编译器在无法将只读元组转换为可变数组时，应尽量使用可变版本的只读元组，主要是为了 as const 的可用性。这种性能影响较小，因为运行此检查的条件有限。

TypeScript 版本： 3.7.x-dev.20200123
搜索词：
代码：

([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[];

预期行为：

通过

实际行为：

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 链接：**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
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