1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
|
// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package types declares the data types and implements
// the algorithms for type-checking of Go packages. Use
// Config.Check to invoke the type checker for a package.
// Alternatively, create a new type checker with NewChecker
// and invoke it incrementally by calling Checker.Files.
//
// Type-checking consists of several interdependent phases:
//
// Name resolution maps each identifier (ast.Ident) in the program to the
// language object (Object) it denotes.
// Use Info.{Defs,Uses,Implicits} for the results of name resolution.
//
// Constant folding computes the exact constant value (constant.Value)
// for every expression (ast.Expr) that is a compile-time constant.
// Use Info.Types[expr].Value for the results of constant folding.
//
// Type inference computes the type (Type) of every expression (ast.Expr)
// and checks for compliance with the language specification.
// Use Info.Types[expr].Type for the results of type inference.
//
// For a tutorial, see https://golang.org/s/types-tutorial.
//
package types
import (
"bytes"
"fmt"
"go/ast"
"go/constant"
"go/token"
)
// An Error describes a type-checking error; it implements the error interface.
// A "soft" error is an error that still permits a valid interpretation of a
// package (such as "unused variable"); "hard" errors may lead to unpredictable
// behavior if ignored.
type Error struct {
Fset *token.FileSet // file set for interpretation of Pos
Pos token.Pos // error position
Msg string // error message
Soft bool // if set, error is "soft"
}
// Error returns an error string formatted as follows:
// filename:line:column: message
func (err Error) Error() string {
return fmt.Sprintf("%s: %s", err.Fset.Position(err.Pos), err.Msg)
}
// An Importer resolves import paths to Packages.
//
// CAUTION: This interface does not support the import of locally
// vendored packages. See https://golang.org/s/go15vendor.
// If possible, external implementations should implement ImporterFrom.
type Importer interface {
// Import returns the imported package for the given import path.
// The semantics is like for ImporterFrom.ImportFrom except that
// dir and mode are ignored (since they are not present).
Import(path string) (*Package, error)
}
// ImportMode is reserved for future use.
type ImportMode int
// An ImporterFrom resolves import paths to packages; it
// supports vendoring per https://golang.org/s/go15vendor.
// Use go/importer to obtain an ImporterFrom implementation.
type ImporterFrom interface {
// Importer is present for backward-compatibility. Calling
// Import(path) is the same as calling ImportFrom(path, "", 0);
// i.e., locally vendored packages may not be found.
// The types package does not call Import if an ImporterFrom
// is present.
Importer
// ImportFrom returns the imported package for the given import
// path when imported by a package file located in dir.
// If the import failed, besides returning an error, ImportFrom
// is encouraged to cache and return a package anyway, if one
// was created. This will reduce package inconsistencies and
// follow-on type checker errors due to the missing package.
// The mode value must be 0; it is reserved for future use.
// Two calls to ImportFrom with the same path and dir must
// return the same package.
ImportFrom(path, dir string, mode ImportMode) (*Package, error)
}
// A Config specifies the configuration for type checking.
// The zero value for Config is a ready-to-use default configuration.
type Config struct {
// If IgnoreFuncBodies is set, function bodies are not
// type-checked.
IgnoreFuncBodies bool
// If FakeImportC is set, `import "C"` (for packages requiring Cgo)
// declares an empty "C" package and errors are omitted for qualified
// identifiers referring to package C (which won't find an object).
// This feature is intended for the standard library cmd/api tool.
//
// Caution: Effects may be unpredictable due to follow-on errors.
// Do not use casually!
FakeImportC bool
// If Error != nil, it is called with each error found
// during type checking; err has dynamic type Error.
// Secondary errors (for instance, to enumerate all types
// involved in an invalid recursive type declaration) have
// error strings that start with a '\t' character.
// If Error == nil, type-checking stops with the first
// error found.
Error func(err error)
// An importer is used to import packages referred to from
// import declarations.
// If the installed importer implements ImporterFrom, the type
// checker calls ImportFrom instead of Import.
// The type checker reports an error if an importer is needed
// but none was installed.
Importer Importer
// If Sizes != nil, it provides the sizing functions for package unsafe.
// Otherwise SizesFor("gc", "amd64") is used instead.
Sizes Sizes
// If DisableUnusedImportCheck is set, packages are not checked
// for unused imports.
DisableUnusedImportCheck bool
}
// Info holds result type information for a type-checked package.
// Only the information for which a map is provided is collected.
// If the package has type errors, the collected information may
// be incomplete.
type Info struct {
// Types maps expressions to their types, and for constant
// expressions, also their values. Invalid expressions are
// omitted.
//
// For (possibly parenthesized) identifiers denoting built-in
// functions, the recorded signatures are call-site specific:
// if the call result is not a constant, the recorded type is
// an argument-specific signature. Otherwise, the recorded type
// is invalid.
//
// The Types map does not record the type of every identifier,
// only those that appear where an arbitrary expression is
// permitted. For instance, the identifier f in a selector
// expression x.f is found only in the Selections map, the
// identifier z in a variable declaration 'var z int' is found
// only in the Defs map, and identifiers denoting packages in
// qualified identifiers are collected in the Uses map.
Types map[ast.Expr]TypeAndValue
// Defs maps identifiers to the objects they define (including
// package names, dots "." of dot-imports, and blank "_" identifiers).
// For identifiers that do not denote objects (e.g., the package name
// in package clauses, or symbolic variables t in t := x.(type) of
// type switch headers), the corresponding objects are nil.
//
// For an anonymous field, Defs returns the field *Var it defines.
//
// Invariant: Defs[id] == nil || Defs[id].Pos() == id.Pos()
Defs map[*ast.Ident]Object
// Uses maps identifiers to the objects they denote.
//
// For an anonymous field, Uses returns the *TypeName it denotes.
//
// Invariant: Uses[id].Pos() != id.Pos()
Uses map[*ast.Ident]Object
// Implicits maps nodes to their implicitly declared objects, if any.
// The following node and object types may appear:
//
// node declared object
//
// *ast.ImportSpec *PkgName for imports without renames
// *ast.CaseClause type-specific *Var for each type switch case clause (incl. default)
// *ast.Field anonymous parameter *Var
//
Implicits map[ast.Node]Object
// Selections maps selector expressions (excluding qualified identifiers)
// to their corresponding selections.
Selections map[*ast.SelectorExpr]*Selection
// Scopes maps ast.Nodes to the scopes they define. Package scopes are not
// associated with a specific node but with all files belonging to a package.
// Thus, the package scope can be found in the type-checked Package object.
// Scopes nest, with the Universe scope being the outermost scope, enclosing
// the package scope, which contains (one or more) files scopes, which enclose
// function scopes which in turn enclose statement and function literal scopes.
// Note that even though package-level functions are declared in the package
// scope, the function scopes are embedded in the file scope of the file
// containing the function declaration.
//
// The following node types may appear in Scopes:
//
// *ast.File
// *ast.FuncType
// *ast.BlockStmt
// *ast.IfStmt
// *ast.SwitchStmt
// *ast.TypeSwitchStmt
// *ast.CaseClause
// *ast.CommClause
// *ast.ForStmt
// *ast.RangeStmt
//
Scopes map[ast.Node]*Scope
// InitOrder is the list of package-level initializers in the order in which
// they must be executed. Initializers referring to variables related by an
// initialization dependency appear in topological order, the others appear
// in source order. Variables without an initialization expression do not
// appear in this list.
InitOrder []*Initializer
}
// TypeOf returns the type of expression e, or nil if not found.
// Precondition: the Types, Uses and Defs maps are populated.
//
func (info *Info) TypeOf(e ast.Expr) Type {
if t, ok := info.Types[e]; ok {
return t.Type
}
if id, _ := e.(*ast.Ident); id != nil {
if obj := info.ObjectOf(id); obj != nil {
return obj.Type()
}
}
return nil
}
// ObjectOf returns the object denoted by the specified id,
// or nil if not found.
//
// If id is an anonymous struct field, ObjectOf returns the field (*Var)
// it uses, not the type (*TypeName) it defines.
//
// Precondition: the Uses and Defs maps are populated.
//
func (info *Info) ObjectOf(id *ast.Ident) Object {
if obj := info.Defs[id]; obj != nil {
return obj
}
return info.Uses[id]
}
// TypeAndValue reports the type and value (for constants)
// of the corresponding expression.
type TypeAndValue struct {
mode operandMode
Type Type
Value constant.Value
}
// TODO(gri) Consider eliminating the IsVoid predicate. Instead, report
// "void" values as regular values but with the empty tuple type.
// IsVoid reports whether the corresponding expression
// is a function call without results.
func (tv TypeAndValue) IsVoid() bool {
return tv.mode == novalue
}
// IsType reports whether the corresponding expression specifies a type.
func (tv TypeAndValue) IsType() bool {
return tv.mode == typexpr
}
// IsBuiltin reports whether the corresponding expression denotes
// a (possibly parenthesized) built-in function.
func (tv TypeAndValue) IsBuiltin() bool {
return tv.mode == builtin
}
// IsValue reports whether the corresponding expression is a value.
// Builtins are not considered values. Constant values have a non-
// nil Value.
func (tv TypeAndValue) IsValue() bool {
switch tv.mode {
case constant_, variable, mapindex, value, commaok:
return true
}
return false
}
// IsNil reports whether the corresponding expression denotes the
// predeclared value nil.
func (tv TypeAndValue) IsNil() bool {
return tv.mode == value && tv.Type == Typ[UntypedNil]
}
// Addressable reports whether the corresponding expression
// is addressable (https://golang.org/ref/spec#Address_operators).
func (tv TypeAndValue) Addressable() bool {
return tv.mode == variable
}
// Assignable reports whether the corresponding expression
// is assignable to (provided a value of the right type).
func (tv TypeAndValue) Assignable() bool {
return tv.mode == variable || tv.mode == mapindex
}
// HasOk reports whether the corresponding expression may be
// used on the lhs of a comma-ok assignment.
func (tv TypeAndValue) HasOk() bool {
return tv.mode == commaok || tv.mode == mapindex
}
// An Initializer describes a package-level variable, or a list of variables in case
// of a multi-valued initialization expression, and the corresponding initialization
// expression.
type Initializer struct {
Lhs []*Var // var Lhs = Rhs
Rhs ast.Expr
}
func (init *Initializer) String() string {
var buf bytes.Buffer
for i, lhs := range init.Lhs {
if i > 0 {
buf.WriteString(", ")
}
buf.WriteString(lhs.Name())
}
buf.WriteString(" = ")
WriteExpr(&buf, init.Rhs)
return buf.String()
}
// Check type-checks a package and returns the resulting package object and
// the first error if any. Additionally, if info != nil, Check populates each
// of the non-nil maps in the Info struct.
//
// The package is marked as complete if no errors occurred, otherwise it is
// incomplete. See Config.Error for controlling behavior in the presence of
// errors.
//
// The package is specified by a list of *ast.Files and corresponding
// file set, and the package path the package is identified with.
// The clean path must not be empty or dot (".").
func (conf *Config) Check(path string, fset *token.FileSet, files []*ast.File, info *Info) (*Package, error) {
pkg := NewPackage(path, "")
return pkg, NewChecker(conf, fset, pkg, info).Files(files)
}
// AssertableTo reports whether a value of type V can be asserted to have type T.
func AssertableTo(V *Interface, T Type) bool {
m, _ := assertableTo(V, T)
return m == nil
}
// AssignableTo reports whether a value of type V is assignable to a variable of type T.
func AssignableTo(V, T Type) bool {
x := operand{mode: value, typ: V}
return x.assignableTo(nil, T, nil) // config not needed for non-constant x
}
// ConvertibleTo reports whether a value of type V is convertible to a value of type T.
func ConvertibleTo(V, T Type) bool {
x := operand{mode: value, typ: V}
return x.convertibleTo(nil, T) // config not needed for non-constant x
}
// Implements reports whether type V implements interface T.
func Implements(V Type, T *Interface) bool {
f, _ := MissingMethod(V, T, true)
return f == nil
}
|