Bug: [no-unnecessary-condition] false positives on type predicates with generic types #10142
Closed as not planned
Description
Before You File a Bug Report Please Confirm You Have Done The Following...
- I have tried restarting my IDE and the issue persists.
- I have updated to the latest version of the packages.
- I have searched for related issues and found none that matched my issue.
- I have read the FAQ and my problem is not listed.
Playground Link
Repro Code
// From https://github.com/sindresorhus/type-fest/blob/HEAD/source/set-non-nullable.d.ts
export type SetNonNullable<BaseType, Keys extends keyof BaseType = keyof BaseType> = {
[Key in keyof BaseType]: Key extends Keys
? NonNullable<BaseType[Key]>
: BaseType[Key];
};
export const nonNullish = <T>(value: T | null | undefined): value is T => value != null;
export const hasNonNullishField = <T, K extends keyof T>(
obj: T,
key: K,
): obj is SetNonNullable<T, K> => nonNullish(obj[key]); // <--ESLint Config
{
"rules": {
"@typescript-eslint/no-unnecessary-condition": ["error", { "checkTypePredicates": true }]
}
}tsconfig
Expected Result
The type of obj[key] in the example can be nullish and therefore the error should not be reported.
Actual Result
The error is reported.
Additional Info
No response
{ "compilerOptions": { // ... } }