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
23 // If forceStrict is set, the type-checker enforces additional
24 // rules not specified by the Go 1 spec, but which will
25 // catch guaranteed run-time errors if the respective
26 // code is executed. In other words, programs passing in
27 // strict mode are Go 1 compliant, but not all Go 1 programs
28 // will pass in strict mode. The additional rules are:
30 // - A type assertion x.(T) where T is an interface type
31 // is invalid if any (statically known) method that exists
32 // for both x and T have different signatures.
34 const forceStrict = false
36 // exprInfo stores information about an untyped expression.
37 type exprInfo struct {
38 isLhs bool // expression is lhs operand of a shift with delayed type-check
41 val constant.Value // constant value; or nil (if not a constant)
44 // A context represents the context within which an object is type-checked.
46 decl *declInfo // package-level declaration whose init expression/function body is checked
47 scope *Scope // top-most scope for lookups
48 pos token.Pos // if valid, identifiers are looked up as if at position pos (used by Eval)
49 iota constant.Value // value of iota in a constant declaration; nil otherwise
50 errpos positioner // if set, identifier position of a constant with inherited initializer
51 sig *Signature // function signature if inside a function; nil otherwise
52 isPanic map[*ast.CallExpr]bool // set of panic call expressions (used for termination check)
53 hasLabel bool // set if a function makes use of labels (only ~1% of functions); unused outside functions
54 hasCallOrRecv bool // set if an expression contains a function call or channel receive operation
57 // lookup looks up name in the current context and returns the matching object, or nil.
58 func (ctxt *context) lookup(name string) Object {
59 _, obj := ctxt.scope.LookupParent(name, ctxt.pos)
63 // An importKey identifies an imported package by import path and source directory
64 // (directory containing the file containing the import). In practice, the directory
65 // may always be the same, or may not matter. Given an (import path, directory), an
66 // importer must always return the same package (but given two different import paths,
67 // an importer may still return the same package by mapping them to the same package
69 type importKey struct {
73 // A dotImportKey describes a dot-imported object in the given scope.
74 type dotImportKey struct {
79 // A Checker maintains the state of the type checker.
80 // It must be created with NewChecker.
82 // package information
83 // (initialized by NewChecker, valid for the life-time of checker)
88 version version // accepted language version
89 nextId uint64 // unique Id for type parameters (first valid Id is 1)
90 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
91 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
92 posMap map[*Interface][]token.Pos // maps interface types to lists of embedded interface positions
93 typMap map[string]*Named // maps an instantiated named type hash to a *Named type
94 pkgCnt map[string]int // counts number of imported packages with a given name (for better error messages)
96 // information collected during type-checking of a set of package files
97 // (initialized by Files, valid only for the duration of check.Files;
98 // maps and lists are allocated on demand)
99 files []*ast.File // package files
100 imports []*PkgName // list of imported packages
101 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
103 firstErr error // first error encountered
104 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
105 untyped map[ast.Expr]exprInfo // map of expressions without final type
106 delayed []func() // stack of delayed action segments; segments are processed in FIFO order
107 objPath []Object // path of object dependencies during type inference (for cycle reporting)
109 // context within which the current object is type-checked
110 // (valid only for the duration of type-checking a specific object)
114 indent int // indentation for tracing
117 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
118 func (check *Checker) addDeclDep(to Object) {
121 return // not in a package-level init expression
123 if _, found := check.objMap[to]; !found {
124 return // to is not a package-level object
129 func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
132 m = make(map[ast.Expr]exprInfo)
135 m[e] = exprInfo{lhs, mode, typ, val}
138 // later pushes f on to the stack of actions that will be processed later;
139 // either at the end of the current statement, or in case of a local constant
140 // or variable declaration, before the constant or variable is in scope
141 // (so that f still sees the scope before any new declarations).
142 func (check *Checker) later(f func()) {
143 check.delayed = append(check.delayed, f)
146 // push pushes obj onto the object path and returns its index in the path.
147 func (check *Checker) push(obj Object) int {
148 check.objPath = append(check.objPath, obj)
149 return len(check.objPath) - 1
152 // pop pops and returns the topmost object from the object path.
153 func (check *Checker) pop() Object {
154 i := len(check.objPath) - 1
155 obj := check.objPath[i]
156 check.objPath[i] = nil
157 check.objPath = check.objPath[:i]
161 // NewChecker returns a new Checker instance for a given package.
162 // Package files may be added incrementally via checker.Files.
163 func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {
164 // make sure we have a configuration
169 // make sure we have an info struct
174 version, err := parseGoVersion(conf.GoVersion)
176 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
186 objMap: make(map[Object]*declInfo),
187 impMap: make(map[importKey]*Package),
188 posMap: make(map[*Interface][]token.Pos),
189 typMap: make(map[string]*Named),
190 pkgCnt: make(map[string]int),
194 // initFiles initializes the files-specific portion of checker.
195 // The provided files must all belong to the same package.
196 func (check *Checker) initFiles(files []*ast.File) {
197 // start with a clean slate (check.Files may be called multiple times)
200 check.dotImportMap = nil
207 // determine package name and collect valid files
209 for _, file := range files {
210 switch name := file.Name.Name; pkg.name {
215 check.errorf(file.Name, _BlankPkgName, "invalid package name _")
220 check.files = append(check.files, file)
223 check.errorf(atPos(file.Package), _MismatchedPkgName, "package %s; expected %s", name, pkg.name)
229 // A bailout panic is used for early termination.
230 type bailout struct{}
232 func (check *Checker) handleBailout(err *error) {
233 switch p := recover().(type) {
235 // normal return or early exit
236 *err = check.firstErr
243 // Files checks the provided files as part of the checker's package.
244 func (check *Checker) Files(files []*ast.File) error { return check.checkFiles(files) }
246 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
248 func (check *Checker) checkFiles(files []*ast.File) (err error) {
249 if check.conf.FakeImportC && check.conf.go115UsesCgo {
253 defer check.handleBailout(&err)
255 check.initFiles(files)
257 check.collectObjects()
259 check.packageObjects()
261 check.processDelayed(0) // incl. all functions
265 if !check.conf.DisableUnusedImportCheck {
266 check.unusedImports()
268 // no longer needed - release memory
270 check.dotImportMap = nil
272 check.recordUntyped()
274 if check.Info != nil {
275 sanitizeInfo(check.Info)
278 check.pkg.complete = true
280 // TODO(rFindley) There's more memory we should release at this point.
285 // processDelayed processes all delayed actions pushed after top.
286 func (check *Checker) processDelayed(top int) {
287 // If each delayed action pushes a new action, the
288 // stack will continue to grow during this loop.
289 // However, it is only processing functions (which
290 // are processed in a delayed fashion) that may
291 // add more actions (such as nested functions), so
292 // this is a sufficiently bounded process.
293 for i := top; i < len(check.delayed); i++ {
294 check.delayed[i]() // may append to check.delayed
296 assert(top <= len(check.delayed)) // stack must not have shrunk
297 check.delayed = check.delayed[:top]
300 func (check *Checker) recordUntyped() {
301 if !debug && check.Types == nil {
302 return // nothing to do
305 for x, info := range check.untyped {
306 if debug && isTyped(info.typ) {
307 check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ)
310 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
314 func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
320 if mode == constant_ {
322 // We check is(typ, IsConstType) here as constant expressions may be
323 // recorded as type parameters.
324 assert(typ == Typ[Invalid] || is(typ, IsConstType))
326 if m := check.Types; m != nil {
327 m[x] = TypeAndValue{mode, typ, val}
331 func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
332 // f must be a (possibly parenthesized) identifier denoting a built-in
333 // (built-ins in package unsafe always produce a constant result and
334 // we don't record their signatures, so we don't see qualified idents
335 // here): record the signature for f and possible children.
337 check.recordTypeAndValue(f, builtin, sig, nil)
338 switch p := f.(type) {
349 func (check *Checker) recordCommaOkTypes(x ast.Expr, a [2]Type) {
351 if a[0] == nil || a[1] == nil {
354 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
355 if m := check.Types; m != nil {
358 assert(tv.Type != nil) // should have been recorded already
361 NewVar(pos, check.pkg, "", a[0]),
362 NewVar(pos, check.pkg, "", a[1]),
365 // if x is a parenthesized expression (p.X), update p.X
366 p, _ := x.(*ast.ParenExpr)
375 func (check *Checker) recordInferred(call ast.Expr, targs []Type, sig *Signature) {
378 if m := check._Inferred; m != nil {
379 m[call] = _Inferred{targs, sig}
383 func (check *Checker) recordDef(id *ast.Ident, obj Object) {
385 if m := check.Defs; m != nil {
390 func (check *Checker) recordUse(id *ast.Ident, obj Object) {
393 if m := check.Uses; m != nil {
398 func (check *Checker) recordImplicit(node ast.Node, obj Object) {
401 if m := check.Implicits; m != nil {
406 func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
407 assert(obj != nil && (recv == nil || len(index) > 0))
408 check.recordUse(x.Sel, obj)
409 if m := check.Selections; m != nil {
410 m[x] = &Selection{kind, recv, obj, index, indirect}
414 func (check *Checker) recordScope(node ast.Node, scope *Scope) {
417 if m := check.Scopes; m != nil {