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 Strict 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.
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 pkgCnt map[string]int // counts number of imported packages with a given name (for better error messages)
94 // information collected during type-checking of a set of package files
95 // (initialized by Files, valid only for the duration of check.Files;
96 // maps and lists are allocated on demand)
97 files []*ast.File // package files
98 imports []*PkgName // list of imported packages
99 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
101 firstErr error // first error encountered
102 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
103 untyped map[ast.Expr]exprInfo // map of expressions without final type
104 delayed []func() // stack of delayed action segments; segments are processed in FIFO order
105 finals []func() // list of final actions; processed at the end of type-checking the current set of files
106 objPath []Object // path of object dependencies during type inference (for cycle reporting)
108 // context within which the current object is type-checked
109 // (valid only for the duration of type-checking a specific object)
113 indent int // indentation for tracing
116 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
117 func (check *Checker) addDeclDep(to Object) {
120 return // not in a package-level init expression
122 if _, found := check.objMap[to]; !found {
123 return // to is not a package-level object
128 func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
131 m = make(map[ast.Expr]exprInfo)
134 m[e] = exprInfo{lhs, mode, typ, val}
137 // later pushes f on to the stack of actions that will be processed later;
138 // either at the end of the current statement, or in case of a local constant
139 // or variable declaration, before the constant or variable is in scope
140 // (so that f still sees the scope before any new declarations).
141 func (check *Checker) later(f func()) {
142 check.delayed = append(check.delayed, f)
145 // atEnd adds f to the list of actions processed at the end
146 // of type-checking, before initialization order computation.
147 // Actions added by atEnd are processed after any actions
149 func (check *Checker) atEnd(f func()) {
150 check.finals = append(check.finals, f)
153 // push pushes obj onto the object path and returns its index in the path.
154 func (check *Checker) push(obj Object) int {
155 check.objPath = append(check.objPath, obj)
156 return len(check.objPath) - 1
159 // pop pops and returns the topmost object from the object path.
160 func (check *Checker) pop() Object {
161 i := len(check.objPath) - 1
162 obj := check.objPath[i]
163 check.objPath[i] = nil
164 check.objPath = check.objPath[:i]
168 // NewChecker returns a new Checker instance for a given package.
169 // Package files may be added incrementally via checker.Files.
170 func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {
171 // make sure we have a configuration
176 // make sure we have an info struct
181 version, err := parseGoVersion(conf.GoVersion)
183 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
192 objMap: make(map[Object]*declInfo),
193 impMap: make(map[importKey]*Package),
194 posMap: make(map[*Interface][]token.Pos),
195 pkgCnt: make(map[string]int),
199 // initFiles initializes the files-specific portion of checker.
200 // The provided files must all belong to the same package.
201 func (check *Checker) initFiles(files []*ast.File) {
202 // start with a clean slate (check.Files may be called multiple times)
205 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
268 check.processFinals()
272 if !check.conf.DisableUnusedImportCheck {
273 check.unusedImports()
275 // no longer needed - release memory
277 check.dotImportMap = nil
279 check.recordUntyped()
281 check.pkg.complete = true
283 // TODO(rFindley) There's more memory we should release at this point.
288 // processDelayed processes all delayed actions pushed after top.
289 func (check *Checker) processDelayed(top int) {
290 // If each delayed action pushes a new action, the
291 // stack will continue to grow during this loop.
292 // However, it is only processing functions (which
293 // are processed in a delayed fashion) that may
294 // add more actions (such as nested functions), so
295 // this is a sufficiently bounded process.
296 for i := top; i < len(check.delayed); i++ {
297 check.delayed[i]() // may append to check.delayed
299 assert(top <= len(check.delayed)) // stack must not have shrunk
300 check.delayed = check.delayed[:top]
303 func (check *Checker) processFinals() {
304 n := len(check.finals)
305 for _, f := range check.finals {
306 f() // must not append to check.finals
308 if len(check.finals) != n {
309 panic("internal error: final action list grew")
313 func (check *Checker) recordUntyped() {
314 if !debug && check.Types == nil {
315 return // nothing to do
318 for x, info := range check.untyped {
319 if debug && isTyped(info.typ) {
320 check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ)
323 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
327 func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
333 if mode == constant_ {
335 assert(typ == Typ[Invalid] || isConstType(typ))
337 if m := check.Types; m != nil {
338 m[x] = TypeAndValue{mode, typ, val}
342 func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
343 // f must be a (possibly parenthesized) identifier denoting a built-in
344 // (built-ins in package unsafe always produce a constant result and
345 // we don't record their signatures, so we don't see qualified idents
346 // here): record the signature for f and possible children.
348 check.recordTypeAndValue(f, builtin, sig, nil)
349 switch p := f.(type) {
360 func (check *Checker) recordCommaOkTypes(x ast.Expr, a [2]Type) {
362 if a[0] == nil || a[1] == nil {
365 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
366 if m := check.Types; m != nil {
369 assert(tv.Type != nil) // should have been recorded already
372 NewVar(pos, check.pkg, "", a[0]),
373 NewVar(pos, check.pkg, "", a[1]),
376 // if x is a parenthesized expression (p.X), update p.X
377 p, _ := x.(*ast.ParenExpr)
386 func (check *Checker) recordDef(id *ast.Ident, obj Object) {
388 if m := check.Defs; m != nil {
393 func (check *Checker) recordUse(id *ast.Ident, obj Object) {
396 if m := check.Uses; m != nil {
401 func (check *Checker) recordImplicit(node ast.Node, obj Object) {
404 if m := check.Implicits; m != nil {
409 func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
410 assert(obj != nil && (recv == nil || len(index) > 0))
411 check.recordUse(x.Sel, obj)
412 if m := check.Selections; m != nil {
413 m[x] = &Selection{kind, recv, obj, index, indirect}
417 func (check *Checker) recordScope(node ast.Node, scope *Scope) {
420 if m := check.Scopes; m != nil {