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 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info
87 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package
88 posMap map[*Interface][]syntax.Pos // maps interface types to lists of embedded interface positions
89 typMap map[string]*Named // maps an instantiated named type hash to a *Named type
90 pkgCnt map[string]int // counts number of imported packages with a given name (for better error messages)
92 // information collected during type-checking of a set of package files
93 // (initialized by Files, valid only for the duration of check.Files;
94 // maps and lists are allocated on demand)
95 files []*syntax.File // list of package files
96 imports []*PkgName // list of imported packages
97 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through
99 firstErr error // first error encountered
100 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods
101 untyped map[syntax.Expr]exprInfo // map of expressions without final type
102 delayed []func() // stack of delayed action segments; segments are processed in FIFO order
103 objPath []Object // path of object dependencies during type inference (for cycle reporting)
105 // context within which the current object is type-checked
106 // (valid only for the duration of type-checking a specific object)
110 indent int // indentation for tracing
113 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists
114 func (check *Checker) addDeclDep(to Object) {
117 return // not in a package-level init expression
119 if _, found := check.objMap[to]; !found {
120 return // to is not a package-level object
125 func (check *Checker) rememberUntyped(e syntax.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) {
128 m = make(map[syntax.Expr]exprInfo)
131 m[e] = exprInfo{lhs, mode, typ, val}
134 // later pushes f on to the stack of actions that will be processed later;
135 // either at the end of the current statement, or in case of a local constant
136 // or variable declaration, before the constant or variable is in scope
137 // (so that f still sees the scope before any new declarations).
138 func (check *Checker) later(f func()) {
139 check.delayed = append(check.delayed, f)
142 // push pushes obj onto the object path and returns its index in the path.
143 func (check *Checker) push(obj Object) int {
144 check.objPath = append(check.objPath, obj)
145 return len(check.objPath) - 1
148 // pop pops and returns the topmost object from the object path.
149 func (check *Checker) pop() Object {
150 i := len(check.objPath) - 1
151 obj := check.objPath[i]
152 check.objPath[i] = nil
153 check.objPath = check.objPath[:i]
157 // NewChecker returns a new Checker instance for a given package.
158 // Package files may be added incrementally via checker.Files.
159 func NewChecker(conf *Config, pkg *Package, info *Info) *Checker {
160 // make sure we have a configuration
165 // make sure we have an info struct
170 version, err := parseGoVersion(conf.GoVersion)
172 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err))
180 objMap: make(map[Object]*declInfo),
181 impMap: make(map[importKey]*Package),
182 posMap: make(map[*Interface][]syntax.Pos),
183 typMap: make(map[string]*Named),
184 pkgCnt: make(map[string]int),
188 // initFiles initializes the files-specific portion of checker.
189 // The provided files must all belong to the same package.
190 func (check *Checker) initFiles(files []*syntax.File) {
191 // start with a clean slate (check.Files may be called multiple times)
194 check.dotImportMap = nil
201 // determine package name and collect valid files
203 for _, file := range files {
204 switch name := file.PkgName.Value; pkg.name {
209 check.error(file.PkgName, "invalid package name _")
214 check.files = append(check.files, file)
217 check.errorf(file, "package %s; expected %s", name, pkg.name)
223 // A bailout panic is used for early termination.
224 type bailout struct{}
226 func (check *Checker) handleBailout(err *error) {
227 switch p := recover().(type) {
229 // normal return or early exit
230 *err = check.firstErr
237 // Files checks the provided files as part of the checker's package.
238 func (check *Checker) Files(files []*syntax.File) error { return check.checkFiles(files) }
240 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together")
242 func (check *Checker) checkFiles(files []*syntax.File) (err error) {
243 if check.conf.FakeImportC && check.conf.go115UsesCgo {
247 defer check.handleBailout(&err)
249 print := func(msg string) {
250 if check.conf.Trace {
255 print("== initFiles ==")
256 check.initFiles(files)
258 print("== collectObjects ==")
259 check.collectObjects()
261 print("== packageObjects ==")
262 check.packageObjects()
264 print("== processDelayed ==")
265 check.processDelayed(0) // incl. all functions
267 print("== initOrder ==")
270 if !check.conf.DisableUnusedImportCheck {
271 print("== unusedImports ==")
272 check.unusedImports()
274 // no longer needed - release memory
276 check.dotImportMap = nil
278 print("== recordUntyped ==")
279 check.recordUntyped()
281 if check.Info != nil {
282 print("== sanitizeInfo ==")
283 sanitizeInfo(check.Info)
286 check.pkg.complete = true
288 // TODO(gri) There's more memory we should release at this point.
293 // processDelayed processes all delayed actions pushed after top.
294 func (check *Checker) processDelayed(top int) {
295 // If each delayed action pushes a new action, the
296 // stack will continue to grow during this loop.
297 // However, it is only processing functions (which
298 // are processed in a delayed fashion) that may
299 // add more actions (such as nested functions), so
300 // this is a sufficiently bounded process.
301 for i := top; i < len(check.delayed); i++ {
302 check.delayed[i]() // may append to check.delayed
304 assert(top <= len(check.delayed)) // stack must not have shrunk
305 check.delayed = check.delayed[:top]
308 func (check *Checker) record(x *operand) {
309 // convert x into a user-friendly set of values
310 // TODO(gri) this code can be simplified
312 var val constant.Value
324 assert(x.expr != nil && typ != nil)
327 // delay type and value recording until we know the type
328 // or until the end of type checking
329 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val)
331 check.recordTypeAndValue(x.expr, x.mode, typ, val)
335 func (check *Checker) recordUntyped() {
336 if !debug && check.Types == nil {
337 return // nothing to do
340 for x, info := range check.untyped {
341 if debug && isTyped(info.typ) {
342 check.dump("%v: %s (type %s) is typed", posFor(x), x, info.typ)
345 check.recordTypeAndValue(x, info.mode, info.typ, info.val)
349 func (check *Checker) recordTypeAndValue(x syntax.Expr, mode operandMode, typ Type, val constant.Value) {
355 if mode == constant_ {
357 // We check is(typ, IsConstType) here as constant expressions may be
358 // recorded as type parameters.
359 assert(typ == Typ[Invalid] || is(typ, IsConstType))
361 if m := check.Types; m != nil {
362 m[x] = TypeAndValue{mode, typ, val}
366 func (check *Checker) recordBuiltinType(f syntax.Expr, sig *Signature) {
367 // f must be a (possibly parenthesized) identifier denoting a built-in
368 // (built-ins in package unsafe always produce a constant result and
369 // we don't record their signatures, so we don't see qualified idents
370 // here): record the signature for f and possible children.
372 check.recordTypeAndValue(f, builtin, sig, nil)
373 switch p := f.(type) {
376 case *syntax.ParenExpr:
384 func (check *Checker) recordCommaOkTypes(x syntax.Expr, a [2]Type) {
386 if a[0] == nil || a[1] == nil {
389 assert(isTyped(a[0]) && isTyped(a[1]) && (isBoolean(a[1]) || a[1] == universeError))
390 if m := check.Types; m != nil {
393 assert(tv.Type != nil) // should have been recorded already
396 NewVar(pos, check.pkg, "", a[0]),
397 NewVar(pos, check.pkg, "", a[1]),
400 // if x is a parenthesized expression (p.X), update p.X
401 p, _ := x.(*syntax.ParenExpr)
410 func (check *Checker) recordInferred(call syntax.Expr, targs []Type, sig *Signature) {
413 if m := check.Inferred; m != nil {
414 m[call] = Inferred{targs, sig}
418 func (check *Checker) recordDef(id *syntax.Name, obj Object) {
420 if m := check.Defs; m != nil {
425 func (check *Checker) recordUse(id *syntax.Name, obj Object) {
428 if m := check.Uses; m != nil {
433 func (check *Checker) recordImplicit(node syntax.Node, obj Object) {
436 if m := check.Implicits; m != nil {
441 func (check *Checker) recordSelection(x *syntax.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) {
442 assert(obj != nil && (recv == nil || len(index) > 0))
443 check.recordUse(x.Sel, obj)
444 if m := check.Selections; m != nil {
445 m[x] = &Selection{kind, recv, obj, index, indirect}
449 func (check *Checker) recordScope(node syntax.Node, scope *Scope) {
452 if m := check.Scopes; m != nil {