ufuzz failure

[alexlamsl]

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

function f0(let_1, yield_2) {
    {
        var expr1 = {
            var: a++ + [ , typeof await !== "undefined", --b + (let_1 && let_1.length), (c = c + 1) + let_1, a++ + (--_calls_ >= 0 && new class C0 {
                c = b = a;
                [(1 ?? 23..toString()) * ([] !== -1) | (c = c + 1, 25 < 4)](b_1, undefined, NaN_2) {
                    let Infinity_2 = (c = c + 1) + (typeof f1 == "function" && --_calls_ >= 0 && f1((c = 1 + c, 
                    ("undefined" * "c" === (c = c + 1, null)) <= ((c = c + 1, 4) < "a" + 24..toString()))));
                    {
                        var brake2 = 5;
                        do {
                            c = 1 + c, ((c = c + 1, [ , 0 ].length === 2) ^ /[a2][^e]+$/ == ([ , 0 ].length === 2)) != ("a" === 38..toString() && {} % 23..toString());
                        } while ((c = 1 + c, (Object.isExtensible(Infinity_2) && (Infinity_2[--b + (undefined && undefined[c = 1 + c, 
                        ("undefined" + 2, -4 >> "c") | (Object.isExtensible(NaN_2) && (NaN_2[void function b_1() {
                        }()] &&= (38..toString() == "bar") <= ("a" | Infinity)))])] %= (Object.isExtensible(undefined) && (undefined[c = 1 + c, 
                        ~(2 !== 0) | (-1 ^ true) != (false || "bar")] = [ , 0 ].length === 2 ?? NaN)) >= -4 * 23..toString())) / ((this - "undefined") * (3 < "a"))) && --brake2 > 0);
                    }
                    this[typeof f1 == "function" && --_calls_ >= 0 && f1(25)] = (1 + 3, 
                    -3 >> this) & ("undefined" << "function" & NaN < NaN);
                    L290675: for (var brake4 = 5; (c = 1 + c, ((c = c + 1, true) ^ "number" >> null) !== (c = c + 1, 
                    5 + (-42n).toString())) && brake4 > 0; --brake4) {
                        c = 1 + c, Object.isExtensible(Infinity_2) && (Infinity_2.undefined = ([ , 0 ][1] === 22, 
                        NaN <= -0) & (Infinity, 38..toString()) - (Object.isExtensible(yield_2) && (yield_2[c = 1 + c, 
                        0 >> "bar" <= (Infinity !== "") == ((Infinity && -2) | (4 || ""))] ^= null !== 4)));
                    }
                }
                static "\t" = {
                    [(c = 1 + c, (null ^ {}) <= (NaN > 22) < +(5 == "number"))]: (c = 1 + c, 
                    ((-5 || 5) !== -0 % "undefined") << ((-3 !== 25) > (false ?? 2))),
                    c: (c = 1 + c, (null & NaN) % (22 * /[a2][^e]+$/) - ((Infinity, 
                    [ 3n ][0] > 2) === null >>> 0)),
                    1.5: (c = 1 + c, (c = c + 1, (-42n).toString() === 25) * (-1 !== null !== "number" << "a")),
                    ...yield_2
                }.null;
                [(c = c + 1) + function(NaN_1, bar, a) {
                    c = 1 + c, (null === {}) / (false % 2) | (null < ([ , 0 ].length === 2) ?? "object" * NaN);
                    c = 1 + c, c = c + 1, Object.isExtensible(NaN_1) && ([ NaN_1[--b + {
                        bar: bar
                    }] ] = [ "b" <= false ?? 5 >>> -2 ]);
                    c = 1 + c, (this ^ "function" && this >> "foo") % (-5 / [ , 0 ][1] < (Infinity ?? 0));
                    c = 1 + c, (-0 >> "undefined") + (null <= {}) - (5 * false > (4 != -3));
                }((c = 1 + c, (let_1 = -5 >= -2) + (this || 38..toString()) !== "b" >> "undefined" >>> ([ , 0 ].length === 2 == "foo")))] = a++ + (b = a);
            }(25, --b + {
                "-2": (c = 1 + c, ("bar" & null ^ (23..toString() | 5)) > ((c = c + 1, 
                -3) ^ (yield_2 && (yield_2[c = 1 + c, let_1 && (let_1[a++ + {}.value] += ([ , 0 ][1] << "number" && ([ , 0 ].length === 2) >>> 2) ** ((undefined | "undefined") >= -0 - 22))] += 24..toString() !== true)))),
                set: (c = 1 + c, (25 !== {} !== (let_1 = -3 ^ /[a2][^e]+$/)) >= (yield_2 && (yield_2.async = 22 % "")) / (yield_2 >>>= /[a2][^e]+$/ > -0)),
                1.5: (c = 1 + c, (c = c + 1, 1 >> "c") <= -({} > null)),
                value: (c = 1 + c, -4 ^ null | this + Infinity && (this <= "a", 
                undefined || -4))
            }[--b + (yield_2 && yield_2[c = 1 + c, (c = c + 1, true ^ null) | ("" | [ , 0 ].length === 2) !== "" - "a"])])) ]
        }.next;
        for (var key1 in expr1) {
        }
    }
}

var b_2 = f0(-2, 3);

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

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

function f0(let_1, yield_2) {
    a++, --b, let_1 && let_1.length, c += 1, a++, 0 <= --_calls_ && new class {
        c = b = a;
        [+(-1 !== []) | (c += 1, !1)](b_1, undefined, NaN_2) {
            let Infinity_2 = (c += 1) + ("function" == typeof f1 && 0 <= --_calls_ && f1((NaN === null) <= (c = (c = 1 + c) + 1 + 1, 
            4 < "a" + 24..toString())));
            for (var brake2 = 5; c = 1 + c, c += 1, "a" === 38..toString() && 23..toString(), 
            c = 1 + c, (Object.isExtensible(Infinity_2) && (Infinity_2[--b + (undefined && undefined[c = 1 + c, 
            -4 | (Object.isExtensible(NaN_2) && (NaN_2[void 0] &&= ("bar" == 38..toString()) <= 0))])] %= (Object.isExtensible(undefined) && (undefined[c = 1 + c, 
            -1] = 2 === [ , 0 ].length ?? NaN)) >= -4 * 23..toString())) / (!1 * (this - "undefined")) && 0 < --brake2; ) {}
            this["function" == typeof f1 && 0 <= --_calls_ && f1(25)] = -3 >> this & 0;
            for (var brake4 = 5; (0 ^ !0) !== (c = (c = 1 + c) + 1 + 1, 5 + (-42n).toString()) && 0 < brake4; --brake4) {
                c = 1 + c, Object.isExtensible(Infinity_2) && (Infinity_2.undefined = !1 & 38..toString() - (Object.isExtensible(yield_2) && (yield_2[c = 1 + c, 
                !1] ^= !0)));
            }
        }
        static "\t" = {
            [(c = 1 + c, (null ^ {}) <= !1 < 0)]: (c = 1 + c, 2),
            c: (c = 1 + c, NaN - (2 < 3n === 0)),
            1.5: (c = 1 + c, !0 * (c += 1, 25 === (-42n).toString())),
            ...yield_2
        }.null;
        [(c += 1) + (c = 1 + c, let_1 = (let_1 = !1) + (this || 38..toString()) !== 0 >>> (2 === [ , 0 ].length == "foo"), 
        c = 1 + (c = 1 + c), c += 1, Object.isExtensible(let_1) && ([ let_1[--b + {
            bar: void 0
        }] ] = [ !1 ]), void (c = 1 + (c = 1 + c)))] = a++ + (b = a);
    }(25, --b + {
        "-2": (c = 1 + c, (0 ^ (5 | 23..toString())) > (c += 1, -3 ^ (yield_2 && (yield_2[c = 1 + c, 
        let_1 && (let_1[a++ + {}.value] += 0)] += !0 !== 24..toString())))),
        set: (c = 1 + c, (25 !== {} !== (let_1 = -3)) >= (yield_2 && (yield_2.async = NaN)) / (yield_2 >>>= !1)),
        1.5: (c = 1 + c, 1 <= -(null < {})),
        value: (c = 1 + (c += 1), -4 | this + 1 / 0 && -4)
    }[--b + (yield_2 && yield_2[c = 1 + c, c += 1, 1 | NaN !== ("" | 2 === [ , 0 ].length)])]);
}

var b_2 = f0(-2, 3);

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

original result:
null 103 103 23 Infinity NaN undefined

uglified result:
null 104 104 23 Infinity NaN undefined

// reduced test case (output will differ)

// (beautified)
function f0(let_1) {
    new class C0 {
        [function(NaN_1) {
            Object(NaN_1);
        }(console.log())] = 0;
    }(let_1[0]);
}

f0(3);
// output: 
// 
// minify: TypeError: Cannot read properties of undefined (reading '0')
// options: {
//   "mangle": false,
//   "output": {
//     "v8": true
//   },
//   "validate": true
// }

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

Suspicious compress options:
  inline
  merge_vars
  sequences
  side_effects
  unused

[alexlamsl]

@kzc TIL

$ echo 'new function({[console.log("func arg")]:a}){}([console.log("func call")]);' | node
func call
func arg

$ echo 'new class{[console.log("class field")]}(console.log("class call"));' | node
class field
class call

[kzc]

I don't even know what that is.

$ echo 'new class {[1]; 2;}' | node
$ 
$ echo 'new class {[1]; 2;}' | acorn --module --ecma2022 | egrep -v 'start|end|raw'
{
  "type": "Program",
  "body": [
    {
      "type": "ExpressionStatement",
      "expression": {
        "type": "NewExpression",
        "callee": {
          "type": "ClassExpression",
          "id": null,
          "superClass": null,
          "body": {
            "type": "ClassBody",
            "body": [
              {
                "type": "PropertyDefinition",
                "static": false,
                "computed": true,
                "key": {
                  "type": "Literal",
                  "value": 1,
                },
                "value": null
              },
              {
                "type": "PropertyDefinition",
                "static": false,
                "computed": false,
                "key": {
                  "type": "Literal",
                  "value": 2,
                },
                "value": null
              }
            ]
          }
        },
        "arguments": []
      }
    }
  ],
  "sourceType": "module"
}

A property key without a value. What else can be in a PropertyDefinition?

[alexlamsl]

Oh that value-less property is one of the first oddity I encountered when implementing support for class 🤣

[kzc]

What the heck is this?

$ echo 'var x = 1; console.log(new class {[x] = 2; 3 = 4;});' | node
{ '1': 2, '3': 4 }

$ echo 'var x = 1; console.log(new class {[[[x]]] = 2; 3 = 4;});' | node
{ '1': 2, '3': 4 }

$ echo 'var x = 1; console.log(new class {[[x,0]] = 2; 3 = 4;});' | node
{ '3': 4, '1,0': 2 }

So it appears if there's a computed key, its toString() is used. This is useful why?

[alexlamsl]

This is useful why?

You are preaching to the choir − I guess the saving grace would be that they do the same for computed keys in object literal & destructuring syntax?