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.
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.
11 // Type-checking consists of several interdependent phases:
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.
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.
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.
27 "cmd/compile/internal/syntax"
30 . "internal/types/errors"
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.
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
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)
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)
59 // An ArgumentError holds an error associated with an argument index.
60 type ArgumentError struct {
65 func (e *ArgumentError) Error() string { return e.Err.Error() }
66 func (e *ArgumentError) Unwrap() error { return e.Err }
68 // An Importer resolves import paths to Packages.
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)
80 // ImportMode is reserved for future use.
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
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)
106 // A Config specifies the configuration for type checking.
107 // The zero value for Config is a ready-to-use default configuration.
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.
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.
120 // If IgnoreFuncBodies is set, function bodies are not
122 IgnoreFuncBodies bool
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.
129 // Caution: Effects may be unpredictable due to follow-on errors.
130 // Do not use casually!
133 // If IgnoreBranchErrors is set, branch/label errors are ignored.
134 IgnoreBranchErrors bool
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.
142 // It is an error to set both FakeImportC and go115UsesCgo.
145 // If Trace is set, a debug trace is printed to stdout.
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
155 Error func(err error)
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.
165 // If Sizes != nil, it provides the sizing functions for package unsafe.
166 // Otherwise SizesFor("gc", "amd64") is used instead.
169 // If DisableUnusedImportCheck is set, packages are not checked
170 // for unused imports.
171 DisableUnusedImportCheck bool
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]".
180 func srcimporter_setUsesCgo(conf *Config) {
181 conf.go115UsesCgo = true
184 // Info holds result type information for a type-checked package.
185 // Only the information for which a map is provided is collected.
186 // If the package has type errors, the collected information may
189 // Types maps expressions to their types, and for constant
190 // expressions, also their values. Invalid expressions are
193 // For (possibly parenthesized) identifiers denoting built-in
194 // functions, the recorded signatures are call-site specific:
195 // if the call result is not a constant, the recorded type is
196 // an argument-specific signature. Otherwise, the recorded type
199 // The Types map does not record the type of every identifier,
200 // only those that appear where an arbitrary expression is
201 // permitted. For instance, the identifier f in a selector
202 // expression x.f is found only in the Selections map, the
203 // identifier z in a variable declaration 'var z int' is found
204 // only in the Defs map, and identifiers denoting packages in
205 // qualified identifiers are collected in the Uses map.
206 Types map[syntax.Expr]TypeAndValue
208 // If StoreTypesInSyntax is set, type information identical to
209 // that which would be put in the Types map, will be set in
210 // syntax.Expr.TypeAndValue (independently of whether Types
212 StoreTypesInSyntax bool
214 // Instances maps identifiers denoting generic types or functions to their
215 // type arguments and instantiated type.
217 // For example, Instances will map the identifier for 'T' in the type
218 // instantiation T[int, string] to the type arguments [int, string] and
219 // resulting instantiated *Named type. Given a generic function
220 // func F[A any](A), Instances will map the identifier for 'F' in the call
221 // expression F(int(1)) to the inferred type arguments [int], and resulting
222 // instantiated *Signature.
224 // Invariant: Instantiating Uses[id].Type() with Instances[id].TypeArgs
225 // results in an equivalent of Instances[id].Type.
226 Instances map[*syntax.Name]Instance
228 // Defs maps identifiers to the objects they define (including
229 // package names, dots "." of dot-imports, and blank "_" identifiers).
230 // For identifiers that do not denote objects (e.g., the package name
231 // in package clauses, or symbolic variables t in t := x.(type) of
232 // type switch headers), the corresponding objects are nil.
234 // For an embedded field, Defs returns the field *Var it defines.
236 // Invariant: Defs[id] == nil || Defs[id].Pos() == id.Pos()
237 Defs map[*syntax.Name]Object
239 // Uses maps identifiers to the objects they denote.
241 // For an embedded field, Uses returns the *TypeName it denotes.
243 // Invariant: Uses[id].Pos() != id.Pos()
244 Uses map[*syntax.Name]Object
246 // Implicits maps nodes to their implicitly declared objects, if any.
247 // The following node and object types may appear:
249 // node declared object
251 // *syntax.ImportDecl *PkgName for imports without renames
252 // *syntax.CaseClause type-specific *Var for each type switch case clause (incl. default)
253 // *syntax.Field anonymous parameter *Var (incl. unnamed results)
255 Implicits map[syntax.Node]Object
257 // Selections maps selector expressions (excluding qualified identifiers)
258 // to their corresponding selections.
259 Selections map[*syntax.SelectorExpr]*Selection
261 // Scopes maps syntax.Nodes to the scopes they define. Package scopes are not
262 // associated with a specific node but with all files belonging to a package.
263 // Thus, the package scope can be found in the type-checked Package object.
264 // Scopes nest, with the Universe scope being the outermost scope, enclosing
265 // the package scope, which contains (one or more) files scopes, which enclose
266 // function scopes which in turn enclose statement and function literal scopes.
267 // Note that even though package-level functions are declared in the package
268 // scope, the function scopes are embedded in the file scope of the file
269 // containing the function declaration.
271 // The following node types may appear in Scopes:
278 // *syntax.SwitchStmt
279 // *syntax.CaseClause
280 // *syntax.CommClause
283 Scopes map[syntax.Node]*Scope
285 // InitOrder is the list of package-level initializers in the order in which
286 // they must be executed. Initializers referring to variables related by an
287 // initialization dependency appear in topological order, the others appear
288 // in source order. Variables without an initialization expression do not
289 // appear in this list.
290 InitOrder []*Initializer
292 // FileVersions maps a file to its Go version string.
293 // If the file doesn't specify a version, the reported
294 // string is Config.GoVersion.
295 // Version strings begin with “go”, like “go1.21”, and
296 // are suitable for use with the [go/version] package.
297 FileVersions map[*syntax.PosBase]string
300 func (info *Info) recordTypes() bool {
301 return info.Types != nil || info.StoreTypesInSyntax
304 // TypeOf returns the type of expression e, or nil if not found.
305 // Precondition 1: the Types map is populated or StoreTypesInSynax is set.
306 // Precondition 2: Uses and Defs maps are populated.
307 func (info *Info) TypeOf(e syntax.Expr) Type {
308 if info.Types != nil {
309 if t, ok := info.Types[e]; ok {
312 } else if info.StoreTypesInSyntax {
313 if tv := e.GetTypeInfo(); tv.Type != nil {
318 if id, _ := e.(*syntax.Name); id != nil {
319 if obj := info.ObjectOf(id); obj != nil {
326 // ObjectOf returns the object denoted by the specified id,
327 // or nil if not found.
329 // If id is an embedded struct field, ObjectOf returns the field (*Var)
330 // it defines, not the type (*TypeName) it uses.
332 // Precondition: the Uses and Defs maps are populated.
333 func (info *Info) ObjectOf(id *syntax.Name) Object {
334 if obj := info.Defs[id]; obj != nil {
340 // PkgNameOf returns the local package name defined by the import,
341 // or nil if not found.
343 // For dot-imports, the package name is ".".
345 // Precondition: the Defs and Implicts maps are populated.
346 func (info *Info) PkgNameOf(imp *syntax.ImportDecl) *PkgName {
348 if imp.LocalPkgName != nil {
349 obj = info.Defs[imp.LocalPkgName]
351 obj = info.Implicits[imp]
353 pkgname, _ := obj.(*PkgName)
357 // TypeAndValue reports the type and value (for constants)
358 // of the corresponding expression.
359 type TypeAndValue struct {
365 // IsVoid reports whether the corresponding expression
366 // is a function call without results.
367 func (tv TypeAndValue) IsVoid() bool {
368 return tv.mode == novalue
371 // IsType reports whether the corresponding expression specifies a type.
372 func (tv TypeAndValue) IsType() bool {
373 return tv.mode == typexpr
376 // IsBuiltin reports whether the corresponding expression denotes
377 // a (possibly parenthesized) built-in function.
378 func (tv TypeAndValue) IsBuiltin() bool {
379 return tv.mode == builtin
382 // IsValue reports whether the corresponding expression is a value.
383 // Builtins are not considered values. Constant values have a non-
385 func (tv TypeAndValue) IsValue() bool {
387 case constant_, variable, mapindex, value, nilvalue, commaok, commaerr:
393 // IsNil reports whether the corresponding expression denotes the
394 // predeclared value nil. Depending on context, it may have been
395 // given a type different from UntypedNil.
396 func (tv TypeAndValue) IsNil() bool {
397 return tv.mode == nilvalue
400 // Addressable reports whether the corresponding expression
401 // is addressable (https://golang.org/ref/spec#Address_operators).
402 func (tv TypeAndValue) Addressable() bool {
403 return tv.mode == variable
406 // Assignable reports whether the corresponding expression
407 // is assignable to (provided a value of the right type).
408 func (tv TypeAndValue) Assignable() bool {
409 return tv.mode == variable || tv.mode == mapindex
412 // HasOk reports whether the corresponding expression may be
413 // used on the rhs of a comma-ok assignment.
414 func (tv TypeAndValue) HasOk() bool {
415 return tv.mode == commaok || tv.mode == mapindex
418 // Instance reports the type arguments and instantiated type for type and
419 // function instantiations. For type instantiations, Type will be of dynamic
420 // type *Named. For function instantiations, Type will be of dynamic type
422 type Instance struct {
427 // An Initializer describes a package-level variable, or a list of variables in case
428 // of a multi-valued initialization expression, and the corresponding initialization
430 type Initializer struct {
431 Lhs []*Var // var Lhs = Rhs
435 func (init *Initializer) String() string {
436 var buf strings.Builder
437 for i, lhs := range init.Lhs {
439 buf.WriteString(", ")
441 buf.WriteString(lhs.Name())
443 buf.WriteString(" = ")
444 syntax.Fprint(&buf, init.Rhs, syntax.ShortForm)
448 // Check type-checks a package and returns the resulting package object and
449 // the first error if any. Additionally, if info != nil, Check populates each
450 // of the non-nil maps in the Info struct.
452 // The package is marked as complete if no errors occurred, otherwise it is
453 // incomplete. See Config.Error for controlling behavior in the presence of
456 // The package is specified by a list of *syntax.Files and corresponding
457 // file set, and the package path the package is identified with.
458 // The clean path must not be empty or dot (".").
459 func (conf *Config) Check(path string, files []*syntax.File, info *Info) (*Package, error) {
460 pkg := NewPackage(path, "")
461 return pkg, NewChecker(conf, pkg, info).Files(files)
464 // AssertableTo reports whether a value of type V can be asserted to have type T.
466 // The behavior of AssertableTo is unspecified in three cases:
467 // - if T is Typ[Invalid]
468 // - if V is a generalized interface; i.e., an interface that may only be used
469 // as a type constraint in Go code
470 // - if T is an uninstantiated generic type
471 func AssertableTo(V *Interface, T Type) bool {
472 // Checker.newAssertableTo suppresses errors for invalid types, so we need special
474 if !isValid(T.Underlying()) {
477 return (*Checker)(nil).newAssertableTo(nopos, V, T, nil)
480 // AssignableTo reports whether a value of type V is assignable to a variable
483 // The behavior of AssignableTo is unspecified if V or T is Typ[Invalid] or an
484 // uninstantiated generic type.
485 func AssignableTo(V, T Type) bool {
486 x := operand{mode: value, typ: V}
487 ok, _ := x.assignableTo(nil, T, nil) // check not needed for non-constant x
491 // ConvertibleTo reports whether a value of type V is convertible to a value of
494 // The behavior of ConvertibleTo is unspecified if V or T is Typ[Invalid] or an
495 // uninstantiated generic type.
496 func ConvertibleTo(V, T Type) bool {
497 x := operand{mode: value, typ: V}
498 return x.convertibleTo(nil, T, nil) // check not needed for non-constant x
501 // Implements reports whether type V implements interface T.
503 // The behavior of Implements is unspecified if V is Typ[Invalid] or an uninstantiated
505 func Implements(V Type, T *Interface) bool {
507 // All types (even Typ[Invalid]) implement the empty interface.
510 // Checker.implements suppresses errors for invalid types, so we need special
512 if !isValid(V.Underlying()) {
515 return (*Checker)(nil).implements(nopos, V, T, false, nil)
518 // Satisfies reports whether type V satisfies the constraint T.
520 // The behavior of Satisfies is unspecified if V is Typ[Invalid] or an uninstantiated
522 func Satisfies(V Type, T *Interface) bool {
523 return (*Checker)(nil).implements(nopos, V, T, true, nil)
526 // Identical reports whether x and y are identical types.
527 // Receivers of Signature types are ignored.
528 func Identical(x, y Type) bool {
530 return c.identical(x, y, nil)
533 // IdenticalIgnoreTags reports whether x and y are identical types if tags are ignored.
534 // Receivers of Signature types are ignored.
535 func IdenticalIgnoreTags(x, y Type) bool {
538 return c.identical(x, y, nil)