ufuzz failure

[alexlamsl]

// original code
// (beautified)
export var _calls_ = 10, a = 100, b = 10, c = 0;

function f0(a_2, c_1) {
    if (--b + [ --b + (c_1 && (c_1[Infinity in [ (c = 1 + c, "bar" * 22 > ("" > -1) != (5 ^ 38..toString()) % (undefined || "c")), (c = 1 + c, 
    ("bar" << 2 ^ true === "bar") <= (22 >= 1) % ("number" < "a")), , (c = 1 + c, undefined << 38..toString() === (0 & false) !== (null << 24..toString()) + +38..toString()), (c = 1 + c, 
    delete ("number" * "function") ^ "" << 4 << (([ , 0 ].length === 2) >>> -2)) ]] = (22 ^ -3, 
    c = c + 1, 22)) && ([ , 0 ][1] === 5) + (this ^ "foo")) ]) {
        var brake2 = 5;
        while ((c = c + 1) + (a_2 && a_2.done) && --brake2 > 0) {}
    } else {
        var brake4 = 5;
        while (--b + (b = a) && --brake4 > 0) {
            var expr5 = [ (c = c + 1) + (typeof a_1 != "special"), a_2 && a_2.null ];
            L10587: for (c_1 of expr5) {
                c = 1 + c;
                var Infinity_1 = expr5[c_1];
                {
                    var brake6 = 5;
                    do {
                        return typeof f1 == "function" && --_calls_ >= 0 && f1();
                    } while (void function() {
                        {
                            return a++ + /[abc4]/g.exec(((c = c + 1) + +function() {
                            }() || b || 5).toString());
                        }
                        var b_2 = (a++ + [ (c = 1 + c, ("" <= Infinity || -1 > "a") * (1 + "b" & -2 < false)), (c = 1 + c, 
                        (false || 3) + ("object" > ([ , 0 ].length === 2)) - ((undefined && NaN) != (true && 38..toString()))), (c = 1 + c, 
                        (a_2 >>>= (-0 !== 38..toString()) >= ("" <= 5)) & 24..toString() >> 4 >= {} >> true) ] || 9).toString()[!b], b_2_1 = a++ + b_2_1;
                        try {
                            return --b + b_2;
                        } catch (a_2) {
                            for (var brake12 = 5; (c = 1 + c, c = c + 1, (/[a2][^e]+$/ ^ [ , 0 ][1]) & 24..toString() << 3) && brake12 > 0; --brake12) {
                                c = 1 + c, ("function" | -0) * ([ , 0 ].length === 2 || "a") && ((2, []) || [] ^ "bar");
                            }
                            try {
                                c = 1 + c, (b_2 && (b_2.async = ([ , 0 ][1] != -4) << (38..toString() === null))) > (NaN > "number" ^ [ , 0 ][1] / "b");
                            } finally {
                            }
                        } finally {
                            try {
                                c = 1 + c, "foo" - {} == "" * "", void 2 == undefined <= "function";
                            } catch (async) {
                            }
                        }
                        {
                            var brake19 = 5;
                            while (--b + (b_2_1 && typeof b_2_1.then == "function" && --_calls_ >= 0 && (((c = 1 + c, 
                            ((1 == 3) <= (Infinity <= 0)) / (-1 << 0 < ({} | "function"))) || a || 3).toString(), 
                            b_2_1.then)([ , 0 ].length === 2, (c = 1 + c, (b_2_1 && (b_2_1.undefined /= 38..toString() === -3 && 23..toString() < [])) | (/[a2][^e]+$/ != 5) % (c_1 = 2 + "bar")))) && --brake19 > 0) {
                                try {
                                    {
                                    }
                                } catch (arguments_1) {
                                    c = 1 + c, ((c = c + 1, NaN) && "number" != 0) << ((-5 <= -0) >> (23..toString() && "bar"));
                                    c = 1 + c, "undefined" - NaN << (23..toString() & "b"), a_2 && (a_2.Infinity = Infinity + [] !== 2 <= ([ , 0 ].length === 2));
                                }
                            }
                        }
                    }() && --brake6 > 0);
                }
            }
        }
    }
    {
        var brake24 = 5;
        while (--b + a_2 && --brake24 > 0) {
            var brake25 = 5;
            while ({
                ...{
                    set 3(a_2) {
                        {
                            return ++a;
                        }
                        this.Infinity = ((c = c + 1, null) * ("object" / 2), (a_2 >>>= this || Infinity) > (c = c + 1, 
                        false)) && (-1 >> [] < -"undefined") << (+0 ^ (a_2 = 5 >>> "c"));
                    },
                    3: --b + (typeof c_1 == "function" && --_calls_ >= 0 && c_1()),
                    set: typeof c_1 == "function" && --_calls_ >= 0 && c_1(..."" + a_2, b--),
                    1.5: (c = c + 1) + -a
                }
            }[(c = c + 1) + (5 in [ {
                value: --b + ({}[c = 1 + c, "a" - 0 ^ 3 & 22 ^ (/[a2][^e]+$/ < 2) << (-5 !== "function")] || 2).toString()[(c = 1 + c, 
                (NaN * 1 ^ -1 + 5) <= (-0 && 2 || 4 >= 22)) ? (c = 1 + c, (22 === /[a2][^e]+$/) >> (24..toString() >> 23..toString()) === ("foo" >> "object") % (c_1 && (c_1[c = 1 + c, 
                ((1 ^ Infinity) & (c = c + 1, "bar")) == (c_1 && (c_1.c = true >>> {} != (23..toString() === {})))] = 22 & false))) : (c = 1 + c, 
                (a_2 && (a_2.done += "undefined" || 2) || "undefined" << 38..toString()) >> ((c_1 += -4 ^ null) >> ("function" & -4)))],
                ...a++ + (1 === 1 ? a : b),
                "": /[abc4]/g.exec((((c = 1 + c, (1 & "object" | delete NaN) >= (a_2 = 24..toString() % Infinity) >> (a_2 /= 0 - "b")) ? (c = 1 + c, 
                [] >> false | (c_1 *= ([ , 0 ].length === 2) >>> "bar") && (a_2 && (a_2[c = 1 + c, 
                c_1 && (c_1[(typeof a_2 == "function" && --_calls_ >= 0 && a_2() || a || 3).toString()] %= ((1 === NaN) <= (4 & 0)) % ((c_1 = -3 >>> false) >>> (c_1 += -3 !== "bar")))] -= "a" | 4)) >= Infinity ** -0) : (c = 1 + c, 
                ("function" << 38..toString() ^ (null ^ "c")) + (this === "c" === (c_1 && (c_1[c = 1 + c, 
                (38..toString() * -4 ^ 5 / 38..toString()) % (c_1 && (c_1[--b + (b += a)] ^= -2 > -1 === ("" ^ 24..toString())))] *= 23..toString() > true))))) || b || 5).toString()),
                set next(bar) {
                    {
                        var expr27 = (c = 1 + c, (-0 % "c" | -4 >> undefined) === (a_2 && (a_2.value = {} / 2 != 22 > 1)));
                        for (c_1 in expr27) {
                            c = 1 + c;
                            const await_2 = expr27[c_1];
                            c = 1 + c, (c = c + 1, "a" >>> 23..toString()) > ((await_2 && (await_2.var *= true || "object")) != -2 >= -5);
                        }
                    }
                    this.set /= -4 >= "number" >= (2 && -3) > (a_2 && (a_2.var = (-4 <= 0) << (2 || NaN)));
                },
                value: (c = c + 1) + c_1
            }.value ])] && --brake25 > 0) {
                var brake29 = 5;
                do {
                    var bar;
                } while (bar && typeof bar.async == "function" && --_calls_ >= 0 && bar.async((c = c + 1) + typeof (a++ + [ a++ + (c = 1 + c, 
                (23..toString() / "b" << (-2 & 5)) * (c_1 && (c_1[1 === 1 ? a : b] ^= (24..toString() | -5) % !"a"))), b = a, void function Infinity() {
                }() ][--b + (+(-2 != -5) | ("undefined" === 5) << (Infinity & true))]), 2, null) && --brake29 > 0);
            }
        }
    }
}

var yield_2 = f0(-5, false, 38..toString());

console.log(null, a, b, c, Infinity, NaN, undefined);

// uglified code
// (beautified)
var _calls_ = 10, a = 100, b = 10, c = 0;

function f0(a_2, c_1) {
    if (--b + [ --b + (c_1 && (c_1[1 / 0 in [ (c = 1 + c, 0 != (5 ^ 38..toString()) % "c"), !1, , (c = 1 + (c = 1 + c), 
    void 0 << 38..toString() == 0 !== (null << 24..toString()) + +38..toString()), (c = 1 + c, 
    !0 ^ 0 << ((2 === [ , 0 ].length) >>> -2)) ]] = (c += 1, 22)) && !1 + ("foo" ^ this)) ]) {
        for (var brake2 = 5; (c += 1) + (a_2 && a_2.done) && 0 < --brake2; ) {}
    } else {
        for (var brake4 = 5; --b + (b = a) && 0 < --brake4; ) {
            var expr5 = [ (c += 1) + ("special" != typeof a_1), a_2 && a_2.null ];
            for (c_1 of expr5) {
                c = 1 + c;
                return "function" == typeof f1 && 0 <= --_calls_ && f1();
            }
        }
    }
    for (var brake24 = 5; --b + a_2 && 0 < --brake24; ) {
        for (var brake25 = 5; {
            [3]: void 0,
            3: --b + ("function" == typeof c_1 && 0 <= --_calls_ && c_1()),
            set: "function" == typeof c_1 && 0 <= --_calls_ && c_1(..."" + a_2, b--),
            1.5: (c += 1) + -a
        }[(c += 1) + (5 in [ {
            value: --b + ({}[c = 1 + c, 2] || 2).toString()[c = 1 + (c = 1 + c), (a_2 && (a_2.done += "undefined") || "undefined" << 38..toString()) >> ((c_1 += -4) >> 0)],
            ...a++ + a,
            "": /[abc4]/g.exec((c = 1 + c, (((0 | delete NaN) >= (a_2 = 24..toString() % (1 / 0)) >> (a_2 /= NaN) ? (c = 1 + c, 
            [] >> !1 | (c_1 *= (2 === [ , 0 ].length) >>> "bar") && 1 <= (a_2 && (a_2[c = 1 + c, 
            c_1 && (c_1[("function" == typeof a_2 && 0 <= --_calls_ && a_2() || a || 3).toString()] %= !0 % ((c_1 = -3 >>> !1) >>> (c_1 += !0)))] -= 4))) : (c = 1 + c, 
            ("function" << 38..toString() ^ 0) + ("c" === this === (c_1 && (c_1[c = 1 + c, (-4 * 38..toString() ^ 5 / 38..toString()) % (c_1 && (c_1[--b + (b += a)] ^= !1 === ("" ^ 24..toString())))] *= !0 < 23..toString()))))) || b || 5).toString())),
            set next(bar) {
                var expr27 = (c = 1 + c, -4 === (a_2 && (a_2.value = {} / 2 != 1)));
                for (c_1 in expr27) {
                    const await_2 = expr27[c_1];
                    c = 1 + (c = 1 + c), c += 1, 23..toString(), await_2 && (await_2.var *= !0);
                }
                this.set /= (a_2 && (a_2.var = 4)) < !0;
            },
            value: (c += 1) + c_1
        }.value ])] && 0 < --brake25; ) {}
    }
}

var yield_2 = f0(-5, !1, 38..toString());

console.log(null, a, b, c, 1 / 0, NaN, void 0);

export {
    _calls_,
    a,
    b,
    c
};

original result:
null 101 104 10 Infinity NaN undefined

uglified result:
null 102 203 19 Infinity NaN undefined

// reduced test case (output will differ)

// (beautified)
console.log({
    ...{
        set 3(a_2) {},
        3: 0
    }
});
// output: { '3': undefined }
// 
// minify: { '3': 0 }
// 
// options: {
//   "mangle": false,
//   "output": {
//     "v8": true
//   },
//   "validate": true
// }

minify(options):
{
  "mangle": false,
  "output": {
    "v8": true
  }
}

Suspicious compress options:
  objects
  spreads

[alexlamsl]

Looks like V8 bug:

$ cat test.js
console.log({
    ...{
        0: "PASS",
        set 0(v) {},
    },
});
console.log({
    ...{
        set 1(v) {},
        1: "PASS",
    },
});
console.log({
    ...{
        a: "PASS",
        set a(v) {},
    },
});
console.log({
    ...{
        set b(v) {},
        b: "PASS",
    },
});

$ cat test.js | node
{ '0': undefined }
{ '1': undefined }
{ a: undefined }
{ b: 'PASS' }

Since Firefox gives more consistent behaviour:

>> [[ test.js ]]
> Object { 0: undefined }
> Object { 1: "PASS" }
> Object { a: undefined }
> Object { b: "PASS" }

[alexlamsl]

Not even quite consistent without V8 itself:

console.log({
    0: "PASS",
    ...{
        set 0(v) {},
    },
});
console.log({
    ...{
        set 1(v) {},
    },
    1: "PASS",
});
console.log({
    a: "PASS",
    ...{
        set a(v) {},
    },
});
console.log({
    ...{
        set b(v) {},
    },
    b: "PASS",
});

$ cat test.js | node
{ '0': undefined }
{ '1': 'PASS' }
{ a: undefined }
{ b: 'PASS' }

Setter on the outer layer:

console.log({
    ...{
        0: "PASS",
    },
    set 0(v) {},
});
console.log({
    set 1(v) {},
    ...{
        1: "PASS",
    },
});
console.log({
    ...{
        a: "PASS",
    },
    set a(v) {},
});
console.log({
    set b(v) {},
    ...{
        b: "PASS",
    },
});

$ cat test.js | node
{ '0': [Setter] }
{ '1': 'PASS' }
{ a: [Setter] }
{ b: 'PASS' }

[alexlamsl]

Simple redefinition for completeness:

console.log({
    ...{
        0: "PASS",
        0: void 0,
    },
});
console.log({
    ...{
        1: void 0,
        1: "PASS",
    },
});
console.log({
    ...{
        a: "PASS",
        a: void 0,
    },
});
console.log({
    ...{
        b: void 0,
        b: "PASS",
    },
});

$ cat test.js | node
{ '0': undefined }
{ '1': 'PASS' }
{ a: undefined }
{ b: 'PASS' }