在stable、nightly都安裝的情況下：
從stable->nightly
C:\Users\rustr>rustc --version
rustc 1.32.0 (9fda7c223 2019-01-16)
C:\Users\rustr>rustup override set nightly
info: using existing install for 'nightly-x86_64-pc-windows-msvc'
info: override toolchain for 'C:\Users\rustr' set to 'nightly-x86_64-pc-windows-msvc'
nightly-x86_64-pc-windows-msvc unchanged - rustc 1.36.0-nightly (dec4c5201 2019-05-24)
C:\Users\rustr>rustc --version
rustc 1.36.0-nightly (dec4c5201 2019-05-24)
從nightly->stable
C:\Users\rustr>rustc --version
rustc 1.36.0-nightly (dec4c5201 2019-05-24)
C:\Users\rustr>rustup override set stable
info: using existing install for 'stable-x86_64-pc-windows-msvc'
info: override toolchain for 'C:\Users\rustr' set to 'stable-x86_64-pc-windows-msvc'
stable-x86_64-pc-windows-msvc unchanged - rustc 1.32.0 (9fda7c223 2019-01-16)
C:\Users\rustr>rustc --version
rustc 1.32.0 (9fda7c223 2019-01-16)
默認設置
C:\Users\rustr>rustup default stable
info: using existing install for 'stable-x86_64-pc-windows-msvc'
info: default toolchain set to 'stable-x86_64-pc-windows-msvc'
stable-x86_64-pc-windows-msvc unchanged - rustc 1.32.0 (9fda7c223 2019-01-16)
C:\Users\rustr>rustup default nightly
info: using existing install for 'nightly-x86_64-pc-windows-msvc'
info: default toolchain set to 'nightly-x86_64-pc-windows-msvc'
nightly-x86_64-pc-windows-msvc unchanged - rustc 1.36.0-nightly (dec4c5201 2019-05-24)