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.
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.
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"
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
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)
62 // An ArgumentError holds an error associated with an argument index.
63 type ArgumentError struct {
68 func (e *ArgumentError) Error() string { return e.Err.Error() }
69 func (e *ArgumentError) Unwrap() error { return e.Err }
71 // An Importer resolves import paths to Packages.
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)
83 // ImportMode is reserved for future use.
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
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)
109 // A Config specifies the configuration for type checking.
110 // The zero value for Config is a ready-to-use default configuration.
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.
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
123 // If IgnoreFuncBodies is set, function bodies are not
125 IgnoreFuncBodies bool
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.
132 // Caution: Effects may be unpredictable due to follow-on errors.
133 // Do not use casually!
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 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
152 Error func(err error)
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.
162 // If Sizes != nil, it provides the sizing functions for package unsafe.
163 // Otherwise SizesFor("gc", "amd64") is used instead.
166 // If DisableUnusedImportCheck is set, packages are not checked
167 // for unused imports.
168 DisableUnusedImportCheck bool
171 func srcimporter_setUsesCgo(conf *Config) {
172 conf.go115UsesCgo = true
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
180 // Types maps expressions to their types, and for constant
181 // expressions, also their values. Invalid expressions are
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
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
199 // Instances maps identifiers denoting generic types or functions to their
200 // type arguments and instantiated type.
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.
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
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.
219 // For an embedded field, Defs returns the field *Var it defines.
221 // Invariant: Defs[id] == nil || Defs[id].Pos() == id.Pos()
222 Defs map[*ast.Ident]Object
224 // Uses maps identifiers to the objects they denote.
226 // For an embedded field, Uses returns the *TypeName it denotes.
228 // Invariant: Uses[id].Pos() != id.Pos()
229 Uses map[*ast.Ident]Object
231 // Implicits maps nodes to their implicitly declared objects, if any.
232 // The following node and object types may appear:
234 // node declared object
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)
240 Implicits map[ast.Node]Object
242 // Selections maps selector expressions (excluding qualified identifiers)
243 // to their corresponding selections.
244 Selections map[*ast.SelectorExpr]*Selection
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.
256 // The following node types may appear in Scopes:
264 // *ast.TypeSwitchStmt
270 Scopes map[ast.Node]*Scope
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
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 {
286 if id, _ := e.(*ast.Ident); id != nil {
287 if obj := info.ObjectOf(id); obj != nil {
294 // ObjectOf returns the object denoted by the specified id,
295 // or nil if not found.
297 // If id is an embedded struct field, ObjectOf returns the field (*Var)
298 // it defines, not the type (*TypeName) it uses.
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 {
308 // TypeAndValue reports the type and value (for constants)
309 // of the corresponding expression.
310 type TypeAndValue struct {
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
322 // IsType reports whether the corresponding expression specifies a type.
323 func (tv TypeAndValue) IsType() bool {
324 return tv.mode == typexpr
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
333 // IsValue reports whether the corresponding expression is a value.
334 // Builtins are not considered values. Constant values have a non-
336 func (tv TypeAndValue) IsValue() bool {
338 case constant_, variable, mapindex, value, commaok, commaerr:
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]
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
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
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
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
372 type Instance struct {
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
380 type Initializer struct {
381 Lhs []*Var // var Lhs = Rhs
385 func (init *Initializer) String() string {
387 for i, lhs := range init.Lhs {
389 buf.WriteString(", ")
391 buf.WriteString(lhs.Name())
393 buf.WriteString(" = ")
394 WriteExpr(&buf, init.Rhs)
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.
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
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)
414 // AssertableTo reports whether a value of type V can be asserted to have type T.
416 // The behavior of AssertableTo is undefined in two cases:
417 // - if V is a generalized interface; i.e., an interface that may only be used
418 // as a type constraint in Go code
419 // - if T is an uninstantiated generic type
420 func AssertableTo(V *Interface, T Type) bool {
421 // Checker.newAssertableTo suppresses errors for invalid types, so we need special
423 if T.Underlying() == Typ[Invalid] {
426 return (*Checker)(nil).newAssertableTo(V, T) == nil
429 // AssignableTo reports whether a value of type V is assignable to a variable
432 // The behavior of AssignableTo is undefined if V or T is an uninstantiated
434 func AssignableTo(V, T Type) bool {
435 x := operand{mode: value, typ: V}
436 ok, _ := x.assignableTo(nil, T, nil) // check not needed for non-constant x
440 // ConvertibleTo reports whether a value of type V is convertible to a value of
443 // The behavior of ConvertibleTo is undefined if V or T is an uninstantiated
445 func ConvertibleTo(V, T Type) bool {
446 x := operand{mode: value, typ: V}
447 return x.convertibleTo(nil, T, nil) // check not needed for non-constant x
450 // Implements reports whether type V implements interface T.
452 // The behavior of Implements is undefined if V is an uninstantiated generic
454 func Implements(V Type, T *Interface) bool {
456 // All types (even Typ[Invalid]) implement the empty interface.
459 // Checker.implements suppresses errors for invalid types, so we need special
461 if V.Underlying() == Typ[Invalid] {
464 return (*Checker)(nil).implements(V, T) == nil
467 // Identical reports whether x and y are identical types.
468 // Receivers of Signature types are ignored.
469 func Identical(x, y Type) bool {
470 return identical(x, y, true, nil)
473 // IdenticalIgnoreTags reports whether x and y are identical types if tags are ignored.
474 // Receivers of Signature types are ignored.
475 func IdenticalIgnoreTags(x, y Type) bool {
476 return identical(x, y, false, nil)