Source file src/go/types/named.go
1 // Code generated by "go test -run=Generate -write=all"; DO NOT EDIT. 2 // Source: ../../cmd/compile/internal/types2/named.go 3 4 // Copyright 2011 The Go Authors. All rights reserved. 5 // Use of this source code is governed by a BSD-style 6 // license that can be found in the LICENSE file. 7 8 package types 9 10 import ( 11 "go/token" 12 "strings" 13 "sync" 14 "sync/atomic" 15 ) 16 17 // Type-checking Named types is subtle, because they may be recursively 18 // defined, and because their full details may be spread across multiple 19 // declarations (via methods). For this reason they are type-checked lazily, 20 // to avoid information being accessed before it is complete. 21 // 22 // Conceptually, it is helpful to think of named types as having two distinct 23 // sets of information: 24 // - "LHS" information, defining their identity: Obj() and TypeArgs() 25 // - "RHS" information, defining their details: TypeParams(), Underlying(), 26 // and methods. 27 // 28 // In this taxonomy, LHS information is available immediately, but RHS 29 // information is lazy. Specifically, a named type N may be constructed in any 30 // of the following ways: 31 // 1. type-checked from the source 32 // 2. loaded eagerly from export data 33 // 3. loaded lazily from export data (when using unified IR) 34 // 4. instantiated from a generic type 35 // 36 // In cases 1, 3, and 4, it is possible that the underlying type or methods of 37 // N may not be immediately available. 38 // - During type-checking, we allocate N before type-checking its underlying 39 // type or methods, so that we may resolve recursive references. 40 // - When loading from export data, we may load its methods and underlying 41 // type lazily using a provided load function. 42 // - After instantiating, we lazily expand the underlying type and methods 43 // (note that instances may be created while still in the process of 44 // type-checking the original type declaration). 45 // 46 // In cases 3 and 4 this lazy construction may also occur concurrently, due to 47 // concurrent use of the type checker API (after type checking or importing has 48 // finished). It is critical that we keep track of state, so that Named types 49 // are constructed exactly once and so that we do not access their details too 50 // soon. 51 // 52 // We achieve this by tracking state with an atomic state variable, and 53 // guarding potentially concurrent calculations with a mutex. At any point in 54 // time this state variable determines which data on N may be accessed. As 55 // state monotonically progresses, any data available at state M may be 56 // accessed without acquiring the mutex at state N, provided N >= M. 57 // 58 // GLOSSARY: Here are a few terms used in this file to describe Named types: 59 // - We say that a Named type is "instantiated" if it has been constructed by 60 // instantiating a generic named type with type arguments. 61 // - We say that a Named type is "declared" if it corresponds to a type 62 // declaration in the source. Instantiated named types correspond to a type 63 // instantiation in the source, not a declaration. But their Origin type is 64 // a declared type. 65 // - We say that a Named type is "resolved" if its RHS information has been 66 // loaded or fully type-checked. For Named types constructed from export 67 // data, this may involve invoking a loader function to extract information 68 // from export data. For instantiated named types this involves reading 69 // information from their origin. 70 // - We say that a Named type is "expanded" if it is an instantiated type and 71 // type parameters in its underlying type and methods have been substituted 72 // with the type arguments from the instantiation. A type may be partially 73 // expanded if some but not all of these details have been substituted. 74 // Similarly, we refer to these individual details (underlying type or 75 // method) as being "expanded". 76 // - When all information is known for a named type, we say it is "complete". 77 // 78 // Some invariants to keep in mind: each declared Named type has a single 79 // corresponding object, and that object's type is the (possibly generic) Named 80 // type. Declared Named types are identical if and only if their pointers are 81 // identical. On the other hand, multiple instantiated Named types may be 82 // identical even though their pointers are not identical. One has to use 83 // Identical to compare them. For instantiated named types, their obj is a 84 // synthetic placeholder that records their position of the corresponding 85 // instantiation in the source (if they were constructed during type checking). 86 // 87 // To prevent infinite expansion of named instances that are created outside of 88 // type-checking, instances share a Context with other instances created during 89 // their expansion. Via the pidgeonhole principle, this guarantees that in the 90 // presence of a cycle of named types, expansion will eventually find an 91 // existing instance in the Context and short-circuit the expansion. 92 // 93 // Once an instance is complete, we can nil out this shared Context to unpin 94 // memory, though this Context may still be held by other incomplete instances 95 // in its "lineage". 96 97 // A Named represents a named (defined) type. 98 type Named struct { 99 check *Checker // non-nil during type-checking; nil otherwise 100 obj *TypeName // corresponding declared object for declared types; see above for instantiated types 101 102 // fromRHS holds the type (on RHS of declaration) this *Named type is derived 103 // from (for cycle reporting). Only used by validType, and therefore does not 104 // require synchronization. 105 fromRHS Type 106 107 // information for instantiated types; nil otherwise 108 inst *instance 109 110 mu sync.Mutex // guards all fields below 111 state_ uint32 // the current state of this type; must only be accessed atomically 112 underlying Type // possibly a *Named during setup; never a *Named once set up completely 113 tparams *TypeParamList // type parameters, or nil 114 115 // methods declared for this type (not the method set of this type) 116 // Signatures are type-checked lazily. 117 // For non-instantiated types, this is a fully populated list of methods. For 118 // instantiated types, methods are individually expanded when they are first 119 // accessed. 120 methods []*Func 121 122 // loader may be provided to lazily load type parameters, underlying type, and methods. 123 loader func(*Named) (tparams []*TypeParam, underlying Type, methods []*Func) 124 } 125 126 // instance holds information that is only necessary for instantiated named 127 // types. 128 type instance struct { 129 orig *Named // original, uninstantiated type 130 targs *TypeList // type arguments 131 expandedMethods int // number of expanded methods; expandedMethods <= len(orig.methods) 132 ctxt *Context // local Context; set to nil after full expansion 133 } 134 135 // namedState represents the possible states that a named type may assume. 136 type namedState uint32 137 138 const ( 139 unresolved namedState = iota // tparams, underlying type and methods might be unavailable 140 resolved // resolve has run; methods might be incomplete (for instances) 141 complete // all data is known 142 ) 143 144 // NewNamed returns a new named type for the given type name, underlying type, and associated methods. 145 // If the given type name obj doesn't have a type yet, its type is set to the returned named type. 146 // The underlying type must not be a *Named. 147 func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named { 148 if asNamed(underlying) != nil { 149 panic("underlying type must not be *Named") 150 } 151 return (*Checker)(nil).newNamed(obj, underlying, methods) 152 } 153 154 // resolve resolves the type parameters, methods, and underlying type of n. 155 // This information may be loaded from a provided loader function, or computed 156 // from an origin type (in the case of instances). 157 // 158 // After resolution, the type parameters, methods, and underlying type of n are 159 // accessible; but if n is an instantiated type, its methods may still be 160 // unexpanded. 161 func (n *Named) resolve() *Named { 162 if n.state() >= resolved { // avoid locking below 163 return n 164 } 165 166 // TODO(rfindley): if n.check is non-nil we can avoid locking here, since 167 // type-checking is not concurrent. Evaluate if this is worth doing. 168 n.mu.Lock() 169 defer n.mu.Unlock() 170 171 if n.state() >= resolved { 172 return n 173 } 174 175 if n.inst != nil { 176 assert(n.underlying == nil) // n is an unresolved instance 177 assert(n.loader == nil) // instances are created by instantiation, in which case n.loader is nil 178 179 orig := n.inst.orig 180 orig.resolve() 181 underlying := n.expandUnderlying() 182 183 n.tparams = orig.tparams 184 n.underlying = underlying 185 n.fromRHS = orig.fromRHS // for cycle detection 186 187 if len(orig.methods) == 0 { 188 n.setState(complete) // nothing further to do 189 n.inst.ctxt = nil 190 } else { 191 n.setState(resolved) 192 } 193 return n 194 } 195 196 // TODO(mdempsky): Since we're passing n to the loader anyway 197 // (necessary because types2 expects the receiver type for methods 198 // on defined interface types to be the Named rather than the 199 // underlying Interface), maybe it should just handle calling 200 // SetTypeParams, SetUnderlying, and AddMethod instead? Those 201 // methods would need to support reentrant calls though. It would 202 // also make the API more future-proof towards further extensions. 203 if n.loader != nil { 204 assert(n.underlying == nil) 205 assert(n.TypeArgs().Len() == 0) // instances are created by instantiation, in which case n.loader is nil 206 207 tparams, underlying, methods := n.loader(n) 208 209 n.tparams = bindTParams(tparams) 210 n.underlying = underlying 211 n.fromRHS = underlying // for cycle detection 212 n.methods = methods 213 n.loader = nil 214 } 215 216 n.setState(complete) 217 return n 218 } 219 220 // state atomically accesses the current state of the receiver. 221 func (n *Named) state() namedState { 222 return namedState(atomic.LoadUint32(&n.state_)) 223 } 224 225 // setState atomically stores the given state for n. 226 // Must only be called while holding n.mu. 227 func (n *Named) setState(state namedState) { 228 atomic.StoreUint32(&n.state_, uint32(state)) 229 } 230 231 // newNamed is like NewNamed but with a *Checker receiver. 232 func (check *Checker) newNamed(obj *TypeName, underlying Type, methods []*Func) *Named { 233 typ := &Named{check: check, obj: obj, fromRHS: underlying, underlying: underlying, methods: methods} 234 if obj.typ == nil { 235 obj.typ = typ 236 } 237 // Ensure that typ is always sanity-checked. 238 if check != nil { 239 check.needsCleanup(typ) 240 } 241 return typ 242 } 243 244 // newNamedInstance creates a new named instance for the given origin and type 245 // arguments, recording pos as the position of its synthetic object (for error 246 // reporting). 247 // 248 // If set, expanding is the named type instance currently being expanded, that 249 // led to the creation of this instance. 250 func (check *Checker) newNamedInstance(pos token.Pos, orig *Named, targs []Type, expanding *Named) *Named { 251 assert(len(targs) > 0) 252 253 obj := NewTypeName(pos, orig.obj.pkg, orig.obj.name, nil) 254 inst := &instance{orig: orig, targs: newTypeList(targs)} 255 256 // Only pass the expanding context to the new instance if their packages 257 // match. Since type reference cycles are only possible within a single 258 // package, this is sufficient for the purposes of short-circuiting cycles. 259 // Avoiding passing the context in other cases prevents unnecessary coupling 260 // of types across packages. 261 if expanding != nil && expanding.Obj().pkg == obj.pkg { 262 inst.ctxt = expanding.inst.ctxt 263 } 264 typ := &Named{check: check, obj: obj, inst: inst} 265 obj.typ = typ 266 // Ensure that typ is always sanity-checked. 267 if check != nil { 268 check.needsCleanup(typ) 269 } 270 return typ 271 } 272 273 func (t *Named) cleanup() { 274 assert(t.inst == nil || t.inst.orig.inst == nil) 275 // Ensure that every defined type created in the course of type-checking has 276 // either non-*Named underlying type, or is unexpanded. 277 // 278 // This guarantees that we don't leak any types whose underlying type is 279 // *Named, because any unexpanded instances will lazily compute their 280 // underlying type by substituting in the underlying type of their origin. 281 // The origin must have either been imported or type-checked and expanded 282 // here, and in either case its underlying type will be fully expanded. 283 switch t.underlying.(type) { 284 case nil: 285 if t.TypeArgs().Len() == 0 { 286 panic("nil underlying") 287 } 288 case *Named: 289 t.under() // t.under may add entries to check.cleaners 290 } 291 t.check = nil 292 } 293 294 // Obj returns the type name for the declaration defining the named type t. For 295 // instantiated types, this is same as the type name of the origin type. 296 func (t *Named) Obj() *TypeName { 297 if t.inst == nil { 298 return t.obj 299 } 300 return t.inst.orig.obj 301 } 302 303 // Origin returns the generic type from which the named type t is 304 // instantiated. If t is not an instantiated type, the result is t. 305 func (t *Named) Origin() *Named { 306 if t.inst == nil { 307 return t 308 } 309 return t.inst.orig 310 } 311 312 // TypeParams returns the type parameters of the named type t, or nil. 313 // The result is non-nil for an (originally) generic type even if it is instantiated. 314 func (t *Named) TypeParams() *TypeParamList { return t.resolve().tparams } 315 316 // SetTypeParams sets the type parameters of the named type t. 317 // t must not have type arguments. 318 func (t *Named) SetTypeParams(tparams []*TypeParam) { 319 assert(t.inst == nil) 320 t.resolve().tparams = bindTParams(tparams) 321 } 322 323 // TypeArgs returns the type arguments used to instantiate the named type t. 324 func (t *Named) TypeArgs() *TypeList { 325 if t.inst == nil { 326 return nil 327 } 328 return t.inst.targs 329 } 330 331 // NumMethods returns the number of explicit methods defined for t. 332 func (t *Named) NumMethods() int { 333 return len(t.Origin().resolve().methods) 334 } 335 336 // Method returns the i'th method of named type t for 0 <= i < t.NumMethods(). 337 // 338 // For an ordinary or instantiated type t, the receiver base type of this 339 // method is the named type t. For an uninstantiated generic type t, each 340 // method receiver is instantiated with its receiver type parameters. 341 // 342 // Methods are numbered deterministically: given the same list of source files 343 // presented to the type checker, or the same sequence of NewMethod and AddMethod 344 // calls, the mapping from method index to corresponding method remains the same. 345 // But the specific ordering is not specified and must not be relied on as it may 346 // change in the future. 347 func (t *Named) Method(i int) *Func { 348 t.resolve() 349 350 if t.state() >= complete { 351 return t.methods[i] 352 } 353 354 assert(t.inst != nil) // only instances should have incomplete methods 355 orig := t.inst.orig 356 357 t.mu.Lock() 358 defer t.mu.Unlock() 359 360 if len(t.methods) != len(orig.methods) { 361 assert(len(t.methods) == 0) 362 t.methods = make([]*Func, len(orig.methods)) 363 } 364 365 if t.methods[i] == nil { 366 assert(t.inst.ctxt != nil) // we should still have a context remaining from the resolution phase 367 t.methods[i] = t.expandMethod(i) 368 t.inst.expandedMethods++ 369 370 // Check if we've created all methods at this point. If we have, mark the 371 // type as fully expanded. 372 if t.inst.expandedMethods == len(orig.methods) { 373 t.setState(complete) 374 t.inst.ctxt = nil // no need for a context anymore 375 } 376 } 377 378 return t.methods[i] 379 } 380 381 // expandMethod substitutes type arguments in the i'th method for an 382 // instantiated receiver. 383 func (t *Named) expandMethod(i int) *Func { 384 // t.orig.methods is not lazy. origm is the method instantiated with its 385 // receiver type parameters (the "origin" method). 386 origm := t.inst.orig.Method(i) 387 assert(origm != nil) 388 389 check := t.check 390 // Ensure that the original method is type-checked. 391 if check != nil { 392 check.objDecl(origm, nil) 393 } 394 395 origSig := origm.typ.(*Signature) 396 rbase, _ := deref(origSig.Recv().Type()) 397 398 // If rbase is t, then origm is already the instantiated method we're looking 399 // for. In this case, we return origm to preserve the invariant that 400 // traversing Method->Receiver Type->Method should get back to the same 401 // method. 402 // 403 // This occurs if t is instantiated with the receiver type parameters, as in 404 // the use of m in func (r T[_]) m() { r.m() }. 405 if rbase == t { 406 return origm 407 } 408 409 sig := origSig 410 // We can only substitute if we have a correspondence between type arguments 411 // and type parameters. This check is necessary in the presence of invalid 412 // code. 413 if origSig.RecvTypeParams().Len() == t.inst.targs.Len() { 414 smap := makeSubstMap(origSig.RecvTypeParams().list(), t.inst.targs.list()) 415 var ctxt *Context 416 if check != nil { 417 ctxt = check.context() 418 } 419 sig = check.subst(origm.pos, origSig, smap, t, ctxt).(*Signature) 420 } 421 422 if sig == origSig { 423 // No substitution occurred, but we still need to create a new signature to 424 // hold the instantiated receiver. 425 copy := *origSig 426 sig = © 427 } 428 429 var rtyp Type 430 if origm.hasPtrRecv() { 431 rtyp = NewPointer(t) 432 } else { 433 rtyp = t 434 } 435 436 sig.recv = substVar(origSig.recv, rtyp) 437 return substFunc(origm, sig) 438 } 439 440 // SetUnderlying sets the underlying type and marks t as complete. 441 // t must not have type arguments. 442 func (t *Named) SetUnderlying(underlying Type) { 443 assert(t.inst == nil) 444 if underlying == nil { 445 panic("underlying type must not be nil") 446 } 447 if asNamed(underlying) != nil { 448 panic("underlying type must not be *Named") 449 } 450 t.resolve().underlying = underlying 451 if t.fromRHS == nil { 452 t.fromRHS = underlying // for cycle detection 453 } 454 } 455 456 // AddMethod adds method m unless it is already in the method list. 457 // The method must be in the same package as t, and t must not have 458 // type arguments. 459 func (t *Named) AddMethod(m *Func) { 460 assert(samePkg(t.obj.pkg, m.pkg)) 461 assert(t.inst == nil) 462 t.resolve() 463 if t.methodIndex(m.name, false) < 0 { 464 t.methods = append(t.methods, m) 465 } 466 } 467 468 // methodIndex returns the index of the method with the given name. 469 // If foldCase is set, capitalization in the name is ignored. 470 // The result is negative if no such method exists. 471 func (t *Named) methodIndex(name string, foldCase bool) int { 472 if name == "_" { 473 return -1 474 } 475 if foldCase { 476 for i, m := range t.methods { 477 if strings.EqualFold(m.name, name) { 478 return i 479 } 480 } 481 } else { 482 for i, m := range t.methods { 483 if m.name == name { 484 return i 485 } 486 } 487 } 488 return -1 489 } 490 491 // TODO(gri) Investigate if Unalias can be moved to where underlying is set. 492 func (t *Named) Underlying() Type { return Unalias(t.resolve().underlying) } 493 func (t *Named) String() string { return TypeString(t, nil) } 494 495 // ---------------------------------------------------------------------------- 496 // Implementation 497 // 498 // TODO(rfindley): reorganize the loading and expansion methods under this 499 // heading. 500 501 // under returns the expanded underlying type of n0; possibly by following 502 // forward chains of named types. If an underlying type is found, resolve 503 // the chain by setting the underlying type for each defined type in the 504 // chain before returning it. If no underlying type is found or a cycle 505 // is detected, the result is Typ[Invalid]. If a cycle is detected and 506 // n0.check != nil, the cycle is reported. 507 // 508 // This is necessary because the underlying type of named may be itself a 509 // named type that is incomplete: 510 // 511 // type ( 512 // A B 513 // B *C 514 // C A 515 // ) 516 // 517 // The type of C is the (named) type of A which is incomplete, 518 // and which has as its underlying type the named type B. 519 func (n0 *Named) under() Type { 520 u := n0.Underlying() 521 522 // If the underlying type of a defined type is not a defined 523 // (incl. instance) type, then that is the desired underlying 524 // type. 525 var n1 *Named 526 switch u1 := u.(type) { 527 case nil: 528 // After expansion via Underlying(), we should never encounter a nil 529 // underlying. 530 panic("nil underlying") 531 default: 532 // common case 533 return u 534 case *Named: 535 // handled below 536 n1 = u1 537 } 538 539 if n0.check == nil { 540 panic("Named.check == nil but type is incomplete") 541 } 542 543 // Invariant: after this point n0 as well as any named types in its 544 // underlying chain should be set up when this function exits. 545 check := n0.check 546 n := n0 547 548 seen := make(map[*Named]int) // types that need their underlying type resolved 549 var path []Object // objects encountered, for cycle reporting 550 551 loop: 552 for { 553 seen[n] = len(seen) 554 path = append(path, n.obj) 555 n = n1 556 if i, ok := seen[n]; ok { 557 // cycle 558 check.cycleError(path[i:], firstInSrc(path[i:])) 559 u = Typ[Invalid] 560 break 561 } 562 u = n.Underlying() 563 switch u1 := u.(type) { 564 case nil: 565 u = Typ[Invalid] 566 break loop 567 default: 568 break loop 569 case *Named: 570 // Continue collecting *Named types in the chain. 571 n1 = u1 572 } 573 } 574 575 for n := range seen { 576 // We should never have to update the underlying type of an imported type; 577 // those underlying types should have been resolved during the import. 578 // Also, doing so would lead to a race condition (was go.dev/issue/31749). 579 // Do this check always, not just in debug mode (it's cheap). 580 if n.obj.pkg != check.pkg { 581 panic("imported type with unresolved underlying type") 582 } 583 n.underlying = u 584 } 585 586 return u 587 } 588 589 func (n *Named) lookupMethod(pkg *Package, name string, foldCase bool) (int, *Func) { 590 n.resolve() 591 if samePkg(n.obj.pkg, pkg) || isExported(name) || foldCase { 592 // If n is an instance, we may not have yet instantiated all of its methods. 593 // Look up the method index in orig, and only instantiate method at the 594 // matching index (if any). 595 if i := n.Origin().methodIndex(name, foldCase); i >= 0 { 596 // For instances, m.Method(i) will be different from the orig method. 597 return i, n.Method(i) 598 } 599 } 600 return -1, nil 601 } 602 603 // context returns the type-checker context. 604 func (check *Checker) context() *Context { 605 if check.ctxt == nil { 606 check.ctxt = NewContext() 607 } 608 return check.ctxt 609 } 610 611 // expandUnderlying substitutes type arguments in the underlying type n.orig, 612 // returning the result. Returns Typ[Invalid] if there was an error. 613 func (n *Named) expandUnderlying() Type { 614 check := n.check 615 if check != nil && check.conf._Trace { 616 check.trace(n.obj.pos, "-- Named.expandUnderlying %s", n) 617 check.indent++ 618 defer func() { 619 check.indent-- 620 check.trace(n.obj.pos, "=> %s (tparams = %s, under = %s)", n, n.tparams.list(), n.underlying) 621 }() 622 } 623 624 assert(n.inst.orig.underlying != nil) 625 if n.inst.ctxt == nil { 626 n.inst.ctxt = NewContext() 627 } 628 629 orig := n.inst.orig 630 targs := n.inst.targs 631 632 if asNamed(orig.underlying) != nil { 633 // We should only get a Named underlying type here during type checking 634 // (for example, in recursive type declarations). 635 assert(check != nil) 636 } 637 638 if orig.tparams.Len() != targs.Len() { 639 // Mismatching arg and tparam length may be checked elsewhere. 640 return Typ[Invalid] 641 } 642 643 // Ensure that an instance is recorded before substituting, so that we 644 // resolve n for any recursive references. 645 h := n.inst.ctxt.instanceHash(orig, targs.list()) 646 n2 := n.inst.ctxt.update(h, orig, n.TypeArgs().list(), n) 647 assert(n == n2) 648 649 smap := makeSubstMap(orig.tparams.list(), targs.list()) 650 var ctxt *Context 651 if check != nil { 652 ctxt = check.context() 653 } 654 underlying := n.check.subst(n.obj.pos, orig.underlying, smap, n, ctxt) 655 // If the underlying type of n is an interface, we need to set the receiver of 656 // its methods accurately -- we set the receiver of interface methods on 657 // the RHS of a type declaration to the defined type. 658 if iface, _ := underlying.(*Interface); iface != nil { 659 if methods, copied := replaceRecvType(iface.methods, orig, n); copied { 660 // If the underlying type doesn't actually use type parameters, it's 661 // possible that it wasn't substituted. In this case we need to create 662 // a new *Interface before modifying receivers. 663 if iface == orig.underlying { 664 old := iface 665 iface = check.newInterface() 666 iface.embeddeds = old.embeddeds 667 assert(old.complete) // otherwise we are copying incomplete data 668 iface.complete = old.complete 669 iface.implicit = old.implicit // should be false but be conservative 670 underlying = iface 671 } 672 iface.methods = methods 673 iface.tset = nil // recompute type set with new methods 674 675 // If check != nil, check.newInterface will have saved the interface for later completion. 676 if check == nil { // golang/go#61561: all newly created interfaces must be fully evaluated 677 iface.typeSet() 678 } 679 } 680 } 681 682 return underlying 683 } 684 685 // safeUnderlying returns the underlying type of typ without expanding 686 // instances, to avoid infinite recursion. 687 // 688 // TODO(rfindley): eliminate this function or give it a better name. 689 func safeUnderlying(typ Type) Type { 690 if t := asNamed(typ); t != nil { 691 return t.underlying 692 } 693 return typ.Underlying() 694 } 695