GHC 9.0, supporting linear types

Re:GHC 9.0, supporting linear types by paavohtl on Wednesday December 30, 2020 @05:54PM (#25587256)

I don't find this answer satisfactory, because you also need to specify in Rust whether or not a function moves its argument(s).

  // This moves the argument
  fn func(a: A) -> B { .. }
  func(x); // x is not accessible after this line
  
  // This borrows the argument, and therefore won't move it
  fn func(a: &A) -> B { .. }
  func(&x); // x remains accessible after this line

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Re:GHC 9.0, supporting linear types by Ericson2314 on Wednesday December 30, 2020 @11:39PM (#25589649)

From the perspective of Rust, Linear Haskell is going to seem quite weird, and I say that as Haskeller wishing that language extension was more like Rust.

I'm not really sure how to explain it, but basically only functions that are themselves linear can have linear parameters, It's vaguely like "`Fn(A) -> B` only if `A: Copy`", and `FnOnce(A) -> B` only if `A: !Copy`, except there is no `Copy` or `!Copy` and the only say to determine it is `Fn` vs `FnOnce`.

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