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.
10 "cmd/compile/internal/syntax"
18 // debugging/development support
19 const debug = false // leave on during development
21 // If forceStrict is set, the type-checker enforces additional
22 // rules not specified by the Go 1 spec, but which will
23 // catch guaranteed run-time errors if the respective
24 // code is executed. In other words, programs passing in
25 // strict mode are Go 1 compliant, but not all Go 1 programs
26 // will pass in strict mode. The additional rules are:
28 // - A type assertion x.(T) where T is an interface type
29 // is invalid if any (statically known) method that exists
30 // for both x and T have different signatures.
32 const forceStrict = false
34 // exprInfo stores information about an untyped expression.
35 type exprInfo struct {
36 isLhs bool // expression is lhs operand of a shift with delayed type-check
39 val constant.Value // constant value; or nil (if not a constant)
42 // A context represents the context within which an object is type-checked.
44 decl *declInfo // package-level declaration whose init expression/function body is checked
45 scope *Scope // top-most scope for lookups
46 pos syntax.Pos // if valid, identifiers are looked up as if at position pos (used by Eval)
47 iota constant.Value // value of iota in a constant declaration; nil otherwise
48 errpos syntax.Pos // if valid, identifier position of a constant with inherited initializer
49 sig *Signature // function signature if inside a function; nil otherwise
50 isPanic map[*syntax.CallExpr]bool // set of panic call expressions (used for termination check)
51 hasLabel bool // set if a function makes use of labels (only ~1% of functions); unused outside functions
52 hasCallOrRecv bool // set if an expression contains a function call or channel receive operation
55 // lookup looks up name in the current context and returns the matching object, or nil.
56 func (ctxt *context) lookup(name string) Object {
57 _, obj := ctxt.scope.LookupParent(name, ctxt.pos)
61 // An importKey identifies an imported package by import path and source directory
62 // (directory containing the file containing the import). In practice, the directory
63 // may always be the same, or may not matter. Given an (import path, directory), an
64 // importer must always return the same package (but given two different import paths,
65 // an importer may still return the same package by mapping them to the same package
67 type importKey struct {
71 // A dotImportKey describes a dot-imported object in the given scope.
72 type dotImportKey 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 version version // accepted language version
86 nextID uint64 // unique Id for type parameters (first valid Id is 1)
87 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
88 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
90 // pkgPathMap maps package names to the set of distinct import paths we've
91 // seen for that name, anywhere in the import graph. It is used for
92 // disambiguating package names in error messages.
94 // pkgPathMap is allocated lazily, so that we don't pay the price of building
95 // it on the happy path. seenPkgMap tracks the packages that we've already
97 pkgPathMap map[string]map[string]bool
98 seenPkgMap map[*Package]bool
100 // information collected during type-checking of a set of package files
101 // (initialized by Files, valid only for the duration of check.Files;
102 // maps and lists are allocated on demand)
103 files []*syntax.File // list of package files
104 imports []*PkgName // list of imported packages
105 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
107 firstErr error // first error encountered
108 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
109 untyped map[syntax.Expr]exprInfo // map of expressions without final type
110 delayed []func() // stack of delayed action segments; segments are processed in FIFO order
111 objPath []Object // path of object dependencies during type inference (for cycle reporting)
113 // context within which the current object is type-checked
114 // (valid only for the duration of type-checking a specific object)
118 indent int // indentation for tracing
121 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
122 func (check *Checker) addDeclDep(to Object) {
125 return // not in a package-level init expression
127 if _, found := check.objMap[to]; !found {
128 return // to is not a package-level object
133 func (check *Checker) rememberUntyped(e syntax.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
136 m = make(map[syntax.Expr]exprInfo)
139 m[e] = exprInfo{lhs, mode, typ, val}
142 // later pushes f on to the stack of actions that will be processed later;
143 // either at the end of the current statement, or in case of a local constant
144 // or variable declaration, before the constant or variable is in scope
145 // (so that f still sees the scope before any new declarations).
146 func (check *Checker) later(f func()) {
147 check.delayed = append(check.delayed, f)
150 // push pushes obj onto the object path and returns its index in the path.
151 func (check *Checker) push(obj Object) int {
152 check.objPath = append(check.objPath, obj)
153 return len(check.objPath) - 1
156 // pop pops and returns the topmost object from the object path.
157 func (check *Checker) pop() Object {
158 i := len(check.objPath) - 1
159 obj := check.objPath[i]
160 check.objPath[i] = nil
161 check.objPath = check.objPath[:i]
165 // NewChecker returns a new Checker instance for a given package.
166 // Package files may be added incrementally via checker.Files.
167 func NewChecker(conf *Config, pkg *Package, info *Info) *Checker {
168 // make sure we have a configuration
173 // make sure we have an environment
174 if conf.Environment == nil {
175 conf.Environment = NewEnvironment()
178 // make sure we have an info struct
183 version, err := parseGoVersion(conf.GoVersion)
185 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
193 objMap: make(map[Object]*declInfo),
194 impMap: make(map[importKey]*Package),
198 // initFiles initializes the files-specific portion of checker.
199 // The provided files must all belong to the same package.
200 func (check *Checker) initFiles(files []*syntax.File) {
201 // start with a clean slate (check.Files may be called multiple times)
204 check.dotImportMap = nil
211 // determine package name and collect valid files
213 for _, file := range files {
214 switch name := file.PkgName.Value; pkg.name {
219 check.error(file.PkgName, "invalid package name _")
224 check.files = append(check.files, file)
227 check.errorf(file, "package %s; expected %s", name, pkg.name)
233 // A bailout panic is used for early termination.
234 type bailout struct{}
236 func (check *Checker) handleBailout(err *error) {
237 switch p := recover().(type) {
239 // normal return or early exit
240 *err = check.firstErr
247 // Files checks the provided files as part of the checker's package.
248 func (check *Checker) Files(files []*syntax.File) error { return check.checkFiles(files) }
250 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
252 func (check *Checker) checkFiles(files []*syntax.File) (err error) {
253 if check.conf.FakeImportC && check.conf.go115UsesCgo {
257 defer check.handleBailout(&err)
259 print := func(msg string) {
260 if check.conf.Trace {
265 print("== initFiles ==")
266 check.initFiles(files)
268 print("== collectObjects ==")
269 check.collectObjects()
271 print("== packageObjects ==")
272 check.packageObjects()
274 print("== processDelayed ==")
275 check.processDelayed(0) // incl. all functions
277 print("== initOrder ==")
280 if !check.conf.DisableUnusedImportCheck {
281 print("== unusedImports ==")
282 check.unusedImports()
285 print("== recordUntyped ==")
286 check.recordUntyped()
288 check.pkg.complete = true
290 // no longer needed - release memory
292 check.dotImportMap = nil
293 check.pkgPathMap = nil
294 check.seenPkgMap = nil
296 // TODO(gri) There's more memory we should release at this point.
301 // processDelayed processes all delayed actions pushed after top.
302 func (check *Checker) processDelayed(top int) {
303 // If each delayed action pushes a new action, the
304 // stack will continue to grow during this loop.
305 // However, it is only processing functions (which
306 // are processed in a delayed fashion) that may
307 // add more actions (such as nested functions), so
308 // this is a sufficiently bounded process.
309 for i := top; i < len(check.delayed); i++ {
310 check.delayed[i]() // may append to check.delayed
312 assert(top <= len(check.delayed)) // stack must not have shrunk
313 check.delayed = check.delayed[:top]
316 func (check *Checker) record(x *operand) {
317 // convert x into a user-friendly set of values
318 // TODO(gri) this code can be simplified
320 var val constant.Value
332 assert(x.expr != nil && typ != nil)
335 // delay type and value recording until we know the type
336 // or until the end of type checking
337 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
339 check.recordTypeAndValue(x.expr, x.mode, typ, val)
343 func (check *Checker) recordUntyped() {
344 if !debug && check.Types == nil {
345 return // nothing to do
348 for x, info := range check.untyped {
349 if debug && isTyped(info.typ) {
350 check.dump("%v: %s (type %s) is typed", posFor(x), x, info.typ)
353 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
357 func (check *Checker) recordTypeAndValue(x syntax.Expr, mode operandMode, typ Type, val constant.Value) {
363 if mode == constant_ {
365 // We check is(typ, IsConstType) here as constant expressions may be
366 // recorded as type parameters.
367 assert(typ == Typ[Invalid] || is(typ, IsConstType))
369 if m := check.Types; m != nil {
370 m[x] = TypeAndValue{mode, typ, val}
374 func (check *Checker) recordBuiltinType(f syntax.Expr, sig *Signature) {
375 // f must be a (possibly parenthesized, possibly qualified)
376 // identifier denoting a built-in (including unsafe's non-constant
377 // functions Add and Slice): record the signature for f and possible
380 check.recordTypeAndValue(f, builtin, sig, nil)
381 switch p := f.(type) {
382 case *syntax.Name, *syntax.SelectorExpr:
384 case *syntax.ParenExpr:
392 func (check *Checker) recordCommaOkTypes(x syntax.Expr, a [2]Type) {
394 if a[0] == nil || a[1] == nil {
397 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
398 if m := check.Types; m != nil {
401 assert(tv.Type != nil) // should have been recorded already
404 NewVar(pos, check.pkg, "", a[0]),
405 NewVar(pos, check.pkg, "", a[1]),
408 // if x is a parenthesized expression (p.X), update p.X
409 p, _ := x.(*syntax.ParenExpr)
418 func (check *Checker) recordInferred(call syntax.Expr, targs []Type, sig *Signature) {
421 if m := check.Inferred; m != nil {
422 m[call] = Inferred{NewTypeList(targs), sig}
426 func (check *Checker) recordDef(id *syntax.Name, obj Object) {
428 if m := check.Defs; m != nil {
433 func (check *Checker) recordUse(id *syntax.Name, obj Object) {
436 if m := check.Uses; m != nil {
441 func (check *Checker) recordImplicit(node syntax.Node, obj Object) {
444 if m := check.Implicits; m != nil {
449 func (check *Checker) recordSelection(x *syntax.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
450 assert(obj != nil && (recv == nil || len(index) > 0))
451 check.recordUse(x.Sel, obj)
452 if m := check.Selections; m != nil {
453 m[x] = &Selection{kind, recv, obj, index, indirect}
457 func (check *Checker) recordScope(node syntax.Node, scope *Scope) {
460 if m := check.Scopes; m != nil {