github.com/lovishpuri/go-40569/src@v0.0.0-20230519171745-f8623e7c56cf/go/types/check.go (about) 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. 4 5 // This file implements the Check function, which drives type-checking. 6 7 package types 8 9 import ( 10 "errors" 11 "fmt" 12 "go/ast" 13 "go/constant" 14 "go/token" 15 . "internal/types/errors" 16 ) 17 18 // nopos indicates an unknown position 19 var nopos token.Pos 20 21 // debugging/development support 22 const debug = false // leave on during development 23 24 // exprInfo stores information about an untyped expression. 25 type exprInfo struct { 26 isLhs bool // expression is lhs operand of a shift with delayed type-check 27 mode operandMode 28 typ *Basic 29 val constant.Value // constant value; or nil (if not a constant) 30 } 31 32 // An environment represents the environment within which an object is 33 // type-checked. 34 type environment struct { 35 decl *declInfo // package-level declaration whose init expression/function body is checked 36 scope *Scope // top-most scope for lookups 37 pos token.Pos // if valid, identifiers are looked up as if at position pos (used by Eval) 38 iota constant.Value // value of iota in a constant declaration; nil otherwise 39 errpos positioner // if set, identifier position of a constant with inherited initializer 40 inTParamList bool // set if inside a type parameter list 41 sig *Signature // function signature if inside a function; nil otherwise 42 isPanic map[*ast.CallExpr]bool // set of panic call expressions (used for termination check) 43 hasLabel bool // set if a function makes use of labels (only ~1% of functions); unused outside functions 44 hasCallOrRecv bool // set if an expression contains a function call or channel receive operation 45 } 46 47 // lookup looks up name in the current environment and returns the matching object, or nil. 48 func (env *environment) lookup(name string) Object { 49 _, obj := env.scope.LookupParent(name, env.pos) 50 return obj 51 } 52 53 // An importKey identifies an imported package by import path and source directory 54 // (directory containing the file containing the import). In practice, the directory 55 // may always be the same, or may not matter. Given an (import path, directory), an 56 // importer must always return the same package (but given two different import paths, 57 // an importer may still return the same package by mapping them to the same package 58 // paths). 59 type importKey struct { 60 path, dir string 61 } 62 63 // A dotImportKey describes a dot-imported object in the given scope. 64 type dotImportKey struct { 65 scope *Scope 66 name string 67 } 68 69 // An action describes a (delayed) action. 70 type action struct { 71 f func() // action to be executed 72 desc *actionDesc // action description; may be nil, requires debug to be set 73 } 74 75 // If debug is set, describef sets a printf-formatted description for action a. 76 // Otherwise, it is a no-op. 77 func (a *action) describef(pos positioner, format string, args ...any) { 78 if debug { 79 a.desc = &actionDesc{pos, format, args} 80 } 81 } 82 83 // An actionDesc provides information on an action. 84 // For debugging only. 85 type actionDesc struct { 86 pos positioner 87 format string 88 args []any 89 } 90 91 // A Checker maintains the state of the type checker. 92 // It must be created with NewChecker. 93 type Checker struct { 94 // package information 95 // (initialized by NewChecker, valid for the life-time of checker) 96 conf *Config 97 ctxt *Context // context for de-duplicating instances 98 fset *token.FileSet 99 pkg *Package 100 *Info 101 version version // accepted language version 102 nextID uint64 // unique Id for type parameters (first valid Id is 1) 103 objMap map[Object]*declInfo // maps package-level objects and (non-interface) methods to declaration info 104 impMap map[importKey]*Package // maps (import path, source directory) to (complete or fake) package 105 valids instanceLookup // valid *Named (incl. instantiated) types per the validType check 106 107 // pkgPathMap maps package names to the set of distinct import paths we've 108 // seen for that name, anywhere in the import graph. It is used for 109 // disambiguating package names in error messages. 110 // 111 // pkgPathMap is allocated lazily, so that we don't pay the price of building 112 // it on the happy path. seenPkgMap tracks the packages that we've already 113 // walked. 114 pkgPathMap map[string]map[string]bool 115 seenPkgMap map[*Package]bool 116 117 // information collected during type-checking of a set of package files 118 // (initialized by Files, valid only for the duration of check.Files; 119 // maps and lists are allocated on demand) 120 files []*ast.File // package files 121 posVers map[*token.File]version // Pos -> Go version mapping 122 imports []*PkgName // list of imported packages 123 dotImportMap map[dotImportKey]*PkgName // maps dot-imported objects to the package they were dot-imported through 124 recvTParamMap map[*ast.Ident]*TypeParam // maps blank receiver type parameters to their type 125 brokenAliases map[*TypeName]bool // set of aliases with broken (not yet determined) types 126 unionTypeSets map[*Union]*_TypeSet // computed type sets for union types 127 mono monoGraph // graph for detecting non-monomorphizable instantiation loops 128 129 firstErr error // first error encountered 130 methods map[*TypeName][]*Func // maps package scope type names to associated non-blank (non-interface) methods 131 untyped map[ast.Expr]exprInfo // map of expressions without final type 132 delayed []action // stack of delayed action segments; segments are processed in FIFO order 133 objPath []Object // path of object dependencies during type inference (for cycle reporting) 134 cleaners []cleaner // list of types that may need a final cleanup at the end of type-checking 135 136 // environment within which the current object is type-checked (valid only 137 // for the duration of type-checking a specific object) 138 environment 139 140 // debugging 141 indent int // indentation for tracing 142 } 143 144 // addDeclDep adds the dependency edge (check.decl -> to) if check.decl exists 145 func (check *Checker) addDeclDep(to Object) { 146 from := check.decl 147 if from == nil { 148 return // not in a package-level init expression 149 } 150 if _, found := check.objMap[to]; !found { 151 return // to is not a package-level object 152 } 153 from.addDep(to) 154 } 155 156 // brokenAlias records that alias doesn't have a determined type yet. 157 // It also sets alias.typ to Typ[Invalid]. 158 func (check *Checker) brokenAlias(alias *TypeName) { 159 if check.brokenAliases == nil { 160 check.brokenAliases = make(map[*TypeName]bool) 161 } 162 check.brokenAliases[alias] = true 163 alias.typ = Typ[Invalid] 164 } 165 166 // validAlias records that alias has the valid type typ (possibly Typ[Invalid]). 167 func (check *Checker) validAlias(alias *TypeName, typ Type) { 168 delete(check.brokenAliases, alias) 169 alias.typ = typ 170 } 171 172 // isBrokenAlias reports whether alias doesn't have a determined type yet. 173 func (check *Checker) isBrokenAlias(alias *TypeName) bool { 174 return alias.typ == Typ[Invalid] && check.brokenAliases[alias] 175 } 176 177 func (check *Checker) rememberUntyped(e ast.Expr, lhs bool, mode operandMode, typ *Basic, val constant.Value) { 178 m := check.untyped 179 if m == nil { 180 m = make(map[ast.Expr]exprInfo) 181 check.untyped = m 182 } 183 m[e] = exprInfo{lhs, mode, typ, val} 184 } 185 186 // later pushes f on to the stack of actions that will be processed later; 187 // either at the end of the current statement, or in case of a local constant 188 // or variable declaration, before the constant or variable is in scope 189 // (so that f still sees the scope before any new declarations). 190 // later returns the pushed action so one can provide a description 191 // via action.describef for debugging, if desired. 192 func (check *Checker) later(f func()) *action { 193 i := len(check.delayed) 194 check.delayed = append(check.delayed, action{f: f}) 195 return &check.delayed[i] 196 } 197 198 // push pushes obj onto the object path and returns its index in the path. 199 func (check *Checker) push(obj Object) int { 200 check.objPath = append(check.objPath, obj) 201 return len(check.objPath) - 1 202 } 203 204 // pop pops and returns the topmost object from the object path. 205 func (check *Checker) pop() Object { 206 i := len(check.objPath) - 1 207 obj := check.objPath[i] 208 check.objPath[i] = nil 209 check.objPath = check.objPath[:i] 210 return obj 211 } 212 213 type cleaner interface { 214 cleanup() 215 } 216 217 // needsCleanup records objects/types that implement the cleanup method 218 // which will be called at the end of type-checking. 219 func (check *Checker) needsCleanup(c cleaner) { 220 check.cleaners = append(check.cleaners, c) 221 } 222 223 // NewChecker returns a new Checker instance for a given package. 224 // Package files may be added incrementally via checker.Files. 225 func NewChecker(conf *Config, fset *token.FileSet, pkg *Package, info *Info) *Checker { 226 // make sure we have a configuration 227 if conf == nil { 228 conf = new(Config) 229 } 230 231 // make sure we have an info struct 232 if info == nil { 233 info = new(Info) 234 } 235 236 version, err := parseGoVersion(conf.GoVersion) 237 if err != nil { 238 panic(fmt.Sprintf("invalid Go version %q (%v)", conf.GoVersion, err)) 239 } 240 241 return &Checker{ 242 conf: conf, 243 ctxt: conf.Context, 244 fset: fset, 245 pkg: pkg, 246 Info: info, 247 version: version, 248 objMap: make(map[Object]*declInfo), 249 impMap: make(map[importKey]*Package), 250 } 251 } 252 253 // initFiles initializes the files-specific portion of checker. 254 // The provided files must all belong to the same package. 255 func (check *Checker) initFiles(files []*ast.File) { 256 // start with a clean slate (check.Files may be called multiple times) 257 check.files = nil 258 check.imports = nil 259 check.dotImportMap = nil 260 261 check.firstErr = nil 262 check.methods = nil 263 check.untyped = nil 264 check.delayed = nil 265 check.objPath = nil 266 check.cleaners = nil 267 268 // determine package name and collect valid files 269 pkg := check.pkg 270 for _, file := range files { 271 switch name := file.Name.Name; pkg.name { 272 case "": 273 if name != "_" { 274 pkg.name = name 275 } else { 276 check.error(file.Name, BlankPkgName, "invalid package name _") 277 } 278 fallthrough 279 280 case name: 281 check.files = append(check.files, file) 282 283 default: 284 check.errorf(atPos(file.Package), MismatchedPkgName, "package %s; expected %s", name, pkg.name) 285 // ignore this file 286 } 287 } 288 289 for _, file := range check.files { 290 v, _ := parseGoVersion(file.GoVersion) 291 if v.major > 0 { 292 if v.equal(check.version) { 293 continue 294 } 295 // Go 1.21 introduced the feature of setting the go.mod 296 // go line to an early version of Go and allowing //go:build lines 297 // to “upgrade” the Go version in a given file. 298 // We can do that backwards compatibly. 299 // Go 1.21 also introduced the feature of allowing //go:build lines 300 // to “downgrade” the Go version in a given file. 301 // That can't be done compatibly in general, since before the 302 // build lines were ignored and code got the module's Go version. 303 // To work around this, downgrades are only allowed when the 304 // module's Go version is Go 1.21 or later. 305 // If there is no check.version, then we don't really know what Go version to apply. 306 // Legacy tools may do this, and they historically have accepted everything. 307 // Preserve that behavior by ignoring //go:build constraints entirely in that case. 308 if (v.before(check.version) && check.version.before(version{1, 21})) || check.version.equal(version{0, 0}) { 309 continue 310 } 311 if check.posVers == nil { 312 check.posVers = make(map[*token.File]version) 313 } 314 check.posVers[check.fset.File(file.FileStart)] = v 315 } 316 } 317 } 318 319 // A posVers records that the file starting at pos declares the Go version vers. 320 type posVers struct { 321 pos token.Pos 322 vers version 323 } 324 325 // A bailout panic is used for early termination. 326 type bailout struct{} 327 328 func (check *Checker) handleBailout(err *error) { 329 switch p := recover().(type) { 330 case nil, bailout: 331 // normal return or early exit 332 *err = check.firstErr 333 default: 334 // re-panic 335 panic(p) 336 } 337 } 338 339 // Files checks the provided files as part of the checker's package. 340 func (check *Checker) Files(files []*ast.File) error { return check.checkFiles(files) } 341 342 var errBadCgo = errors.New("cannot use FakeImportC and go115UsesCgo together") 343 344 func (check *Checker) checkFiles(files []*ast.File) (err error) { 345 if check.conf.FakeImportC && check.conf.go115UsesCgo { 346 return errBadCgo 347 } 348 349 defer check.handleBailout(&err) 350 351 print := func(msg string) { 352 if check.conf._Trace { 353 fmt.Println() 354 fmt.Println(msg) 355 } 356 } 357 358 print("== initFiles ==") 359 check.initFiles(files) 360 361 print("== collectObjects ==") 362 check.collectObjects() 363 364 print("== packageObjects ==") 365 check.packageObjects() 366 367 print("== processDelayed ==") 368 check.processDelayed(0) // incl. all functions 369 370 print("== cleanup ==") 371 check.cleanup() 372 373 print("== initOrder ==") 374 check.initOrder() 375 376 if !check.conf.DisableUnusedImportCheck { 377 print("== unusedImports ==") 378 check.unusedImports() 379 } 380 381 print("== recordUntyped ==") 382 check.recordUntyped() 383 384 if check.firstErr == nil { 385 // TODO(mdempsky): Ensure monomorph is safe when errors exist. 386 check.monomorph() 387 } 388 389 check.pkg.complete = true 390 391 // no longer needed - release memory 392 check.imports = nil 393 check.dotImportMap = nil 394 check.pkgPathMap = nil 395 check.seenPkgMap = nil 396 check.recvTParamMap = nil 397 check.brokenAliases = nil 398 check.unionTypeSets = nil 399 check.ctxt = nil 400 401 // TODO(rFindley) There's more memory we should release at this point. 402 403 return 404 } 405 406 // processDelayed processes all delayed actions pushed after top. 407 func (check *Checker) processDelayed(top int) { 408 // If each delayed action pushes a new action, the 409 // stack will continue to grow during this loop. 410 // However, it is only processing functions (which 411 // are processed in a delayed fashion) that may 412 // add more actions (such as nested functions), so 413 // this is a sufficiently bounded process. 414 for i := top; i < len(check.delayed); i++ { 415 a := &check.delayed[i] 416 if check.conf._Trace { 417 if a.desc != nil { 418 check.trace(a.desc.pos.Pos(), "-- "+a.desc.format, a.desc.args...) 419 } else { 420 check.trace(nopos, "-- delayed %p", a.f) 421 } 422 } 423 a.f() // may append to check.delayed 424 if check.conf._Trace { 425 fmt.Println() 426 } 427 } 428 assert(top <= len(check.delayed)) // stack must not have shrunk 429 check.delayed = check.delayed[:top] 430 } 431 432 // cleanup runs cleanup for all collected cleaners. 433 func (check *Checker) cleanup() { 434 // Don't use a range clause since Named.cleanup may add more cleaners. 435 for i := 0; i < len(check.cleaners); i++ { 436 check.cleaners[i].cleanup() 437 } 438 check.cleaners = nil 439 } 440 441 func (check *Checker) record(x *operand) { 442 // convert x into a user-friendly set of values 443 // TODO(gri) this code can be simplified 444 var typ Type 445 var val constant.Value 446 switch x.mode { 447 case invalid: 448 typ = Typ[Invalid] 449 case novalue: 450 typ = (*Tuple)(nil) 451 case constant_: 452 typ = x.typ 453 val = x.val 454 default: 455 typ = x.typ 456 } 457 assert(x.expr != nil && typ != nil) 458 459 if isUntyped(typ) { 460 // delay type and value recording until we know the type 461 // or until the end of type checking 462 check.rememberUntyped(x.expr, false, x.mode, typ.(*Basic), val) 463 } else { 464 check.recordTypeAndValue(x.expr, x.mode, typ, val) 465 } 466 } 467 468 func (check *Checker) recordUntyped() { 469 if !debug && check.Types == nil { 470 return // nothing to do 471 } 472 473 for x, info := range check.untyped { 474 if debug && isTyped(info.typ) { 475 check.dump("%v: %s (type %s) is typed", x.Pos(), x, info.typ) 476 unreachable() 477 } 478 check.recordTypeAndValue(x, info.mode, info.typ, info.val) 479 } 480 } 481 482 func (check *Checker) recordTypeAndValue(x ast.Expr, mode operandMode, typ Type, val constant.Value) { 483 assert(x != nil) 484 assert(typ != nil) 485 if mode == invalid { 486 return // omit 487 } 488 if mode == constant_ { 489 assert(val != nil) 490 // We check allBasic(typ, IsConstType) here as constant expressions may be 491 // recorded as type parameters. 492 assert(typ == Typ[Invalid] || allBasic(typ, IsConstType)) 493 } 494 if m := check.Types; m != nil { 495 m[x] = TypeAndValue{mode, typ, val} 496 } 497 } 498 499 func (check *Checker) recordBuiltinType(f ast.Expr, sig *Signature) { 500 // f must be a (possibly parenthesized, possibly qualified) 501 // identifier denoting a built-in (including unsafe's non-constant 502 // functions Add and Slice): record the signature for f and possible 503 // children. 504 for { 505 check.recordTypeAndValue(f, builtin, sig, nil) 506 switch p := f.(type) { 507 case *ast.Ident, *ast.SelectorExpr: 508 return // we're done 509 case *ast.ParenExpr: 510 f = p.X 511 default: 512 unreachable() 513 } 514 } 515 } 516 517 // recordCommaOkTypes updates recorded types to reflect that x is used in a commaOk context 518 // (and therefore has tuple type). 519 func (check *Checker) recordCommaOkTypes(x ast.Expr, a []*operand) { 520 assert(x != nil) 521 assert(len(a) == 2) 522 if a[0].mode == invalid { 523 return 524 } 525 t0, t1 := a[0].typ, a[1].typ 526 assert(isTyped(t0) && isTyped(t1) && (isBoolean(t1) || t1 == universeError)) 527 if m := check.Types; m != nil { 528 for { 529 tv := m[x] 530 assert(tv.Type != nil) // should have been recorded already 531 pos := x.Pos() 532 tv.Type = NewTuple( 533 NewVar(pos, check.pkg, "", t0), 534 NewVar(pos, check.pkg, "", t1), 535 ) 536 m[x] = tv 537 // if x is a parenthesized expression (p.X), update p.X 538 p, _ := x.(*ast.ParenExpr) 539 if p == nil { 540 break 541 } 542 x = p.X 543 } 544 } 545 } 546 547 // recordInstance records instantiation information into check.Info, if the 548 // Instances map is non-nil. The given expr must be an ident, selector, or 549 // index (list) expr with ident or selector operand. 550 // 551 // TODO(rfindley): the expr parameter is fragile. See if we can access the 552 // instantiated identifier in some other way. 553 func (check *Checker) recordInstance(expr ast.Expr, targs []Type, typ Type) { 554 ident := instantiatedIdent(expr) 555 assert(ident != nil) 556 assert(typ != nil) 557 if m := check.Instances; m != nil { 558 m[ident] = Instance{newTypeList(targs), typ} 559 } 560 } 561 562 func instantiatedIdent(expr ast.Expr) *ast.Ident { 563 var selOrIdent ast.Expr 564 switch e := expr.(type) { 565 case *ast.IndexExpr: 566 selOrIdent = e.X 567 case *ast.IndexListExpr: 568 selOrIdent = e.X 569 case *ast.SelectorExpr, *ast.Ident: 570 selOrIdent = e 571 } 572 switch x := selOrIdent.(type) { 573 case *ast.Ident: 574 return x 575 case *ast.SelectorExpr: 576 return x.Sel 577 } 578 panic("instantiated ident not found") 579 } 580 581 func (check *Checker) recordDef(id *ast.Ident, obj Object) { 582 assert(id != nil) 583 if m := check.Defs; m != nil { 584 m[id] = obj 585 } 586 } 587 588 func (check *Checker) recordUse(id *ast.Ident, obj Object) { 589 assert(id != nil) 590 assert(obj != nil) 591 if m := check.Uses; m != nil { 592 m[id] = obj 593 } 594 } 595 596 func (check *Checker) recordImplicit(node ast.Node, obj Object) { 597 assert(node != nil) 598 assert(obj != nil) 599 if m := check.Implicits; m != nil { 600 m[node] = obj 601 } 602 } 603 604 func (check *Checker) recordSelection(x *ast.SelectorExpr, kind SelectionKind, recv Type, obj Object, index []int, indirect bool) { 605 assert(obj != nil && (recv == nil || len(index) > 0)) 606 check.recordUse(x.Sel, obj) 607 if m := check.Selections; m != nil { 608 m[x] = &Selection{kind, recv, obj, index, indirect} 609 } 610 } 611 612 func (check *Checker) recordScope(node ast.Node, scope *Scope) { 613 assert(node != nil) 614 assert(scope != nil) 615 if m := check.Scopes; m != nil { 616 m[node] = scope 617 } 618 }