if a[0] == nil || a[1] == nil {
384 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
385 if m := check.Types; m != nil {
388 assert(tv.Type != nil) // should have been recorded already
391 NewVar(pos, check.pkg, "", a[0]),
392 NewVar(pos, check.pkg, "", a[1]),
395 // if x is a parenthesized expression (p.X), update p.X
396 p, _ := x.(*syntax.ParenExpr)
405 func (check *Checker) recordInferred(call syntax.Expr, targs []Type, sig *Signature) {
408 if m := check.Inferred; m != nil {
409 m[call] = Inferred{targs, sig}
413 func (check *Checker) recordDef(id *syntax.Name, obj Object) {
415 if m := check.Defs; m != nil {
420 func (check *Checker) recordUse(id *syntax.Name, obj Object) {
423 if m := check.Uses; m != nil {
428 func (check *Checker) recordImplicit(node syntax.Node, obj Object) {
431 if m := check.Implicits; m != nil {
436 func (check *Checker) recordSelection(x *syntax.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
437 assert(obj != nil && (recv == nil || len(index) > 0))
438 check.recordUse(x.Sel, obj)
439 if m := check.Selections; m != nil {
440 m[x] = &Selection{kind, recv, obj, index, indirect}
444 func (check *Checker) recordScope(node syntax.Node, scope *Scope) {
447 if m := check.Scopes; m != nil {