invalid example code on language spec 3.7 Specifying Types

[vvakame]

https://github.com/Microsoft/TypeScript/blob/af4a12151c7f1b0cfe6b913d7c092b825cf4f641/doc/spec.md#3.7

following code is invalid.

((x: string) => string) | (x: number) => number)

in 3.7

parentheses are required around function or constructor types in union types.

I think this example should be

((x: string) => string) | ((x: number) => number)