"malformed attribute" for `should_panic` missing closing quotes

[ChayimFriedman2]

Given the following code: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=f5f8842e55751ce384c7d40390bde7e1

#[should_panic = 1]
fn test() {}

The current output is:

error: malformed `should_panic` attribute input
 --> src/lib.rs:1:1
  |
1 | #[should_panic = 1]
  | ^^^^^^^^^^^^^^^^^^^
  |
help: the following are the possible correct uses
  |
1 | #[should_panic = "reason"]
  |
1 | #[should_panic(expected = "reason)]
  |
1 | #[should_panic]
  |

Note that in #[should_panic(expected = "reason)] we miss the closing quotes.

This is because the attribute template is missing it:

rust/compiler/rustc_feature/src/builtin_attrs.rs

Lines 278 to 281 in 80ed61f

	ungated!(
	should_panic, Normal,
	template!(Word, List: r#"expected = "reason"#, NameValueStr: "reason"), FutureWarnFollowing,
	),

Fixing that should be simple as introducing it there.

[Rageking8]

@rustbot claim