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 // An action describes a (delayed) action.
79 f func() // action to be executed
80 desc *actionDesc // action description; may be nil, requires debug to be set
83 // If debug is set, describef sets a printf-formatted description for action a.
84 // Otherwise, it is a no-op.
85 func (a *action) describef(pos poser, format string, args ...interface{}) {
87 a.desc = &actionDesc{pos, format, args}
91 // An actionDesc provides information on an action.
92 // For debugging only.
93 type actionDesc struct {
99 // A Checker maintains the state of the type checker.
100 // It must be created with NewChecker.
101 type Checker struct {
102 // package information
103 // (initialized by NewChecker, valid for the life-time of checker)
107 version version // accepted language version
108 nextID uint64 // unique Id for type parameters (first valid Id is 1)
109 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
110 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
112 // pkgPathMap maps package names to the set of distinct import paths we've
113 // seen for that name, anywhere in the import graph. It is used for
114 // disambiguating package names in error messages.
116 // pkgPathMap is allocated lazily, so that we don't pay the price of building
117 // it on the happy path. seenPkgMap tracks the packages that we've already
119 pkgPathMap map[string]map[string]bool
120 seenPkgMap map[*Package]bool
122 // information collected during type-checking of a set of package files
123 // (initialized by Files, valid only for the duration of check.Files;
124 // maps and lists are allocated on demand)
125 files []*syntax.File // list of package files
126 imports []*PkgName // list of imported packages
127 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
128 recvTParamMap map[*syntax.Name]*TypeParam // maps blank receiver type parameters to their type
130 firstErr error // first error encountered
131 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
132 untyped map[syntax.Expr]exprInfo // map of expressions without final type
133 delayed []action // stack of delayed action segments; segments are processed in FIFO order
134 objPath []Object // path of object dependencies during type inference (for cycle reporting)
136 // context within which the current object is type-checked
137 // (valid only for the duration of type-checking a specific object)
141 indent int // indentation for tracing
144 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
145 func (check *Checker) addDeclDep(to Object) {
148 return // not in a package-level init expression
150 if _, found := check.objMap[to]; !found {
151 return // to is not a package-level object
156 func (check *Checker) rememberUntyped(e syntax.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
159 m = make(map[syntax.Expr]exprInfo)
162 m[e] = exprInfo{lhs, mode, typ, val}
165 // later pushes f on to the stack of actions that will be processed later;
166 // either at the end of the current statement, or in case of a local constant
167 // or variable declaration, before the constant or variable is in scope
168 // (so that f still sees the scope before any new declarations).
169 // later returns the pushed action so one can provide a description
170 // via action.describef for debugging, if desired.
171 func (check *Checker) later(f func()) *action {
172 i := len(check.delayed)
173 check.delayed = append(check.delayed, action{f: f})
174 return &check.delayed[i]
177 // push pushes obj onto the object path and returns its index in the path.
178 func (check *Checker) push(obj Object) int {
179 check.objPath = append(check.objPath, obj)
180 return len(check.objPath) - 1
183 // pop pops and returns the topmost object from the object path.
184 func (check *Checker) pop() Object {
185 i := len(check.objPath) - 1
186 obj := check.objPath[i]
187 check.objPath[i] = nil
188 check.objPath = check.objPath[:i]
192 // NewChecker returns a new Checker instance for a given package.
193 // Package files may be added incrementally via checker.Files.
194 func NewChecker(conf *Config, pkg *Package, info *Info) *Checker {
195 // make sure we have a configuration
200 // make sure we have a context
201 if conf.Context == nil {
202 conf.Context = NewContext()
205 // make sure we have an info struct
210 version, err := parseGoVersion(conf.GoVersion)
212 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
220 objMap: make(map[Object]*declInfo),
221 impMap: make(map[importKey]*Package),
225 // initFiles initializes the files-specific portion of checker.
226 // The provided files must all belong to the same package.
227 func (check *Checker) initFiles(files []*syntax.File) {
228 // start with a clean slate (check.Files may be called multiple times)
231 check.dotImportMap = nil
238 // determine package name and collect valid files
240 for _, file := range files {
241 switch name := file.PkgName.Value; pkg.name {
246 check.error(file.PkgName, "invalid package name _")
251 check.files = append(check.files, file)
254 check.errorf(file, "package %s; expected %s", name, pkg.name)
260 // A bailout panic is used for early termination.
261 type bailout struct{}
263 func (check *Checker) handleBailout(err *error) {
264 switch p := recover().(type) {
266 // normal return or early exit
267 *err = check.firstErr
274 // Files checks the provided files as part of the checker's package.
275 func (check *Checker) Files(files []*syntax.File) error { return check.checkFiles(files) }
277 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
279 func (check *Checker) checkFiles(files []*syntax.File) (err error) {
280 if check.conf.FakeImportC && check.conf.go115UsesCgo {
284 defer check.handleBailout(&err)
286 print := func(msg string) {
287 if check.conf.Trace {
293 print("== initFiles ==")
294 check.initFiles(files)
296 print("== collectObjects ==")
297 check.collectObjects()
299 print("== packageObjects ==")
300 check.packageObjects()
302 print("== processDelayed ==")
303 check.processDelayed(0) // incl. all functions
305 print("== initOrder ==")
308 if !check.conf.DisableUnusedImportCheck {
309 print("== unusedImports ==")
310 check.unusedImports()
313 print("== recordUntyped ==")
314 check.recordUntyped()
316 check.pkg.complete = true
318 // no longer needed - release memory
320 check.dotImportMap = nil
321 check.pkgPathMap = nil
322 check.seenPkgMap = nil
323 check.recvTParamMap = nil
325 // TODO(gri) There's more memory we should release at this point.
330 // processDelayed processes all delayed actions pushed after top.
331 func (check *Checker) processDelayed(top int) {
332 // If each delayed action pushes a new action, the
333 // stack will continue to grow during this loop.
334 // However, it is only processing functions (which
335 // are processed in a delayed fashion) that may
336 // add more actions (such as nested functions), so
337 // this is a sufficiently bounded process.
338 for i := top; i < len(check.delayed); i++ {
339 a := &check.delayed[i]
340 if check.conf.Trace && a.desc != nil {
342 check.trace(a.desc.pos.Pos(), "-- "+a.desc.format, a.desc.args...)
344 a.f() // may append to check.delayed
346 assert(top <= len(check.delayed)) // stack must not have shrunk
347 check.delayed = check.delayed[:top]
350 func (check *Checker) record(x *operand) {
351 // convert x into a user-friendly set of values
352 // TODO(gri) this code can be simplified
354 var val constant.Value
366 assert(x.expr != nil && typ != nil)
369 // delay type and value recording until we know the type
370 // or until the end of type checking
371 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
373 check.recordTypeAndValue(x.expr, x.mode, typ, val)
377 func (check *Checker) recordUntyped() {
378 if !debug && check.Types == nil {
379 return // nothing to do
382 for x, info := range check.untyped {
383 if debug && isTyped(info.typ) {
384 check.dump("%v: %s (type %s) is typed", posFor(x), x, info.typ)
387 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
391 func (check *Checker) recordTypeAndValue(x syntax.Expr, mode operandMode, typ Type, val constant.Value) {
397 if mode == constant_ {
399 // We check is(typ, IsConstType) here as constant expressions may be
400 // recorded as type parameters.
401 assert(typ == Typ[Invalid] || is(typ, IsConstType))
403 if m := check.Types; m != nil {
404 m[x] = TypeAndValue{mode, typ, val}
408 func (check *Checker) recordBuiltinType(f syntax.Expr, sig *Signature) {
409 // f must be a (possibly parenthesized, possibly qualified)
410 // identifier denoting a built-in (including unsafe's non-constant
411 // functions Add and Slice): record the signature for f and possible
414 check.recordTypeAndValue(f, builtin, sig, nil)
415 switch p := f.(type) {
416 case *syntax.Name, *syntax.SelectorExpr:
418 case *syntax.ParenExpr:
426 func (check *Checker) recordCommaOkTypes(x syntax.Expr, a [2]Type) {
428 if a[0] == nil || a[1] == nil {
431 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
432 if m := check.Types; m != nil {
435 assert(tv.Type != nil) // should have been recorded already
438 NewVar(pos, check.pkg, "", a[0]),
439 NewVar(pos, check.pkg, "", a[1]),
442 // if x is a parenthesized expression (p.X), update p.X
443 p, _ := x.(*syntax.ParenExpr)
452 // recordInstance records instantiation information into check.Info, if the
453 // Instances map is non-nil. The given expr must be an ident, selector, or
454 // index (list) expr with ident or selector operand.
456 // TODO(rfindley): the expr parameter is fragile. See if we can access the
457 // instantiated identifier in some other way.
458 func (check *Checker) recordInstance(expr syntax.Expr, targs []Type, typ Type) {
459 ident := instantiatedIdent(expr)
462 if m := check.Instances; m != nil {
463 m[ident] = Instance{NewTypeList(targs), typ}
467 func instantiatedIdent(expr syntax.Expr) *syntax.Name {
468 var selOrIdent syntax.Expr
469 switch e := expr.(type) {
470 case *syntax.IndexExpr:
472 case *syntax.SelectorExpr, *syntax.Name:
475 switch x := selOrIdent.(type) {
478 case *syntax.SelectorExpr:
481 panic("instantiated ident not found")
484 func (check *Checker) recordDef(id *syntax.Name, obj Object) {
486 if m := check.Defs; m != nil {
491 func (check *Checker) recordUse(id *syntax.Name, obj Object) {
494 if m := check.Uses; m != nil {
499 func (check *Checker) recordImplicit(node syntax.Node, obj Object) {
502 if m := check.Implicits; m != nil {
507 func (check *Checker) recordSelection(x *syntax.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
508 assert(obj != nil && (recv == nil || len(index) > 0))
509 check.recordUse(x.Sel, obj)
510 if m := check.Selections; m != nil {
511 m[x] = &Selection{kind, recv, obj, index, indirect}
515 func (check *Checker) recordScope(node syntax.Node, scope *Scope) {
518 if m := check.Scopes; m != nil {