TS2352

Suspicious type conversion

Conversion of type 'string' to type 'number' may be a mistake because neither type sufficiently overlaps with the other.

The compiler’s own words. Not translated — this is the string you pasted into a search box.

A type assertion jumps between unrelated types and would not perform the runtime conversion its spelling suggests.

Reproduction

const count = '12' as number

The build asserts this emits exactly this code.

Why the compiler says this

Assertions change the checker’s view, never the JavaScript value. A string asserted as `number` is still a string at runtime, so TypeScript blocks the most obviously unrelated jumps and asks you to make the intent explicit.

Fixes

01
```
const count = Number('12')
```
Perform a real runtime conversion when the value must become a number.

const input: unknown = '12'

if (typeof input !== 'string') {
  throw new Error('Expected text')
}

const count = Number(input)

For external data, validate from `unknown` before converting it.

Takeaway

`as` is not a cast in the runtime sense. Parse or validate values; reserve assertions for information the compiler genuinely cannot observe.

Where to go next

Type aliases Try it in the Lab

Errors