Check expr usage for `manual_flatten` by dswij · Pull Request #7566 · rust-lang...
source link: https://github.com/rust-lang/rust-clippy/pull/7566
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r? @flip1995
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@@ -47,6 +48,9 @@ pub(super) fn check<'tcx>(
let some_ctor = is_lang_ctor(cx, qpath, OptionSome);
let ok_ctor = is_lang_ctor(cx, qpath, ResultOk);
if some_ctor || ok_ctor;
// Ensure epxr in `if let` is not used afterwards
let mut used_visitor = LocalUsedVisitor::new(cx, pat_hir_id);
if !match_arms.iter().any(|arm| used_visitor.check_arm(arm));
xFrednet 4 days ago •
Member
Small NIT: The usage of an iterator can be avoided here by deconstructing the slice in line 40ff like this:
if let ExprKind::Match(
match_expr, [true_arm, _else_arm], MatchSource::IfLetDesugar{ contains_else_clause: false }
) = inner_expr.kind;Then it should be possible to directly call if !LocalUsedVisitor::new(cx, pat_hir_id).check_arm(true_arm); and the direct index call in line 47 can also be avoided.
The rest looks good to me. I'm happy to merge this afterwards 
dswij 3 days ago
Author
Contributor
Ah that was a nice one. I should re-emphasize Rust's powerful pattern matching in my bible :)
xFrednet 3 days ago
Member
Looking at this, it's actually surprising that we don't have a lint for this. I'll create am issue, even if this might ignore macros as most lints do
xFrednet 3 days ago
Member
Created #7569 and also liked this PR as an example how this improves code quality. I also suggested to lint inside if_chain! macros to catch these cases inside Clippy. Thank you again for the contributing and inspiration
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