forked from kubernetes/kubernetes
-
Notifications
You must be signed in to change notification settings - Fork 1
/
assignments.go
335 lines (298 loc) · 8.47 KB
/
assignments.go
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
// Copyright 2013 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.
// This file implements initialization and assignment checks.
package types
import (
"go/ast"
"go/token"
)
// assignment reports whether x can be assigned to a variable of type T,
// if necessary by attempting to convert untyped values to the appropriate
// type. context describes the context in which the assignment takes place.
// Use T == nil to indicate assignment to an untyped blank identifier.
// x.mode is set to invalid if the assignment failed.
func (check *Checker) assignment(x *operand, T Type, context string) {
check.singleValue(x)
switch x.mode {
case invalid:
return // error reported before
case constant_, variable, mapindex, value, commaok:
// ok
default:
unreachable()
}
if isUntyped(x.typ) {
target := T
// spec: "If an untyped constant is assigned to a variable of interface
// type or the blank identifier, the constant is first converted to type
// bool, rune, int, float64, complex128 or string respectively, depending
// on whether the value is a boolean, rune, integer, floating-point, complex,
// or string constant."
if T == nil || IsInterface(T) {
if T == nil && x.typ == Typ[UntypedNil] {
check.errorf(x.pos(), "use of untyped nil in %s", context)
x.mode = invalid
return
}
target = Default(x.typ)
}
check.convertUntyped(x, target)
if x.mode == invalid {
return
}
}
// x.typ is typed
// spec: "If a left-hand side is the blank identifier, any typed or
// non-constant value except for the predeclared identifier nil may
// be assigned to it."
if T == nil {
return
}
if reason := ""; !x.assignableTo(check.conf, T, &reason) {
if reason != "" {
check.errorf(x.pos(), "cannot use %s as %s value in %s: %s", x, T, context, reason)
} else {
check.errorf(x.pos(), "cannot use %s as %s value in %s", x, T, context)
}
x.mode = invalid
}
}
func (check *Checker) initConst(lhs *Const, x *operand) {
if x.mode == invalid || x.typ == Typ[Invalid] || lhs.typ == Typ[Invalid] {
if lhs.typ == nil {
lhs.typ = Typ[Invalid]
}
return
}
// rhs must be a constant
if x.mode != constant_ {
check.errorf(x.pos(), "%s is not constant", x)
if lhs.typ == nil {
lhs.typ = Typ[Invalid]
}
return
}
assert(isConstType(x.typ))
// If the lhs doesn't have a type yet, use the type of x.
if lhs.typ == nil {
lhs.typ = x.typ
}
check.assignment(x, lhs.typ, "constant declaration")
if x.mode == invalid {
return
}
lhs.val = x.val
}
func (check *Checker) initVar(lhs *Var, x *operand, context string) Type {
if x.mode == invalid || x.typ == Typ[Invalid] || lhs.typ == Typ[Invalid] {
if lhs.typ == nil {
lhs.typ = Typ[Invalid]
}
return nil
}
// If the lhs doesn't have a type yet, use the type of x.
if lhs.typ == nil {
typ := x.typ
if isUntyped(typ) {
// convert untyped types to default types
if typ == Typ[UntypedNil] {
check.errorf(x.pos(), "use of untyped nil in %s", context)
lhs.typ = Typ[Invalid]
return nil
}
typ = Default(typ)
}
lhs.typ = typ
}
check.assignment(x, lhs.typ, context)
if x.mode == invalid {
return nil
}
return x.typ
}
func (check *Checker) assignVar(lhs ast.Expr, x *operand) Type {
if x.mode == invalid || x.typ == Typ[Invalid] {
return nil
}
// Determine if the lhs is a (possibly parenthesized) identifier.
ident, _ := unparen(lhs).(*ast.Ident)
// Don't evaluate lhs if it is the blank identifier.
if ident != nil && ident.Name == "_" {
check.recordDef(ident, nil)
check.assignment(x, nil, "assignment to _ identifier")
if x.mode == invalid {
return nil
}
return x.typ
}
// If the lhs is an identifier denoting a variable v, this assignment
// is not a 'use' of v. Remember current value of v.used and restore
// after evaluating the lhs via check.expr.
var v *Var
var v_used bool
if ident != nil {
if _, obj := check.scope.LookupParent(ident.Name, token.NoPos); obj != nil {
// It's ok to mark non-local variables, but ignore variables
// from other packages to avoid potential race conditions with
// dot-imported variables.
if w, _ := obj.(*Var); w != nil && w.pkg == check.pkg {
v = w
v_used = v.used
}
}
}
var z operand
check.expr(&z, lhs)
if v != nil {
v.used = v_used // restore v.used
}
if z.mode == invalid || z.typ == Typ[Invalid] {
return nil
}
// spec: "Each left-hand side operand must be addressable, a map index
// expression, or the blank identifier. Operands may be parenthesized."
switch z.mode {
case invalid:
return nil
case variable, mapindex:
// ok
default:
if sel, ok := z.expr.(*ast.SelectorExpr); ok {
var op operand
check.expr(&op, sel.X)
if op.mode == mapindex {
check.errorf(z.pos(), "cannot assign to struct field %s in map", ExprString(z.expr))
return nil
}
}
check.errorf(z.pos(), "cannot assign to %s", &z)
return nil
}
check.assignment(x, z.typ, "assignment")
if x.mode == invalid {
return nil
}
return x.typ
}
// If returnPos is valid, initVars is called to type-check the assignment of
// return expressions, and returnPos is the position of the return statement.
func (check *Checker) initVars(lhs []*Var, rhs []ast.Expr, returnPos token.Pos) {
l := len(lhs)
get, r, commaOk := unpack(func(x *operand, i int) { check.multiExpr(x, rhs[i]) }, len(rhs), l == 2 && !returnPos.IsValid())
if get == nil || l != r {
// invalidate lhs and use rhs
for _, obj := range lhs {
if obj.typ == nil {
obj.typ = Typ[Invalid]
}
}
if get == nil {
return // error reported by unpack
}
check.useGetter(get, r)
if returnPos.IsValid() {
check.errorf(returnPos, "wrong number of return values (want %d, got %d)", l, r)
return
}
check.errorf(rhs[0].Pos(), "cannot initialize %d variables with %d values", l, r)
return
}
context := "assignment"
if returnPos.IsValid() {
context = "return statement"
}
var x operand
if commaOk {
var a [2]Type
for i := range a {
get(&x, i)
a[i] = check.initVar(lhs[i], &x, context)
}
check.recordCommaOkTypes(rhs[0], a)
return
}
for i, lhs := range lhs {
get(&x, i)
check.initVar(lhs, &x, context)
}
}
func (check *Checker) assignVars(lhs, rhs []ast.Expr) {
l := len(lhs)
get, r, commaOk := unpack(func(x *operand, i int) { check.multiExpr(x, rhs[i]) }, len(rhs), l == 2)
if get == nil {
check.useLHS(lhs...)
return // error reported by unpack
}
if l != r {
check.useGetter(get, r)
check.errorf(rhs[0].Pos(), "cannot assign %d values to %d variables", r, l)
return
}
var x operand
if commaOk {
var a [2]Type
for i := range a {
get(&x, i)
a[i] = check.assignVar(lhs[i], &x)
}
check.recordCommaOkTypes(rhs[0], a)
return
}
for i, lhs := range lhs {
get(&x, i)
check.assignVar(lhs, &x)
}
}
func (check *Checker) shortVarDecl(pos token.Pos, lhs, rhs []ast.Expr) {
scope := check.scope
// collect lhs variables
var newVars []*Var
var lhsVars = make([]*Var, len(lhs))
for i, lhs := range lhs {
var obj *Var
if ident, _ := lhs.(*ast.Ident); ident != nil {
// Use the correct obj if the ident is redeclared. The
// variable's scope starts after the declaration; so we
// must use Scope.Lookup here and call Scope.Insert
// (via check.declare) later.
name := ident.Name
if alt := scope.Lookup(name); alt != nil {
// redeclared object must be a variable
if alt, _ := alt.(*Var); alt != nil {
obj = alt
} else {
check.errorf(lhs.Pos(), "cannot assign to %s", lhs)
}
check.recordUse(ident, alt)
} else {
// declare new variable, possibly a blank (_) variable
obj = NewVar(ident.Pos(), check.pkg, name, nil)
if name != "_" {
newVars = append(newVars, obj)
}
check.recordDef(ident, obj)
}
} else {
check.errorf(lhs.Pos(), "cannot declare %s", lhs)
}
if obj == nil {
obj = NewVar(lhs.Pos(), check.pkg, "_", nil) // dummy variable
}
lhsVars[i] = obj
}
check.initVars(lhsVars, rhs, token.NoPos)
// declare new variables
if len(newVars) > 0 {
// spec: "The scope of a constant or variable identifier declared inside
// a function begins at the end of the ConstSpec or VarSpec (ShortVarDecl
// for short variable declarations) and ends at the end of the innermost
// containing block."
scopePos := rhs[len(rhs)-1].End()
for _, obj := range newVars {
check.declare(scope, nil, obj, scopePos) // recordObject already called
}
} else {
check.softErrorf(pos, "no new variables on left side of :=")
}
}