4 ms·

You still write `panic!()`. It type checks using polymorphism only, without any coercions.

• kibwen 28d ago
  But `panic!()` is just a macro invocation that needs to expand to something, and the question here is what that something ought to be in order to produce a valid program. Currently it expands to this: https://github.com/rust-lang/rust/blob/98fd715edd3a0a5aa8f2041d7e20a3143b0fc0d3/library/core/src/panicking.rs#L138 https://github.com/rust-lang/rust/blob/98fd715edd3a0a5aa8f20... , which is a function with a return type of `!`, which has indicated a diverging function since long before Rust even considered having a first-class never type.
  • kccqzy 28d ago
    Right. And the whole discussion boils down to, why can’t this function return type be polymorphic in the first place? This avoids the never type, the coercions from the never type, and all the issues caused by that described in the article.