No default toolchain configured after installing rustup

Question

If it seems that rustup did not successfully install and configure the stable toolchain, you can do it manually:

rustup install stable
rustup default stable

After testing, it seems like my incomplete installation may have been caused by a network error. You can also try to reinstall to solve the problem.

The problem is due to my connection and my proxy which didn't allow rustc, cargo, and others to be downloaded.

I thought that the all the executables were all-in-one but apparently not.

In my case, I had multirust installed and the following worked for me:

multirust install stable
multirust default stable

I installed rust by root,but my IDEA works on user,then I installed rust on user,all worked well.