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 (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.
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.
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.
25 // For a tutorial, see https://golang.org/s/types-tutorial.
37 const allowTypeLists = false
39 // An Error describes a type-checking error; it implements the error interface.
40 // A "soft" error is an error that still permits a valid interpretation of a
41 // package (such as "unused variable"); "hard" errors may lead to unpredictable
42 // behavior if ignored.
44 Fset *token.FileSet // file set for interpretation of Pos
45 Pos token.Pos // error position
46 Msg string // error message
47 Soft bool // if set, error is "soft"
49 // go116code is a future API, unexported as the set of error codes is large
50 // and likely to change significantly during experimentation. Tools wishing
51 // to preview this feature may read go116code using reflection (see
52 // errorcodes_test.go), but beware that there is no guarantee of future
59 // Error returns an error string formatted as follows:
60 // filename:line:column: message
61 func (err Error) Error() string {
62 return fmt.Sprintf("%s: %s", err.Fset.Position(err.Pos), err.Msg)
65 // An ArgumentError holds an error associated with an argument index.
66 type ArgumentError struct {
71 func (e *ArgumentError) Error() string { return e.Err.Error() }
72 func (e *ArgumentError) Unwrap() error { return e.Err }
74 // An Importer resolves import paths to Packages.
76 // CAUTION: This interface does not support the import of locally
77 // vendored packages. See https://golang.org/s/go15vendor.
78 // If possible, external implementations should implement ImporterFrom.
79 type Importer interface {
80 // Import returns the imported package for the given import path.
81 // The semantics is like for ImporterFrom.ImportFrom except that
82 // dir and mode are ignored (since they are not present).
83 Import(path string) (*Package, error)
86 // ImportMode is reserved for future use.
89 // An ImporterFrom resolves import paths to packages; it
90 // supports vendoring per https://golang.org/s/go15vendor.
91 // Use go/importer to obtain an ImporterFrom implementation.
92 type ImporterFrom interface {
93 // Importer is present for backward-compatibility. Calling
94 // Import(path) is the same as calling ImportFrom(path, "", 0);
95 // i.e., locally vendored packages may not be found.
96 // The types package does not call Import if an ImporterFrom
100 // ImportFrom returns the imported package for the given import
101 // path when imported by a package file located in dir.
102 // If the import failed, besides returning an error, ImportFrom
103 // is encouraged to cache and return a package anyway, if one
104 // was created. This will reduce package inconsistencies and
105 // follow-on type checker errors due to the missing package.
106 // The mode value must be 0; it is reserved for future use.
107 // Two calls to ImportFrom with the same path and dir must
108 // return the same package.
109 ImportFrom(path, dir string, mode ImportMode) (*Package, error)
112 // A Config specifies the configuration for type checking.
113 // The zero value for Config is a ready-to-use default configuration.
115 // Context is the context used for resolving global identifiers. If nil, the
116 // type checker will initialize this field with a newly created context.
119 // GoVersion describes the accepted Go language version. The string
120 // must follow the format "go%d.%d" (e.g. "go1.12") or it must be
121 // empty; an empty string indicates the latest language version.
122 // If the format is invalid, invoking the type checker will cause a
126 // If IgnoreFuncBodies is set, function bodies are not
128 IgnoreFuncBodies bool
130 // If FakeImportC is set, `import "C"` (for packages requiring Cgo)
131 // declares an empty "C" package and errors are omitted for qualified
132 // identifiers referring to package C (which won't find an object).
133 // This feature is intended for the standard library cmd/api tool.
135 // Caution: Effects may be unpredictable due to follow-on errors.
136 // Do not use casually!
139 // If go115UsesCgo is set, the type checker expects the
140 // _cgo_gotypes.go file generated by running cmd/cgo to be
141 // provided as a package source file. Qualified identifiers
142 // referring to package C will be resolved to cgo-provided
143 // declarations within _cgo_gotypes.go.
145 // It is an error to set both FakeImportC and go115UsesCgo.
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
174 func srcimporter_setUsesCgo(conf *Config) {
175 conf.go115UsesCgo = true
178 // Info holds result type information for a type-checked package.
179 // Only the information for which a map is provided is collected.
180 // If the package has type errors, the collected information may
183 // Types maps expressions to their types, and for constant
184 // expressions, also their values. Invalid expressions are
187 // For (possibly parenthesized) identifiers denoting built-in
188 // functions, the recorded signatures are call-site specific:
189 // if the call result is not a constant, the recorded type is
190 // an argument-specific signature. Otherwise, the recorded type
193 // The Types map does not record the type of every identifier,
194 // only those that appear where an arbitrary expression is
195 // permitted. For instance, the identifier f in a selector
196 // expression x.f is found only in the Selections map, the
197 // identifier z in a variable declaration 'var z int' is found
198 // only in the Defs map, and identifiers denoting packages in
199 // qualified identifiers are collected in the Uses map.
200 Types map[ast.Expr]TypeAndValue
202 // Instances maps identifiers denoting parameterized types or functions to
203 // their type arguments and instantiated type.
205 // For example, Instances will map the identifier for 'T' in the type
206 // instantiation T[int, string] to the type arguments [int, string] and
207 // resulting instantiated *Named type. Given a parameterized function
208 // func F[A any](A), Instances will map the identifier for 'F' in the call
209 // expression F(int(1)) to the inferred type arguments [int], and resulting
210 // instantiated *Signature.
212 // Invariant: Instantiating Uses[id].Type() with Instances[id].TypeArgs
213 // results in an equivalent of Instances[id].Type.
214 Instances map[*ast.Ident]Instance
216 // Defs maps identifiers to the objects they define (including
217 // package names, dots "." of dot-imports, and blank "_" identifiers).
218 // For identifiers that do not denote objects (e.g., the package name
219 // in package clauses, or symbolic variables t in t := x.(type) of
220 // type switch headers), the corresponding objects are nil.
222 // For an embedded field, Defs returns the field *Var it defines.
224 // Invariant: Defs[id] == nil || Defs[id].Pos() == id.Pos()
225 Defs map[*ast.Ident]Object
227 // Uses maps identifiers to the objects they denote.
229 // For an embedded field, Uses returns the *TypeName it denotes.
231 // Invariant: Uses[id].Pos() != id.Pos()
232 Uses map[*ast.Ident]Object
234 // Implicits maps nodes to their implicitly declared objects, if any.
235 // The following node and object types may appear:
237 // node declared object
239 // *ast.ImportSpec *PkgName for imports without renames
240 // *ast.CaseClause type-specific *Var for each type switch case clause (incl. default)
241 // *ast.Field anonymous parameter *Var (incl. unnamed results)
243 Implicits map[ast.Node]Object
245 // Selections maps selector expressions (excluding qualified identifiers)
246 // to their corresponding selections.
247 Selections map[*ast.SelectorExpr]*Selection
249 // Scopes maps ast.Nodes to the scopes they define. Package scopes are not
250 // associated with a specific node but with all files belonging to a package.
251 // Thus, the package scope can be found in the type-checked Package object.
252 // Scopes nest, with the Universe scope being the outermost scope, enclosing
253 // the package scope, which contains (one or more) files scopes, which enclose
254 // function scopes which in turn enclose statement and function literal scopes.
255 // Note that even though package-level functions are declared in the package
256 // scope, the function scopes are embedded in the file scope of the file
257 // containing the function declaration.
259 // The following node types may appear in Scopes:
267 // *ast.TypeSwitchStmt
273 Scopes map[ast.Node]*Scope
275 // InitOrder is the list of package-level initializers in the order in which
276 // they must be executed. Initializers referring to variables related by an
277 // initialization dependency appear in topological order, the others appear
278 // in source order. Variables without an initialization expression do not
279 // appear in this list.
280 InitOrder []*Initializer
283 // TypeOf returns the type of expression e, or nil if not found.
284 // Precondition: the Types, Uses and Defs maps are populated.
286 func (info *Info) TypeOf(e ast.Expr) Type {
287 if t, ok := info.Types[e]; ok {
290 if id, _ := e.(*ast.Ident); id != nil {
291 if obj := info.ObjectOf(id); obj != nil {
298 // ObjectOf returns the object denoted by the specified id,
299 // or nil if not found.
301 // If id is an embedded struct field, ObjectOf returns the field (*Var)
302 // it defines, not the type (*TypeName) it uses.
304 // Precondition: the Uses and Defs maps are populated.
306 func (info *Info) ObjectOf(id *ast.Ident) Object {
307 if obj := info.Defs[id]; obj != nil {
313 // TypeAndValue reports the type and value (for constants)
314 // of the corresponding expression.
315 type TypeAndValue struct {
321 // IsVoid reports whether the corresponding expression
322 // is a function call without results.
323 func (tv TypeAndValue) IsVoid() bool {
324 return tv.mode == novalue
327 // IsType reports whether the corresponding expression specifies a type.
328 func (tv TypeAndValue) IsType() bool {
329 return tv.mode == typexpr
332 // IsBuiltin reports whether the corresponding expression denotes
333 // a (possibly parenthesized) built-in function.
334 func (tv TypeAndValue) IsBuiltin() bool {
335 return tv.mode == builtin
338 // IsValue reports whether the corresponding expression is a value.
339 // Builtins are not considered values. Constant values have a non-
341 func (tv TypeAndValue) IsValue() bool {
343 case constant_, variable, mapindex, value, commaok, commaerr:
349 // IsNil reports whether the corresponding expression denotes the
350 // predeclared value nil.
351 func (tv TypeAndValue) IsNil() bool {
352 return tv.mode == value && tv.Type == Typ[UntypedNil]
355 // Addressable reports whether the corresponding expression
356 // is addressable (https://golang.org/ref/spec#Address_operators).
357 func (tv TypeAndValue) Addressable() bool {
358 return tv.mode == variable
361 // Assignable reports whether the corresponding expression
362 // is assignable to (provided a value of the right type).
363 func (tv TypeAndValue) Assignable() bool {
364 return tv.mode == variable || tv.mode == mapindex
367 // HasOk reports whether the corresponding expression may be
368 // used on the rhs of a comma-ok assignment.
369 func (tv TypeAndValue) HasOk() bool {
370 return tv.mode == commaok || tv.mode == mapindex
373 // Instance reports the type arguments and instantiated type for type and
374 // function instantiations. For type instantiations, Type will be of dynamic
375 // type *Named. For function instantiations, Type will be of dynamic type
377 type Instance struct {
382 // An Initializer describes a package-level variable, or a list of variables in case
383 // of a multi-valued initialization expression, and the corresponding initialization
385 type Initializer struct {
386 Lhs []*Var // var Lhs = Rhs
390 func (init *Initializer) String() string {
392 for i, lhs := range init.Lhs {
394 buf.WriteString(", ")
396 buf.WriteString(lhs.Name())
398 buf.WriteString(" = ")
399 WriteExpr(&buf, init.Rhs)
403 // Check type-checks a package and returns the resulting package object and
404 // the first error if any. Additionally, if info != nil, Check populates each
405 // of the non-nil maps in the Info struct.
407 // The package is marked as complete if no errors occurred, otherwise it is
408 // incomplete. See Config.Error for controlling behavior in the presence of
411 // The package is specified by a list of *ast.Files and corresponding
412 // file set, and the package path the package is identified with.
413 // The clean path must not be empty or dot (".").
414 func (conf *Config) Check(path string, fset *token.FileSet, files []*ast.File, info *Info) (*Package, error) {
415 pkg := NewPackage(path, "")
416 return pkg, NewChecker(conf, fset, pkg, info).Files(files)
419 // AssertableTo reports whether a value of type V can be asserted to have type T.
420 func AssertableTo(V *Interface, T Type) bool {
421 m, _ := (*Checker)(nil).assertableTo(V, T)
425 // AssignableTo reports whether a value of type V is assignable to a variable of type T.
426 func AssignableTo(V, T Type) bool {
427 x := operand{mode: value, typ: V}
428 ok, _ := x.assignableTo(nil, T, nil) // check not needed for non-constant x
432 // ConvertibleTo reports whether a value of type V is convertible to a value of type T.
433 func ConvertibleTo(V, T Type) bool {
434 x := operand{mode: value, typ: V}
435 return x.convertibleTo(nil, T, nil) // check not needed for non-constant x
438 // Implements reports whether type V implements interface T.
439 func Implements(V Type, T *Interface) bool {
441 // All types (even Typ[Invalid]) implement the empty interface.
444 // Checker.implements suppresses errors for invalid types, so we need special
446 if V.Underlying() == Typ[Invalid] {
449 return (*Checker)(nil).implements(V, T) == nil
452 // Identical reports whether x and y are identical types.
453 // Receivers of Signature types are ignored.
454 func Identical(x, y Type) bool {
455 return identical(x, y, true, nil)
458 // IdenticalIgnoreTags reports whether x and y are identical types if tags are ignored.
459 // Receivers of Signature types are ignored.
460 func IdenticalIgnoreTags(x, y Type) bool {
461 return identical(x, y, false, nil)