TypeScript: Tooltip.labelFormatter type is overly restrictive and causes TS2322 error

[terminal007]

When using Tooltip with labelFormatter in a TypeScript project, the expected function signature is too restrictive and causes a TypeScript error when the formatter is typed more strictly (e.g., (t: number) => string).

The current typing requires:

(label: ReactNode, payload: readonly Payload<ValueType, NameType>[]) => ReactNode
This makes it impossible to strongly type label as number, even when the corresponding XAxis is explicitly defined as numeric.

TS2322: Type '(t: number) => string' is not assignable to type
'((label: ReactNode, payload: readonly Payload<ValueType, NameType>[]) => ReactNode)
 & ((label: any, payload: Payload<ValueType, NameType>[]) => ReactNode)'.

Type '(t: number) => string' is not assignable to type
'(label: ReactNode, payload: readonly Payload<ValueType, NameType>[]) => ReactNode'.

Types of parameters 't' and 'label' are incompatible.
Type 'ReactNode' is not assignable to type 'number'.
Type 'undefined' is not assignable to type 'number'.

import { LineChart, Line, XAxis, YAxis, Tooltip } from 'recharts';

<LineChart data={data}>
  <XAxis dataKey="timestamp" type="number" />
  <YAxis />
  <Tooltip
    labelFormatter={(t: number) =>
      new Date(t).toLocaleTimeString()
    }
  />
  <Line dataKey="avg" />
</LineChart>

Expected Behavior

If XAxis is defined as:

<XAxis dataKey="timestamp" type="number" />
Then labelFormatter should allow:

(label: number) => ReactNode
Or the type should be widened to something more practical such as:

(label: unknown, payload: Payload[]) => ReactNode
This would allow proper narrowing inside the formatter without forcing unsafe casts.

Workaround

Currently, the only safe workaround is:

<Tooltip
  labelFormatter={(label) =>
    new Date(Number(label)).toLocaleTimeString()
  }
/>

But this removes type safety and forces casting.