Allow wrapped values to be used in place of primitives.

class NumberWrapper {
    constructor(private value: number) {}
    valueOf(): number { return this.value; }
}

var x = new NumberWrapper(1);

// The right-hand side of an arithmetic operation 
// must be of type 'any', 'number' or an enum type.
console.log(2 + x);

It would be nice if an arithmetic operation could allow using the wrapped number because it's valueOf() method returns the expected primitive type.

This can be generalized to: if type T is expected, then a value that implements the following interface can be used.

interface Wrapped<T> {
    valueOf(): T;
}

首先复现 issue 中的算术示例，并跟踪 TypeScript 的算术操作数类型检查路径；payload 未指定源文件、测试或入口点。当带有返回预期原始类型的 valueOf() 方法的包装值能在相关算术运算中被接受，且该行为有测试覆盖时，即视为完成。