Type cast should try to remove readonly modifier

The compiler should try to use mutable versions of readonly tuples when couldn't cast readonly tuples to mutable arrays mainly for usability of as const. The performance impact of this would be a little because the condition when this check runs is limited.

TypeScript Version: 3.7.x-dev.20200123

Search Terms:

Code

([0] as [0]) as number[];
([0] as [0]) as readonly number[];
// As the expansion of [0] as const
([0] as readonly [0]) as number[]; // error
([0] as readonly [0]) as readonly number[];

Expected behavior:
pass
Actual behavior:

Conversion of type 'readonly [0]' to type 'number[]' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
  The type 'readonly [0]' is 'readonly' and cannot be assigned to the mutable type 'number[]'.(2352)

Playground Link: http://www.typescriptlang.org/play/index.html?target=99&ts=3.8.0-dev.20200123&ssl=1&ssc=1&pln=6&pc=1#code/BQbQDAugBAhgzlcECUsEDsCuBbARgUwCcQIBuAKFEjUUlXikPxgBMB7dAGwE8os8iJCgHphUAIIIALgAt8UfAA8ADjHRwAlhyhsAZrWgMAxhzhTKSGk1YceB+hhwFiZKKIWFCbQheoNr7Fy8SA6MzIF2-M5C5EA

Related Issues:

Inizia riproducendo gli esempi di cast di tuple readonly nel TypeScript Playground o con TypeScript 3.7.x-dev.20200123, quindi segui i controlli del compilatore relativi a insufficient-overlap e all'assegnabilità di readonly. Il lavoro è completato quando il cast della tupla readonly a number[] ha esito positivo come previsto senza richiedere un cast intermedio a unknown, mentre i controlli di sicurezza esistenti rimangono intatti.