Docs are not optional / removable for MSVC nigtly toolchain

[GabrielMajeri]

According to this old post, "Rust documentation is now optional and opt-in".

I am currently using rustup on Windows with the nightly-x86_64-msvc toolchain, and I am trying to opt-out of using the docs.

> rustup component remove rust-docs
error: component 'rust-docs' for target 'x86_64-pc-windows-msvc' is 
required for toolchain 'nightly-x86_64-pc-windows-msvc' and cannot be removed

Am I doing something wrong? Why are the docs required?

[Diggsey]

See #998