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 Importer resolves import paths to Packages.
67 // CAUTION: This interface does not support the import of locally
68 // vendored packages. See https://golang.org/s/go15vendor.
69 // If possible, external implementations should implement ImporterFrom.
70 type Importer interface {
71 // Import returns the imported package for the given import path.
72 // The semantics is like for ImporterFrom.ImportFrom except that
73 // dir and mode are ignored (since they are not present).
74 Import(path string) (*Package, error)
77 // ImportMode is reserved for future use.
80 // An ImporterFrom resolves import paths to packages; it
81 // supports vendoring per https://golang.org/s/go15vendor.
82 // Use go/importer to obtain an ImporterFrom implementation.
83 type ImporterFrom interface {
84 // Importer is present for backward-compatibility. Calling
85 // Import(path) is the same as calling ImportFrom(path, "", 0);
86 // i.e., locally vendored packages may not be found.
87 // The types package does not call Import if an ImporterFrom
91 // ImportFrom returns the imported package for the given import
92 // path when imported by a package file located in dir.
93 // If the import failed, besides returning an error, ImportFrom
94 // is encouraged to cache and return a package anyway, if one
95 // was created. This will reduce package inconsistencies and
96 // follow-on type checker errors due to the missing package.
97 // The mode value must be 0; it is reserved for future use.
98 // Two calls to ImportFrom with the same path and dir must
99 // return the same package.
100 ImportFrom(path, dir string, mode ImportMode) (*Package, error)
103 // A Config specifies the configuration for type checking.
104 // The zero value for Config is a ready-to-use default configuration.
106 // goVersion describes the accepted Go language version. The string
107 // must follow the format "go%d.%d" (e.g. "go1.12") or it must be
108 // empty; an empty string indicates the latest language version.
109 // If the format is invalid, invoking the type checker will cause a
113 // If IgnoreFuncBodies is set, function bodies are not
115 IgnoreFuncBodies bool
117 // If FakeImportC is set, `import "C"` (for packages requiring Cgo)
118 // declares an empty "C" package and errors are omitted for qualified
119 // identifiers referring to package C (which won't find an object).
120 // This feature is intended for the standard library cmd/api tool.
122 // Caution: Effects may be unpredictable due to follow-on errors.
123 // Do not use casually!
126 // If go115UsesCgo is set, the type checker expects the
127 // _cgo_gotypes.go file generated by running cmd/cgo to be
128 // provided as a package source file. Qualified identifiers
129 // referring to package C will be resolved to cgo-provided
130 // declarations within _cgo_gotypes.go.
132 // It is an error to set both FakeImportC and go115UsesCgo.
135 // If Error != nil, it is called with each error found
136 // during type checking; err has dynamic type Error.
137 // Secondary errors (for instance, to enumerate all types
138 // involved in an invalid recursive type declaration) have
139 // error strings that start with a '\t' character.
140 // If Error == nil, type-checking stops with the first
142 Error func(err error)
144 // An importer is used to import packages referred to from
145 // import declarations.
146 // If the installed importer implements ImporterFrom, the type
147 // checker calls ImportFrom instead of Import.
148 // The type checker reports an error if an importer is needed
149 // but none was installed.
152 // If Sizes != nil, it provides the sizing functions for package unsafe.
153 // Otherwise SizesFor("gc", "amd64") is used instead.
156 // If DisableUnusedImportCheck is set, packages are not checked
157 // for unused imports.
158 DisableUnusedImportCheck bool
161 func srcimporter_setUsesCgo(conf *Config) {
162 conf.go115UsesCgo = true
165 // The Info struct is found in api_notypeparams.go and api_typeparams.go.
167 // TypeOf returns the type of expression e, or nil if not found.
168 // Precondition: the Types, Uses and Defs maps are populated.
170 func (info *Info) TypeOf(e ast.Expr) Type {
171 if t, ok := info.Types[e]; ok {
174 if id, _ := e.(*ast.Ident); id != nil {
175 if obj := info.ObjectOf(id); obj != nil {
182 // ObjectOf returns the object denoted by the specified id,
183 // or nil if not found.
185 // If id is an embedded struct field, ObjectOf returns the field (*Var)
186 // it defines, not the type (*TypeName) it uses.
188 // Precondition: the Uses and Defs maps are populated.
190 func (info *Info) ObjectOf(id *ast.Ident) Object {
191 if obj := info.Defs[id]; obj != nil {
197 // TypeAndValue reports the type and value (for constants)
198 // of the corresponding expression.
199 type TypeAndValue struct {
205 // IsVoid reports whether the corresponding expression
206 // is a function call without results.
207 func (tv TypeAndValue) IsVoid() bool {
208 return tv.mode == novalue
211 // IsType reports whether the corresponding expression specifies a type.
212 func (tv TypeAndValue) IsType() bool {
213 return tv.mode == typexpr
216 // IsBuiltin reports whether the corresponding expression denotes
217 // a (possibly parenthesized) built-in function.
218 func (tv TypeAndValue) IsBuiltin() bool {
219 return tv.mode == builtin
222 // IsValue reports whether the corresponding expression is a value.
223 // Builtins are not considered values. Constant values have a non-
225 func (tv TypeAndValue) IsValue() bool {
227 case constant_, variable, mapindex, value, commaok, commaerr:
233 // IsNil reports whether the corresponding expression denotes the
234 // predeclared value nil.
235 func (tv TypeAndValue) IsNil() bool {
236 return tv.mode == value && tv.Type == Typ[UntypedNil]
239 // Addressable reports whether the corresponding expression
240 // is addressable (https://golang.org/ref/spec#Address_operators).
241 func (tv TypeAndValue) Addressable() bool {
242 return tv.mode == variable
245 // Assignable reports whether the corresponding expression
246 // is assignable to (provided a value of the right type).
247 func (tv TypeAndValue) Assignable() bool {
248 return tv.mode == variable || tv.mode == mapindex
251 // HasOk reports whether the corresponding expression may be
252 // used on the rhs of a comma-ok assignment.
253 func (tv TypeAndValue) HasOk() bool {
254 return tv.mode == commaok || tv.mode == mapindex
257 // _Inferred reports the _Inferred type arguments and signature
258 // for a parameterized function call that uses type inference.
259 type _Inferred struct {
264 // An Initializer describes a package-level variable, or a list of variables in case
265 // of a multi-valued initialization expression, and the corresponding initialization
267 type Initializer struct {
268 Lhs []*Var // var Lhs = Rhs
272 func (init *Initializer) String() string {
274 for i, lhs := range init.Lhs {
276 buf.WriteString(", ")
278 buf.WriteString(lhs.Name())
280 buf.WriteString(" = ")
281 WriteExpr(&buf, init.Rhs)
285 // Check type-checks a package and returns the resulting package object and
286 // the first error if any. Additionally, if info != nil, Check populates each
287 // of the non-nil maps in the Info struct.
289 // The package is marked as complete if no errors occurred, otherwise it is
290 // incomplete. See Config.Error for controlling behavior in the presence of
293 // The package is specified by a list of *ast.Files and corresponding
294 // file set, and the package path the package is identified with.
295 // The clean path must not be empty or dot (".").
296 func (conf *Config) Check(path string, fset *token.FileSet, files []*ast.File, info *Info) (*Package, error) {
297 pkg := NewPackage(path, "")
298 return pkg, NewChecker(conf, fset, pkg, info).Files(files)
301 // AssertableTo reports whether a value of type V can be asserted to have type T.
302 func AssertableTo(V *Interface, T Type) bool {
303 m, _ := (*Checker)(nil).assertableTo(V, T)
307 // AssignableTo reports whether a value of type V is assignable to a variable of type T.
308 func AssignableTo(V, T Type) bool {
309 x := operand{mode: value, typ: V}
310 ok, _ := x.assignableTo(nil, T, nil) // check not needed for non-constant x
314 // ConvertibleTo reports whether a value of type V is convertible to a value of type T.
315 func ConvertibleTo(V, T Type) bool {
316 x := operand{mode: value, typ: V}
317 return x.convertibleTo(nil, T, nil) // check not needed for non-constant x
320 // Implements reports whether type V implements interface T.
321 func Implements(V Type, T *Interface) bool {
322 f, _ := MissingMethod(V, T, true)
326 // Identical reports whether x and y are identical types.
327 // Receivers of Signature types are ignored.
328 func Identical(x, y Type) bool {
329 return (*Checker)(nil).identical(x, y)
332 // IdenticalIgnoreTags reports whether x and y are identical types if tags are ignored.
333 // Receivers of Signature types are ignored.
334 func IdenticalIgnoreTags(x, y Type) bool {
335 return (*Checker)(nil).identicalIgnoreTags(x, y)