[PRE-RFC] generalized return/escape/continue from scopes

[cuviper]

You do know that you can use labels for break and continue already, right?

As for return, there were sort of similar ideas in this thread:

pre-RFC: Allow return, continue, and break to affect the captured environment

The general idea is that inside a closure, return; would return from the defining function instead of the closure. fn main() { // `return` would be a divergent expression and return from `main` let id: i32 = "321".parse().or_else(|| return); } This would allow Rust to satisfy the Tennent’s Correspondence Principle. In short, Tennent’s Correspondence Principle says: For a given expression expr, || expr should be equivalent. You could wrap arbitrary parts function body (even the whole f…