&'borrow mut dyn FnMut(BrokenLink<'input>) -> CowStr<'input>
and other valid rust programs

from blog the website of jyn, | ↗ original
This is a story about type signatures, Higher Ranked Trait Bounds (HRTB), and the most confusing diagnostics bug I've seen in the Rust compiler. Along the way we'll learn how pulldown-cmark has been trying to fix the same API for 3 different releases, and discover that some bugs only appear at the compile time of downstream crates. If you don't...