Source file src/go/types/api.go
1 // Copyright 2012 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 types declares the data types and implements 6 // the algorithms for type-checking of Go packages. Use 7 // [Config.Check] to invoke the type checker for a package. 8 // Alternatively, create a new type checker with [NewChecker] 9 // and invoke it incrementally by calling [Checker.Files]. 10 // 11 // Type-checking consists of several interdependent phases: 12 // 13 // Name resolution maps each identifier ([ast.Ident]) in the program 14 // to the symbol ([Object]) it denotes. Use the Defs and Uses fields 15 // of [Info] or the [Info.ObjectOf] method to find the symbol for an 16 // identifier, and use the Implicits field of [Info] to find the 17 // symbol for certain other kinds of syntax node. 18 // 19 // Constant folding computes the exact constant value 20 // ([constant.Value]) of every expression ([ast.Expr]) that is a 21 // compile-time constant. Use the Types field of [Info] to find the 22 // results of constant folding for an expression. 23 // 24 // Type deduction computes the type ([Type]) of every expression 25 // ([ast.Expr]) and checks for compliance with the language 26 // specification. Use the Types field of [Info] for the results of 27 // type deduction. 28 // 29 // Applications that need to type-check one or more complete packages 30 // of Go source code may find it more convenient not to invoke the 31 // type checker directly but instead to use the Load function in 32 // package [golang.org/x/tools/go/packages]. 33 // 34 // For a tutorial, see https://go.dev/s/types-tutorial. 35 package types 36 37 import ( 38 "bytes" 39 "fmt" 40 "go/ast" 41 "go/constant" 42 "go/token" 43 . "internal/types/errors" 44 _ "unsafe" // for linkname 45 ) 46 47 // An Error describes a type-checking error; it implements the error interface. 48 // A "soft" error is an error that still permits a valid interpretation of a 49 // package (such as "unused variable"); "hard" errors may lead to unpredictable 50 // behavior if ignored. 51 type Error struct { 52 Fset *token.FileSet // file set for interpretation of Pos 53 Pos token.Pos // error position 54 Msg string // error message 55 Soft bool // if set, error is "soft" 56 57 // go116code is a future API, unexported as the set of error codes is large 58 // and likely to change significantly during experimentation. Tools wishing 59 // to preview this feature may read go116code using reflection (see 60 // errorcodes_test.go), but beware that there is no guarantee of future 61 // compatibility. 62 go116code Code 63 go116start token.Pos 64 go116end token.Pos 65 } 66 67 // Error returns an error string formatted as follows: 68 // filename:line:column: message 69 func (err Error) Error() string { 70 return fmt.Sprintf("%s: %s", err.Fset.Position(err.Pos), err.Msg) 71 } 72 73 // An ArgumentError holds an error associated with an argument index. 74 type ArgumentError struct { 75 Index int 76 Err error 77 } 78 79 func (e *ArgumentError) Error() string { return e.Err.Error() } 80 func (e *ArgumentError) Unwrap() error { return e.Err } 81 82 // An Importer resolves import paths to Packages. 83 // 84 // CAUTION: This interface does not support the import of locally 85 // vendored packages. See https://golang.org/s/go15vendor. 86 // If possible, external implementations should implement [ImporterFrom]. 87 type Importer interface { 88 // Import returns the imported package for the given import path. 89 // The semantics is like for ImporterFrom.ImportFrom except that 90 // dir and mode are ignored (since they are not present). 91 Import(path string) (*Package, error) 92 } 93 94 // ImportMode is reserved for future use. 95 type ImportMode int 96 97 // An ImporterFrom resolves import paths to packages; it 98 // supports vendoring per https://golang.org/s/go15vendor. 99 // Use go/importer to obtain an ImporterFrom implementation. 100 type ImporterFrom interface { 101 // Importer is present for backward-compatibility. Calling 102 // Import(path) is the same as calling ImportFrom(path, "", 0); 103 // i.e., locally vendored packages may not be found. 104 // The types package does not call Import if an ImporterFrom 105 // is present. 106 Importer 107 108 // ImportFrom returns the imported package for the given import 109 // path when imported by a package file located in dir. 110 // If the import failed, besides returning an error, ImportFrom 111 // is encouraged to cache and return a package anyway, if one 112 // was created. This will reduce package inconsistencies and 113 // follow-on type checker errors due to the missing package. 114 // The mode value must be 0; it is reserved for future use. 115 // Two calls to ImportFrom with the same path and dir must 116 // return the same package. 117 ImportFrom(path, dir string, mode ImportMode) (*Package, error) 118 } 119 120 // A Config specifies the configuration for type checking. 121 // The zero value for Config is a ready-to-use default configuration. 122 type Config struct { 123 // Context is the context used for resolving global identifiers. If nil, the 124 // type checker will initialize this field with a newly created context. 125 Context *Context 126 127 // GoVersion describes the accepted Go language version. The string must 128 // start with a prefix of the form "go%d.%d" (e.g. "go1.20", "go1.21rc1", or 129 // "go1.21.0") or it must be empty; an empty string disables Go language 130 // version checks. If the format is invalid, invoking the type checker will 131 // result in an error. 132 GoVersion string 133 134 // If IgnoreFuncBodies is set, function bodies are not 135 // type-checked. 136 IgnoreFuncBodies bool 137 138 // If FakeImportC is set, `import "C"` (for packages requiring Cgo) 139 // declares an empty "C" package and errors are omitted for qualified 140 // identifiers referring to package C (which won't find an object). 141 // This feature is intended for the standard library cmd/api tool. 142 // 143 // Caution: Effects may be unpredictable due to follow-on errors. 144 // Do not use casually! 145 FakeImportC bool 146 147 // If go115UsesCgo is set, the type checker expects the 148 // _cgo_gotypes.go file generated by running cmd/cgo to be 149 // provided as a package source file. Qualified identifiers 150 // referring to package C will be resolved to cgo-provided 151 // declarations within _cgo_gotypes.go. 152 // 153 // It is an error to set both FakeImportC and go115UsesCgo. 154 go115UsesCgo bool 155 156 // If _Trace is set, a debug trace is printed to stdout. 157 _Trace bool 158 159 // If Error != nil, it is called with each error found 160 // during type checking; err has dynamic type Error. 161 // Secondary errors (for instance, to enumerate all types 162 // involved in an invalid recursive type declaration) have 163 // error strings that start with a '\t' character. 164 // If Error == nil, type-checking stops with the first 165 // error found. 166 Error func(err error) 167 168 // An importer is used to import packages referred to from 169 // import declarations. 170 // If the installed importer implements ImporterFrom, the type 171 // checker calls ImportFrom instead of Import. 172 // The type checker reports an error if an importer is needed 173 // but none was installed. 174 Importer Importer 175 176 // If Sizes != nil, it provides the sizing functions for package unsafe. 177 // Otherwise SizesFor("gc", "amd64") is used instead. 178 Sizes Sizes 179 180 // If DisableUnusedImportCheck is set, packages are not checked 181 // for unused imports. 182 DisableUnusedImportCheck bool 183 184 // If a non-empty _ErrorURL format string is provided, it is used 185 // to format an error URL link that is appended to the first line 186 // of an error message. ErrorURL must be a format string containing 187 // exactly one "%s" format, e.g. "[go.dev/e/%s]". 188 _ErrorURL string 189 190 // If EnableAlias is set, alias declarations produce an Alias type. Otherwise 191 // the alias information is only in the type name, which points directly to 192 // the actual (aliased) type. 193 // 194 // This setting must not differ among concurrent type-checking operations, 195 // since it affects the behavior of Universe.Lookup("any"). 196 // 197 // This flag will eventually be removed (with Go 1.24 at the earliest). 198 _EnableAlias bool 199 } 200 201 // Linkname for use from srcimporter. 202 //go:linkname srcimporter_setUsesCgo 203 204 func srcimporter_setUsesCgo(conf *Config) { 205 conf.go115UsesCgo = true 206 } 207 208 // Info holds result type information for a type-checked package. 209 // Only the information for which a map is provided is collected. 210 // If the package has type errors, the collected information may 211 // be incomplete. 212 type Info struct { 213 // Types maps expressions to their types, and for constant 214 // expressions, also their values. Invalid expressions are 215 // omitted. 216 // 217 // For (possibly parenthesized) identifiers denoting built-in 218 // functions, the recorded signatures are call-site specific: 219 // if the call result is not a constant, the recorded type is 220 // an argument-specific signature. Otherwise, the recorded type 221 // is invalid. 222 // 223 // The Types map does not record the type of every identifier, 224 // only those that appear where an arbitrary expression is 225 // permitted. For instance: 226 // - an identifier f in a selector expression x.f is found 227 // only in the Selections map; 228 // - an identifier z in a variable declaration 'var z int' 229 // is found only in the Defs map; 230 // - an identifier p denoting a package in a qualified 231 // identifier p.X is found only in the Uses map. 232 // 233 // Similarly, no type is recorded for the (synthetic) FuncType 234 // node in a FuncDecl.Type field, since there is no corresponding 235 // syntactic function type expression in the source in this case 236 // Instead, the function type is found in the Defs map entry for 237 // the corresponding function declaration. 238 Types map[ast.Expr]TypeAndValue 239 240 // Instances maps identifiers denoting generic types or functions to their 241 // type arguments and instantiated type. 242 // 243 // For example, Instances will map the identifier for 'T' in the type 244 // instantiation T[int, string] to the type arguments [int, string] and 245 // resulting instantiated *Named type. Given a generic function 246 // func F[A any](A), Instances will map the identifier for 'F' in the call 247 // expression F(int(1)) to the inferred type arguments [int], and resulting 248 // instantiated *Signature. 249 // 250 // Invariant: Instantiating Uses[id].Type() with Instances[id].TypeArgs 251 // results in an equivalent of Instances[id].Type. 252 Instances map[*ast.Ident]Instance 253 254 // Defs maps identifiers to the objects they define (including 255 // package names, dots "." of dot-imports, and blank "_" identifiers). 256 // For identifiers that do not denote objects (e.g., the package name 257 // in package clauses, or symbolic variables t in t := x.(type) of 258 // type switch headers), the corresponding objects are nil. 259 // 260 // For an embedded field, Defs returns the field *Var it defines. 261 // 262 // In ill-typed code, such as a duplicate declaration of the 263 // same name, Defs may lack an entry for a declaring identifier. 264 // 265 // Invariant: Defs[id] == nil || Defs[id].Pos() == id.Pos() 266 Defs map[*ast.Ident]Object 267 268 // Uses maps identifiers to the objects they denote. 269 // 270 // For an embedded field, Uses returns the *TypeName it denotes. 271 // 272 // Invariant: Uses[id].Pos() != id.Pos() 273 Uses map[*ast.Ident]Object 274 275 // Implicits maps nodes to their implicitly declared objects, if any. 276 // The following node and object types may appear: 277 // 278 // node declared object 279 // 280 // *ast.ImportSpec *PkgName for imports without renames 281 // *ast.CaseClause type-specific *Var for each type switch case clause (incl. default) 282 // *ast.Field anonymous parameter *Var (incl. unnamed results) 283 // 284 Implicits map[ast.Node]Object 285 286 // Selections maps selector expressions (excluding qualified identifiers) 287 // to their corresponding selections. 288 Selections map[*ast.SelectorExpr]*Selection 289 290 // Scopes maps ast.Nodes to the scopes they define. Package scopes are not 291 // associated with a specific node but with all files belonging to a package. 292 // Thus, the package scope can be found in the type-checked Package object. 293 // Scopes nest, with the Universe scope being the outermost scope, enclosing 294 // the package scope, which contains (one or more) files scopes, which enclose 295 // function scopes which in turn enclose statement and function literal scopes. 296 // Note that even though package-level functions are declared in the package 297 // scope, the function scopes are embedded in the file scope of the file 298 // containing the function declaration. 299 // 300 // The Scope of a function contains the declarations of any 301 // type parameters, parameters, and named results, plus any 302 // local declarations in the body block. 303 // It is coextensive with the complete extent of the 304 // function's syntax ([*ast.FuncDecl] or [*ast.FuncLit]). 305 // The Scopes mapping does not contain an entry for the 306 // function body ([*ast.BlockStmt]); the function's scope is 307 // associated with the [*ast.FuncType]. 308 // 309 // The following node types may appear in Scopes: 310 // 311 // *ast.File 312 // *ast.FuncType 313 // *ast.TypeSpec 314 // *ast.BlockStmt 315 // *ast.IfStmt 316 // *ast.SwitchStmt 317 // *ast.TypeSwitchStmt 318 // *ast.CaseClause 319 // *ast.CommClause 320 // *ast.ForStmt 321 // *ast.RangeStmt 322 // 323 Scopes map[ast.Node]*Scope 324 325 // InitOrder is the list of package-level initializers in the order in which 326 // they must be executed. Initializers referring to variables related by an 327 // initialization dependency appear in topological order, the others appear 328 // in source order. Variables without an initialization expression do not 329 // appear in this list. 330 InitOrder []*Initializer 331 332 // FileVersions maps a file to its Go version string. 333 // If the file doesn't specify a version, the reported 334 // string is Config.GoVersion. 335 // Version strings begin with “go”, like “go1.21”, and 336 // are suitable for use with the [go/version] package. 337 FileVersions map[*ast.File]string 338 } 339 340 func (info *Info) recordTypes() bool { 341 return info.Types != nil 342 } 343 344 // TypeOf returns the type of expression e, or nil if not found. 345 // Precondition: the Types, Uses and Defs maps are populated. 346 func (info *Info) TypeOf(e ast.Expr) Type { 347 if t, ok := info.Types[e]; ok { 348 return t.Type 349 } 350 if id, _ := e.(*ast.Ident); id != nil { 351 if obj := info.ObjectOf(id); obj != nil { 352 return obj.Type() 353 } 354 } 355 return nil 356 } 357 358 // ObjectOf returns the object denoted by the specified id, 359 // or nil if not found. 360 // 361 // If id is an embedded struct field, [Info.ObjectOf] returns the field (*[Var]) 362 // it defines, not the type (*[TypeName]) it uses. 363 // 364 // Precondition: the Uses and Defs maps are populated. 365 func (info *Info) ObjectOf(id *ast.Ident) Object { 366 if obj := info.Defs[id]; obj != nil { 367 return obj 368 } 369 return info.Uses[id] 370 } 371 372 // PkgNameOf returns the local package name defined by the import, 373 // or nil if not found. 374 // 375 // For dot-imports, the package name is ".". 376 // 377 // Precondition: the Defs and Implicts maps are populated. 378 func (info *Info) PkgNameOf(imp *ast.ImportSpec) *PkgName { 379 var obj Object 380 if imp.Name != nil { 381 obj = info.Defs[imp.Name] 382 } else { 383 obj = info.Implicits[imp] 384 } 385 pkgname, _ := obj.(*PkgName) 386 return pkgname 387 } 388 389 // TypeAndValue reports the type and value (for constants) 390 // of the corresponding expression. 391 type TypeAndValue struct { 392 mode operandMode 393 Type Type 394 Value constant.Value 395 } 396 397 // IsVoid reports whether the corresponding expression 398 // is a function call without results. 399 func (tv TypeAndValue) IsVoid() bool { 400 return tv.mode == novalue 401 } 402 403 // IsType reports whether the corresponding expression specifies a type. 404 func (tv TypeAndValue) IsType() bool { 405 return tv.mode == typexpr 406 } 407 408 // IsBuiltin reports whether the corresponding expression denotes 409 // a (possibly parenthesized) built-in function. 410 func (tv TypeAndValue) IsBuiltin() bool { 411 return tv.mode == builtin 412 } 413 414 // IsValue reports whether the corresponding expression is a value. 415 // Builtins are not considered values. Constant values have a non- 416 // nil Value. 417 func (tv TypeAndValue) IsValue() bool { 418 switch tv.mode { 419 case constant_, variable, mapindex, value, commaok, commaerr: 420 return true 421 } 422 return false 423 } 424 425 // IsNil reports whether the corresponding expression denotes the 426 // predeclared value nil. 427 func (tv TypeAndValue) IsNil() bool { 428 return tv.mode == value && tv.Type == Typ[UntypedNil] 429 } 430 431 // Addressable reports whether the corresponding expression 432 // is addressable (https://golang.org/ref/spec#Address_operators). 433 func (tv TypeAndValue) Addressable() bool { 434 return tv.mode == variable 435 } 436 437 // Assignable reports whether the corresponding expression 438 // is assignable to (provided a value of the right type). 439 func (tv TypeAndValue) Assignable() bool { 440 return tv.mode == variable || tv.mode == mapindex 441 } 442 443 // HasOk reports whether the corresponding expression may be 444 // used on the rhs of a comma-ok assignment. 445 func (tv TypeAndValue) HasOk() bool { 446 return tv.mode == commaok || tv.mode == mapindex 447 } 448 449 // Instance reports the type arguments and instantiated type for type and 450 // function instantiations. For type instantiations, [Type] will be of dynamic 451 // type *[Named]. For function instantiations, [Type] will be of dynamic type 452 // *Signature. 453 type Instance struct { 454 TypeArgs *TypeList 455 Type Type 456 } 457 458 // An Initializer describes a package-level variable, or a list of variables in case 459 // of a multi-valued initialization expression, and the corresponding initialization 460 // expression. 461 type Initializer struct { 462 Lhs []*Var // var Lhs = Rhs 463 Rhs ast.Expr 464 } 465 466 func (init *Initializer) String() string { 467 var buf bytes.Buffer 468 for i, lhs := range init.Lhs { 469 if i > 0 { 470 buf.WriteString(", ") 471 } 472 buf.WriteString(lhs.Name()) 473 } 474 buf.WriteString(" = ") 475 WriteExpr(&buf, init.Rhs) 476 return buf.String() 477 } 478 479 // Check type-checks a package and returns the resulting package object and 480 // the first error if any. Additionally, if info != nil, Check populates each 481 // of the non-nil maps in the [Info] struct. 482 // 483 // The package is marked as complete if no errors occurred, otherwise it is 484 // incomplete. See [Config.Error] for controlling behavior in the presence of 485 // errors. 486 // 487 // The package is specified by a list of *ast.Files and corresponding 488 // file set, and the package path the package is identified with. 489 // The clean path must not be empty or dot ("."). 490 func (conf *Config) Check(path string, fset *token.FileSet, files []*ast.File, info *Info) (*Package, error) { 491 pkg := NewPackage(path, "") 492 return pkg, NewChecker(conf, fset, pkg, info).Files(files) 493 } 494