Hope to improve the error messages of cargo or rustup

tools and infrastructure cargo
1

When I was installing mdbook, the following error suddenly popped up:

\rustbook_zhcn-main> cargo install mdbook
error: process didn't exit successfully: rustc -vV (exit code: 1)
--- stderr
error: Missing manifest in toolchain '1.90-aarch64-pc-windows-msvc'

As someone not very familiar with the rust-lang toolchain architecture, I had no idea what happened. I asked AI and searched online, but all I got was content about how to configure the MSVC toolchain on Windows. But I had obviously already configured it, otherwise I wouldn't have successfully built and compiled other projects before. Later, I found it in the mirror list — 1.90-aarch64-pc-windows-msvc. It was under the rustup list, and I began to realize that perhaps during installation, the toolchain automatically executed rustup update, and coincidentally my device had network problems, causing 1.90-aarch64-pc-windows-msvc not to be installed properly.

Finally, I manually executed rustup update again:

info: downloading 6 components
        rustc installed                       68.52 MiB
        cargo installed                        9.25 MiB
     rust-std installed                       19.68 MiB
    rust-docs installed                       20.52 MiB
      rustfmt installed                        2.68 MiB
       clippy installed                        3.84 MiB
  stable-aarch64-pc-windows-msvc unchanged - rustc 1.95.0 (59807616e 2026-04-14)
    1.90-aarch64-pc-windows-msvc installed - rustc 1.90.0 (1159e78c4 2025-09-14)

I knew I had succeeded.

1.90-aarch64-pc-windows-msvc, this package name is very misleading, and the error message is not detailed enough. I hope Rust can improve them in the future. Thanks a lot.

2

I think this error message comes from rustup. It looks like it has already seen some improvement here

-   #[error("Missing manifest in toolchain '{}'", .0)]
+   #[error(
+       "missing manifest in toolchain '{0}'\n\
+    help: this may happen if the toolchain installation was interrupted\n\
+    help: try reinstalling or updating the toolchain"
+   )]

but rustup currently has a really slow release cycle (as far as I know there are people wanting to improve that), so it isn't in your installed version yet.

Nonetheless, I wonder if further improvement is needed. I assume in your case it wasn't clear to you that this is a rustup error, since I came up from a call to rustc (which does - with a rustup install of rustc - go through a rustup binary internally to select the version). If you'd agree that that's useful / needed (i.e. that "try updating the toolchain" wouldn't have helped you to know to invoke rustup update in your context) then feel free to open an issue on the rustup repo for this ^^

5 Likes
3

Thank you for your reply,and I have open an issue on the rustup repo for this question: Hope to improve the error messages and Improve error-handling abilities of rustup #4863