| 1 | // Copyright 2018 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 | // Package objectpath defines a naming scheme for types.Objects |
| 6 | // (that is, named entities in Go programs) relative to their enclosing |
| 7 | // package. |
| 8 | // |
| 9 | // Type-checker objects are canonical, so they are usually identified by |
| 10 | // their address in memory (a pointer), but a pointer has meaning only |
| 11 | // within one address space. By contrast, objectpath names allow the |
| 12 | // identity of an object to be sent from one program to another, |
| 13 | // establishing a correspondence between types.Object variables that are |
| 14 | // distinct but logically equivalent. |
| 15 | // |
| 16 | // A single object may have multiple paths. In this example, |
| 17 | // |
| 18 | // type A struct{ X int } |
| 19 | // type B A |
| 20 | // |
| 21 | // the field X has two paths due to its membership of both A and B. |
| 22 | // The For(obj) function always returns one of these paths, arbitrarily |
| 23 | // but consistently. |
| 24 | package objectpath |
| 25 | |
| 26 | import ( |
| 27 | "fmt" |
| 28 | "go/types" |
| 29 | "sort" |
| 30 | "strconv" |
| 31 | "strings" |
| 32 | |
| 33 | "golang.org/x/tools/internal/typeparams" |
| 34 | ) |
| 35 | |
| 36 | // A Path is an opaque name that identifies a types.Object |
| 37 | // relative to its package. Conceptually, the name consists of a |
| 38 | // sequence of destructuring operations applied to the package scope |
| 39 | // to obtain the original object. |
| 40 | // The name does not include the package itself. |
| 41 | type Path string |
| 42 | |
| 43 | // Encoding |
| 44 | // |
| 45 | // An object path is a textual and (with training) human-readable encoding |
| 46 | // of a sequence of destructuring operators, starting from a types.Package. |
| 47 | // The sequences represent a path through the package/object/type graph. |
| 48 | // We classify these operators by their type: |
| 49 | // |
| 50 | // PO package->object Package.Scope.Lookup |
| 51 | // OT object->type Object.Type |
| 52 | // TT type->type Type.{Elem,Key,Params,Results,Underlying} [EKPRU] |
| 53 | // TO type->object Type.{At,Field,Method,Obj} [AFMO] |
| 54 | // |
| 55 | // All valid paths start with a package and end at an object |
| 56 | // and thus may be defined by the regular language: |
| 57 | // |
| 58 | // objectpath = PO (OT TT* TO)* |
| 59 | // |
| 60 | // The concrete encoding follows directly: |
| 61 | // - The only PO operator is Package.Scope.Lookup, which requires an identifier. |
| 62 | // - The only OT operator is Object.Type, |
| 63 | // which we encode as '.' because dot cannot appear in an identifier. |
| 64 | // - The TT operators are encoded as [EKPRUTC]; |
| 65 | // one of these (TypeParam) requires an integer operand, |
| 66 | // which is encoded as a string of decimal digits. |
| 67 | // - The TO operators are encoded as [AFMO]; |
| 68 | // three of these (At,Field,Method) require an integer operand, |
| 69 | // which is encoded as a string of decimal digits. |
| 70 | // These indices are stable across different representations |
| 71 | // of the same package, even source and export data. |
| 72 | // The indices used are implementation specific and may not correspond to |
| 73 | // the argument to the go/types function. |
| 74 | // |
| 75 | // In the example below, |
| 76 | // |
| 77 | // package p |
| 78 | // |
| 79 | // type T interface { |
| 80 | // f() (a string, b struct{ X int }) |
| 81 | // } |
| 82 | // |
| 83 | // field X has the path "T.UM0.RA1.F0", |
| 84 | // representing the following sequence of operations: |
| 85 | // |
| 86 | // p.Lookup("T") T |
| 87 | // .Type().Underlying().Method(0). f |
| 88 | // .Type().Results().At(1) b |
| 89 | // .Type().Field(0) X |
| 90 | // |
| 91 | // The encoding is not maximally compact---every R or P is |
| 92 | // followed by an A, for example---but this simplifies the |
| 93 | // encoder and decoder. |
| 94 | const ( |
| 95 | // object->type operators |
| 96 | opType = '.' // .Type() (Object) |
| 97 | |
| 98 | // type->type operators |
| 99 | opElem = 'E' // .Elem() (Pointer, Slice, Array, Chan, Map) |
| 100 | opKey = 'K' // .Key() (Map) |
| 101 | opParams = 'P' // .Params() (Signature) |
| 102 | opResults = 'R' // .Results() (Signature) |
| 103 | opUnderlying = 'U' // .Underlying() (Named) |
| 104 | opTypeParam = 'T' // .TypeParams.At(i) (Named, Signature) |
| 105 | opConstraint = 'C' // .Constraint() (TypeParam) |
| 106 | |
| 107 | // type->object operators |
| 108 | opAt = 'A' // .At(i) (Tuple) |
| 109 | opField = 'F' // .Field(i) (Struct) |
| 110 | opMethod = 'M' // .Method(i) (Named or Interface; not Struct: "promoted" names are ignored) |
| 111 | opObj = 'O' // .Obj() (Named, TypeParam) |
| 112 | ) |
| 113 | |
| 114 | // The For function returns the path to an object relative to its package, |
| 115 | // or an error if the object is not accessible from the package's Scope. |
| 116 | // |
| 117 | // The For function guarantees to return a path only for the following objects: |
| 118 | // - package-level types |
| 119 | // - exported package-level non-types |
| 120 | // - methods |
| 121 | // - parameter and result variables |
| 122 | // - struct fields |
| 123 | // These objects are sufficient to define the API of their package. |
| 124 | // The objects described by a package's export data are drawn from this set. |
| 125 | // |
| 126 | // For does not return a path for predeclared names, imported package |
| 127 | // names, local names, and unexported package-level names (except |
| 128 | // types). |
| 129 | // |
| 130 | // Example: given this definition, |
| 131 | // |
| 132 | // package p |
| 133 | // |
| 134 | // type T interface { |
| 135 | // f() (a string, b struct{ X int }) |
| 136 | // } |
| 137 | // |
| 138 | // For(X) would return a path that denotes the following sequence of operations: |
| 139 | // |
| 140 | // p.Scope().Lookup("T") (TypeName T) |
| 141 | // .Type().Underlying().Method(0). (method Func f) |
| 142 | // .Type().Results().At(1) (field Var b) |
| 143 | // .Type().Field(0) (field Var X) |
| 144 | // |
| 145 | // where p is the package (*types.Package) to which X belongs. |
| 146 | func For(obj types.Object) (Path, error) { |
| 147 | pkg := obj.Pkg() |
| 148 | |
| 149 | // This table lists the cases of interest. |
| 150 | // |
| 151 | // Object Action |
| 152 | // ------ ------ |
| 153 | // nil reject |
| 154 | // builtin reject |
| 155 | // pkgname reject |
| 156 | // label reject |
| 157 | // var |
| 158 | // package-level accept |
| 159 | // func param/result accept |
| 160 | // local reject |
| 161 | // struct field accept |
| 162 | // const |
| 163 | // package-level accept |
| 164 | // local reject |
| 165 | // func |
| 166 | // package-level accept |
| 167 | // init functions reject |
| 168 | // concrete method accept |
| 169 | // interface method accept |
| 170 | // type |
| 171 | // package-level accept |
| 172 | // local reject |
| 173 | // |
| 174 | // The only accessible package-level objects are members of pkg itself. |
| 175 | // |
| 176 | // The cases are handled in four steps: |
| 177 | // |
| 178 | // 1. reject nil and builtin |
| 179 | // 2. accept package-level objects |
| 180 | // 3. reject obviously invalid objects |
| 181 | // 4. search the API for the path to the param/result/field/method. |
| 182 | |
| 183 | // 1. reference to nil or builtin? |
| 184 | if pkg == nil { |
| 185 | return "", fmt.Errorf("predeclared %s has no path", obj) |
| 186 | } |
| 187 | scope := pkg.Scope() |
| 188 | |
| 189 | // 2. package-level object? |
| 190 | if scope.Lookup(obj.Name()) == obj { |
| 191 | // Only exported objects (and non-exported types) have a path. |
| 192 | // Non-exported types may be referenced by other objects. |
| 193 | if _, ok := obj.(*types.TypeName); !ok && !obj.Exported() { |
| 194 | return "", fmt.Errorf("no path for non-exported %v", obj) |
| 195 | } |
| 196 | return Path(obj.Name()), nil |
| 197 | } |
| 198 | |
| 199 | // 3. Not a package-level object. |
| 200 | // Reject obviously non-viable cases. |
| 201 | switch obj := obj.(type) { |
| 202 | case *types.TypeName: |
| 203 | if _, ok := obj.Type().(*typeparams.TypeParam); !ok { |
| 204 | // With the exception of type parameters, only package-level type names |
| 205 | // have a path. |
| 206 | return "", fmt.Errorf("no path for %v", obj) |
| 207 | } |
| 208 | case *types.Const, // Only package-level constants have a path. |
| 209 | *types.Label, // Labels are function-local. |
| 210 | *types.PkgName: // PkgNames are file-local. |
| 211 | return "", fmt.Errorf("no path for %v", obj) |
| 212 | |
| 213 | case *types.Var: |
| 214 | // Could be: |
| 215 | // - a field (obj.IsField()) |
| 216 | // - a func parameter or result |
| 217 | // - a local var. |
| 218 | // Sadly there is no way to distinguish |
| 219 | // a param/result from a local |
| 220 | // so we must proceed to the find. |
| 221 | |
| 222 | case *types.Func: |
| 223 | // A func, if not package-level, must be a method. |
| 224 | if recv := obj.Type().(*types.Signature).Recv(); recv == nil { |
| 225 | return "", fmt.Errorf("func is not a method: %v", obj) |
| 226 | } |
| 227 | |
| 228 | if path, ok := concreteMethod(obj); ok { |
| 229 | // Fast path for concrete methods that avoids looping over scope. |
| 230 | return path, nil |
| 231 | } |
| 232 | |
| 233 | default: |
| 234 | panic(obj) |
| 235 | } |
| 236 | |
| 237 | // 4. Search the API for the path to the var (field/param/result) or method. |
| 238 | |
| 239 | // First inspect package-level named types. |
| 240 | // In the presence of path aliases, these give |
| 241 | // the best paths because non-types may |
| 242 | // refer to types, but not the reverse. |
| 243 | empty := make([]byte, 0, 48) // initial space |
| 244 | names := scope.Names() |
| 245 | for _, name := range names { |
| 246 | o := scope.Lookup(name) |
| 247 | tname, ok := o.(*types.TypeName) |
| 248 | if !ok { |
| 249 | continue // handle non-types in second pass |
| 250 | } |
| 251 | |
| 252 | path := append(empty, name...) |
| 253 | path = append(path, opType) |
| 254 | |
| 255 | T := o.Type() |
| 256 | |
| 257 | if tname.IsAlias() { |
| 258 | // type alias |
| 259 | if r := find(obj, T, path, nil); r != nil { |
| 260 | return Path(r), nil |
| 261 | } |
| 262 | } else { |
| 263 | if named, _ := T.(*types.Named); named != nil { |
| 264 | if r := findTypeParam(obj, typeparams.ForNamed(named), path, nil); r != nil { |
| 265 | // generic named type |
| 266 | return Path(r), nil |
| 267 | } |
| 268 | } |
| 269 | // defined (named) type |
| 270 | if r := find(obj, T.Underlying(), append(path, opUnderlying), nil); r != nil { |
| 271 | return Path(r), nil |
| 272 | } |
| 273 | } |
| 274 | } |
| 275 | |
| 276 | // Then inspect everything else: |
| 277 | // non-types, and declared methods of defined types. |
| 278 | for _, name := range names { |
| 279 | o := scope.Lookup(name) |
| 280 | path := append(empty, name...) |
| 281 | if _, ok := o.(*types.TypeName); !ok { |
| 282 | if o.Exported() { |
| 283 | // exported non-type (const, var, func) |
| 284 | if r := find(obj, o.Type(), append(path, opType), nil); r != nil { |
| 285 | return Path(r), nil |
| 286 | } |
| 287 | } |
| 288 | continue |
| 289 | } |
| 290 | |
| 291 | // Inspect declared methods of defined types. |
| 292 | if T, ok := o.Type().(*types.Named); ok { |
| 293 | path = append(path, opType) |
| 294 | // Note that method index here is always with respect |
| 295 | // to canonical ordering of methods, regardless of how |
| 296 | // they appear in the underlying type. |
| 297 | canonical := canonicalize(T) |
| 298 | for i := 0; i < len(canonical); i++ { |
| 299 | m := canonical[i] |
| 300 | path2 := appendOpArg(path, opMethod, i) |
| 301 | if m == obj { |
| 302 | return Path(path2), nil // found declared method |
| 303 | } |
| 304 | if r := find(obj, m.Type(), append(path2, opType), nil); r != nil { |
| 305 | return Path(r), nil |
| 306 | } |
| 307 | } |
| 308 | } |
| 309 | } |
| 310 | |
| 311 | return "", fmt.Errorf("can't find path for %v in %s", obj, pkg.Path()) |
| 312 | } |
| 313 | |
| 314 | func appendOpArg(path []byte, op byte, arg int) []byte { |
| 315 | path = append(path, op) |
| 316 | path = strconv.AppendInt(path, int64(arg), 10) |
| 317 | return path |
| 318 | } |
| 319 | |
| 320 | // concreteMethod returns the path for meth, which must have a non-nil receiver. |
| 321 | // The second return value indicates success and may be false if the method is |
| 322 | // an interface method or if it is an instantiated method. |
| 323 | // |
| 324 | // This function is just an optimization that avoids the general scope walking |
| 325 | // approach. You are expected to fall back to the general approach if this |
| 326 | // function fails. |
| 327 | func concreteMethod(meth *types.Func) (Path, bool) { |
| 328 | // Concrete methods can only be declared on package-scoped named types. For |
| 329 | // that reason we can skip the expensive walk over the package scope: the |
| 330 | // path will always be package -> named type -> method. We can trivially get |
| 331 | // the type name from the receiver, and only have to look over the type's |
| 332 | // methods to find the method index. |
| 333 | // |
| 334 | // Methods on generic types require special consideration, however. Consider |
| 335 | // the following package: |
| 336 | // |
| 337 | // L1: type S[T any] struct{} |
| 338 | // L2: func (recv S[A]) Foo() { recv.Bar() } |
| 339 | // L3: func (recv S[B]) Bar() { } |
| 340 | // L4: type Alias = S[int] |
| 341 | // L5: func _[T any]() { var s S[int]; s.Foo() } |
| 342 | // |
| 343 | // The receivers of methods on generic types are instantiations. L2 and L3 |
| 344 | // instantiate S with the type-parameters A and B, which are scoped to the |
| 345 | // respective methods. L4 and L5 each instantiate S with int. Each of these |
| 346 | // instantiations has its own method set, full of methods (and thus objects) |
| 347 | // with receivers whose types are the respective instantiations. In other |
| 348 | // words, we have |
| 349 | // |
| 350 | // S[A].Foo, S[A].Bar |
| 351 | // S[B].Foo, S[B].Bar |
| 352 | // S[int].Foo, S[int].Bar |
| 353 | // |
| 354 | // We may thus be trying to produce object paths for any of these objects. |
| 355 | // |
| 356 | // S[A].Foo and S[B].Bar are the origin methods, and their paths are S.Foo |
| 357 | // and S.Bar, which are the paths that this function naturally produces. |
| 358 | // |
| 359 | // S[A].Bar, S[B].Foo, and both methods on S[int] are instantiations that |
| 360 | // don't correspond to the origin methods. For S[int], this is significant. |
| 361 | // The most precise object path for S[int].Foo, for example, is Alias.Foo, |
| 362 | // not S.Foo. Our function, however, would produce S.Foo, which would |
| 363 | // resolve to a different object. |
| 364 | // |
| 365 | // For S[A].Bar and S[B].Foo it could be argued that S.Bar and S.Foo are |
| 366 | // still the correct paths, since only the origin methods have meaningful |
| 367 | // paths. But this is likely only true for trivial cases and has edge cases. |
| 368 | // Since this function is only an optimization, we err on the side of giving |
| 369 | // up, deferring to the slower but definitely correct algorithm. Most users |
| 370 | // of objectpath will only be giving us origin methods, anyway, as referring |
| 371 | // to instantiated methods is usually not useful. |
| 372 | |
| 373 | if typeparams.OriginMethod(meth) != meth { |
| 374 | return "", false |
| 375 | } |
| 376 | |
| 377 | recvT := meth.Type().(*types.Signature).Recv().Type() |
| 378 | if ptr, ok := recvT.(*types.Pointer); ok { |
| 379 | recvT = ptr.Elem() |
| 380 | } |
| 381 | |
| 382 | named, ok := recvT.(*types.Named) |
| 383 | if !ok { |
| 384 | return "", false |
| 385 | } |
| 386 | |
| 387 | if types.IsInterface(named) { |
| 388 | // Named interfaces don't have to be package-scoped |
| 389 | // |
| 390 | // TODO(dominikh): opt: if scope.Lookup(name) == named, then we can apply this optimization to interface |
| 391 | // methods, too, I think. |
| 392 | return "", false |
| 393 | } |
| 394 | |
| 395 | // Preallocate space for the name, opType, opMethod, and some digits. |
| 396 | name := named.Obj().Name() |
| 397 | path := make([]byte, 0, len(name)+8) |
| 398 | path = append(path, name...) |
| 399 | path = append(path, opType) |
| 400 | canonical := canonicalize(named) |
| 401 | for i, m := range canonical { |
| 402 | if m == meth { |
| 403 | path = appendOpArg(path, opMethod, i) |
| 404 | return Path(path), true |
| 405 | } |
| 406 | } |
| 407 | |
| 408 | panic(fmt.Sprintf("couldn't find method %s on type %s", meth, named)) |
| 409 | } |
| 410 | |
| 411 | // find finds obj within type T, returning the path to it, or nil if not found. |
| 412 | // |
| 413 | // The seen map is used to short circuit cycles through type parameters. If |
| 414 | // nil, it will be allocated as necessary. |
| 415 | func find(obj types.Object, T types.Type, path []byte, seen map[*types.TypeName]bool) []byte { |
| 416 | switch T := T.(type) { |
| 417 | case *types.Basic, *types.Named: |
| 418 | // Named types belonging to pkg were handled already, |
| 419 | // so T must belong to another package. No path. |
| 420 | return nil |
| 421 | case *types.Pointer: |
| 422 | return find(obj, T.Elem(), append(path, opElem), seen) |
| 423 | case *types.Slice: |
| 424 | return find(obj, T.Elem(), append(path, opElem), seen) |
| 425 | case *types.Array: |
| 426 | return find(obj, T.Elem(), append(path, opElem), seen) |
| 427 | case *types.Chan: |
| 428 | return find(obj, T.Elem(), append(path, opElem), seen) |
| 429 | case *types.Map: |
| 430 | if r := find(obj, T.Key(), append(path, opKey), seen); r != nil { |
| 431 | return r |
| 432 | } |
| 433 | return find(obj, T.Elem(), append(path, opElem), seen) |
| 434 | case *types.Signature: |
| 435 | if r := findTypeParam(obj, typeparams.ForSignature(T), path, seen); r != nil { |
| 436 | return r |
| 437 | } |
| 438 | if r := find(obj, T.Params(), append(path, opParams), seen); r != nil { |
| 439 | return r |
| 440 | } |
| 441 | return find(obj, T.Results(), append(path, opResults), seen) |
| 442 | case *types.Struct: |
| 443 | for i := 0; i < T.NumFields(); i++ { |
| 444 | fld := T.Field(i) |
| 445 | path2 := appendOpArg(path, opField, i) |
| 446 | if fld == obj { |
| 447 | return path2 // found field var |
| 448 | } |
| 449 | if r := find(obj, fld.Type(), append(path2, opType), seen); r != nil { |
| 450 | return r |
| 451 | } |
| 452 | } |
| 453 | return nil |
| 454 | case *types.Tuple: |
| 455 | for i := 0; i < T.Len(); i++ { |
| 456 | v := T.At(i) |
| 457 | path2 := appendOpArg(path, opAt, i) |
| 458 | if v == obj { |
| 459 | return path2 // found param/result var |
| 460 | } |
| 461 | if r := find(obj, v.Type(), append(path2, opType), seen); r != nil { |
| 462 | return r |
| 463 | } |
| 464 | } |
| 465 | return nil |
| 466 | case *types.Interface: |
| 467 | for i := 0; i < T.NumMethods(); i++ { |
| 468 | m := T.Method(i) |
| 469 | path2 := appendOpArg(path, opMethod, i) |
| 470 | if m == obj { |
| 471 | return path2 // found interface method |
| 472 | } |
| 473 | if r := find(obj, m.Type(), append(path2, opType), seen); r != nil { |
| 474 | return r |
| 475 | } |
| 476 | } |
| 477 | return nil |
| 478 | case *typeparams.TypeParam: |
| 479 | name := T.Obj() |
| 480 | if name == obj { |
| 481 | return append(path, opObj) |
| 482 | } |
| 483 | if seen[name] { |
| 484 | return nil |
| 485 | } |
| 486 | if seen == nil { |
| 487 | seen = make(map[*types.TypeName]bool) |
| 488 | } |
| 489 | seen[name] = true |
| 490 | if r := find(obj, T.Constraint(), append(path, opConstraint), seen); r != nil { |
| 491 | return r |
| 492 | } |
| 493 | return nil |
| 494 | } |
| 495 | panic(T) |
| 496 | } |
| 497 | |
| 498 | func findTypeParam(obj types.Object, list *typeparams.TypeParamList, path []byte, seen map[*types.TypeName]bool) []byte { |
| 499 | for i := 0; i < list.Len(); i++ { |
| 500 | tparam := list.At(i) |
| 501 | path2 := appendOpArg(path, opTypeParam, i) |
| 502 | if r := find(obj, tparam, path2, seen); r != nil { |
| 503 | return r |
| 504 | } |
| 505 | } |
| 506 | return nil |
| 507 | } |
| 508 | |
| 509 | // Object returns the object denoted by path p within the package pkg. |
| 510 | func Object(pkg *types.Package, p Path) (types.Object, error) { |
| 511 | if p == "" { |
| 512 | return nil, fmt.Errorf("empty path") |
| 513 | } |
| 514 | |
| 515 | pathstr := string(p) |
| 516 | var pkgobj, suffix string |
| 517 | if dot := strings.IndexByte(pathstr, opType); dot < 0 { |
| 518 | pkgobj = pathstr |
| 519 | } else { |
| 520 | pkgobj = pathstr[:dot] |
| 521 | suffix = pathstr[dot:] // suffix starts with "." |
| 522 | } |
| 523 | |
| 524 | obj := pkg.Scope().Lookup(pkgobj) |
| 525 | if obj == nil { |
| 526 | return nil, fmt.Errorf("package %s does not contain %q", pkg.Path(), pkgobj) |
| 527 | } |
| 528 | |
| 529 | // abstraction of *types.{Pointer,Slice,Array,Chan,Map} |
| 530 | type hasElem interface { |
| 531 | Elem() types.Type |
| 532 | } |
| 533 | // abstraction of *types.{Named,Signature} |
| 534 | type hasTypeParams interface { |
| 535 | TypeParams() *typeparams.TypeParamList |
| 536 | } |
| 537 | // abstraction of *types.{Named,TypeParam} |
| 538 | type hasObj interface { |
| 539 | Obj() *types.TypeName |
| 540 | } |
| 541 | |
| 542 | // The loop state is the pair (t, obj), |
| 543 | // exactly one of which is non-nil, initially obj. |
| 544 | // All suffixes start with '.' (the only object->type operation), |
| 545 | // followed by optional type->type operations, |
| 546 | // then a type->object operation. |
| 547 | // The cycle then repeats. |
| 548 | var t types.Type |
| 549 | for suffix != "" { |
| 550 | code := suffix[0] |
| 551 | suffix = suffix[1:] |
| 552 | |
| 553 | // Codes [AFM] have an integer operand. |
| 554 | var index int |
| 555 | switch code { |
| 556 | case opAt, opField, opMethod, opTypeParam: |
| 557 | rest := strings.TrimLeft(suffix, "0123456789") |
| 558 | numerals := suffix[:len(suffix)-len(rest)] |
| 559 | suffix = rest |
| 560 | i, err := strconv.Atoi(numerals) |
| 561 | if err != nil { |
| 562 | return nil, fmt.Errorf("invalid path: bad numeric operand %q for code %q", numerals, code) |
| 563 | } |
| 564 | index = int(i) |
| 565 | case opObj: |
| 566 | // no operand |
| 567 | default: |
| 568 | // The suffix must end with a type->object operation. |
| 569 | if suffix == "" { |
| 570 | return nil, fmt.Errorf("invalid path: ends with %q, want [AFMO]", code) |
| 571 | } |
| 572 | } |
| 573 | |
| 574 | if code == opType { |
| 575 | if t != nil { |
| 576 | return nil, fmt.Errorf("invalid path: unexpected %q in type context", opType) |
| 577 | } |
| 578 | t = obj.Type() |
| 579 | obj = nil |
| 580 | continue |
| 581 | } |
| 582 | |
| 583 | if t == nil { |
| 584 | return nil, fmt.Errorf("invalid path: code %q in object context", code) |
| 585 | } |
| 586 | |
| 587 | // Inv: t != nil, obj == nil |
| 588 | |
| 589 | switch code { |
| 590 | case opElem: |
| 591 | hasElem, ok := t.(hasElem) // Pointer, Slice, Array, Chan, Map |
| 592 | if !ok { |
| 593 | return nil, fmt.Errorf("cannot apply %q to %s (got %T, want pointer, slice, array, chan or map)", code, t, t) |
| 594 | } |
| 595 | t = hasElem.Elem() |
| 596 | |
| 597 | case opKey: |
| 598 | mapType, ok := t.(*types.Map) |
| 599 | if !ok { |
| 600 | return nil, fmt.Errorf("cannot apply %q to %s (got %T, want map)", code, t, t) |
| 601 | } |
| 602 | t = mapType.Key() |
| 603 | |
| 604 | case opParams: |
| 605 | sig, ok := t.(*types.Signature) |
| 606 | if !ok { |
| 607 | return nil, fmt.Errorf("cannot apply %q to %s (got %T, want signature)", code, t, t) |
| 608 | } |
| 609 | t = sig.Params() |
| 610 | |
| 611 | case opResults: |
| 612 | sig, ok := t.(*types.Signature) |
| 613 | if !ok { |
| 614 | return nil, fmt.Errorf("cannot apply %q to %s (got %T, want signature)", code, t, t) |
| 615 | } |
| 616 | t = sig.Results() |
| 617 | |
| 618 | case opUnderlying: |
| 619 | named, ok := t.(*types.Named) |
| 620 | if !ok { |
| 621 | return nil, fmt.Errorf("cannot apply %q to %s (got %T, want named)", code, t, t) |
| 622 | } |
| 623 | t = named.Underlying() |
| 624 | |
| 625 | case opTypeParam: |
| 626 | hasTypeParams, ok := t.(hasTypeParams) // Named, Signature |
| 627 | if !ok { |
| 628 | return nil, fmt.Errorf("cannot apply %q to %s (got %T, want named or signature)", code, t, t) |
| 629 | } |
| 630 | tparams := hasTypeParams.TypeParams() |
| 631 | if n := tparams.Len(); index >= n { |
| 632 | return nil, fmt.Errorf("tuple index %d out of range [0-%d)", index, n) |
| 633 | } |
| 634 | t = tparams.At(index) |
| 635 | |
| 636 | case opConstraint: |
| 637 | tparam, ok := t.(*typeparams.TypeParam) |
| 638 | if !ok { |
| 639 | return nil, fmt.Errorf("cannot apply %q to %s (got %T, want type parameter)", code, t, t) |
| 640 | } |
| 641 | t = tparam.Constraint() |
| 642 | |
| 643 | case opAt: |
| 644 | tuple, ok := t.(*types.Tuple) |
| 645 | if !ok { |
| 646 | return nil, fmt.Errorf("cannot apply %q to %s (got %T, want tuple)", code, t, t) |
| 647 | } |
| 648 | if n := tuple.Len(); index >= n { |
| 649 | return nil, fmt.Errorf("tuple index %d out of range [0-%d)", index, n) |
| 650 | } |
| 651 | obj = tuple.At(index) |
| 652 | t = nil |
| 653 | |
| 654 | case opField: |
| 655 | structType, ok := t.(*types.Struct) |
| 656 | if !ok { |
| 657 | return nil, fmt.Errorf("cannot apply %q to %s (got %T, want struct)", code, t, t) |
| 658 | } |
| 659 | if n := structType.NumFields(); index >= n { |
| 660 | return nil, fmt.Errorf("field index %d out of range [0-%d)", index, n) |
| 661 | } |
| 662 | obj = structType.Field(index) |
| 663 | t = nil |
| 664 | |
| 665 | case opMethod: |
| 666 | hasMethods, ok := t.(hasMethods) // Interface or Named |
| 667 | if !ok { |
| 668 | return nil, fmt.Errorf("cannot apply %q to %s (got %T, want interface or named)", code, t, t) |
| 669 | } |
| 670 | canonical := canonicalize(hasMethods) |
| 671 | if n := len(canonical); index >= n { |
| 672 | return nil, fmt.Errorf("method index %d out of range [0-%d)", index, n) |
| 673 | } |
| 674 | obj = canonical[index] |
| 675 | t = nil |
| 676 | |
| 677 | case opObj: |
| 678 | hasObj, ok := t.(hasObj) |
| 679 | if !ok { |
| 680 | return nil, fmt.Errorf("cannot apply %q to %s (got %T, want named or type param)", code, t, t) |
| 681 | } |
| 682 | obj = hasObj.Obj() |
| 683 | t = nil |
| 684 | |
| 685 | default: |
| 686 | return nil, fmt.Errorf("invalid path: unknown code %q", code) |
| 687 | } |
| 688 | } |
| 689 | |
| 690 | if obj.Pkg() != pkg { |
| 691 | return nil, fmt.Errorf("path denotes %s, which belongs to a different package", obj) |
| 692 | } |
| 693 | |
| 694 | return obj, nil // success |
| 695 | } |
| 696 | |
| 697 | // hasMethods is an abstraction of *types.{Interface,Named}. This is pulled up |
| 698 | // because it is used by methodOrdering, which is in turn used by both encoding |
| 699 | // and decoding. |
| 700 | type hasMethods interface { |
| 701 | Method(int) *types.Func |
| 702 | NumMethods() int |
| 703 | } |
| 704 | |
| 705 | // canonicalize returns a canonical order for the methods in a hasMethod. |
| 706 | func canonicalize(hm hasMethods) []*types.Func { |
| 707 | count := hm.NumMethods() |
| 708 | if count <= 0 { |
| 709 | return nil |
| 710 | } |
| 711 | canon := make([]*types.Func, count) |
| 712 | for i := 0; i < count; i++ { |
| 713 | canon[i] = hm.Method(i) |
| 714 | } |
| 715 | less := func(i, j int) bool { |
| 716 | return canon[i].Id() < canon[j].Id() |
| 717 | } |
| 718 | sort.Slice(canon, less) |
| 719 | return canon |
| 720 | } |
| 721 |
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