If I create a new crate with ```bash cargo new --lib rustdocissue ``` Then add a dependency on gfx-backend-empty version 0.5: ```toml [dependencies] gfx-backend-empty = "0.5" ``` Then run `cargo doc` on stable: ```bash cargo +stable doc --lib --no-deps ``` `cargo doc` succeeds with warnings. I'm not sure if the warnings are relevant, but the warnings in `cargo +stable doc` are for some empty blocks in examples that haven't been populated, such as: ``` /// ```no_run /// /// ``` ``` Now if I run the same command on nightly (`nightly-2020-04-06`): ```bash cargo +nightly doc --lib --no-deps ``` `cargo doc` panics with the following error: ``` thread 'rustc' panicked at 'could not find markdown in source', src/librustdoc/passes/mod.rs:411:31 ``` The panic originates in https://github.com/rust-lang/rust/blob/1ccb0b4a020cac07a9772d0da722869096a46cef/src/librustdoc/passes/mod.rs#L411 Besides `stable` and `nightly`, I tried the `nightly-2020-03-19` toolchain which succeeds with warnings (like `stable`). I also created a repo which reproduces the issue at https://github.com/grovesNL/rustdocissue if it's convenient to clone that instead of following the steps above.