Hygienic bug in macro (Ok function)

[dcecile]

Similar to #16, but this time self_cell doesn't allow a custom Ok function:

use self_cell::self_cell;

// Remove this, and it compiles
pub fn Ok<T>(t: T) -> Result<T, ()> {
  Result::Ok(t)
}

#[derive(Debug, Eq, PartialEq)]
struct Ast<'a>(pub Vec<&'a str>);

self_cell!(
    struct AstCell {
        owner: String,

        #[covariant]
        dependent: Ast,
    }

    impl {Debug, Eq, PartialEq}
);

fn build_ast_cell(code: &str) -> AstCell {
  // Create owning String on stack.
  let pre_processed_code = code.trim().to_string();

  // Move String into AstCell, then build Ast inplace.
  AstCell::new(pre_processed_code, |code| {
    Ast(code.split(' ').filter(|word| word.len() > 1).collect())
  })
}

fn main() {
  let ast_cell = build_ast_cell("fox = cat + dog");

  println!("ast_cell -> {:?}", &ast_cell);
  println!("ast_cell.borrow_owner() -> {:?}", ast_cell.borrow_owner());
  println!(
    "ast_cell.borrow_dependent().0[1] -> {:?}",
    ast_cell.borrow_dependent().0[1]
  );
}

Compile error:

error[E0308]: mismatched types
  --> svc-gateway-host-run/src/e.rs:11:1
   |
11 | / self_cell!(
12 | |     struct AstCell {
13 | |         owner: String,
14 | |
...  |
19 | |     impl {Debug, Eq, PartialEq}
20 | | );
   | | ^
   | | |
   | | expected `Result<AstCell, Err>`, found `Result<AstCell, ()>`
   | |_expected this type parameter
   |   expected `Result<AstCell, Err>` because of return type
   |
   = note: expected enum `Result<_, Err>`
              found enum `Result<_, ()>`
   = note: this error originates in the macro `self_cell` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0308]: mismatched types
  --> svc-gateway-host-run/src/e.rs:11:1
   |
11 | / self_cell!(
12 | |     struct AstCell {
13 | |         owner: String,
14 | |
...  |
19 | |     impl {Debug, Eq, PartialEq}
20 | | );
   | | ^
   | | |
   | |_expected `Result<AstCell, (..., ...)>`, found `Result<AstCell, ()>`
   |   expected `Result<AstCell, (String, Err)>` because of return type
   |
   = note: expected enum `Result<_, (String, Err)>`
              found enum `Result<_, ()>`
   = note: this error originates in the macro `self_cell` (in Nightly builds, run with -Z macro-backtrace for more info)

Context: was trying out anyhow's Ok helper

[Voultapher]

Thanks for bringing up the issue. I've created a PR with a fix for the issue. Please let me know if that addresses your issues.

[Voultapher]

I just released https://github.com/Voultapher/self_cell/releases/tag/v1.0.3 which contains the fix.

[dcecile]

Thanks!