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 // Info holds result type information for a type-checked package.
164 // Only the information for which a map is provided is collected.
165 // If the package has type errors, the collected information may
168 // Types maps expressions to their types, and for constant
169 // expressions, also their values. Invalid expressions are
172 // For (possibly parenthesized) identifiers denoting built-in
173 // functions, the recorded signatures are call-site specific:
174 // if the call result is not a constant, the recorded type is
175 // an argument-specific signature. Otherwise, the recorded type
178 // The Types map does not record the type of every identifier,
179 // only those that appear where an arbitrary expression is
180 // permitted. For instance, the identifier f in a selector
181 // expression x.f is found only in the Selections map, the
182 // identifier z in a variable declaration 'var z int' is found
183 // only in the Defs map, and identifiers denoting packages in
184 // qualified identifiers are collected in the Uses map.
185 Types map[ast.Expr]TypeAndValue
187 // _Inferred maps calls of parameterized functions that use
188 // type inference to the _Inferred type arguments and signature
189 // of the function called. The recorded "call" expression may be
190 // an *ast.CallExpr (as in f(x)), or an *ast.IndexExpr (s in f[T]).
191 _Inferred map[ast.Expr]_Inferred
193 // Defs maps identifiers to the objects they define (including
194 // package names, dots "." of dot-imports, and blank "_" identifiers).
195 // For identifiers that do not denote objects (e.g., the package name
196 // in package clauses, or symbolic variables t in t := x.(type) of
197 // type switch headers), the corresponding objects are nil.
199 // For an embedded field, Defs returns the field *Var it defines.
201 // Invariant: Defs[id] == nil || Defs[id].Pos() == id.Pos()
202 Defs map[*ast.Ident]Object
204 // Uses maps identifiers to the objects they denote.
206 // For an embedded field, Uses returns the *TypeName it denotes.
208 // Invariant: Uses[id].Pos() != id.Pos()
209 Uses map[*ast.Ident]Object
211 // Implicits maps nodes to their implicitly declared objects, if any.
212 // The following node and object types may appear:
214 // node declared object
216 // *ast.ImportSpec *PkgName for imports without renames
217 // *ast.CaseClause type-specific *Var for each type switch case clause (incl. default)
218 // *ast.Field anonymous parameter *Var (incl. unnamed results)
220 Implicits map[ast.Node]Object
222 // Selections maps selector expressions (excluding qualified identifiers)
223 // to their corresponding selections.
224 Selections map[*ast.SelectorExpr]*Selection
226 // Scopes maps ast.Nodes to the scopes they define. Package scopes are not
227 // associated with a specific node but with all files belonging to a package.
228 // Thus, the package scope can be found in the type-checked Package object.
229 // Scopes nest, with the Universe scope being the outermost scope, enclosing
230 // the package scope, which contains (one or more) files scopes, which enclose
231 // function scopes which in turn enclose statement and function literal scopes.
232 // Note that even though package-level functions are declared in the package
233 // scope, the function scopes are embedded in the file scope of the file
234 // containing the function declaration.
236 // The following node types may appear in Scopes:
243 // *ast.TypeSwitchStmt
249 Scopes map[ast.Node]*Scope
251 // InitOrder is the list of package-level initializers in the order in which
252 // they must be executed. Initializers referring to variables related by an
253 // initialization dependency appear in topological order, the others appear
254 // in source order. Variables without an initialization expression do not
255 // appear in this list.
256 InitOrder []*Initializer
259 // TypeOf returns the type of expression e, or nil if not found.
260 // Precondition: the Types, Uses and Defs maps are populated.
262 func (info *Info) TypeOf(e ast.Expr) Type {
263 if t, ok := info.Types[e]; ok {
266 if id, _ := e.(*ast.Ident); id != nil {
267 if obj := info.ObjectOf(id); obj != nil {
274 // ObjectOf returns the object denoted by the specified id,
275 // or nil if not found.
277 // If id is an embedded struct field, ObjectOf returns the field (*Var)
278 // it defines, not the type (*TypeName) it uses.
280 // Precondition: the Uses and Defs maps are populated.
282 func (info *Info) ObjectOf(id *ast.Ident) Object {
283 if obj := info.Defs[id]; obj != nil {
289 // TypeAndValue reports the type and value (for constants)
290 // of the corresponding expression.
291 type TypeAndValue struct {
297 // IsVoid reports whether the corresponding expression
298 // is a function call without results.
299 func (tv TypeAndValue) IsVoid() bool {
300 return tv.mode == novalue
303 // IsType reports whether the corresponding expression specifies a type.
304 func (tv TypeAndValue) IsType() bool {
305 return tv.mode == typexpr
308 // IsBuiltin reports whether the corresponding expression denotes
309 // a (possibly parenthesized) built-in function.
310 func (tv TypeAndValue) IsBuiltin() bool {
311 return tv.mode == builtin
314 // IsValue reports whether the corresponding expression is a value.
315 // Builtins are not considered values. Constant values have a non-
317 func (tv TypeAndValue) IsValue() bool {
319 case constant_, variable, mapindex, value, commaok, commaerr:
325 // IsNil reports whether the corresponding expression denotes the
326 // predeclared value nil.
327 func (tv TypeAndValue) IsNil() bool {
328 return tv.mode == value && tv.Type == Typ[UntypedNil]
331 // Addressable reports whether the corresponding expression
332 // is addressable (https://golang.org/ref/spec#Address_operators).
333 func (tv TypeAndValue) Addressable() bool {
334 return tv.mode == variable
337 // Assignable reports whether the corresponding expression
338 // is assignable to (provided a value of the right type).
339 func (tv TypeAndValue) Assignable() bool {
340 return tv.mode == variable || tv.mode == mapindex
343 // HasOk reports whether the corresponding expression may be
344 // used on the rhs of a comma-ok assignment.
345 func (tv TypeAndValue) HasOk() bool {
346 return tv.mode == commaok || tv.mode == mapindex
349 // _Inferred reports the _Inferred type arguments and signature
350 // for a parameterized function call that uses type inference.
351 type _Inferred struct {
356 // An Initializer describes a package-level variable, or a list of variables in case
357 // of a multi-valued initialization expression, and the corresponding initialization
359 type Initializer struct {
360 Lhs []*Var // var Lhs = Rhs
364 func (init *Initializer) String() string {
366 for i, lhs := range init.Lhs {
368 buf.WriteString(", ")
370 buf.WriteString(lhs.Name())
372 buf.WriteString(" = ")
373 WriteExpr(&buf, init.Rhs)
377 // Check type-checks a package and returns the resulting package object and
378 // the first error if any. Additionally, if info != nil, Check populates each
379 // of the non-nil maps in the Info struct.
381 // The package is marked as complete if no errors occurred, otherwise it is
382 // incomplete. See Config.Error for controlling behavior in the presence of
385 // The package is specified by a list of *ast.Files and corresponding
386 // file set, and the package path the package is identified with.
387 // The clean path must not be empty or dot (".").
388 func (conf *Config) Check(path string, fset *token.FileSet, files []*ast.File, info *Info) (*Package, error) {
389 pkg := NewPackage(path, "")
390 return pkg, NewChecker(conf, fset, pkg, info).Files(files)
393 // AssertableTo reports whether a value of type V can be asserted to have type T.
394 func AssertableTo(V *Interface, T Type) bool {
395 m, _ := (*Checker)(nil).assertableTo(V, T)
399 // AssignableTo reports whether a value of type V is assignable to a variable of type T.
400 func AssignableTo(V, T Type) bool {
401 x := operand{mode: value, typ: V}
402 ok, _ := x.assignableTo(nil, T, nil) // check not needed for non-constant x
406 // ConvertibleTo reports whether a value of type V is convertible to a value of type T.
407 func ConvertibleTo(V, T Type) bool {
408 x := operand{mode: value, typ: V}
409 return x.convertibleTo(nil, T, nil) // check not needed for non-constant x
412 // Implements reports whether type V implements interface T.
413 func Implements(V Type, T *Interface) bool {
414 f, _ := MissingMethod(V, T, true)
418 // Identical reports whether x and y are identical types.
419 // Receivers of Signature types are ignored.
420 func Identical(x, y Type) bool {
421 return (*Checker)(nil).identical(x, y)
424 // IdenticalIgnoreTags reports whether x and y are identical types if tags are ignored.
425 // Receivers of Signature types are ignored.
426 func IdenticalIgnoreTags(x, y Type) bool {
427 return (*Checker)(nil).identicalIgnoreTags(x, y)