Blog Post: Beating std::visit Without Really Trying

[Joseph Rushton Wakeling]

Speaking of performance, I was intrigued by the Reddit response 
noting that Rust can go one better by eliminating the error path 
at compile time:
https://www.reddit.com/r/programming/comments/ddi5wb/comment/f2iow4u

The commenter suggests that's because Rust bakes the 
functionality into the compiler instead of making it a library 
type. @Walter, @Andrei, that might be an interesting data point 
for the question of what should have compiler vs. library support?