Tuple enum variant generates unused_parens warning for Deserialize

[compressed]

After updating to 1.0.28 I started receiving an unused parens warning for an enum containing a tuple variant with at least two arguments (i.e. A(usize) won't trigger the warning). I don't get this warning on 1.0.27.

Example:

extern crate serde;
#[macro_use]
extern crate serde_derive;

#[derive(Serialize, Deserialize)]
enum A {
    A(usize, usize),
}

Output:

warning: unnecessary parentheses around function argument
 --> src/lib.rs:5:21
  |
5 | #[derive(Serialize, Deserialize)]
  |                     ^^^^^^^^^^^ help: remove these parentheses
  |
  = note: #[warn(unused_parens)] on by default

warning: unnecessary parentheses around function argument
 --> src/lib.rs:5:21
  |
5 | #[derive(Serialize, Deserialize)]
  |                     ^^^^^^^^^^^ help: remove these parentheses

    Finished dev [unoptimized + debuginfo] target(s) in 0.19 secs

[dtolnay]

Thanks! The parentheses used to be a workaround for a compiler issue that has since been fixed: rust-lang/rust#47311. I removed the workaround in 30361ac and released 1.0.29 which should have no warnings.

[compressed]

Thanks for the quick turnaround! No more warnings now 😸