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