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The introduction mentions "view propagation", which does borrow checking without annotations. Is this documented anywhere? Also, I wish more languages had home

The introduction mentions "view propagation", which does borrow checking without annotations. Is this documented anywhere? Also, I wish more languages had homepages like the Go one[0]. It takes a lot of reading to get to the point where you can see some non-trivial code[1], which is frustrating. [0]: https://golang.org https://golang.org [1]: https://scopes.readthedocs.io/en/latest/tutorial.html#a-mild-breeze-of-programming https://scopes.readthedocs.io/en/latest/tutorial.html#a-mild...

Rusky 7y ago
There's no technical reason the Rust borrow checker couldn't run without annotations either- that's a design choice, similar to the way Rust requires function types even though it could infer them. It makes inter-function contracts clearer, which improves error messages, and avoid the need for whole-program analysis. I couldn't find anything more about "view propagation" either but I strongly suspect it's no more powerful. Probably less and/or buggier at this point, given its relative maturity.
- giornogiovanna 7y ago
  But how would you distinguish between struct A<'a, 'b>(&'a u8, &'b u8); and struct B<'a>(&'a u8, &'a u8); without lifetime annotations?
  - sanxiyn 7y ago
    You can always assume the former(all lifetimes are different). It is strictly more general.
    - giornogiovanna 7y ago
      Thanks, so lifetimes can definitely be inferred for safe code (although just like type inference, they can lead to leaky abstractions). But aren't lifetime annotations necessary for unsafe code? How could you cast a pointer into a struct into a raw pointer and back, while preserving the lifetime, without them?
  - nudq 7y ago
    We'd start by making sure these lifetimes need distinguishing, i.e. that they aren't actually equivalent.
jonathanstrange 7y ago
I was thinking the same, the pages need redesign. The best way to make people try out a language is to give an example on the first page (without scrolling). It should be more than "hello world", e.g. 99 bottles of beer or Fibonacci numbers, anything that shows me how the language looks & "feels". That being said, this looks like a really interesting and promising language. If the borrow-checker is unobtrusive and doesn't require ridiculous boilerplate, then you can count me in! Good work!

Rusky 7y ago

There's no technical reason the Rust borrow checker couldn't run without annotations either- that's a design choice, similar to the way Rust requires function types even though it could infer them. It makes inter-function contracts clearer, which improves error messages, and avoid the need for whole-program analysis. I couldn't find anything more about "view propagation" either but I strongly suspect it's no more powerful. Probably less and/or buggier at this point, given its relative maturity.

giornogiovanna 7y ago
But how would you distinguish between struct A<'a, 'b>(&'a u8, &'b u8); and struct B<'a>(&'a u8, &'a u8); without lifetime annotations?
- sanxiyn 7y ago
  You can always assume the former(all lifetimes are different). It is strictly more general.
  - giornogiovanna 7y ago
    Thanks, so lifetimes can definitely be inferred for safe code (although just like type inference, they can lead to leaky abstractions). But aren't lifetime annotations necessary for unsafe code? How could you cast a pointer into a struct into a raw pointer and back, while preserving the lifetime, without them?
- nudq 7y ago
  We'd start by making sure these lifetimes need distinguishing, i.e. that they aren't actually equivalent.

jonathanstrange 7y ago

I was thinking the same, the pages need redesign. The best way to make people try out a language is to give an example on the first page (without scrolling). It should be more than "hello world", e.g. 99 bottles of beer or Fibonacci numbers, anything that shows me how the language looks & "feels". That being said, this looks like a really interesting and promising language. If the borrow-checker is unobtrusive and doesn't require ridiculous boilerplate, then you can count me in! Good work!