rust-lang
rustfmt removes inner attributes from inline const blocks
Clippy unfortunately warns about asserts whose conditions can be evaluated at compile-time even in inline const blocks. It's a known issue, it'll hopefully be solved at some point.
In the meantime, if one wishes to perform such compile-time asserts without disabling the lint globally, one can simply allow the offending lint:
fn main() {
const {
#![allow(clippy::assertions_on_constants)]
assert!(1 < 2);
}
}
Unfortunately, running rustfmt on the above will simply remove the attribute (try it on the playground), resulting in:
fn main() {
const {
assert!(1 < 2);
}
}
And then Clippy nags at us again :'(
With inline const blocks due to being stabilized for 1.79 (in 6 weeks), it would be nice to fix rustfmt to not eat their code away.
Meta
rustfmt version:
1.7.0-nightly (2024-05-03 d2d24e3)
I think the issue here is that the inner attributes are stored on the outer ast::Expr node with the kind of ast::ExprKind::ConstBlock(AnonConst). Internally the ast::AnonConst holds a reference to an ast::ExprKind::Block expression that we want to rewrite, but it doesn't hold a reference to the attributes.
We can probably solve this by matching on the AnonConst's inner expression kind and calling rewrite_block if it's an ast::ExprKind::Block:
https://github.com/rust-lang/rustfmt/blob/d5f1200ed6a8e375f963e0c59a8bee45c0018c55/src/expr.rs#L141-L143
