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 // An environment represents the environment within which an object is
46 type environment struct {
47 decl *declInfo // package-level declaration whose init expression/function body is checked
48 scope *Scope // top-most scope for lookups
49 pos token.Pos // if valid, identifiers are looked up as if at position pos (used by Eval)
50 iota constant.Value // value of iota in a constant declaration; nil otherwise
51 errpos positioner // if set, identifier position of a constant with inherited initializer
52 inTParamList bool // set if inside a type parameter list
53 sig *Signature // function signature if inside a function; nil otherwise
54 isPanic map[*ast.CallExpr]bool // set of panic call expressions (used for termination check)
55 hasLabel bool // set if a function makes use of labels (only ~1% of functions); unused outside functions
56 hasCallOrRecv bool // set if an expression contains a function call or channel receive operation
59 // lookup looks up name in the current environment and returns the matching object, or nil.
60 func (env *environment) lookup(name string) Object {
61 _, obj := env.scope.LookupParent(name, env.pos)
65 // An importKey identifies an imported package by import path and source directory
66 // (directory containing the file containing the import). In practice, the directory
67 // may always be the same, or may not matter. Given an (import path, directory), an
68 // importer must always return the same package (but given two different import paths,
69 // an importer may still return the same package by mapping them to the same package
71 type importKey struct {
75 // A dotImportKey describes a dot-imported object in the given scope.
76 type dotImportKey struct {
81 // An action describes a (delayed) action.
83 f func() // action to be executed
84 desc *actionDesc // action description; may be nil, requires debug to be set
87 // If debug is set, describef sets a printf-formatted description for action a.
88 // Otherwise, it is a no-op.
89 func (a *action) describef(pos positioner, format string, args ...interface{}) {
91 a.desc = &actionDesc{pos, format, args}
95 // An actionDesc provides information on an action.
96 // For debugging only.
97 type actionDesc struct {
103 // A Checker maintains the state of the type checker.
104 // It must be created with NewChecker.
105 type Checker struct {
106 // package information
107 // (initialized by NewChecker, valid for the life-time of checker)
109 ctxt *Context // context for de-duplicating instances
113 version version // accepted language version
114 nextID uint64 // unique Id for type parameters (first valid Id is 1)
115 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
116 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
118 // pkgPathMap maps package names to the set of distinct import paths we've
119 // seen for that name, anywhere in the import graph. It is used for
120 // disambiguating package names in error messages.
122 // pkgPathMap is allocated lazily, so that we don't pay the price of building
123 // it on the happy path. seenPkgMap tracks the packages that we've already
125 pkgPathMap map[string]map[string]bool
126 seenPkgMap map[*Package]bool
128 // information collected during type-checking of a set of package files
129 // (initialized by Files, valid only for the duration of check.Files;
130 // maps and lists are allocated on demand)
131 files []*ast.File // package files
132 imports []*PkgName // list of imported packages
133 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
134 recvTParamMap map[*ast.Ident]*TypeParam // maps blank receiver type parameters to their type
135 mono monoGraph // graph for detecting non-monomorphizable instantiation loops
137 firstErr error // first error encountered
138 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
139 untyped map[ast.Expr]exprInfo // map of expressions without final type
140 delayed []action // stack of delayed action segments; segments are processed in FIFO order
141 objPath []Object // path of object dependencies during type inference (for cycle reporting)
142 defTypes []*Named // defined types created during type checking, for final validation.
144 // environment within which the current object is type-checked (valid only
145 // for the duration of type-checking a specific object)
149 indent int // indentation for tracing
152 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
153 func (check *Checker) addDeclDep(to Object) {
156 return // not in a package-level init expression
158 if _, found := check.objMap[to]; !found {
159 return // to is not a package-level object
164 func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
167 m = make(map[ast.Expr]exprInfo)
170 m[e] = exprInfo{lhs, mode, typ, val}
173 // later pushes f on to the stack of actions that will be processed later;
174 // either at the end of the current statement, or in case of a local constant
175 // or variable declaration, before the constant or variable is in scope
176 // (so that f still sees the scope before any new declarations).
177 // later returns the pushed action so one can provide a description
178 // via action.describef for debugging, if desired.
179 func (check *Checker) later(f func()) *action {
180 i := len(check.delayed)
181 check.delayed = append(check.delayed, action{f: f})
182 return &check.delayed[i]
185 // push pushes obj onto the object path and returns its index in the path.
186 func (check *Checker) push(obj Object) int {
187 check.objPath = append(check.objPath, obj)
188 return len(check.objPath) - 1
191 // pop pops and returns the topmost object from the object path.
192 func (check *Checker) pop() Object {
193 i := len(check.objPath) - 1
194 obj := check.objPath[i]
195 check.objPath[i] = nil
196 check.objPath = check.objPath[:i]
200 // NewChecker returns a new Checker instance for a given package.
201 // Package files may be added incrementally via checker.Files.
202 func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {
203 // make sure we have a configuration
208 // make sure we have an info struct
213 version, err := parseGoVersion(conf.GoVersion)
215 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
225 objMap: make(map[Object]*declInfo),
226 impMap: make(map[importKey]*Package),
230 // initFiles initializes the files-specific portion of checker.
231 // The provided files must all belong to the same package.
232 func (check *Checker) initFiles(files []*ast.File) {
233 // start with a clean slate (check.Files may be called multiple times)
236 check.dotImportMap = nil
243 // determine package name and collect valid files
245 for _, file := range files {
246 switch name := file.Name.Name; pkg.name {
251 check.errorf(file.Name, _BlankPkgName, "invalid package name _")
256 check.files = append(check.files, file)
259 check.errorf(atPos(file.Package), _MismatchedPkgName, "package %s; expected %s", name, pkg.name)
265 // A bailout panic is used for early termination.
266 type bailout struct{}
268 func (check *Checker) handleBailout(err *error) {
269 switch p := recover().(type) {
271 // normal return or early exit
272 *err = check.firstErr
279 // Files checks the provided files as part of the checker's package.
280 func (check *Checker) Files(files []*ast.File) error { return check.checkFiles(files) }
282 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
284 func (check *Checker) checkFiles(files []*ast.File) (err error) {
285 if check.conf.FakeImportC && check.conf.go115UsesCgo {
289 defer check.handleBailout(&err)
291 check.initFiles(files)
293 check.collectObjects()
295 check.packageObjects()
297 check.processDelayed(0) // incl. all functions
299 check.expandDefTypes()
303 if !check.conf.DisableUnusedImportCheck {
304 check.unusedImports()
307 check.recordUntyped()
309 if check.firstErr == nil {
310 // TODO(mdempsky): Ensure monomorph is safe when errors exist.
314 check.pkg.complete = true
316 // no longer needed - release memory
318 check.dotImportMap = nil
319 check.pkgPathMap = nil
320 check.seenPkgMap = nil
321 check.recvTParamMap = nil
325 // TODO(rFindley) 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 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) expandDefTypes() {
351 // Ensure that every defined type created in the course of type-checking has
352 // either non-*Named underlying, or is unresolved.
354 // This guarantees that we don't leak any types whose underlying is *Named,
355 // because any unresolved instances will lazily compute their underlying by
356 // substituting in the underlying of their origin. The origin must have
357 // either been imported or type-checked and expanded here, and in either case
358 // its underlying will be fully expanded.
359 for i := 0; i < len(check.defTypes); i++ {
360 n := check.defTypes[i]
361 switch n.underlying.(type) {
363 if n.resolver == nil {
364 panic("nil underlying")
367 n.under() // n.under may add entries to check.defTypes
373 func (check *Checker) record(x *operand) {
374 // convert x into a user-friendly set of values
375 // TODO(gri) this code can be simplified
377 var val constant.Value
389 assert(x.expr != nil && typ != nil)
392 // delay type and value recording until we know the type
393 // or until the end of type checking
394 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
396 check.recordTypeAndValue(x.expr, x.mode, typ, val)
400 func (check *Checker) recordUntyped() {
401 if !debug && check.Types == nil {
402 return // nothing to do
405 for x, info := range check.untyped {
406 if debug && isTyped(info.typ) {
407 check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ)
410 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
414 func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
420 if mode == constant_ {
422 // We check allBasic(typ, IsConstType) here as constant expressions may be
423 // recorded as type parameters.
424 assert(typ == Typ[Invalid] || allBasic(typ, IsConstType))
426 if m := check.Types; m != nil {
427 m[x] = TypeAndValue{mode, typ, val}
431 func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
432 // f must be a (possibly parenthesized, possibly qualified)
433 // identifier denoting a built-in (including unsafe's non-constant
434 // functions Add and Slice): record the signature for f and possible
437 check.recordTypeAndValue(f, builtin, sig, nil)
438 switch p := f.(type) {
439 case *ast.Ident, *ast.SelectorExpr:
449 func (check *Checker) recordCommaOkTypes(x ast.Expr, a [2]Type) {
451 if a[0] == nil || a[1] == nil {
454 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
455 if m := check.Types; m != nil {
458 assert(tv.Type != nil) // should have been recorded already
461 NewVar(pos, check.pkg, "", a[0]),
462 NewVar(pos, check.pkg, "", a[1]),
465 // if x is a parenthesized expression (p.X), update p.X
466 p, _ := x.(*ast.ParenExpr)
475 // recordInstance records instantiation information into check.Info, if the
476 // Instances map is non-nil. The given expr must be an ident, selector, or
477 // index (list) expr with ident or selector operand.
479 // TODO(rfindley): the expr parameter is fragile. See if we can access the
480 // instantiated identifier in some other way.
481 func (check *Checker) recordInstance(expr ast.Expr, targs []Type, typ Type) {
482 ident := instantiatedIdent(expr)
485 if m := check.Instances; m != nil {
486 m[ident] = Instance{NewTypeList(targs), typ}
490 func instantiatedIdent(expr ast.Expr) *ast.Ident {
491 var selOrIdent ast.Expr
492 switch e := expr.(type) {
495 case *ast.IndexListExpr:
497 case *ast.SelectorExpr, *ast.Ident:
500 switch x := selOrIdent.(type) {
503 case *ast.SelectorExpr:
506 panic("instantiated ident not found")
509 func (check *Checker) recordDef(id *ast.Ident, obj Object) {
511 if m := check.Defs; m != nil {
516 func (check *Checker) recordUse(id *ast.Ident, obj Object) {
519 if m := check.Uses; m != nil {
524 func (check *Checker) recordImplicit(node ast.Node, obj Object) {
527 if m := check.Implicits; m != nil {
532 func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
533 assert(obj != nil && (recv == nil || len(index) > 0))
534 check.recordUse(x.Sel, obj)
535 if m := check.Selections; m != nil {
536 m[x] = &Selection{kind, recv, obj, index, indirect}
540 func (check *Checker) recordScope(node ast.Node, scope *Scope) {
543 if m := check.Scopes; m != nil {