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 // An environment represents the environment within which an object is
44 type environment struct {
45 decl *declInfo // package-level declaration whose init expression/function body is checked
46 scope *Scope // top-most scope for lookups
47 pos syntax.Pos // if valid, identifiers are looked up as if at position pos (used by Eval)
48 iota constant.Value // value of iota in a constant declaration; nil otherwise
49 errpos syntax.Pos // if valid, identifier position of a constant with inherited initializer
50 inTParamList bool // set if inside a type parameter list
51 sig *Signature // function signature if inside a function; nil otherwise
52 isPanic map[*syntax.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 environment and returns the matching object, or nil.
58 func (env *environment) lookup(name string) Object {
59 _, obj := env.scope.LookupParent(name, env.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 // An action describes a (delayed) action.
81 f func() // action to be executed
82 desc *actionDesc // action description; may be nil, requires debug to be set
85 // If debug is set, describef sets a printf-formatted description for action a.
86 // Otherwise, it is a no-op.
87 func (a *action) describef(pos poser, format string, args ...interface{}) {
89 a.desc = &actionDesc{pos, format, args}
93 // An actionDesc provides information on an action.
94 // For debugging only.
95 type actionDesc struct {
101 // A Checker maintains the state of the type checker.
102 // It must be created with NewChecker.
103 type Checker struct {
104 // package information
105 // (initialized by NewChecker, valid for the life-time of checker)
107 ctxt *Context // context for de-duplicating instances
110 version version // accepted language version
111 nextID uint64 // unique Id for type parameters (first valid Id is 1)
112 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
113 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
114 infoMap map[*Named]typeInfo // maps named types to their associated type info (for cycle detection)
116 // pkgPathMap maps package names to the set of distinct import paths we've
117 // seen for that name, anywhere in the import graph. It is used for
118 // disambiguating package names in error messages.
120 // pkgPathMap is allocated lazily, so that we don't pay the price of building
121 // it on the happy path. seenPkgMap tracks the packages that we've already
123 pkgPathMap map[string]map[string]bool
124 seenPkgMap map[*Package]bool
126 // information collected during type-checking of a set of package files
127 // (initialized by Files, valid only for the duration of check.Files;
128 // maps and lists are allocated on demand)
129 files []*syntax.File // list of package files
130 imports []*PkgName // list of imported packages
131 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
132 recvTParamMap map[*syntax.Name]*TypeParam // maps blank receiver type parameters to their type
133 unionTypeSets map[*Union]*_TypeSet // computed type sets for union types
134 mono monoGraph // graph for detecting non-monomorphizable instantiation loops
136 firstErr error // first error encountered
137 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
138 untyped map[syntax.Expr]exprInfo // map of expressions without final type
139 delayed []action // stack of delayed action segments; segments are processed in FIFO order
140 objPath []Object // path of object dependencies during type inference (for cycle reporting)
141 defTypes []*Named // defined types created during type checking, for final validation.
143 // environment within which the current object is type-checked (valid only
144 // for the duration of type-checking a specific object)
148 indent int // indentation for tracing
151 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
152 func (check *Checker) addDeclDep(to Object) {
155 return // not in a package-level init expression
157 if _, found := check.objMap[to]; !found {
158 return // to is not a package-level object
163 func (check *Checker) rememberUntyped(e syntax.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
166 m = make(map[syntax.Expr]exprInfo)
169 m[e] = exprInfo{lhs, mode, typ, val}
172 // later pushes f on to the stack of actions that will be processed later;
173 // either at the end of the current statement, or in case of a local constant
174 // or variable declaration, before the constant or variable is in scope
175 // (so that f still sees the scope before any new declarations).
176 // later returns the pushed action so one can provide a description
177 // via action.describef for debugging, if desired.
178 func (check *Checker) later(f func()) *action {
179 i := len(check.delayed)
180 check.delayed = append(check.delayed, action{f: f})
181 return &check.delayed[i]
184 // push pushes obj onto the object path and returns its index in the path.
185 func (check *Checker) push(obj Object) int {
186 check.objPath = append(check.objPath, obj)
187 return len(check.objPath) - 1
190 // pop pops and returns the topmost object from the object path.
191 func (check *Checker) pop() Object {
192 i := len(check.objPath) - 1
193 obj := check.objPath[i]
194 check.objPath[i] = nil
195 check.objPath = check.objPath[:i]
199 // NewChecker returns a new Checker instance for a given package.
200 // Package files may be added incrementally via checker.Files.
201 func NewChecker(conf *Config, pkg *Package, info *Info) *Checker {
202 // make sure we have a configuration
207 // make sure we have an info struct
212 version, err := parseGoVersion(conf.GoVersion)
214 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
223 objMap: make(map[Object]*declInfo),
224 impMap: make(map[importKey]*Package),
225 infoMap: make(map[*Named]typeInfo),
229 // initFiles initializes the files-specific portion of checker.
230 // The provided files must all belong to the same package.
231 func (check *Checker) initFiles(files []*syntax.File) {
232 // start with a clean slate (check.Files may be called multiple times)
235 check.dotImportMap = nil
242 // determine package name and collect valid files
244 for _, file := range files {
245 switch name := file.PkgName.Value; pkg.name {
250 check.error(file.PkgName, "invalid package name _")
255 check.files = append(check.files, file)
258 check.errorf(file, "package %s; expected %s", name, pkg.name)
264 // A bailout panic is used for early termination.
265 type bailout struct{}
267 func (check *Checker) handleBailout(err *error) {
268 switch p := recover().(type) {
270 // normal return or early exit
271 *err = check.firstErr
278 // Files checks the provided files as part of the checker's package.
279 func (check *Checker) Files(files []*syntax.File) error { return check.checkFiles(files) }
281 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
283 func (check *Checker) checkFiles(files []*syntax.File) (err error) {
284 if check.conf.FakeImportC && check.conf.go115UsesCgo {
288 defer check.handleBailout(&err)
290 print := func(msg string) {
291 if check.conf.Trace {
297 print("== initFiles ==")
298 check.initFiles(files)
300 print("== collectObjects ==")
301 check.collectObjects()
303 print("== packageObjects ==")
304 check.packageObjects()
306 print("== processDelayed ==")
307 check.processDelayed(0) // incl. all functions
309 print("== expandDefTypes ==")
310 check.expandDefTypes()
312 print("== initOrder ==")
315 if !check.conf.DisableUnusedImportCheck {
316 print("== unusedImports ==")
317 check.unusedImports()
320 print("== recordUntyped ==")
321 check.recordUntyped()
323 if check.firstErr == nil {
324 // TODO(mdempsky): Ensure monomorph is safe when errors exist.
328 check.pkg.complete = true
330 // no longer needed - release memory
332 check.dotImportMap = nil
333 check.pkgPathMap = nil
334 check.seenPkgMap = nil
335 check.recvTParamMap = nil
336 check.unionTypeSets = nil
340 // TODO(gri) There's more memory we should release at this point.
345 // processDelayed processes all delayed actions pushed after top.
346 func (check *Checker) processDelayed(top int) {
347 // If each delayed action pushes a new action, the
348 // stack will continue to grow during this loop.
349 // However, it is only processing functions (which
350 // are processed in a delayed fashion) that may
351 // add more actions (such as nested functions), so
352 // this is a sufficiently bounded process.
353 for i := top; i < len(check.delayed); i++ {
354 a := &check.delayed[i]
355 if check.conf.Trace && a.desc != nil {
357 check.trace(a.desc.pos.Pos(), "-- "+a.desc.format, a.desc.args...)
359 a.f() // may append to check.delayed
361 assert(top <= len(check.delayed)) // stack must not have shrunk
362 check.delayed = check.delayed[:top]
365 func (check *Checker) expandDefTypes() {
366 // Ensure that every defined type created in the course of type-checking has
367 // either non-*Named underlying, or is unresolved.
369 // This guarantees that we don't leak any types whose underlying is *Named,
370 // because any unresolved instances will lazily compute their underlying by
371 // substituting in the underlying of their origin. The origin must have
372 // either been imported or type-checked and expanded here, and in either case
373 // its underlying will be fully expanded.
374 for i := 0; i < len(check.defTypes); i++ {
375 n := check.defTypes[i]
376 switch n.underlying.(type) {
378 if n.resolver == nil {
379 panic("nil underlying")
382 n.under() // n.under may add entries to check.defTypes
388 func (check *Checker) record(x *operand) {
389 // convert x into a user-friendly set of values
390 // TODO(gri) this code can be simplified
392 var val constant.Value
404 assert(x.expr != nil && typ != nil)
407 // delay type and value recording until we know the type
408 // or until the end of type checking
409 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
411 check.recordTypeAndValue(x.expr, x.mode, typ, val)
415 func (check *Checker) recordUntyped() {
416 if !debug && check.Types == nil {
417 return // nothing to do
420 for x, info := range check.untyped {
421 if debug && isTyped(info.typ) {
422 check.dump("%v: %s (type %s) is typed", posFor(x), x, info.typ)
425 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
429 func (check *Checker) recordTypeAndValue(x syntax.Expr, mode operandMode, typ Type, val constant.Value) {
435 if mode == constant_ {
437 // We check allBasic(typ, IsConstType) here as constant expressions may be
438 // recorded as type parameters.
439 assert(typ == Typ[Invalid] || allBasic(typ, IsConstType))
441 if m := check.Types; m != nil {
442 m[x] = TypeAndValue{mode, typ, val}
446 func (check *Checker) recordBuiltinType(f syntax.Expr, sig *Signature) {
447 // f must be a (possibly parenthesized, possibly qualified)
448 // identifier denoting a built-in (including unsafe's non-constant
449 // functions Add and Slice): record the signature for f and possible
452 check.recordTypeAndValue(f, builtin, sig, nil)
453 switch p := f.(type) {
454 case *syntax.Name, *syntax.SelectorExpr:
456 case *syntax.ParenExpr:
464 func (check *Checker) recordCommaOkTypes(x syntax.Expr, a [2]Type) {
466 if a[0] == nil || a[1] == nil {
469 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
470 if m := check.Types; m != nil {
473 assert(tv.Type != nil) // should have been recorded already
476 NewVar(pos, check.pkg, "", a[0]),
477 NewVar(pos, check.pkg, "", a[1]),
480 // if x is a parenthesized expression (p.X), update p.X
481 p, _ := x.(*syntax.ParenExpr)
490 // recordInstance records instantiation information into check.Info, if the
491 // Instances map is non-nil. The given expr must be an ident, selector, or
492 // index (list) expr with ident or selector operand.
494 // TODO(rfindley): the expr parameter is fragile. See if we can access the
495 // instantiated identifier in some other way.
496 func (check *Checker) recordInstance(expr syntax.Expr, targs []Type, typ Type) {
497 ident := instantiatedIdent(expr)
500 if m := check.Instances; m != nil {
501 m[ident] = Instance{newTypeList(targs), typ}
505 func instantiatedIdent(expr syntax.Expr) *syntax.Name {
506 var selOrIdent syntax.Expr
507 switch e := expr.(type) {
508 case *syntax.IndexExpr:
510 case *syntax.SelectorExpr, *syntax.Name:
513 switch x := selOrIdent.(type) {
516 case *syntax.SelectorExpr:
519 panic("instantiated ident not found")
522 func (check *Checker) recordDef(id *syntax.Name, obj Object) {
524 if m := check.Defs; m != nil {
529 func (check *Checker) recordUse(id *syntax.Name, obj Object) {
532 if m := check.Uses; m != nil {
537 func (check *Checker) recordImplicit(node syntax.Node, obj Object) {
540 if m := check.Implicits; m != nil {
545 func (check *Checker) recordSelection(x *syntax.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
546 assert(obj != nil && (recv == nil || len(index) > 0))
547 check.recordUse(x.Sel, obj)
548 if m := check.Selections; m != nil {
549 m[x] = &Selection{kind, recv, obj, index, indirect}
553 func (check *Checker) recordScope(node syntax.Node, scope *Scope) {
556 if m := check.Scopes; m != nil {