/
no-constant-binary-expression.js
319 lines (295 loc) · 22.8 KB
/
no-constant-binary-expression.js
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
/**
* @fileoverview Tests for no-constant-binary-expression rule.
* @author Jordan Eldredge <https://jordaneldredge.com>
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const rule = require("../../../lib/rules/no-constant-binary-expression");
const { RuleTester } = require("../../../lib/rule-tester");
//------------------------------------------------------------------------------
// Tests
//------------------------------------------------------------------------------
const ruleTester = new RuleTester({ parserOptions: { ecmaVersion: 2021, ecmaFeatures: { jsx: true } } });
ruleTester.run("no-constant-binary-expression", rule, {
valid: [
// While this _would_ be a constant condition in React, ESLint has a policy of not attributing any specific behavior to JSX.
"<p /> && foo",
"<></> && foo",
"<p /> ?? foo",
"<></> ?? foo",
"arbitraryFunction(n) ?? foo",
"foo.Boolean(n) ?? foo",
"(x += 1) && foo",
"`${bar}` && foo",
"bar && foo",
"delete bar.baz && foo",
"true ? foo : bar", // We leave ConditionalExpression for `no-constant-condition`.
"new Foo() == true",
"foo == true",
"`${foo}` == true",
"`${foo}${bar}` == true",
"`0${foo}` == true",
"`00000000${foo}` == true",
"`0${foo}.000` == true",
"[n] == true",
"delete bar.baz === true",
"foo.Boolean(true) && foo",
"function Boolean(n) { return n; }; Boolean(x) ?? foo",
"function String(n) { return n; }; String(x) ?? foo",
"function Number(n) { return n; }; Number(x) ?? foo",
"function Boolean(n) { return Math.random(); }; Boolean(x) === 1",
"function Boolean(n) { return Math.random(); }; Boolean(1) == true",
"new Foo() === x",
"x === new someObj.Promise()",
"Boolean(foo) === true",
"function foo(undefined) { undefined ?? bar;}",
"function foo(undefined) { undefined == true;}",
"function foo(undefined) { undefined === true;}",
"[...arr, 1] == true",
"[,,,] == true",
{ code: "new Foo() === bar;", globals: { Foo: "writable" } }
],
invalid: [
// Error messages
{ code: "[] && greeting", errors: [{ message: "Unexpected constant truthiness on the left-hand side of a `&&` expression." }] },
{ code: "[] || greeting", errors: [{ message: "Unexpected constant truthiness on the left-hand side of a `||` expression." }] },
{ code: "[] ?? greeting", errors: [{ message: "Unexpected constant nullishness on the left-hand side of a `??` expression." }] },
{ code: "[] == true", errors: [{ message: "Unexpected constant binary expression. Compares constantly with the right-hand side of the `==`." }] },
{ code: "true == []", errors: [{ message: "Unexpected constant binary expression. Compares constantly with the left-hand side of the `==`." }] },
{ code: "[] != true", errors: [{ message: "Unexpected constant binary expression. Compares constantly with the right-hand side of the `!=`." }] },
{ code: "[] === true", errors: [{ message: "Unexpected constant binary expression. Compares constantly with the right-hand side of the `===`." }] },
{ code: "[] !== true", errors: [{ message: "Unexpected constant binary expression. Compares constantly with the right-hand side of the `!==`." }] },
// Motivating examples from the original proposal https://github.com/eslint/eslint/issues/13752
{ code: "!foo == null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "!foo ?? bar", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a + b) / 2 ?? bar", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "String(foo.bar) ?? baz", errors: [{ messageId: "constantShortCircuit" }] },
{ code: '"hello" + name ?? ""', errors: [{ messageId: "constantShortCircuit" }] },
{ code: '[foo?.bar ?? ""] ?? []', errors: [{ messageId: "constantShortCircuit" }] },
// Logical expression with constant truthiness
{ code: "true && hello", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "true || hello", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "true && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "'' && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "100 && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "+100 && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "-100 && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "~100 && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "/[a-z]/ && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "Boolean([]) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "Boolean() && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "Boolean([], n) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "({}) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "[] && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(() => {}) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(function() {}) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(class {}) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(class { valueOf() { return x; } }) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(class { [x]() { return x; } }) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "new Foo() && foo", errors: [{ messageId: "constantShortCircuit" }] },
// (boxed values are always truthy)
{ code: "new Boolean(unknown) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(bar = false) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(bar.baz = false) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(bar[0] = false) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "`hello ${hello}` && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "void bar && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "!true && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "typeof bar && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(bar, baz, true) && foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "undefined && foo", errors: [{ messageId: "constantShortCircuit" }] },
// Logical expression with constant nullishness
{ code: "({}) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "([]) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(() => {}) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(function() {}) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(class {}) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "new Foo() ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "1 ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "/[a-z]/ ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "`${''}` ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a = true) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a += 1) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a -= 1) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a *= 1) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a /= 1) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a %= 1) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a <<= 1) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a >>= 1) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a >>>= 1) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a |= 1) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a ^= 1) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(a &= 1) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "undefined ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "!bar ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "void bar ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "typeof bar ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "+bar ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "-bar ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "~bar ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "++bar ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "bar++ ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "--bar ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "bar-- ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(x == y) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(x + y) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(x / y) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(x instanceof String) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "(x in y) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "Boolean(x) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "String(x) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "Number(x) ?? foo", errors: [{ messageId: "constantShortCircuit" }] },
// Binary expression with comparison to null
{ code: "({}) != null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "({}) == null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "null == ({})", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "({}) == undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "undefined == ({})", errors: [{ messageId: "constantBinaryOperand" }] },
// Binary expression with loose comparison to boolean
{ code: "({}) != true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "({}) == true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "([]) == true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "([a, b]) == true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(() => {}) == true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(function() {}) == true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "void foo == true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "typeof foo == true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "![] == true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "true == class {}", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "true == 1", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "undefined == true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "true == undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "`hello` == true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "/[a-z]/ == true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "({}) == Boolean({})", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "({}) == Boolean()", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "({}) == Boolean(() => {}, foo)", errors: [{ messageId: "constantBinaryOperand" }] },
// Binary expression with strict comparison to boolean
{ code: "({}) !== true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "({}) == !({})", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "({}) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "([]) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(function() {}) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(() => {}) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "!{} === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "typeof n === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "void n === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "+n === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "-n === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "~n === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "true === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "1 === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "'hello' === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "/[a-z]/ === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "undefined === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a = {}) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a += 1) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a -= 1) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a *= 1) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a %= 1) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a ** b) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a << b) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a >> b) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a >>> b) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "--a === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "a-- === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "++a === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "a++ === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a + b) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a - b) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a * b) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a / b) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a % b) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a | b) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a ^ b) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a & b) === true", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "Boolean(0) === Boolean(1)", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "true === String(x)", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "true === Number(x)", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "Boolean(0) == !({})", errors: [{ messageId: "constantBinaryOperand" }] },
// Binary expression with strict comparison to null
{ code: "({}) !== null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "({}) === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "([]) === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(() => {}) === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(function() {}) === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(class {}) === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "new Foo() === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "`` === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "1 === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "'hello' === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "/[a-z]/ === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "true === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "null === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "a++ === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "++a === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "--a === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "a-- === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "!a === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "typeof a === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "delete a === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "void a === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "undefined === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(x = {}) === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(x += y) === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(x -= y) === null", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a, b, {}) === null", errors: [{ messageId: "constantBinaryOperand" }] },
// Binary expression with strict comparison to undefined
{ code: "({}) !== undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "({}) === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "([]) === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(() => {}) === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(function() {}) === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(class {}) === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "new Foo() === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "`` === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "1 === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "'hello' === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "/[a-z]/ === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "true === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "null === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "a++ === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "++a === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "--a === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "a-- === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "!a === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "typeof a === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "delete a === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "void a === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "undefined === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(x = {}) === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(x += y) === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(x -= y) === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
{ code: "(a, b, {}) === undefined", errors: [{ messageId: "constantBinaryOperand" }] },
/*
* If both sides are newly constructed objects, we can tell they will
* never be equal, even with == equality.
*/
{ code: "[a] == [a]", errors: [{ messageId: "bothAlwaysNew" }] },
{ code: "[a] != [a]", errors: [{ messageId: "bothAlwaysNew" }] },
{ code: "({}) == []", errors: [{ messageId: "bothAlwaysNew" }] },
// Comparing to always new objects
{ code: "x === {}", errors: [{ messageId: "alwaysNew" }] },
{ code: "x !== {}", errors: [{ messageId: "alwaysNew" }] },
{ code: "x === []", errors: [{ messageId: "alwaysNew" }] },
{ code: "x === (() => {})", errors: [{ messageId: "alwaysNew" }] },
{ code: "x === (function() {})", errors: [{ messageId: "alwaysNew" }] },
{ code: "x === (class {})", errors: [{ messageId: "alwaysNew" }] },
{ code: "x === new Boolean()", errors: [{ messageId: "alwaysNew" }] },
{ code: "x === new Promise()", env: { es6: true }, errors: [{ messageId: "alwaysNew" }] },
{ code: "x === new WeakSet()", env: { es6: true }, errors: [{ messageId: "alwaysNew" }] },
{ code: "x === (foo, {})", errors: [{ messageId: "alwaysNew" }] },
{ code: "x === (y = {})", errors: [{ messageId: "alwaysNew" }] },
{ code: "x === (y ? {} : [])", errors: [{ messageId: "alwaysNew" }] },
{ code: "x === /[a-z]/", errors: [{ messageId: "alwaysNew" }] },
// It's not obvious what this does, but it compares the old value of `x` to the new object.
{ code: "x === (x = {})", errors: [{ messageId: "alwaysNew" }] },
{ code: "window.abc && false && anything", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "window.abc || true || anything", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "window.abc ?? 'non-nullish' ?? 'non-nullish'", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "window.abc ?? undefined ?? 'non-nullish'", errors: [{ messageId: "constantShortCircuit" }] },
{ code: "window.abc ?? null ?? 'non-nullish'", errors: [{ messageId: "constantShortCircuit" }] }
]
});