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
22 // TODO(rfindley): add compiler error message handling from types2, guarded
23 // behind this flag, so that we can keep the code in sync.
24 compilerErrorMessages = false // match compiler error messages
27 // If forceStrict is set, the type-checker enforces additional
28 // rules not specified by the Go 1 spec, but which will
29 // catch guaranteed run-time errors if the respective
30 // code is executed. In other words, programs passing in
31 // strict mode are Go 1 compliant, but not all Go 1 programs
32 // will pass in strict mode. The additional rules are:
34 // - A type assertion x.(T) where T is an interface type
35 // is invalid if any (statically known) method that exists
36 // for both x and T have different signatures.
38 const forceStrict = false
40 // exprInfo stores information about an untyped expression.
41 type exprInfo struct {
42 isLhs bool // expression is lhs operand of a shift with delayed type-check
45 val constant.Value // constant value; or nil (if not a constant)
48 // An environment represents the environment within which an object is
50 type environment struct {
51 decl *declInfo // package-level declaration whose init expression/function body is checked
52 scope *Scope // top-most scope for lookups
53 pos token.Pos // if valid, identifiers are looked up as if at position pos (used by Eval)
54 iota constant.Value // value of iota in a constant declaration; nil otherwise
55 errpos positioner // if set, identifier position of a constant with inherited initializer
56 inTParamList bool // set if inside a type parameter list
57 sig *Signature // function signature if inside a function; nil otherwise
58 isPanic map[*ast.CallExpr]bool // set of panic call expressions (used for termination check)
59 hasLabel bool // set if a function makes use of labels (only ~1% of functions); unused outside functions
60 hasCallOrRecv bool // set if an expression contains a function call or channel receive operation
63 // lookup looks up name in the current environment and returns the matching object, or nil.
64 func (env *environment) lookup(name string) Object {
65 _, obj := env.scope.LookupParent(name, env.pos)
69 // An importKey identifies an imported package by import path and source directory
70 // (directory containing the file containing the import). In practice, the directory
71 // may always be the same, or may not matter. Given an (import path, directory), an
72 // importer must always return the same package (but given two different import paths,
73 // an importer may still return the same package by mapping them to the same package
75 type importKey struct {
79 // A dotImportKey describes a dot-imported object in the given scope.
80 type dotImportKey struct {
85 // An action describes a (delayed) action.
87 f func() // action to be executed
88 desc *actionDesc // action description; may be nil, requires debug to be set
91 // If debug is set, describef sets a printf-formatted description for action a.
92 // Otherwise, it is a no-op.
93 func (a *action) describef(pos positioner, format string, args ...any) {
95 a.desc = &actionDesc{pos, format, args}
99 // An actionDesc provides information on an action.
100 // For debugging only.
101 type actionDesc struct {
107 // A Checker maintains the state of the type checker.
108 // It must be created with NewChecker.
109 type Checker struct {
110 // package information
111 // (initialized by NewChecker, valid for the life-time of checker)
113 ctxt *Context // context for de-duplicating instances
117 version version // accepted language version
118 nextID uint64 // unique Id for type parameters (first valid Id is 1)
119 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
120 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
122 // pkgPathMap maps package names to the set of distinct import paths we've
123 // seen for that name, anywhere in the import graph. It is used for
124 // disambiguating package names in error messages.
126 // pkgPathMap is allocated lazily, so that we don't pay the price of building
127 // it on the happy path. seenPkgMap tracks the packages that we've already
129 pkgPathMap map[string]map[string]bool
130 seenPkgMap map[*Package]bool
132 // information collected during type-checking of a set of package files
133 // (initialized by Files, valid only for the duration of check.Files;
134 // maps and lists are allocated on demand)
135 files []*ast.File // package files
136 imports []*PkgName // list of imported packages
137 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
138 recvTParamMap map[*ast.Ident]*TypeParam // maps blank receiver type parameters to their type
139 unionTypeSets map[*Union]*_TypeSet // computed type sets for union types
140 mono monoGraph // graph for detecting non-monomorphizable instantiation loops
142 firstErr error // first error encountered
143 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
144 untyped map[ast.Expr]exprInfo // map of expressions without final type
145 delayed []action // stack of delayed action segments; segments are processed in FIFO order
146 objPath []Object // path of object dependencies during type inference (for cycle reporting)
147 defTypes []*Named // defined types created during type checking, for final validation.
149 // environment within which the current object is type-checked (valid only
150 // for the duration of type-checking a specific object)
154 indent int // indentation for tracing
157 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
158 func (check *Checker) addDeclDep(to Object) {
161 return // not in a package-level init expression
163 if _, found := check.objMap[to]; !found {
164 return // to is not a package-level object
169 func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
172 m = make(map[ast.Expr]exprInfo)
175 m[e] = exprInfo{lhs, mode, typ, val}
178 // later pushes f on to the stack of actions that will be processed later;
179 // either at the end of the current statement, or in case of a local constant
180 // or variable declaration, before the constant or variable is in scope
181 // (so that f still sees the scope before any new declarations).
182 // later returns the pushed action so one can provide a description
183 // via action.describef for debugging, if desired.
184 func (check *Checker) later(f func()) *action {
185 i := len(check.delayed)
186 check.delayed = append(check.delayed, action{f: f})
187 return &check.delayed[i]
190 // push pushes obj onto the object path and returns its index in the path.
191 func (check *Checker) push(obj Object) int {
192 check.objPath = append(check.objPath, obj)
193 return len(check.objPath) - 1
196 // pop pops and returns the topmost object from the object path.
197 func (check *Checker) pop() Object {
198 i := len(check.objPath) - 1
199 obj := check.objPath[i]
200 check.objPath[i] = nil
201 check.objPath = check.objPath[:i]
205 // NewChecker returns a new Checker instance for a given package.
206 // Package files may be added incrementally via checker.Files.
207 func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker {
208 // make sure we have a configuration
213 // make sure we have an info struct
218 version, err := parseGoVersion(conf.GoVersion)
220 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
230 objMap: make(map[Object]*declInfo),
231 impMap: make(map[importKey]*Package),
235 // initFiles initializes the files-specific portion of checker.
236 // The provided files must all belong to the same package.
237 func (check *Checker) initFiles(files []*ast.File) {
238 // start with a clean slate (check.Files may be called multiple times)
241 check.dotImportMap = nil
248 // determine package name and collect valid files
250 for _, file := range files {
251 switch name := file.Name.Name; pkg.name {
256 check.errorf(file.Name, _BlankPkgName, "invalid package name _")
261 check.files = append(check.files, file)
264 check.errorf(atPos(file.Package), _MismatchedPkgName, "package %s; expected %s", name, pkg.name)
270 // A bailout panic is used for early termination.
271 type bailout struct{}
273 func (check *Checker) handleBailout(err *error) {
274 switch p := recover().(type) {
276 // normal return or early exit
277 *err = check.firstErr
284 // Files checks the provided files as part of the checker's package.
285 func (check *Checker) Files(files []*ast.File) error { return check.checkFiles(files) }
287 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
289 func (check *Checker) checkFiles(files []*ast.File) (err error) {
290 if check.conf.FakeImportC && check.conf.go115UsesCgo {
294 defer check.handleBailout(&err)
296 check.initFiles(files)
298 check.collectObjects()
300 check.packageObjects()
302 check.processDelayed(0) // incl. all functions
304 check.expandDefTypes()
308 if !check.conf.DisableUnusedImportCheck {
309 check.unusedImports()
312 check.recordUntyped()
314 if check.firstErr == nil {
315 // TODO(mdempsky): Ensure monomorph is safe when errors exist.
319 check.pkg.complete = true
321 // no longer needed - release memory
323 check.dotImportMap = nil
324 check.pkgPathMap = nil
325 check.seenPkgMap = nil
326 check.recvTParamMap = nil
327 check.unionTypeSets = nil
331 // TODO(rFindley) There's more memory we should release at this point.
336 // processDelayed processes all delayed actions pushed after top.
337 func (check *Checker) processDelayed(top int) {
338 // If each delayed action pushes a new action, the
339 // stack will continue to grow during this loop.
340 // However, it is only processing functions (which
341 // are processed in a delayed fashion) that may
342 // add more actions (such as nested functions), so
343 // this is a sufficiently bounded process.
344 for i := top; i < len(check.delayed); i++ {
345 a := &check.delayed[i]
346 if trace && a.desc != nil {
348 check.trace(a.desc.pos.Pos(), "-- "+a.desc.format, a.desc.args...)
350 a.f() // may append to check.delayed
352 assert(top <= len(check.delayed)) // stack must not have shrunk
353 check.delayed = check.delayed[:top]
356 func (check *Checker) expandDefTypes() {
357 // Ensure that every defined type created in the course of type-checking has
358 // either non-*Named underlying, or is unresolved.
360 // This guarantees that we don't leak any types whose underlying is *Named,
361 // because any unresolved instances will lazily compute their underlying by
362 // substituting in the underlying of their origin. The origin must have
363 // either been imported or type-checked and expanded here, and in either case
364 // its underlying will be fully expanded.
365 for i := 0; i < len(check.defTypes); i++ {
366 n := check.defTypes[i]
367 switch n.underlying.(type) {
369 if n.resolver == nil {
370 panic("nil underlying")
373 n.under() // n.under may add entries to check.defTypes
379 func (check *Checker) record(x *operand) {
380 // convert x into a user-friendly set of values
381 // TODO(gri) this code can be simplified
383 var val constant.Value
395 assert(x.expr != nil && typ != nil)
398 // delay type and value recording until we know the type
399 // or until the end of type checking
400 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
402 check.recordTypeAndValue(x.expr, x.mode, typ, val)
406 func (check *Checker) recordUntyped() {
407 if !debug && check.Types == nil {
408 return // nothing to do
411 for x, info := range check.untyped {
412 if debug && isTyped(info.typ) {
413 check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ)
416 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
420 func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) {
426 if mode == constant_ {
428 // We check allBasic(typ, IsConstType) here as constant expressions may be
429 // recorded as type parameters.
430 assert(typ == Typ[Invalid] || allBasic(typ, IsConstType))
432 if m := check.Types; m != nil {
433 m[x] = TypeAndValue{mode, typ, val}
437 func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) {
438 // f must be a (possibly parenthesized, possibly qualified)
439 // identifier denoting a built-in (including unsafe's non-constant
440 // functions Add and Slice): record the signature for f and possible
443 check.recordTypeAndValue(f, builtin, sig, nil)
444 switch p := f.(type) {
445 case *ast.Ident, *ast.SelectorExpr:
455 func (check *Checker) recordCommaOkTypes(x ast.Expr, a [2]Type) {
457 if a[0] == nil || a[1] == nil {
460 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
461 if m := check.Types; m != nil {
464 assert(tv.Type != nil) // should have been recorded already
467 NewVar(pos, check.pkg, "", a[0]),
468 NewVar(pos, check.pkg, "", a[1]),
471 // if x is a parenthesized expression (p.X), update p.X
472 p, _ := x.(*ast.ParenExpr)
481 // recordInstance records instantiation information into check.Info, if the
482 // Instances map is non-nil. The given expr must be an ident, selector, or
483 // index (list) expr with ident or selector operand.
485 // TODO(rfindley): the expr parameter is fragile. See if we can access the
486 // instantiated identifier in some other way.
487 func (check *Checker) recordInstance(expr ast.Expr, targs []Type, typ Type) {
488 ident := instantiatedIdent(expr)
491 if m := check.Instances; m != nil {
492 m[ident] = Instance{newTypeList(targs), typ}
496 func instantiatedIdent(expr ast.Expr) *ast.Ident {
497 var selOrIdent ast.Expr
498 switch e := expr.(type) {
501 case *ast.IndexListExpr:
503 case *ast.SelectorExpr, *ast.Ident:
506 switch x := selOrIdent.(type) {
509 case *ast.SelectorExpr:
512 panic("instantiated ident not found")
515 func (check *Checker) recordDef(id *ast.Ident, obj Object) {
517 if m := check.Defs; m != nil {
522 func (check *Checker) recordUse(id *ast.Ident, obj Object) {
525 if m := check.Uses; m != nil {
530 func (check *Checker) recordImplicit(node ast.Node, obj Object) {
533 if m := check.Implicits; m != nil {
538 func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
539 assert(obj != nil && (recv == nil || len(index) > 0))
540 check.recordUse(x.Sel, obj)
541 if m := check.Selections; m != nil {
542 m[x] = &Selection{kind, recv, obj, index, indirect}
546 func (check *Checker) recordScope(node ast.Node, scope *Scope) {
549 if m := check.Scopes; m != nil {