Merge pull request #288 from Veetaha/feat/add-rust-src-caveat-warning

Warn about the `rust-src` component footgun in the docs

README.md

@@ -224,6 +224,16 @@ 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.
 
+## CI
+
+Make sure `rust-src` component is installed on CI, otherwise error messages
+on CI will not include snippets of code from the standard library. This will
+make sure the output on CI is the same as on your local machine.
+
+```bash
+rustup component add rust-src
+```
+
 <br>
 
 #### License

src/lib.rs

@@ -207,6 +207,16 @@
 //! 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.
+//!
+//! # CI
+//!
+//! Make sure `rust-src` component is installed on CI, otherwise error messages
+//! on CI will not include snippets of code from the standard library. This will
+//! make sure the output on CI is the same as on your local machine.
+//!
+//! ```bash
+//! rustup component add rust-src
+//! ```
 
 #![doc(html_root_url = "https://docs.rs/trybuild/1.0.99")]
 #![allow(