core-typescript-non-null-assertion-abuse

What it catches

The non-null assertion operator ! immediately followed by . or [ in TypeScript source. Word-boundary aware — !== and != are NOT matched. Strings and comments are stripped before scan.

Why it matters

value!.field tells TypeScript "trust me, this isn't null" without any runtime check. When the promise is wrong, the next property access throws — the exact bug class TypeScript was supposed to prevent. AI tools reach for !. reflexively whenever the compiler complains, so each one is a place the type system pushed back and got ignored.

Example: failing code

return u!.profile!.email!;     // 3 hits
return arr![0];                // 1 hit

Example: how to fix

// (a) Guard early
if (!u?.profile?.email) throw new Error('email is required');
return u.profile.email;

// (b) Optional chaining + fallback
return u?.profile?.email ?? '';

// (c) Narrow at the type source — refactor the type so `!` is not needed.

Suppression

// codemore-ignore-next-line: core-typescript-non-null-assertion-abuse
return checkedDef!.value;

References

• TypeScript Handbook — Non-null assertion operator