changed algorithm
This commit is contained in:
Jaeyong Sung
parent
8faa938a60
commit
124bb03b15
@ -126,29 +126,36 @@ fn check_fn(
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}
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}
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let mut pre_order = FxHashMap::default();
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visitor.graph.iter().for_each(|(_, next)| {
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next.iter().for_each(|i| {
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*pre_order.entry(*i).or_insert(0) += 1;
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});
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});
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for (id, span, ident) in param_span {
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// if the variable is not used in recursion, it would be marked as unused
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if !visitor.has_side_effect.contains(&id)
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&& *pre_order.get(&id).unwrap_or(&0) > 0
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&& visitor.graph.contains_key(&id)
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{
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span_lint_and_sugg(
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cx,
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ONLY_USED_IN_RECURSION,
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span,
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"parameter is only used in recursion with no side-effects",
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"if this is intentional, prefix with an underscore",
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format!("_{}", ident.name.as_str()),
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Applicability::MaybeIncorrect,
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);
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if !visitor.has_side_effect.contains(&id) {
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let mut queue = VecDeque::new();
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let mut visited = FxHashSet::default();
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queue.push_back(id);
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while let Some(id) = queue.pop_front() {
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if let Some(next) = visitor.graph.get(&id) {
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for i in next {
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if !visited.contains(i) {
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visited.insert(id);
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queue.push_back(*i);
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}
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}
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}
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}
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if visited.contains(&id) {
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span_lint_and_sugg(
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cx,
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ONLY_USED_IN_RECURSION,
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span,
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"parameter is only used in recursion with no side-effects",
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"if this is intentional, prefix with an underscore",
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format!("_{}", ident.name.as_str()),
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Applicability::MaybeIncorrect,
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);
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}
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}
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}
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}
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@ -200,7 +207,7 @@ fn visit_stmt(&mut self, s: &'tcx Stmt<'tcx>) {
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StmtKind::Local(Local {
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pat, init: Some(init), ..
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}) => {
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self.visit_pat_expr(pat, init);
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self.visit_pat_expr(pat, init, false);
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},
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StmtKind::Item(i) => {
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let item = self.ty_ctx.hir().item(i);
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@ -229,7 +236,7 @@ fn visit_expr(&mut self, ex: &'tcx Expr<'tcx>) {
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self.visit_bin_op(lhs, rhs);
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},
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ExprKind::Unary(op, expr) => self.visit_un_op(op, expr),
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ExprKind::Let(Let { pat, init, .. }) => self.visit_pat_expr(pat, init),
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ExprKind::Let(Let { pat, init, .. }) => self.visit_pat_expr(pat, init, false),
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ExprKind::If(bind, then_expr, else_expr) => {
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self.visit_if(bind, then_expr, else_expr);
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},
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@ -333,7 +340,7 @@ fn visit_assign(&mut self, lhs: &'tcx Expr<'tcx>, rhs: &'tcx Expr<'tcx>) {
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let lhs_vars = std::mem::take(&mut self.ret_vars);
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self.visit_expr(rhs);
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let rhs_vars = std::mem::take(&mut self.ret_vars);
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self.connect_assign(&lhs_vars, &rhs_vars);
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self.connect_assign(&lhs_vars, &rhs_vars, false);
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},
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}
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}
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@ -373,12 +380,12 @@ fn visit_un_op(&mut self, op: UnOp, expr: &'tcx Expr<'tcx>) {
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}
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}
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fn visit_pat_expr(&mut self, pat: &'tcx Pat<'tcx>, expr: &'tcx Expr<'tcx>) {
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fn visit_pat_expr(&mut self, pat: &'tcx Pat<'tcx>, expr: &'tcx Expr<'tcx>, connect_self: bool) {
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match (&pat.kind, &expr.kind) {
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(PatKind::Tuple(pats, _), ExprKind::Tup(exprs)) => {
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self.ret_vars = izip!(*pats, *exprs)
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.flat_map(|(pat, expr)| {
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self.visit_pat_expr(pat, expr);
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self.visit_pat_expr(pat, expr, connect_self);
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std::mem::take(&mut self.ret_vars)
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})
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.collect();
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@ -386,13 +393,13 @@ fn visit_pat_expr(&mut self, pat: &'tcx Pat<'tcx>, expr: &'tcx Expr<'tcx>) {
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(PatKind::Slice(front_exprs, _, back_exprs), ExprKind::Array(exprs)) => {
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let mut vars = izip!(*front_exprs, *exprs)
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.flat_map(|(pat, expr)| {
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self.visit_pat_expr(pat, expr);
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self.visit_pat_expr(pat, expr, connect_self);
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std::mem::take(&mut self.ret_vars)
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})
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.collect();
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self.ret_vars = izip!(back_exprs.iter().rev(), exprs.iter().rev())
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.flat_map(|(pat, expr)| {
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self.visit_pat_expr(pat, expr);
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self.visit_pat_expr(pat, expr, connect_self);
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std::mem::take(&mut self.ret_vars)
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})
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.collect();
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@ -403,7 +410,7 @@ fn visit_pat_expr(&mut self, pat: &'tcx Pat<'tcx>, expr: &'tcx Expr<'tcx>) {
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pat.each_binding(|_, id, _, _| lhs_vars.push((id, false)));
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self.visit_expr(expr);
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let rhs_vars = std::mem::take(&mut self.ret_vars);
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self.connect_assign(&lhs_vars, &rhs_vars);
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self.connect_assign(&lhs_vars, &rhs_vars, connect_self);
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self.ret_vars = rhs_vars;
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},
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}
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@ -424,7 +431,7 @@ fn visit_fn(&mut self, callee: &'tcx Expr<'tcx>, args: &'tcx [Expr<'tcx>]) {
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then {
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izip!(self.params.clone(), args)
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.for_each(|(pat, expr)| {
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self.visit_pat_expr(pat, expr);
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self.visit_pat_expr(pat, expr, true);
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self.ret_vars.clear();
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});
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} else {
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@ -463,7 +470,7 @@ fn visit_method_call(&mut self, path: &'tcx PathSegment<'tcx>, args: &'tcx [Expr
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then {
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izip!(self.params.clone(), args.iter())
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.for_each(|(pat, expr)| {
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self.visit_pat_expr(pat, expr);
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self.visit_pat_expr(pat, expr, true);
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self.ret_vars.clear();
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});
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} else {
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@ -511,7 +518,7 @@ fn visit_match(&mut self, expr: &'tcx Expr<'tcx>, arms: &'tcx [Arm<'tcx>]) {
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self.contains_side_effect = false;
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// this would visit `expr` multiple times
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// but couldn't think of a better way
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self.visit_pat_expr(arm.pat, expr);
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self.visit_pat_expr(arm.pat, expr, false);
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let mut vars = std::mem::take(&mut self.ret_vars);
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let _ = arm.guard.as_ref().map(|guard| {
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self.visit_expr(match guard {
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@ -532,7 +539,7 @@ fn visit_match(&mut self, expr: &'tcx Expr<'tcx>, arms: &'tcx [Arm<'tcx>]) {
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self.ret_vars.append(&mut expr_vars);
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}
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fn connect_assign(&mut self, lhs: &[(HirId, bool)], rhs: &[(HirId, bool)]) {
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fn connect_assign(&mut self, lhs: &[(HirId, bool)], rhs: &[(HirId, bool)], connect_self: bool) {
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// if mutable dereference is on assignment it can have side-effect
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// (this can lead to parameter mutable dereference and change the original value)
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// too hard to detect whether this value is from parameter, so this would all
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@ -554,15 +561,19 @@ fn connect_assign(&mut self, lhs: &[(HirId, bool)], rhs: &[(HirId, bool)]) {
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// unwrap is possible since rhs is not empty
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let rhs_first = rhs.first().unwrap();
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for (id, _) in lhs.iter() {
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self.graph
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.entry(*id)
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.or_insert_with(FxHashSet::default)
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.insert(rhs_first.0);
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if connect_self || *id != rhs_first.0 {
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self.graph
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.entry(*id)
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.or_insert_with(FxHashSet::default)
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.insert(rhs_first.0);
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}
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}
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let rhs = rhs.iter();
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izip!(rhs.clone().cycle().skip(1), rhs).for_each(|(from, to)| {
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self.graph.entry(from.0).or_insert_with(FxHashSet::default).insert(to.0);
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if connect_self || from.0 != to.0 {
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self.graph.entry(from.0).or_insert_with(FxHashSet::default).insert(to.0);
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}
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});
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}
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