# `deslop/unnecessary-assertion`

Flag TypeScript assertions that are no-ops or weaken types (`x!!`, `as any`, `as unknown as T`, `<T>x`).

- **Category:** Correctness
- **Severity:** warn
- **Source:** deslop-js
- **Framework:** global
- **Enabled when:** react-doctor deadCode analysis enabled (default true); whole-project scan only — skipped in --diff/--staged modes
- **Documentation:** <https://github.com/millionco/deslop-js>

## Validation prompt

Use this to decide whether a fired diagnostic is real or a false positive.

Fires from deslop's unnecessaryAssertions detector with one of five kinds: double-non-null on `x!!` ("the second `!` is always a no-op"), redundant-non-null-on-literal when `!` trails a literal/array/object/function expression ("those values are never null"), redundant-double-assertion when an outer `as T` wraps an inner `as any`/`as unknown` ("`x as any/unknown as T` first widens just to assert to T"), assertion-to-any on any `as any` ("opts out of TypeScript's type system"), and angle-bracket-assertion on `<T>x` syntax ("parsed as a JSX tag in .tsx and deprecated"). The double-non-null, redundant-non-null-on-literal, and redundant-double-assertion kinds are high confidence; assertion-to-any and angle-bracket-assertion are medium. False positive to SUPPRESS: assertion-to-any on a deliberate, commented escape hatch where no concrete type exists, and redundant-double-assertion on a genuine `x as unknown as T` bridge between two structurally unrelated types where the inner `unknown` is the only legal way to force the cast — judge by whether the intermediate `any`/`unknown` is truly removable without a compile error, not just present.

## Fix prompt

Use this once validation confirms the diagnostic is real.

For double-non-null drop one `!` (`x!!` becomes `x!`); for redundant-non-null-on-literal remove the trailing `!` since the value is never null; for redundant-double-assertion drop the intermediate cast and assert once (`x as any as T` becomes `x as T`), keeping `as unknown as T` only when the direct cast genuinely will not compile; for assertion-to-any replace `as any` with the real type or narrow with `unknown` plus a guard (`if (typeof v === "string")`) instead of opting out of type checking; for angle-bracket-assertion rewrite `<T>x` as `x as T` so it does not parse as JSX. See https://www.typescriptlang.org/docs/handbook/2/everyday-types.html#type-assertions