Source file src/cmd/compile/internal/types2/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 types2 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 (syntax.Name) 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 (syntax.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 (syntax.Expr) 22 // and checks for compliance with the language specification. 23 // Use Info.Types[expr].Type for the results of type inference. 24 package types2 25 26 import ( 27 "cmd/compile/internal/syntax" 28 "fmt" 29 "go/constant" 30 . "internal/types/errors" 31 "strings" 32 ) 33 34 // An Error describes a type-checking error; it implements the error interface. 35 // A "soft" error is an error that still permits a valid interpretation of a 36 // package (such as "unused variable"); "hard" errors may lead to unpredictable 37 // behavior if ignored. 38 type Error struct { 39 Pos syntax.Pos // error position 40 Msg string // default error message, user-friendly 41 Full string // full error message, for debugging (may contain internal details) 42 Soft bool // if set, error is "soft" 43 Code Code // error code 44 } 45 46 // Error returns an error string formatted as follows: 47 // filename:line:column: message 48 func (err Error) Error() string { 49 return fmt.Sprintf("%s: %s", err.Pos, err.Msg) 50 } 51 52 // FullError returns an error string like Error, buy it may contain 53 // type-checker internal details such as subscript indices for type 54 // parameters and more. Useful for debugging. 55 func (err Error) FullError() string { 56 return fmt.Sprintf("%s: %s", err.Pos, err.Full) 57 } 58 59 // An ArgumentError holds an error associated with an argument index. 60 type ArgumentError struct { 61 Index int 62 Err error 63 } 64 65 func (e *ArgumentError) Error() string { return e.Err.Error() } 66 func (e *ArgumentError) Unwrap() error { return e.Err } 67 68 // An Importer resolves import paths to Packages. 69 // 70 // CAUTION: This interface does not support the import of locally 71 // vendored packages. See https://golang.org/s/go15vendor. 72 // If possible, external implementations should implement ImporterFrom. 73 type Importer interface { 74 // Import returns the imported package for the given import path. 75 // The semantics is like for ImporterFrom.ImportFrom except that 76 // dir and mode are ignored (since they are not present). 77 Import(path string) (*Package, error) 78 } 79 80 // ImportMode is reserved for future use. 81 type ImportMode int 82 83 // An ImporterFrom resolves import paths to packages; it 84 // supports vendoring per https://golang.org/s/go15vendor. 85 // Use go/importer to obtain an ImporterFrom implementation. 86 type ImporterFrom interface { 87 // Importer is present for backward-compatibility. Calling 88 // Import(path) is the same as calling ImportFrom(path, "", 0); 89 // i.e., locally vendored packages may not be found. 90 // The types package does not call Import if an ImporterFrom 91 // is present. 92 Importer 93 94 // ImportFrom returns the imported package for the given import 95 // path when imported by a package file located in dir. 96 // If the import failed, besides returning an error, ImportFrom 97 // is encouraged to cache and return a package anyway, if one 98 // was created. This will reduce package inconsistencies and 99 // follow-on type checker errors due to the missing package. 100 // The mode value must be 0; it is reserved for future use. 101 // Two calls to ImportFrom with the same path and dir must 102 // return the same package. 103 ImportFrom(path, dir string, mode ImportMode) (*Package, error) 104 } 105 106 // A Config specifies the configuration for type checking. 107 // The zero value for Config is a ready-to-use default configuration. 108 type Config struct { 109 // Context is the context used for resolving global identifiers. If nil, the 110 // type checker will initialize this field with a newly created context. 111 Context *Context 112 113 // GoVersion describes the accepted Go language version. The string must 114 // start with a prefix of the form "go%d.%d" (e.g. "go1.20", "go1.21rc1", or 115 // "go1.21.0") or it must be empty; an empty string disables Go language 116 // version checks. If the format is invalid, invoking the type checker will 117 // result in an error. 118 GoVersion string 119 120 // If IgnoreFuncBodies is set, function bodies are not 121 // type-checked. 122 IgnoreFuncBodies bool 123 124 // If FakeImportC is set, `import "C"` (for packages requiring Cgo) 125 // declares an empty "C" package and errors are omitted for qualified 126 // identifiers referring to package C (which won't find an object). 127 // This feature is intended for the standard library cmd/api tool. 128 // 129 // Caution: Effects may be unpredictable due to follow-on errors. 130 // Do not use casually! 131 FakeImportC bool 132 133 // If IgnoreBranchErrors is set, branch/label errors are ignored. 134 IgnoreBranchErrors 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 Trace is set, a debug trace is printed to stdout. 146 Trace bool 147 148 // If Error != nil, it is called with each error found 149 // during type checking; err has dynamic type Error. 150 // Secondary errors (for instance, to enumerate all types 151 // involved in an invalid recursive type declaration) have 152 // error strings that start with a '\t' character. 153 // If Error == nil, type-checking stops with the first 154 // error found. 155 Error func(err error) 156 157 // An importer is used to import packages referred to from 158 // import declarations. 159 // If the installed importer implements ImporterFrom, the type 160 // checker calls ImportFrom instead of Import. 161 // The type checker reports an error if an importer is needed 162 // but none was installed. 163 Importer Importer 164 165 // If Sizes != nil, it provides the sizing functions for package unsafe. 166 // Otherwise SizesFor("gc", "amd64") is used instead. 167 Sizes Sizes 168 169 // If DisableUnusedImportCheck is set, packages are not checked 170 // for unused imports. 171 DisableUnusedImportCheck bool 172 173 // If a non-empty ErrorURL format string is provided, it is used 174 // to format an error URL link that is appended to the first line 175 // of an error message. ErrorURL must be a format string containing 176 // exactly one "%s" format, e.g. "[go.dev/e/%s]". 177 ErrorURL string 178 179 // If EnableAlias is set, alias declarations produce an Alias type. Otherwise 180 // the alias information is only in the type name, which points directly to 181 // the actual (aliased) type. 182 // 183 // This setting must not differ among concurrent type-checking operations, 184 // since it affects the behavior of Universe.Lookup("any"). 185 // 186 // This flag will eventually be removed (with Go 1.24 at the earliest). 187 EnableAlias bool 188 } 189 190 // Info holds result type information for a type-checked package. 191 // Only the information for which a map is provided is collected. 192 // If the package has type errors, the collected information may 193 // be incomplete. 194 type Info struct { 195 // Types maps expressions to their types, and for constant 196 // expressions, also their values. Invalid expressions are 197 // omitted. 198 // 199 // For (possibly parenthesized) identifiers denoting built-in 200 // functions, the recorded signatures are call-site specific: 201 // if the call result is not a constant, the recorded type is 202 // an argument-specific signature. Otherwise, the recorded type 203 // is invalid. 204 // 205 // The Types map does not record the type of every identifier, 206 // only those that appear where an arbitrary expression is 207 // permitted. For instance: 208 // - an identifier f in a selector expression x.f is found 209 // only in the Selections map; 210 // - an identifier z in a variable declaration 'var z int' 211 // is found only in the Defs map; 212 // - an identifier p denoting a package in a qualified 213 // identifier p.X is found only in the Uses map. 214 // 215 // Similarly, no type is recorded for the (synthetic) FuncType 216 // node in a FuncDecl.Type field, since there is no corresponding 217 // syntactic function type expression in the source in this case 218 // Instead, the function type is found in the Defs.map entry for 219 // the corresponding function declaration. 220 Types map[syntax.Expr]TypeAndValue 221 222 // If StoreTypesInSyntax is set, type information identical to 223 // that which would be put in the Types map, will be set in 224 // syntax.Expr.TypeAndValue (independently of whether Types 225 // is nil or not). 226 StoreTypesInSyntax bool 227 228 // Instances maps identifiers denoting generic types or functions to their 229 // type arguments and instantiated type. 230 // 231 // For example, Instances will map the identifier for 'T' in the type 232 // instantiation T[int, string] to the type arguments [int, string] and 233 // resulting instantiated *Named type. Given a generic function 234 // func F[A any](A), Instances will map the identifier for 'F' in the call 235 // expression F(int(1)) to the inferred type arguments [int], and resulting 236 // instantiated *Signature. 237 // 238 // Invariant: Instantiating Uses[id].Type() with Instances[id].TypeArgs 239 // results in an equivalent of Instances[id].Type. 240 Instances map[*syntax.Name]Instance 241 242 // Defs maps identifiers to the objects they define (including 243 // package names, dots "." of dot-imports, and blank "_" identifiers). 244 // For identifiers that do not denote objects (e.g., the package name 245 // in package clauses, or symbolic variables t in t := x.(type) of 246 // type switch headers), the corresponding objects are nil. 247 // 248 // For an embedded field, Defs returns the field *Var it defines. 249 // 250 // Invariant: Defs[id] == nil || Defs[id].Pos() == id.Pos() 251 Defs map[*syntax.Name]Object 252 253 // Uses maps identifiers to the objects they denote. 254 // 255 // For an embedded field, Uses returns the *TypeName it denotes. 256 // 257 // Invariant: Uses[id].Pos() != id.Pos() 258 Uses map[*syntax.Name]Object 259 260 // Implicits maps nodes to their implicitly declared objects, if any. 261 // The following node and object types may appear: 262 // 263 // node declared object 264 // 265 // *syntax.ImportDecl *PkgName for imports without renames 266 // *syntax.CaseClause type-specific *Var for each type switch case clause (incl. default) 267 // *syntax.Field anonymous parameter *Var (incl. unnamed results) 268 // 269 Implicits map[syntax.Node]Object 270 271 // Selections maps selector expressions (excluding qualified identifiers) 272 // to their corresponding selections. 273 Selections map[*syntax.SelectorExpr]*Selection 274 275 // Scopes maps syntax.Nodes to the scopes they define. Package scopes are not 276 // associated with a specific node but with all files belonging to a package. 277 // Thus, the package scope can be found in the type-checked Package object. 278 // Scopes nest, with the Universe scope being the outermost scope, enclosing 279 // the package scope, which contains (one or more) files scopes, which enclose 280 // function scopes which in turn enclose statement and function literal scopes. 281 // Note that even though package-level functions are declared in the package 282 // scope, the function scopes are embedded in the file scope of the file 283 // containing the function declaration. 284 // 285 // The Scope of a function contains the declarations of any 286 // type parameters, parameters, and named results, plus any 287 // local declarations in the body block. 288 // It is coextensive with the complete extent of the 289 // function's syntax ([*ast.FuncDecl] or [*ast.FuncLit]). 290 // The Scopes mapping does not contain an entry for the 291 // function body ([*ast.BlockStmt]); the function's scope is 292 // associated with the [*ast.FuncType]. 293 // 294 // The following node types may appear in Scopes: 295 // 296 // *syntax.File 297 // *syntax.FuncType 298 // *syntax.TypeDecl 299 // *syntax.BlockStmt 300 // *syntax.IfStmt 301 // *syntax.SwitchStmt 302 // *syntax.CaseClause 303 // *syntax.CommClause 304 // *syntax.ForStmt 305 // 306 Scopes map[syntax.Node]*Scope 307 308 // InitOrder is the list of package-level initializers in the order in which 309 // they must be executed. Initializers referring to variables related by an 310 // initialization dependency appear in topological order, the others appear 311 // in source order. Variables without an initialization expression do not 312 // appear in this list. 313 InitOrder []*Initializer 314 315 // FileVersions maps a file to its Go version string. 316 // If the file doesn't specify a version, the reported 317 // string is Config.GoVersion. 318 // Version strings begin with “go”, like “go1.21”, and 319 // are suitable for use with the [go/version] package. 320 FileVersions map[*syntax.PosBase]string 321 } 322 323 func (info *Info) recordTypes() bool { 324 return info.Types != nil || info.StoreTypesInSyntax 325 } 326 327 // TypeOf returns the type of expression e, or nil if not found. 328 // Precondition 1: the Types map is populated or StoreTypesInSyntax is set. 329 // Precondition 2: Uses and Defs maps are populated. 330 func (info *Info) TypeOf(e syntax.Expr) Type { 331 if info.Types != nil { 332 if t, ok := info.Types[e]; ok { 333 return t.Type 334 } 335 } else if info.StoreTypesInSyntax { 336 if tv := e.GetTypeInfo(); tv.Type != nil { 337 return tv.Type 338 } 339 } 340 341 if id, _ := e.(*syntax.Name); id != nil { 342 if obj := info.ObjectOf(id); obj != nil { 343 return obj.Type() 344 } 345 } 346 return nil 347 } 348 349 // ObjectOf returns the object denoted by the specified id, 350 // or nil if not found. 351 // 352 // If id is an embedded struct field, ObjectOf returns the field (*Var) 353 // it defines, not the type (*TypeName) it uses. 354 // 355 // Precondition: the Uses and Defs maps are populated. 356 func (info *Info) ObjectOf(id *syntax.Name) Object { 357 if obj := info.Defs[id]; obj != nil { 358 return obj 359 } 360 return info.Uses[id] 361 } 362 363 // PkgNameOf returns the local package name defined by the import, 364 // or nil if not found. 365 // 366 // For dot-imports, the package name is ".". 367 // 368 // Precondition: the Defs and Implicts maps are populated. 369 func (info *Info) PkgNameOf(imp *syntax.ImportDecl) *PkgName { 370 var obj Object 371 if imp.LocalPkgName != nil { 372 obj = info.Defs[imp.LocalPkgName] 373 } else { 374 obj = info.Implicits[imp] 375 } 376 pkgname, _ := obj.(*PkgName) 377 return pkgname 378 } 379 380 // TypeAndValue reports the type and value (for constants) 381 // of the corresponding expression. 382 type TypeAndValue struct { 383 mode operandMode 384 Type Type 385 Value constant.Value 386 } 387 388 // IsVoid reports whether the corresponding expression 389 // is a function call without results. 390 func (tv TypeAndValue) IsVoid() bool { 391 return tv.mode == novalue 392 } 393 394 // IsType reports whether the corresponding expression specifies a type. 395 func (tv TypeAndValue) IsType() bool { 396 return tv.mode == typexpr 397 } 398 399 // IsBuiltin reports whether the corresponding expression denotes 400 // a (possibly parenthesized) built-in function. 401 func (tv TypeAndValue) IsBuiltin() bool { 402 return tv.mode == builtin 403 } 404 405 // IsValue reports whether the corresponding expression is a value. 406 // Builtins are not considered values. Constant values have a non- 407 // nil Value. 408 func (tv TypeAndValue) IsValue() bool { 409 switch tv.mode { 410 case constant_, variable, mapindex, value, nilvalue, commaok, commaerr: 411 return true 412 } 413 return false 414 } 415 416 // IsNil reports whether the corresponding expression denotes the 417 // predeclared value nil. Depending on context, it may have been 418 // given a type different from UntypedNil. 419 func (tv TypeAndValue) IsNil() bool { 420 return tv.mode == nilvalue 421 } 422 423 // Addressable reports whether the corresponding expression 424 // is addressable (https://golang.org/ref/spec#Address_operators). 425 func (tv TypeAndValue) Addressable() bool { 426 return tv.mode == variable 427 } 428 429 // Assignable reports whether the corresponding expression 430 // is assignable to (provided a value of the right type). 431 func (tv TypeAndValue) Assignable() bool { 432 return tv.mode == variable || tv.mode == mapindex 433 } 434 435 // HasOk reports whether the corresponding expression may be 436 // used on the rhs of a comma-ok assignment. 437 func (tv TypeAndValue) HasOk() bool { 438 return tv.mode == commaok || tv.mode == mapindex 439 } 440 441 // Instance reports the type arguments and instantiated type for type and 442 // function instantiations. For type instantiations, Type will be of dynamic 443 // type *Named. For function instantiations, Type will be of dynamic type 444 // *Signature. 445 type Instance struct { 446 TypeArgs *TypeList 447 Type Type 448 } 449 450 // An Initializer describes a package-level variable, or a list of variables in case 451 // of a multi-valued initialization expression, and the corresponding initialization 452 // expression. 453 type Initializer struct { 454 Lhs []*Var // var Lhs = Rhs 455 Rhs syntax.Expr 456 } 457 458 func (init *Initializer) String() string { 459 var buf strings.Builder 460 for i, lhs := range init.Lhs { 461 if i > 0 { 462 buf.WriteString(", ") 463 } 464 buf.WriteString(lhs.Name()) 465 } 466 buf.WriteString(" = ") 467 syntax.Fprint(&buf, init.Rhs, syntax.ShortForm) 468 return buf.String() 469 } 470 471 // Check type-checks a package and returns the resulting package object and 472 // the first error if any. Additionally, if info != nil, Check populates each 473 // of the non-nil maps in the Info struct. 474 // 475 // The package is marked as complete if no errors occurred, otherwise it is 476 // incomplete. See Config.Error for controlling behavior in the presence of 477 // errors. 478 // 479 // The package is specified by a list of *syntax.Files and corresponding 480 // file set, and the package path the package is identified with. 481 // The clean path must not be empty or dot ("."). 482 func (conf *Config) Check(path string, files []*syntax.File, info *Info) (*Package, error) { 483 pkg := NewPackage(path, "") 484 return pkg, NewChecker(conf, pkg, info).Files(files) 485 } 486