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 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
90 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
91 posMap map[*Interface][]token.Pos // maps interface types to lists of embedded interface positions
92 typMap map[string]*Named // maps an instantiated named type hash to a *Named type
94 // pkgPathMap maps package names to the set of distinct import paths we've
95 // seen for that name, anywhere in the import graph. It is used for
96 // disambiguating package names in error messages.
98 // pkgPathMap is allocated lazily, so that we don't pay the price of building
99 // it on the happy path. seenPkgMap tracks the packages that we've already
101 pkgPathMap map[string]map[string]bool
102 seenPkgMap map[*Package]bool
104 // information collected during type-checking of a set of package files
105 // (initialized by Files, valid only for the duration of check.Files;
106 // maps and lists are allocated on demand)
107 files []*ast.File // package files
108 imports []*PkgName // list of imported packages
109 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
111 firstErr error // first error encountered
112 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
113 untyped map[ast.Expr]exprInfo // map of expressions without final type
114 delayed []func() // stack of delayed action segments; segments are processed in FIFO order
115 objPath []Object // path of object dependencies during type inference (for cycle reporting)
117 // context within which the current object is type-checked
118 // (valid only for the duration of type-checking a specific object)
122 indent int // indentation for tracing
125 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
126 func (check *Checker) addDeclDep(to Object) {
129 return // not in a package-level init expression
131 if _, found := check.objMap[to]; !found {
132 return // to is not a package-level object
137 func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
140 m = make(map[ast.Expr]exprInfo)
143 m[e] = exprInfo{lhs, mode, typ, val}
146 // later pushes f on to the stack of actions that will be processed later;
147 // either at the end of the current statement, or in case of a local constant
148 // or variable declaration, before the constant or variable is in scope
149 // (so that f still sees the scope before any new declarations).
150 func (check *Checker) later(f func()) {
151 check.delayed = append(check.delayed, f)
154 // push pushes obj onto the object path and returns its index in the path.
155 func (check *Checker) push(obj Object) int {
156 check.objPath = append(check.objPath, obj)
157 return len(check.objPath) - 1
160 // pop pops and returns the topmost object from the object path.
161 func (check *Checker) pop() Object {
162 i := len(check.objPath) - 1
163 obj := check.objPath[i]
164 check.objPath[i] = nil
165 check.objPath = check.objPath[:i]
169 // NewChecker returns a new Checker instance for a given package.
170 // Package files may be added incrementally via checker.Files.
171 func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {
172 // make sure we have a configuration
177 // make sure we have an info struct
182 version, err := parseGoVersion(conf.GoVersion)
184 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
193 objMap: make(map[Object]*declInfo),
194 impMap: make(map[importKey]*Package),
195 posMap: make(map[*Interface][]token.Pos),
196 typMap: make(map[string]*Named),
200 // initFiles initializes the files-specific portion of checker.
201 // The provided files must all belong to the same package.
202 func (check *Checker) initFiles(files []*ast.File) {
203 // start with a clean slate (check.Files may be called multiple times)
206 check.dotImportMap = nil
213 // determine package name and collect valid files
215 for _, file := range files {
216 switch name := file.Name.Name; pkg.name {
221 check.errorf(file.Name, _BlankPkgName, "invalid package name _")
226 check.files = append(check.files, file)
229 check.errorf(atPos(file.Package), _MismatchedPkgName, "package %s; expected %s", name, pkg.name)
235 // A bailout panic is used for early termination.
236 type bailout struct{}
238 func (check *Checker) handleBailout(err *error) {
239 switch p := recover().(type) {
241 // normal return or early exit
242 *err = check.firstErr
249 // Files checks the provided files as part of the checker's package.
250 func (check *Checker) Files(files []*ast.File) error { return check.checkFiles(files) }
252 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
254 func (check *Checker) checkFiles(files []*ast.File) (err error) {
255 if check.conf.FakeImportC && check.conf.go115UsesCgo {
259 defer check.handleBailout(&err)
261 check.initFiles(files)
263 check.collectObjects()
265 check.packageObjects()
267 check.processDelayed(0) // incl. all functions
271 if !check.conf.DisableUnusedImportCheck {
272 check.unusedImports()
275 check.recordUntyped()
277 if check.Info != nil {
278 sanitizeInfo(check.Info)
281 check.pkg.complete = true
283 // no longer needed - release memory
285 check.dotImportMap = nil
286 check.pkgPathMap = nil
287 check.seenPkgMap = nil
289 // TODO(rFindley) There's more memory we should release at this point.
294 // processDelayed processes all delayed actions pushed after top.
295 func (check *Checker) processDelayed(top int) {
296 // If each delayed action pushes a new action, the
297 // stack will continue to grow during this loop.
298 // However, it is only processing functions (which
299 // are processed in a delayed fashion) that may
300 // add more actions (such as nested functions), so
301 // this is a sufficiently bounded process.
302 for i := top; i < len(check.delayed); i++ {
303 check.delayed[i]() // may append to check.delayed
305 assert(top <= len(check.delayed)) // stack must not have shrunk
306 check.delayed = check.delayed[:top]
309 func (check *Checker) record(x *operand) {
310 // convert x into a user-friendly set of values
311 // TODO(gri) this code can be simplified
313 var val constant.Value
325 assert(x.expr != nil && typ != nil)
328 // delay type and value recording until we know the type
329 // or until the end of type checking
330 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
332 check.recordTypeAndValue(x.expr, x.mode, typ, val)
336 func (check *Checker) recordUntyped() {
337 if !debug && check.Types == nil {
338 return // nothing to do
341 for x, info := range check.untyped {
342 if debug && isTyped(info.typ) {
343 check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ)
346 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
350 func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
356 if mode == constant_ {
358 // We check is(typ, IsConstType) here as constant expressions may be
359 // recorded as type parameters.
360 assert(typ == Typ[Invalid] || is(typ, IsConstType))
362 if m := check.Types; m != nil {
363 m[x] = TypeAndValue{mode, typ, val}
367 func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
368 // f must be a (possibly parenthesized, possibly qualified)
369 // identifier denoting a built-in (including unsafe's non-constant
370 // functions Add and Slice): record the signature for f and possible
373 check.recordTypeAndValue(f, builtin, sig, nil)
374 switch p := f.(type) {
375 case *ast.Ident, *ast.SelectorExpr:
385 func (check *Checker) recordCommaOkTypes(x ast.Expr, a [2]Type) {
387 if a[0] == nil || a[1] == nil {
390 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
391 if m := check.Types; m != nil {
394 assert(tv.Type != nil) // should have been recorded already
397 NewVar(pos, check.pkg, "", a[0]),
398 NewVar(pos, check.pkg, "", a[1]),
401 // if x is a parenthesized expression (p.X), update p.X
402 p, _ := x.(*ast.ParenExpr)
411 func (check *Checker) recordInferred(call ast.Expr, targs []Type, sig *Signature) {
414 if m := getInferred(check.Info); m != nil {
415 m[call] = _Inferred{targs, sig}
419 func (check *Checker) recordDef(id *ast.Ident, obj Object) {
421 if m := check.Defs; m != nil {
426 func (check *Checker) recordUse(id *ast.Ident, obj Object) {
429 if m := check.Uses; m != nil {
434 func (check *Checker) recordImplicit(node ast.Node, obj Object) {
437 if m := check.Implicits; m != nil {
442 func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
443 assert(obj != nil && (recv == nil || len(index) > 0))
444 check.recordUse(x.Sel, obj)
445 if m := check.Selections; m != nil {
446 m[x] = &Selection{kind, recv, obj, index, indirect}
450 func (check *Checker) recordScope(node ast.Node, scope *Scope) {
453 if m := check.Scopes; m != nil {