rust-lang / rust-lang/rustup

Confusing "toolchain does not support components" message when it's not installed

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Dominant language
Rust
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Description

When a toolchain specified in rust-toolchain file is not installed, the output is as follows:

$ cargo clippy
error: process didn't exit successfully: `rustc -vV` (exit code: 1)
--- stderr
error: 'rustc' is not installed for the toolchain '1.40.0-x86_64-unknown-linux-gnu'
To install, run `rustup component add rustc --toolchain 1.40.0-x86_64-unknown-linux-gnu`

Following the suggestion doesn't help:

$ rustup component add rustc --toolchain 1.40.0-x86_64-unknown-linux-gnu
error: toolchain '1.40.0-x86_64-unknown-linux-gnu' does not support components

The correct suggestion would be rustup install 1.40.0, which helps.

$ rustup --version
rustup 1.20.2 (2019-10-16)

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First steps

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  4. Open a pull request that references the issue number.

Research direction

Start by tracing the rustc -vV failure path triggered by an uninstalled toolchain, then inspect how rustup constructs the suggested component command. Reproduce with a rust-toolchain file and cargo clippy; done means the output recommends rustup install 1.40.0 instead of rustup component add.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
cli, tooling
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
48/100

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