nonNullAssertionPlacement

Reports confusing placement of non-null assertions next to comparison or assignment operators.

✅ This rule is included in the ts stylisticStrict presets.

When a non-null assertion (!) appears immediately before an assignment (=) or comparison operator (==, ===, in, instanceof), it can be visually confused with a different operator. For example, a! == b looks similar to a !== b, and a! = b looks similar to a != b.

This visual ambiguity can make code harder to understand and may cause readers to misinterpret the intended logic.

Examples

❌ Incorrect

declare const value: string | null;

value! == "test";

declare let value: string | null;

value! = "new value";

declare const key: string | null;
declare const object: Record<string, number>;

key! in object;

declare const value: object | null;
declare class MyClass {}

value! instanceof MyClass;

✅ Correct

declare const value: string | null;

value! == "test";

declare const value: string | null;

value !== "test";

declare const key: string | null;
declare const object: Record<string, number>;

key! in object;

declare const value: object | null;
declare class MyClass {}

value! instanceof MyClass;

Options

This rule is not configurable.

When Not To Use It

If your team is familiar with non-null assertions and the visual similarity does not cause confusion in your codebase, you may choose to disable this rule. Projects with established conventions around non-null assertion placement may also opt out.

Further Reading

• MDN: Expressions and operators
• TypeScript: Non-null assertion operator

Equivalents in Other Linters

• ESLint: @typescript-eslint/no-confusing-non-null-assertion
• Oxlint: typescript/no-confusing-non-null-assertion