Closed
Description
Repro
{
"parser": "@typescript-eslint/parser",
"parserOptions": {
"project": "./tsconfig.json"
},
"plugins": [
"@typescript-eslint"
],
"rules": {
"@typescript-eslint/prefer-nullish-coalescing": "error"
}
}import assert from 'assert';
function f(arg: null | boolean): null | boolean {
return arg;
}
function g(arg: boolean): boolean {
return arg;
}
function h(a: null | boolean, b: boolean) {
return f(a) || g(b);
}
assert.equal(h(true, true), true);
assert.equal(h(true, false), true);
assert.equal(h(false, true), true); // broken after fix
assert.equal(h(false, false), false); // not broken, but returns `f`'s result(bad sample...)
assert.equal(h(null, true), true);
assert.equal(h(null, false), false);Expected Result
no report. Fallback to g() when f() is falsy.
Actual Result
@typescript-eslint/prefer-nullish-coalescing reports the error, and also the fixed output is broken.
Sample repo to reproduce the behavior: https://github.com/berlysia/typescript-eslint-nullish-coalescing-false-positive
Additional Info
This issue applies not only to boolean but also to number and string.
Versions
| package | version |
|---|---|
@typescript-eslint/eslint-plugin |
2.9.0 |
@typescript-eslint/parser |
2.9.0 |
TypeScript |
3.7.2 |
ESLint |
6.7.2 |
node |
12.4.0 |
npm |
6.9.0 |