From 5e4d8b44f9524f28fd1ebca18f48ecad204cf184 Mon Sep 17 00:00:00 2001 From: Jason Newcomb Date: Mon, 9 Aug 2021 16:26:27 -0400 Subject: [PATCH] Improve doc for `can_move_expr_to_closure_no_visit` --- clippy_utils/src/lib.rs | 33 +++++++++++++++++++++++++++++---- 1 file changed, 29 insertions(+), 4 deletions(-) diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs index eb9ad04527f..b40b42fa6d3 100644 --- a/clippy_utils/src/lib.rs +++ b/clippy_utils/src/lib.rs @@ -631,20 +631,45 @@ pub fn can_mut_borrow_both(cx: &LateContext<'_>, e1: &Expr<'_>, e2: &Expr<'_>) - /// Checks if the top level expression can be moved into a closure as is. /// Currently checks for: -/// * Break/Continue outside the given jump targets +/// * Break/Continue outside the given loop HIR ids. /// * Yield/Return statments. -/// * Inline assembly +/// * Inline assembly. /// * Usages of a field of a local where the type of the local can be partially moved. +/// +/// For example, given the following function: +/// +/// ``` +/// fn f<'a>(iter: &mut impl Iterator) { +/// for item in iter { +/// let s = item.1; +/// if item.0 > 10 { +/// continue; +/// } else { +/// s.clear(); +/// } +/// } +/// } +/// ``` +/// +/// When called on the expression `item.0` this will return false unless the local `item` is in the +/// `ignore_locals` set. The type `(usize, &mut String)` can have the second element moved, so it +/// isn't always safe to move into a closure when only a single field is needed. +/// +/// When called on the `continue` expression this will return false unless the outer loop expression +/// is in the `loop_ids` set. +/// +/// Note that this check is not recursive, so passing the `if` expression will always return true +/// even though sub-expressions might return false. pub fn can_move_expr_to_closure_no_visit( cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, - jump_targets: &[HirId], + loop_ids: &[HirId], ignore_locals: &HirIdSet, ) -> bool { match expr.kind { ExprKind::Break(Destination { target_id: Ok(id), .. }, _) | ExprKind::Continue(Destination { target_id: Ok(id), .. }) - if jump_targets.contains(&id) => + if loop_ids.contains(&id) => { true }, -- 2.44.0