* [`from_expansion`][from_expansion] and [`in_external_macro`][in_external_macro]
* [`Span`][span]
* [`Applicability`][applicability]
+* [Common tools for writing lints](common_tools_writing_lints.md) helps with common operations
* [The rustc-dev-guide][rustc-dev-guide] explains a lot of internal compiler concepts
* [The nightly rustc docs][nightly_docs] which has been linked to throughout
this guide