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 // 99 // A declaration such as: 100 // 101 // type S struct { ... } 102 // 103 // creates a defined type whose underlying type is a struct, 104 // and binds this type to the object S, a [TypeName]. 105 // Use [Named.Underlying] to access the underlying type. 106 // Use [Named.Obj] to obtain the object S. 107 // 108 // Before type aliases (Go 1.9), the spec called defined types "named types". 109 type Named struct { 110 check *Checker // non-nil during type-checking; nil otherwise 111 obj *TypeName // corresponding declared object for declared types; see above for instantiated types 112 113 // fromRHS holds the type (on RHS of declaration) this *Named type is derived 114 // from (for cycle reporting). Only used by validType, and therefore does not 115 // require synchronization. 116 fromRHS Type 117 118 // information for instantiated types; nil otherwise 119 inst *instance 120 121 mu sync.Mutex // guards all fields below 122 state_ uint32 // the current state of this type; must only be accessed atomically 123 underlying Type // possibly a *Named during setup; never a *Named once set up completely 124 tparams *TypeParamList // type parameters, or nil 125 126 // methods declared for this type (not the method set of this type) 127 // Signatures are type-checked lazily. 128 // For non-instantiated types, this is a fully populated list of methods. For 129 // instantiated types, methods are individually expanded when they are first 130 // accessed. 131 methods []*Func 132 133 // loader may be provided to lazily load type parameters, underlying type, methods, and delayed functions 134 loader func(*Named) ([]*TypeParam, Type, []*Func, []func()) 135 } 136 137 // instance holds information that is only necessary for instantiated named 138 // types. 139 type instance struct { 140 orig *Named // original, uninstantiated type 141 targs *TypeList // type arguments 142 expandedMethods int // number of expanded methods; expandedMethods <= len(orig.methods) 143 ctxt *Context // local Context; set to nil after full expansion 144 } 145 146 // namedState represents the possible states that a named type may assume. 147 type namedState uint32 148 149 // Note: the order of states is relevant 150 const ( 151 unresolved namedState = iota // tparams, underlying type and methods might be unavailable 152 resolved // resolve has run; methods might be unexpanded (for instances) 153 loaded // loader has run; constraints might be unexpanded (for generic types) 154 complete // all data is known 155 ) 156 157 // NewNamed returns a new named type for the given type name, underlying type, and associated methods. 158 // If the given type name obj doesn't have a type yet, its type is set to the returned named type. 159 // The underlying type must not be a *Named. 160 func NewNamed(obj *TypeName, underlying Type, methods []*Func) *Named { 161 if asNamed(underlying) != nil { 162 panic("underlying type must not be *Named") 163 } 164 return (*Checker)(nil).newNamed(obj, underlying, methods) 165 } 166 167 // resolve resolves the type parameters, methods, and underlying type of n. 168 // This information may be loaded from a provided loader function, or computed 169 // from an origin type (in the case of instances). 170 // 171 // After resolution, the type parameters, methods, and underlying type of n are 172 // accessible; but if n is an instantiated type, its methods may still be 173 // unexpanded. 174 func (n *Named) resolve() *Named { 175 if n.state() > unresolved { // avoid locking below 176 return n 177 } 178 179 // TODO(rfindley): if n.check is non-nil we can avoid locking here, since 180 // type-checking is not concurrent. Evaluate if this is worth doing. 181 n.mu.Lock() 182 defer n.mu.Unlock() 183 184 if n.state() > unresolved { 185 return n 186 } 187 188 if n.inst != nil { 189 assert(n.underlying == nil) // n is an unresolved instance 190 assert(n.loader == nil) // instances are created by instantiation, in which case n.loader is nil 191 192 orig := n.inst.orig 193 orig.resolve() 194 underlying := n.expandUnderlying() 195 196 n.tparams = orig.tparams 197 n.underlying = underlying 198 n.fromRHS = orig.fromRHS // for cycle detection 199 200 if len(orig.methods) == 0 { 201 n.setState(complete) // nothing further to do 202 n.inst.ctxt = nil 203 } else { 204 n.setState(resolved) 205 } 206 return n 207 } 208 209 // TODO(mdempsky): Since we're passing n to the loader anyway 210 // (necessary because types2 expects the receiver type for methods 211 // on defined interface types to be the Named rather than the 212 // underlying Interface), maybe it should just handle calling 213 // SetTypeParams, SetUnderlying, and AddMethod instead? Those 214 // methods would need to support reentrant calls though. It would 215 // also make the API more future-proof towards further extensions. 216 if n.loader != nil { 217 assert(n.underlying == nil) 218 assert(n.TypeArgs().Len() == 0) // instances are created by instantiation, in which case n.loader is nil 219 220 tparams, underlying, methods, delayed := n.loader(n) 221 n.loader = nil 222 223 n.tparams = bindTParams(tparams) 224 n.underlying = underlying 225 n.fromRHS = underlying // for cycle detection 226 n.methods = methods 227 228 // advance state to avoid deadlock calling delayed functions 229 n.setState(loaded) 230 231 for _, f := range delayed { 232 f() 233 } 234 } 235 236 n.setState(complete) 237 return n 238 } 239 240 // state atomically accesses the current state of the receiver. 241 func (n *Named) state() namedState { 242 return namedState(atomic.LoadUint32(&n.state_)) 243 } 244 245 // setState atomically stores the given state for n. 246 // Must only be called while holding n.mu. 247 func (n *Named) setState(state namedState) { 248 atomic.StoreUint32(&n.state_, uint32(state)) 249 } 250 251 // newNamed is like NewNamed but with a *Checker receiver. 252 func (check *Checker) newNamed(obj *TypeName, underlying Type, methods []*Func) *Named { 253 typ := &Named{check: check, obj: obj, fromRHS: underlying, underlying: underlying, methods: methods} 254 if obj.typ == nil { 255 obj.typ = typ 256 } 257 // Ensure that typ is always sanity-checked. 258 if check != nil { 259 check.needsCleanup(typ) 260 } 261 return typ 262 } 263 264 // newNamedInstance creates a new named instance for the given origin and type 265 // arguments, recording pos as the position of its synthetic object (for error 266 // reporting). 267 // 268 // If set, expanding is the named type instance currently being expanded, that 269 // led to the creation of this instance. 270 func (check *Checker) newNamedInstance(pos token.Pos, orig *Named, targs []Type, expanding *Named) *Named { 271 assert(len(targs) > 0) 272 273 obj := NewTypeName(pos, orig.obj.pkg, orig.obj.name, nil) 274 inst := &instance{orig: orig, targs: newTypeList(targs)} 275 276 // Only pass the expanding context to the new instance if their packages 277 // match. Since type reference cycles are only possible within a single 278 // package, this is sufficient for the purposes of short-circuiting cycles. 279 // Avoiding passing the context in other cases prevents unnecessary coupling 280 // of types across packages. 281 if expanding != nil && expanding.Obj().pkg == obj.pkg { 282 inst.ctxt = expanding.inst.ctxt 283 } 284 typ := &Named{check: check, obj: obj, inst: inst} 285 obj.typ = typ 286 // Ensure that typ is always sanity-checked. 287 if check != nil { 288 check.needsCleanup(typ) 289 } 290 return typ 291 } 292 293 func (t *Named) cleanup() { 294 assert(t.inst == nil || t.inst.orig.inst == nil) 295 // Ensure that every defined type created in the course of type-checking has 296 // either non-*Named underlying type, or is unexpanded. 297 // 298 // This guarantees that we don't leak any types whose underlying type is 299 // *Named, because any unexpanded instances will lazily compute their 300 // underlying type by substituting in the underlying type of their origin. 301 // The origin must have either been imported or type-checked and expanded 302 // here, and in either case its underlying type will be fully expanded. 303 switch t.underlying.(type) { 304 case nil: 305 if t.TypeArgs().Len() == 0 { 306 panic("nil underlying") 307 } 308 case *Named, *Alias: 309 t.under() // t.under may add entries to check.cleaners 310 } 311 t.check = nil 312 } 313 314 // Obj returns the type name for the declaration defining the named type t. For 315 // instantiated types, this is same as the type name of the origin type. 316 func (t *Named) Obj() *TypeName { 317 if t.inst == nil { 318 return t.obj 319 } 320 return t.inst.orig.obj 321 } 322 323 // Origin returns the generic type from which the named type t is 324 // instantiated. If t is not an instantiated type, the result is t. 325 func (t *Named) Origin() *Named { 326 if t.inst == nil { 327 return t 328 } 329 return t.inst.orig 330 } 331 332 // TypeParams returns the type parameters of the named type t, or nil. 333 // The result is non-nil for an (originally) generic type even if it is instantiated. 334 func (t *Named) TypeParams() *TypeParamList { return t.resolve().tparams } 335 336 // SetTypeParams sets the type parameters of the named type t. 337 // t must not have type arguments. 338 func (t *Named) SetTypeParams(tparams []*TypeParam) { 339 assert(t.inst == nil) 340 t.resolve().tparams = bindTParams(tparams) 341 } 342 343 // TypeArgs returns the type arguments used to instantiate the named type t. 344 func (t *Named) TypeArgs() *TypeList { 345 if t.inst == nil { 346 return nil 347 } 348 return t.inst.targs 349 } 350 351 // NumMethods returns the number of explicit methods defined for t. 352 func (t *Named) NumMethods() int { 353 return len(t.Origin().resolve().methods) 354 } 355 356 // Method returns the i'th method of named type t for 0 <= i < t.NumMethods(). 357 // 358 // For an ordinary or instantiated type t, the receiver base type of this 359 // method is the named type t. For an uninstantiated generic type t, each 360 // method receiver is instantiated with its receiver type parameters. 361 // 362 // Methods are numbered deterministically: given the same list of source files 363 // presented to the type checker, or the same sequence of NewMethod and AddMethod 364 // calls, the mapping from method index to corresponding method remains the same. 365 // But the specific ordering is not specified and must not be relied on as it may 366 // change in the future. 367 func (t *Named) Method(i int) *Func { 368 t.resolve() 369 370 if t.state() >= complete { 371 return t.methods[i] 372 } 373 374 assert(t.inst != nil) // only instances should have incomplete methods 375 orig := t.inst.orig 376 377 t.mu.Lock() 378 defer t.mu.Unlock() 379 380 if len(t.methods) != len(orig.methods) { 381 assert(len(t.methods) == 0) 382 t.methods = make([]*Func, len(orig.methods)) 383 } 384 385 if t.methods[i] == nil { 386 assert(t.inst.ctxt != nil) // we should still have a context remaining from the resolution phase 387 t.methods[i] = t.expandMethod(i) 388 t.inst.expandedMethods++ 389 390 // Check if we've created all methods at this point. If we have, mark the 391 // type as fully expanded. 392 if t.inst.expandedMethods == len(orig.methods) { 393 t.setState(complete) 394 t.inst.ctxt = nil // no need for a context anymore 395 } 396 } 397 398 return t.methods[i] 399 } 400 401 // expandMethod substitutes type arguments in the i'th method for an 402 // instantiated receiver. 403 func (t *Named) expandMethod(i int) *Func { 404 // t.orig.methods is not lazy. origm is the method instantiated with its 405 // receiver type parameters (the "origin" method). 406 origm := t.inst.orig.Method(i) 407 assert(origm != nil) 408 409 check := t.check 410 // Ensure that the original method is type-checked. 411 if check != nil { 412 check.objDecl(origm, nil) 413 } 414 415 origSig := origm.typ.(*Signature) 416 rbase, _ := deref(origSig.Recv().Type()) 417 418 // If rbase is t, then origm is already the instantiated method we're looking 419 // for. In this case, we return origm to preserve the invariant that 420 // traversing Method->Receiver Type->Method should get back to the same 421 // method. 422 // 423 // This occurs if t is instantiated with the receiver type parameters, as in 424 // the use of m in func (r T[_]) m() { r.m() }. 425 if rbase == t { 426 return origm 427 } 428 429 sig := origSig 430 // We can only substitute if we have a correspondence between type arguments 431 // and type parameters. This check is necessary in the presence of invalid 432 // code. 433 if origSig.RecvTypeParams().Len() == t.inst.targs.Len() { 434 smap := makeSubstMap(origSig.RecvTypeParams().list(), t.inst.targs.list()) 435 var ctxt *Context 436 if check != nil { 437 ctxt = check.context() 438 } 439 sig = check.subst(origm.pos, origSig, smap, t, ctxt).(*Signature) 440 } 441 442 if sig == origSig { 443 // No substitution occurred, but we still need to create a new signature to 444 // hold the instantiated receiver. 445 copy := *origSig 446 sig = © 447 } 448 449 var rtyp Type 450 if origm.hasPtrRecv() { 451 rtyp = NewPointer(t) 452 } else { 453 rtyp = t 454 } 455 456 sig.recv = cloneVar(origSig.recv, rtyp) 457 return cloneFunc(origm, sig) 458 } 459 460 // SetUnderlying sets the underlying type and marks t as complete. 461 // t must not have type arguments. 462 func (t *Named) SetUnderlying(underlying Type) { 463 assert(t.inst == nil) 464 if underlying == nil { 465 panic("underlying type must not be nil") 466 } 467 if asNamed(underlying) != nil { 468 panic("underlying type must not be *Named") 469 } 470 t.resolve().underlying = underlying 471 if t.fromRHS == nil { 472 t.fromRHS = underlying // for cycle detection 473 } 474 } 475 476 // AddMethod adds method m unless it is already in the method list. 477 // The method must be in the same package as t, and t must not have 478 // type arguments. 479 func (t *Named) AddMethod(m *Func) { 480 assert(samePkg(t.obj.pkg, m.pkg)) 481 assert(t.inst == nil) 482 t.resolve() 483 if t.methodIndex(m.name, false) < 0 { 484 t.methods = append(t.methods, m) 485 } 486 } 487 488 // methodIndex returns the index of the method with the given name. 489 // If foldCase is set, capitalization in the name is ignored. 490 // The result is negative if no such method exists. 491 func (t *Named) methodIndex(name string, foldCase bool) int { 492 if name == "_" { 493 return -1 494 } 495 if foldCase { 496 for i, m := range t.methods { 497 if strings.EqualFold(m.name, name) { 498 return i 499 } 500 } 501 } else { 502 for i, m := range t.methods { 503 if m.name == name { 504 return i 505 } 506 } 507 } 508 return -1 509 } 510 511 // Underlying returns the [underlying type] of the named type t, resolving all 512 // forwarding declarations. Underlying types are never Named, TypeParam, or 513 // Alias types. 514 // 515 // [underlying type]: https://go.dev/ref/spec#Underlying_types. 516 func (t *Named) Underlying() Type { 517 // TODO(gri) Investigate if Unalias can be moved to where underlying is set. 518 return Unalias(t.resolve().underlying) 519 } 520 521 func (t *Named) String() string { return TypeString(t, nil) } 522 523 // ---------------------------------------------------------------------------- 524 // Implementation 525 // 526 // TODO(rfindley): reorganize the loading and expansion methods under this 527 // heading. 528 529 // under returns the expanded underlying type of n0; possibly by following 530 // forward chains of named types. If an underlying type is found, resolve 531 // the chain by setting the underlying type for each defined type in the 532 // chain before returning it. If no underlying type is found or a cycle 533 // is detected, the result is Typ[Invalid]. If a cycle is detected and 534 // n0.check != nil, the cycle is reported. 535 // 536 // This is necessary because the underlying type of named may be itself a 537 // named type that is incomplete: 538 // 539 // type ( 540 // A B 541 // B *C 542 // C A 543 // ) 544 // 545 // The type of C is the (named) type of A which is incomplete, 546 // and which has as its underlying type the named type B. 547 func (n0 *Named) under() Type { 548 u := n0.Underlying() 549 550 // If the underlying type of a defined type is not a defined 551 // (incl. instance) type, then that is the desired underlying 552 // type. 553 var n1 *Named 554 switch u1 := u.(type) { 555 case nil: 556 // After expansion via Underlying(), we should never encounter a nil 557 // underlying. 558 panic("nil underlying") 559 default: 560 // common case 561 return u 562 case *Named: 563 // handled below 564 n1 = u1 565 } 566 567 if n0.check == nil { 568 panic("Named.check == nil but type is incomplete") 569 } 570 571 // Invariant: after this point n0 as well as any named types in its 572 // underlying chain should be set up when this function exits. 573 check := n0.check 574 n := n0 575 576 seen := make(map[*Named]int) // types that need their underlying type resolved 577 var path []Object // objects encountered, for cycle reporting 578 579 loop: 580 for { 581 seen[n] = len(seen) 582 path = append(path, n.obj) 583 n = n1 584 if i, ok := seen[n]; ok { 585 // cycle 586 check.cycleError(path[i:], firstInSrc(path[i:])) 587 u = Typ[Invalid] 588 break 589 } 590 u = n.Underlying() 591 switch u1 := u.(type) { 592 case nil: 593 u = Typ[Invalid] 594 break loop 595 default: 596 break loop 597 case *Named: 598 // Continue collecting *Named types in the chain. 599 n1 = u1 600 } 601 } 602 603 for n := range seen { 604 // We should never have to update the underlying type of an imported type; 605 // those underlying types should have been resolved during the import. 606 // Also, doing so would lead to a race condition (was go.dev/issue/31749). 607 // Do this check always, not just in debug mode (it's cheap). 608 if n.obj.pkg != check.pkg { 609 panic("imported type with unresolved underlying type") 610 } 611 n.underlying = u 612 } 613 614 return u 615 } 616 617 func (n *Named) lookupMethod(pkg *Package, name string, foldCase bool) (int, *Func) { 618 n.resolve() 619 if samePkg(n.obj.pkg, pkg) || isExported(name) || foldCase { 620 // If n is an instance, we may not have yet instantiated all of its methods. 621 // Look up the method index in orig, and only instantiate method at the 622 // matching index (if any). 623 if i := n.Origin().methodIndex(name, foldCase); i >= 0 { 624 // For instances, m.Method(i) will be different from the orig method. 625 return i, n.Method(i) 626 } 627 } 628 return -1, nil 629 } 630 631 // context returns the type-checker context. 632 func (check *Checker) context() *Context { 633 if check.ctxt == nil { 634 check.ctxt = NewContext() 635 } 636 return check.ctxt 637 } 638 639 // expandUnderlying substitutes type arguments in the underlying type n.orig, 640 // returning the result. Returns Typ[Invalid] if there was an error. 641 func (n *Named) expandUnderlying() Type { 642 check := n.check 643 if check != nil && check.conf._Trace { 644 check.trace(n.obj.pos, "-- Named.expandUnderlying %s", n) 645 check.indent++ 646 defer func() { 647 check.indent-- 648 check.trace(n.obj.pos, "=> %s (tparams = %s, under = %s)", n, n.tparams.list(), n.underlying) 649 }() 650 } 651 652 assert(n.inst.orig.underlying != nil) 653 if n.inst.ctxt == nil { 654 n.inst.ctxt = NewContext() 655 } 656 657 orig := n.inst.orig 658 targs := n.inst.targs 659 660 if asNamed(orig.underlying) != nil { 661 // We should only get a Named underlying type here during type checking 662 // (for example, in recursive type declarations). 663 assert(check != nil) 664 } 665 666 if orig.tparams.Len() != targs.Len() { 667 // Mismatching arg and tparam length may be checked elsewhere. 668 return Typ[Invalid] 669 } 670 671 // Ensure that an instance is recorded before substituting, so that we 672 // resolve n for any recursive references. 673 h := n.inst.ctxt.instanceHash(orig, targs.list()) 674 n2 := n.inst.ctxt.update(h, orig, n.TypeArgs().list(), n) 675 assert(n == n2) 676 677 smap := makeSubstMap(orig.tparams.list(), targs.list()) 678 var ctxt *Context 679 if check != nil { 680 ctxt = check.context() 681 } 682 underlying := n.check.subst(n.obj.pos, orig.underlying, smap, n, ctxt) 683 // If the underlying type of n is an interface, we need to set the receiver of 684 // its methods accurately -- we set the receiver of interface methods on 685 // the RHS of a type declaration to the defined type. 686 if iface, _ := underlying.(*Interface); iface != nil { 687 if methods, copied := replaceRecvType(iface.methods, orig, n); copied { 688 // If the underlying type doesn't actually use type parameters, it's 689 // possible that it wasn't substituted. In this case we need to create 690 // a new *Interface before modifying receivers. 691 if iface == orig.underlying { 692 old := iface 693 iface = check.newInterface() 694 iface.embeddeds = old.embeddeds 695 assert(old.complete) // otherwise we are copying incomplete data 696 iface.complete = old.complete 697 iface.implicit = old.implicit // should be false but be conservative 698 underlying = iface 699 } 700 iface.methods = methods 701 iface.tset = nil // recompute type set with new methods 702 703 // If check != nil, check.newInterface will have saved the interface for later completion. 704 if check == nil { // golang/go#61561: all newly created interfaces must be fully evaluated 705 iface.typeSet() 706 } 707 } 708 } 709 710 return underlying 711 } 712 713 // safeUnderlying returns the underlying type of typ without expanding 714 // instances, to avoid infinite recursion. 715 // 716 // TODO(rfindley): eliminate this function or give it a better name. 717 func safeUnderlying(typ Type) Type { 718 if t := asNamed(typ); t != nil { 719 return t.underlying 720 } 721 return typ.Underlying() 722 } 723