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 // Index returns the positional index of the argument associated with the
73 func (e ArgumentError) Index() int {
77 // An Importer resolves import paths to Packages.
79 // CAUTION: This interface does not support the import of locally
80 // vendored packages. See https://golang.org/s/go15vendor.
81 // If possible, external implementations should implement ImporterFrom.
82 type Importer interface {
83 // Import returns the imported package for the given import path.
84 // The semantics is like for ImporterFrom.ImportFrom except that
85 // dir and mode are ignored (since they are not present).
86 Import(path string) (*Package, error)
89 // ImportMode is reserved for future use.
92 // An ImporterFrom resolves import paths to packages; it
93 // supports vendoring per https://golang.org/s/go15vendor.
94 // Use go/importer to obtain an ImporterFrom implementation.
95 type ImporterFrom interface {
96 // Importer is present for backward-compatibility. Calling
97 // Import(path) is the same as calling ImportFrom(path, "", 0);
98 // i.e., locally vendored packages may not be found.
99 // The types package does not call Import if an ImporterFrom
103 // ImportFrom returns the imported package for the given import
104 // path when imported by a package file located in dir.
105 // If the import failed, besides returning an error, ImportFrom
106 // is encouraged to cache and return a package anyway, if one
107 // was created. This will reduce package inconsistencies and
108 // follow-on type checker errors due to the missing package.
109 // The mode value must be 0; it is reserved for future use.
110 // Two calls to ImportFrom with the same path and dir must
111 // return the same package.
112 ImportFrom(path, dir string, mode ImportMode) (*Package, error)
115 // A Config specifies the configuration for type checking.
116 // The zero value for Config is a ready-to-use default configuration.
118 // Environment is the environment used for resolving global
119 // identifiers. If nil, the type checker will initialize this
120 // field with a newly created environment.
121 Environment *Environment
123 // GoVersion describes the accepted Go language version. The string
124 // must follow the format "go%d.%d" (e.g. "go1.12") or it must be
125 // empty; an empty string indicates the latest language version.
126 // If the format is invalid, invoking the type checker will cause a
130 // If IgnoreFuncBodies is set, function bodies are not
132 IgnoreFuncBodies bool
134 // If FakeImportC is set, `import "C"` (for packages requiring Cgo)
135 // declares an empty "C" package and errors are omitted for qualified
136 // identifiers referring to package C (which won't find an object).
137 // This feature is intended for the standard library cmd/api tool.
139 // Caution: Effects may be unpredictable due to follow-on errors.
140 // Do not use casually!
143 // If go115UsesCgo is set, the type checker expects the
144 // _cgo_gotypes.go file generated by running cmd/cgo to be
145 // provided as a package source file. Qualified identifiers
146 // referring to package C will be resolved to cgo-provided
147 // declarations within _cgo_gotypes.go.
149 // It is an error to set both FakeImportC and go115UsesCgo.
152 // If Error != nil, it is called with each error found
153 // during type checking; err has dynamic type Error.
154 // Secondary errors (for instance, to enumerate all types
155 // involved in an invalid recursive type declaration) have
156 // error strings that start with a '\t' character.
157 // If Error == nil, type-checking stops with the first
159 Error func(err error)
161 // An importer is used to import packages referred to from
162 // import declarations.
163 // If the installed importer implements ImporterFrom, the type
164 // checker calls ImportFrom instead of Import.
165 // The type checker reports an error if an importer is needed
166 // but none was installed.
169 // If Sizes != nil, it provides the sizing functions for package unsafe.
170 // Otherwise SizesFor("gc", "amd64") is used instead.
173 // If DisableUnusedImportCheck is set, packages are not checked
174 // for unused imports.
175 DisableUnusedImportCheck bool
178 func srcimporter_setUsesCgo(conf *Config) {
179 conf.go115UsesCgo = true
182 // Info holds result type information for a type-checked package.
183 // Only the information for which a map is provided is collected.
184 // If the package has type errors, the collected information may
187 // Types maps expressions to their types, and for constant
188 // expressions, also their values. Invalid expressions are
191 // For (possibly parenthesized) identifiers denoting built-in
192 // functions, the recorded signatures are call-site specific:
193 // if the call result is not a constant, the recorded type is
194 // an argument-specific signature. Otherwise, the recorded type
197 // The Types map does not record the type of every identifier,
198 // only those that appear where an arbitrary expression is
199 // permitted. For instance, the identifier f in a selector
200 // expression x.f is found only in the Selections map, the
201 // identifier z in a variable declaration 'var z int' is found
202 // only in the Defs map, and identifiers denoting packages in
203 // qualified identifiers are collected in the Uses map.
204 Types map[ast.Expr]TypeAndValue
206 // Inferred maps calls of parameterized functions that use
207 // type inference to the inferred type arguments and signature
208 // of the function called. The recorded "call" expression may be
209 // an *ast.CallExpr (as in f(x)), or an *ast.IndexExpr (s in f[T]).
210 Inferred map[ast.Expr]Inferred
212 // Defs maps identifiers to the objects they define (including
213 // package names, dots "." of dot-imports, and blank "_" identifiers).
214 // For identifiers that do not denote objects (e.g., the package name
215 // in package clauses, or symbolic variables t in t := x.(type) of
216 // type switch headers), the corresponding objects are nil.
218 // For an embedded field, Defs returns the field *Var it defines.
220 // Invariant: Defs[id] == nil || Defs[id].Pos() == id.Pos()
221 Defs map[*ast.Ident]Object
223 // Uses maps identifiers to the objects they denote.
225 // For an embedded field, Uses returns the *TypeName it denotes.
227 // Invariant: Uses[id].Pos() != id.Pos()
228 Uses map[*ast.Ident]Object
230 // Implicits maps nodes to their implicitly declared objects, if any.
231 // The following node and object types may appear:
233 // node declared object
235 // *ast.ImportSpec *PkgName for imports without renames
236 // *ast.CaseClause type-specific *Var for each type switch case clause (incl. default)
237 // *ast.Field anonymous parameter *Var (incl. unnamed results)
239 Implicits map[ast.Node]Object
241 // Selections maps selector expressions (excluding qualified identifiers)
242 // to their corresponding selections.
243 Selections map[*ast.SelectorExpr]*Selection
245 // Scopes maps ast.Nodes to the scopes they define. Package scopes are not
246 // associated with a specific node but with all files belonging to a package.
247 // Thus, the package scope can be found in the type-checked Package object.
248 // Scopes nest, with the Universe scope being the outermost scope, enclosing
249 // the package scope, which contains (one or more) files scopes, which enclose
250 // function scopes which in turn enclose statement and function literal scopes.
251 // Note that even though package-level functions are declared in the package
252 // scope, the function scopes are embedded in the file scope of the file
253 // containing the function declaration.
255 // The following node types may appear in Scopes:
262 // *ast.TypeSwitchStmt
268 Scopes map[ast.Node]*Scope
270 // InitOrder is the list of package-level initializers in the order in which
271 // they must be executed. Initializers referring to variables related by an
272 // initialization dependency appear in topological order, the others appear
273 // in source order. Variables without an initialization expression do not
274 // appear in this list.
275 InitOrder []*Initializer
278 // TypeOf returns the type of expression e, or nil if not found.
279 // Precondition: the Types, Uses and Defs maps are populated.
281 func (info *Info) TypeOf(e ast.Expr) Type {
282 if t, ok := info.Types[e]; ok {
285 if id, _ := e.(*ast.Ident); id != nil {
286 if obj := info.ObjectOf(id); obj != nil {
293 // ObjectOf returns the object denoted by the specified id,
294 // or nil if not found.
296 // If id is an embedded struct field, ObjectOf returns the field (*Var)
297 // it defines, not the type (*TypeName) it uses.
299 // 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 // Inferred reports the Inferred type arguments and signature
369 // for a parameterized function call that uses type inference.
370 type Inferred struct {
375 // An Initializer describes a package-level variable, or a list of variables in case
376 // of a multi-valued initialization expression, and the corresponding initialization
378 type Initializer struct {
379 Lhs []*Var // var Lhs = Rhs
383 func (init *Initializer) String() string {
385 for i, lhs := range init.Lhs {
387 buf.WriteString(", ")
389 buf.WriteString(lhs.Name())
391 buf.WriteString(" = ")
392 WriteExpr(&buf, init.Rhs)
396 // Check type-checks a package and returns the resulting package object and
397 // the first error if any. Additionally, if info != nil, Check populates each
398 // of the non-nil maps in the Info struct.
400 // The package is marked as complete if no errors occurred, otherwise it is
401 // incomplete. See Config.Error for controlling behavior in the presence of
404 // The package is specified by a list of *ast.Files and corresponding
405 // file set, and the package path the package is identified with.
406 // The clean path must not be empty or dot (".").
407 func (conf *Config) Check(path string, fset *token.FileSet, files []*ast.File, info *Info) (*Package, error) {
408 pkg := NewPackage(path, "")
409 return pkg, NewChecker(conf, fset, pkg, info).Files(files)
412 // AssertableTo reports whether a value of type V can be asserted to have type T.
413 func AssertableTo(V *Interface, T Type) bool {
414 m, _ := (*Checker)(nil).assertableTo(V, T)
418 // AssignableTo reports whether a value of type V is assignable to a variable of type T.
419 func AssignableTo(V, T Type) bool {
420 x := operand{mode: value, typ: V}
421 ok, _ := x.assignableTo(nil, T, nil) // check not needed for non-constant x
425 // ConvertibleTo reports whether a value of type V is convertible to a value of type T.
426 func ConvertibleTo(V, T Type) bool {
427 x := operand{mode: value, typ: V}
428 return x.convertibleTo(nil, T, nil) // check not needed for non-constant x
431 // Implements reports whether type V implements interface T.
432 func Implements(V Type, T *Interface) bool {
433 f, _ := MissingMethod(V, T, true)
437 // Identical reports whether x and y are identical types.
438 // Receivers of Signature types are ignored.
439 func Identical(x, y Type) bool {
440 return identical(x, y, true, nil)
443 // IdenticalIgnoreTags reports whether x and y are identical types if tags are ignored.
444 // Receivers of Signature types are ignored.
445 func IdenticalIgnoreTags(x, y Type) bool {
446 return identical(x, y, false, nil)