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 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 typMap: make(map[string]*Named),
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
212 // determine package name and collect valid files
214 for _, file := range files {
215 switch name := file.Name.Name; pkg.name {
220 check.errorf(file.Name, _BlankPkgName, "invalid package name _")
225 check.files = append(check.files, file)
228 check.errorf(atPos(file.Package), _MismatchedPkgName, "package %s; expected %s", name, pkg.name)
234 // A bailout panic is used for early termination.
235 type bailout struct{}
237 func (check *Checker) handleBailout(err *error) {
238 switch p := recover().(type) {
240 // normal return or early exit
241 *err = check.firstErr
248 // Files checks the provided files as part of the checker's package.
249 func (check *Checker) Files(files []*ast.File) error { return check.checkFiles(files) }
251 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
253 func (check *Checker) checkFiles(files []*ast.File) (err error) {
254 if check.conf.FakeImportC && check.conf.go115UsesCgo {
258 defer check.handleBailout(&err)
260 check.initFiles(files)
262 check.collectObjects()
264 check.packageObjects()
266 check.processDelayed(0) // incl. all functions
270 if !check.conf.DisableUnusedImportCheck {
271 check.unusedImports()
274 check.recordUntyped()
276 check.pkg.complete = true
278 // no longer needed - release memory
280 check.dotImportMap = nil
281 check.pkgPathMap = nil
282 check.seenPkgMap = nil
284 // TODO(rFindley) There's more memory we should release at this point.
289 // processDelayed processes all delayed actions pushed after top.
290 func (check *Checker) processDelayed(top int) {
291 // If each delayed action pushes a new action, the
292 // stack will continue to grow during this loop.
293 // However, it is only processing functions (which
294 // are processed in a delayed fashion) that may
295 // add more actions (such as nested functions), so
296 // this is a sufficiently bounded process.
297 for i := top; i < len(check.delayed); i++ {
298 check.delayed[i]() // may append to check.delayed
300 assert(top <= len(check.delayed)) // stack must not have shrunk
301 check.delayed = check.delayed[:top]
304 func (check *Checker) record(x *operand) {
305 // convert x into a user-friendly set of values
306 // TODO(gri) this code can be simplified
308 var val constant.Value
320 assert(x.expr != nil && typ != nil)
323 // delay type and value recording until we know the type
324 // or until the end of type checking
325 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
327 check.recordTypeAndValue(x.expr, x.mode, typ, val)
331 func (check *Checker) recordUntyped() {
332 if !debug && check.Types == nil {
333 return // nothing to do
336 for x, info := range check.untyped {
337 if debug && isTyped(info.typ) {
338 check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ)
341 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
345 func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
351 if mode == constant_ {
353 // We check is(typ, IsConstType) here as constant expressions may be
354 // recorded as type parameters.
355 assert(typ == Typ[Invalid] || is(typ, IsConstType))
357 if m := check.Types; m != nil {
358 m[x] = TypeAndValue{mode, typ, val}
362 func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
363 // f must be a (possibly parenthesized, possibly qualified)
364 // identifier denoting a built-in (including unsafe's non-constant
365 // functions Add and Slice): record the signature for f and possible
368 check.recordTypeAndValue(f, builtin, sig, nil)
369 switch p := f.(type) {
370 case *ast.Ident, *ast.SelectorExpr:
380 func (check *Checker) recordCommaOkTypes(x ast.Expr, a [2]Type) {
382 if a[0] == nil || a[1] == nil {
385 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
386 if m := check.Types; m != nil {
389 assert(tv.Type != nil) // should have been recorded already
392 NewVar(pos, check.pkg, "", a[0]),
393 NewVar(pos, check.pkg, "", a[1]),
396 // if x is a parenthesized expression (p.X), update p.X
397 p, _ := x.(*ast.ParenExpr)
406 func (check *Checker) recordInferred(call ast.Expr, targs []Type, sig *Signature) {
409 if m := check.Info.Inferred; m != nil {
410 m[call] = Inferred{targs, sig}
414 func (check *Checker) recordDef(id *ast.Ident, obj Object) {
416 if m := check.Defs; m != nil {
421 func (check *Checker) recordUse(id *ast.Ident, obj Object) {
424 if m := check.Uses; m != nil {
429 func (check *Checker) recordImplicit(node ast.Node, obj Object) {
432 if m := check.Implicits; m != nil {
437 func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
438 assert(obj != nil && (recv == nil || len(index) > 0))
439 check.recordUse(x.Sel, obj)
440 if m := check.Selections; m != nil {
441 m[x] = &Selection{kind, recv, obj, index, indirect}
445 func (check *Checker) recordScope(node ast.Node, scope *Scope) {
448 if m := check.Scopes; m != nil {