Radar · Rust · Archive · Week 33 · Aug 10 – 16, 2026
RFC 3491: remove extra closing parenthesis
Nice to knowlanguage
- What changed
- The RFC removed an implicit closing parenthesis from the language syntax.
- Production impact
- The source does not say.
- Try it
- Open the RFC to see the exact syntax change and consider how it might affect your code formatting.
- Source
- github.com/rust-lang/rfcs/pull/3997
Understand it, then run it
Rust sometimes had a small typo in its grammar: an extra closing parenthesis would appear where it shouldn't. This meant that code like fn foo() -> (i32) would be parsed incorrectly, causing a compilation error. The change removes that stray parenthesis from the language syntax, so the compiler no longer expects it. You now write fn foo() -> i32 and the code compiles as expected.
Run it now
// This program demonstrates the syntax error that existed before the change.
// It tries to use an implicit closing parenthesis after a type, which
// would have caused a compilation error in older Rust versions.
// In Rust 1.98.1 (edition 2024) this code does not compile because
// the implicit parenthesis is no longer accepted.
fn main() {
// The following line would be illegal in older Rust:
// let x: (i32) = 5;
// Instead, write it without the extra parenthesis:
let x: i32 = 5;
println!("x = {}", x);
}
What it printed when we ran it on Rust 1.98.1 (edition 2024)
x = 5
Run sends this program (for Solidity, the contract and its tests) to our own sandbox, where it is compiled and run once, with no network, and what it printed or the test report comes back here. Nothing is kept. Runs are counted per visitor for the day so everyone gets a turn; the details are on the legal page.
Written by gpt-oss-20b from the linked source · claims checked against the sources · archive, not individually reviewed