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#[inline] is no longer accepted on closures #49632
Description
Since #49291 #[inline] is no longer accepted on closures, despite the fact that this attribute does have an effect on code generation.
The generated LLVM IR (in debug builds) for this example is different if you remove #[inline(always)]:
#![feature(stmt_expr_attributes)]
#![crate_type="rlib"]
pub fn main() {
let x = #[inline(always)] || {};
x();
}Reacted by Felipe S. S. Schneider
Activity
sanxiyn commentedon Apr 5, 2018
While I think this should be fixed, this is not exactly a regression, since
stmt_expr_attributesis unstable and this code never worked on stable.tejom commentedon Apr 6, 2018
I can make a change, since I wrote that original patch. I'm curious if a better change would be to have closures always inlined? That seems like it might have been the expected behavior and the reason why it was suggested to me to write the check like this in the first place?
Amanieu commentedon Apr 6, 2018
I believe closures are currently always effectively
#[inline]. However in some cases I need to force inlining with#[inline(always)]even when LLVM thinks it is a bad idea.tejom commentedon Apr 6, 2018
I would just change the
check_expr_attributesfunction in librustc/hir/check_attr.rs to check the variant ofhir::Exprpassed in when the attribute is inline. if itsExprClosurethen don't emit an error. But Id prefer to have someone who does the reviews say this is what they want instead of having a surprise at the pull request stage.Rollup merge of rust-lang#50273 - Amanieu:issue-49532, r=alexcrichton