Warn about the rust-src component footgun

dtolnay · Oct 14, 2024 · d42f1c8 · d42f1c8
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diff --git a/README.md b/README.md
@@ -224,6 +224,17 @@ to catch. If the compiler changes something that makes error messages that we
 care about substantially worse, it is also important to catch and report as a
 compiler issue.
 
+## Troubleshooting
+
+### CI output differs from local
+
+Make sure `rust-src` component is installed on CI, otherwise error messages
+on CI will not include snippets of code from the standard library.
+
+```bash
+rustup component add rust-src
+```
+
 <br>
 
 #### License

diff --git a/src/lib.rs b/src/lib.rs
@@ -207,6 +207,17 @@
 //! important for a test suite to catch. If the compiler changes something that
 //! makes error messages that we care about substantially worse, it is also
 //! important to catch and report as a compiler issue.
+//!
+//! # Troubleshooting
+//!
+//! ## CI output differs from local
+//!
+//! Make sure `rust-src` component is installed on CI, otherwise error messages
+//! on CI will not include snippets of code from the standard library.
+//!
+//! ```bash
+//! rustup component add rust-src
+//! ```
 
 #![doc(html_root_url = "https://docs.rs/trybuild/1.0.99")]
 #![allow(