Function clippy_utils::can_move_expr_to_closure_no_visit
source · pub fn can_move_expr_to_closure_no_visit<'tcx>(
cx: &LateContext<'tcx>,
expr: &'tcx Expr<'_>,
loop_ids: &[HirId],
ignore_locals: &HirIdSet
) -> bool
Expand description
Checks if the top level expression can be moved into a closure as is. Currently checks for:
- Break/Continue outside the given loop HIR ids.
- Yield/Return statements.
- 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<Item = (usize, &'a mut String)>) {
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.