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 // An Error describes a type-checking error; it implements the error interface.
38 // A "soft" error is an error that still permits a valid interpretation of a
39 // package (such as "unused variable"); "hard" errors may lead to unpredictable
40 // behavior if ignored.
42 Fset *token.FileSet // file set for interpretation of Pos
43 Pos token.Pos // error position
44 Msg string // error message
45 Soft bool // if set, error is "soft"
47 // go116code is a future API, unexported as the set of error codes is large
48 // and likely to change significantly during experimentation. Tools wishing
49 // to preview this feature may read go116code using reflection (see
50 // errorcodes_test.go), but beware that there is no guarantee of future
57 // Error returns an error string formatted as follows:
58 // filename:line:column: message
59 func (err Error) Error() string {
60 return fmt.Sprintf("%s: %s", err.Fset.Position(err.Pos), err.Msg)
63 // An Importer resolves import paths to Packages.
65 // CAUTION: This interface does not support the import of locally
66 // vendored packages. See https://golang.org/s/go15vendor.
67 // If possible, external implementations should implement ImporterFrom.
68 type Importer interface {
69 // Import returns the imported package for the given import path.
70 // The semantics is like for ImporterFrom.ImportFrom except that
71 // dir and mode are ignored (since they are not present).
72 Import(path string) (*Package, error)
75 // ImportMode is reserved for future use.
78 // An ImporterFrom resolves import paths to packages; it
79 // supports vendoring per https://golang.org/s/go15vendor.
80 // Use go/importer to obtain an ImporterFrom implementation.
81 type ImporterFrom interface {
82 // Importer is present for backward-compatibility. Calling
83 // Import(path) is the same as calling ImportFrom(path, "", 0);
84 // i.e., locally vendored packages may not be found.
85 // The types package does not call Import if an ImporterFrom
89 // ImportFrom returns the imported package for the given import
90 // path when imported by a package file located in dir.
91 // If the import failed, besides returning an error, ImportFrom
92 // is encouraged to cache and return a package anyway, if one
93 // was created. This will reduce package inconsistencies and
94 // follow-on type checker errors due to the missing package.
95 // The mode value must be 0; it is reserved for future use.
96 // Two calls to ImportFrom with the same path and dir must
97 // return the same package.
98 ImportFrom(path, dir string, mode ImportMode) (*Package, error)
101 // A Config specifies the configuration for type checking.
102 // The zero value for Config is a ready-to-use default configuration.
104 // goVersion describes the accepted Go language version. The string
105 // must follow the format "go%d.%d" (e.g. "go1.12") or it must be
106 // empty; an empty string indicates the latest language version.
107 // If the format is invalid, invoking the type checker will cause a
111 // If IgnoreFuncBodies is set, function bodies are not
113 IgnoreFuncBodies bool
115 // If FakeImportC is set, `import "C"` (for packages requiring Cgo)
116 // declares an empty "C" package and errors are omitted for qualified
117 // identifiers referring to package C (which won't find an object).
118 // This feature is intended for the standard library cmd/api tool.
120 // Caution: Effects may be unpredictable due to follow-on errors.
121 // Do not use casually!
124 // If go115UsesCgo is set, the type checker expects the
125 // _cgo_gotypes.go file generated by running cmd/cgo to be
126 // provided as a package source file. Qualified identifiers
127 // referring to package C will be resolved to cgo-provided
128 // declarations within _cgo_gotypes.go.
130 // It is an error to set both FakeImportC and go115UsesCgo.
133 // If Error != nil, it is called with each error found
134 // during type checking; err has dynamic type Error.
135 // Secondary errors (for instance, to enumerate all types
136 // involved in an invalid recursive type declaration) have
137 // error strings that start with a '\t' character.
138 // If Error == nil, type-checking stops with the first
140 Error func(err error)
142 // An importer is used to import packages referred to from
143 // import declarations.
144 // If the installed importer implements ImporterFrom, the type
145 // checker calls ImportFrom instead of Import.
146 // The type checker reports an error if an importer is needed
147 // but none was installed.
150 // If Sizes != nil, it provides the sizing functions for package unsafe.
151 // Otherwise SizesFor("gc", "amd64") is used instead.
154 // If DisableUnusedImportCheck is set, packages are not checked
155 // for unused imports.
156 DisableUnusedImportCheck bool
159 func srcimporter_setUsesCgo(conf *Config) {
160 conf.go115UsesCgo = true
163 // The Info struct is found in api_notypeparams.go and api_typeparams.go.
165 // TypeOf returns the type of expression e, or nil if not found.
166 // Precondition: the Types, Uses and Defs maps are populated.
168 func (info *Info) TypeOf(e ast.Expr) Type {
169 if t, ok := info.Types[e]; ok {
172 if id, _ := e.(*ast.Ident); id != nil {
173 if obj := info.ObjectOf(id); obj != nil {
180 // ObjectOf returns the object denoted by the specified id,
181 // or nil if not found.
183 // If id is an embedded struct field, ObjectOf returns the field (*Var)
184 // it defines, not the type (*TypeName) it uses.
186 // Precondition: the Uses and Defs maps are populated.
188 func (info *Info) ObjectOf(id *ast.Ident) Object {
189 if obj := info.Defs[id]; obj != nil {
195 // TypeAndValue reports the type and value (for constants)
196 // of the corresponding expression.
197 type TypeAndValue struct {
203 // IsVoid reports whether the corresponding expression
204 // is a function call without results.
205 func (tv TypeAndValue) IsVoid() bool {
206 return tv.mode == novalue
209 // IsType reports whether the corresponding expression specifies a type.
210 func (tv TypeAndValue) IsType() bool {
211 return tv.mode == typexpr
214 // IsBuiltin reports whether the corresponding expression denotes
215 // a (possibly parenthesized) built-in function.
216 func (tv TypeAndValue) IsBuiltin() bool {
217 return tv.mode == builtin
220 // IsValue reports whether the corresponding expression is a value.
221 // Builtins are not considered values. Constant values have a non-
223 func (tv TypeAndValue) IsValue() bool {
225 case constant_, variable, mapindex, value, commaok, commaerr:
231 // IsNil reports whether the corresponding expression denotes the
232 // predeclared value nil.
233 func (tv TypeAndValue) IsNil() bool {
234 return tv.mode == value && tv.Type == Typ[UntypedNil]
237 // Addressable reports whether the corresponding expression
238 // is addressable (https://golang.org/ref/spec#Address_operators).
239 func (tv TypeAndValue) Addressable() bool {
240 return tv.mode == variable
243 // Assignable reports whether the corresponding expression
244 // is assignable to (provided a value of the right type).
245 func (tv TypeAndValue) Assignable() bool {
246 return tv.mode == variable || tv.mode == mapindex
249 // HasOk reports whether the corresponding expression may be
250 // used on the rhs of a comma-ok assignment.
251 func (tv TypeAndValue) HasOk() bool {
252 return tv.mode == commaok || tv.mode == mapindex
255 // _Inferred reports the _Inferred type arguments and signature
256 // for a parameterized function call that uses type inference.
257 type _Inferred struct {
262 // An Initializer describes a package-level variable, or a list of variables in case
263 // of a multi-valued initialization expression, and the corresponding initialization
265 type Initializer struct {
266 Lhs []*Var // var Lhs = Rhs
270 func (init *Initializer) String() string {
272 for i, lhs := range init.Lhs {
274 buf.WriteString(", ")
276 buf.WriteString(lhs.Name())
278 buf.WriteString(" = ")
279 WriteExpr(&buf, init.Rhs)
283 // Check type-checks a package and returns the resulting package object and
284 // the first error if any. Additionally, if info != nil, Check populates each
285 // of the non-nil maps in the Info struct.
287 // The package is marked as complete if no errors occurred, otherwise it is
288 // incomplete. See Config.Error for controlling behavior in the presence of
291 // The package is specified by a list of *ast.Files and corresponding
292 // file set, and the package path the package is identified with.
293 // The clean path must not be empty or dot (".").
294 func (conf *Config) Check(path string, fset *token.FileSet, files []*ast.File, info *Info) (*Package, error) {
295 pkg := NewPackage(path, "")
296 return pkg, NewChecker(conf, fset, pkg, info).Files(files)
299 // AssertableTo reports whether a value of type V can be asserted to have type T.
300 func AssertableTo(V *Interface, T Type) bool {
301 m, _ := (*Checker)(nil).assertableTo(V, T)
305 // AssignableTo reports whether a value of type V is assignable to a variable of type T.
306 func AssignableTo(V, T Type) bool {
307 x := operand{mode: value, typ: V}
308 ok, _ := x.assignableTo(nil, T, nil) // check not needed for non-constant x
312 // ConvertibleTo reports whether a value of type V is convertible to a value of type T.
313 func ConvertibleTo(V, T Type) bool {
314 x := operand{mode: value, typ: V}
315 return x.convertibleTo(nil, T, nil) // check not needed for non-constant x
318 // Implements reports whether type V implements interface T.
319 func Implements(V Type, T *Interface) bool {
320 f, _ := MissingMethod(V, T, true)
324 // Identical reports whether x and y are identical types.
325 // Receivers of Signature types are ignored.
326 func Identical(x, y Type) bool {
327 return (*Checker)(nil).identical(x, y)
330 // IdenticalIgnoreTags reports whether x and y are identical types if tags are ignored.
331 // Receivers of Signature types are ignored.
332 func IdenticalIgnoreTags(x, y Type) bool {
333 return (*Checker)(nil).identicalIgnoreTags(x, y)