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Add new lint hashset_insert_after_contains 
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‎CHANGELOG.md

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@@ -5342,6 +5342,7 @@ Released 2018-09-13
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[`get_first`]: https://rust-lang.github.io/rust-clippy/master/index.html#get_first
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[`get_last_with_len`]: https://rust-lang.github.io/rust-clippy/master/index.html#get_last_with_len
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[`get_unwrap`]: https://rust-lang.github.io/rust-clippy/master/index.html#get_unwrap
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[`hashset_insert_after_contains`]: https://rust-lang.github.io/rust-clippy/master/index.html#hashset_insert_after_contains
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[`host_endian_bytes`]: https://rust-lang.github.io/rust-clippy/master/index.html#host_endian_bytes
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[`identity_conversion`]: https://rust-lang.github.io/rust-clippy/master/index.html#identity_conversion
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[`identity_op`]: https://rust-lang.github.io/rust-clippy/master/index.html#identity_op

‎clippy_lints/src/declared_lints.rs

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@@ -212,6 +212,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
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crate::functions::TOO_MANY_ARGUMENTS_INFO,
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crate::functions::TOO_MANY_LINES_INFO,
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crate::future_not_send::FUTURE_NOT_SEND_INFO,
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crate::hashset_insert_after_contains::HASHSET_INSERT_AFTER_CONTAINS_INFO,
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crate::if_let_mutex::IF_LET_MUTEX_INFO,
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crate::if_not_else::IF_NOT_ELSE_INFO,
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crate::if_then_some_else_none::IF_THEN_SOME_ELSE_NONE_INFO,

‎clippy_lints/src/hashset_insert_after_contains.rs

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use std::ops::ControlFlow;
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use clippy_utils::diagnostics::span_lint_and_then;
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use clippy_utils::ty::is_type_diagnostic_item;
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use clippy_utils::visitors::for_each_expr;
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use clippy_utils::{higher, peel_hir_expr_while, SpanlessEq};
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use rustc_hir::{Expr, ExprKind, UnOp};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::declare_lint_pass;
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use rustc_span::{sym, Span};
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declare_clippy_lint! {
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/// ### What it does
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/// Checks for usage of `contains` to see if a value is not
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/// present on `HashSet` followed by a `insert`.
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///
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/// ### Why is this bad?
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/// Using just `insert` and checking the returned `bool` is more efficient.
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///
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/// ### Example
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/// ```rust
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/// use std::collections::HashSet;
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/// let mut set = HashSet::new();
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/// let value = 5;
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/// if !set.contains(&value) {
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/// set.insert(value);
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/// println!("inserted {value:?}");
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/// }
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/// ```
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/// Use instead:
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/// ```rust
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/// use std::collections::HashSet;
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/// let mut set = HashSet::new();
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/// let value = 5;
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/// if set.insert(&value) {
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/// println!("inserted {value:?}");
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/// }
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/// ```
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#[clippy::version = "1.80.0"]
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pub HASHSET_INSERT_AFTER_CONTAINS,
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nursery,
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"unnecessary call to `HashSet::contains` followed by `HashSet::insert`"
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}
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declare_lint_pass!(HashsetInsertAfterContains => [HASHSET_INSERT_AFTER_CONTAINS]);
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impl<'tcx> LateLintPass<'tcx> for HashsetInsertAfterContains {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if !expr.span.from_expansion()
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&& let Some(higher::If {
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cond: cond_expr,
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then: then_expr,
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..
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}) = higher::If::hir(expr)
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&& let Some(contains_expr) = try_parse_contains(cx, cond_expr)
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&& find_insert_calls(cx, &contains_expr, then_expr)
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{
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span_lint_and_then(
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cx,
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HASHSET_INSERT_AFTER_CONTAINS,
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expr.span,
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"usage of `HashSet::insert` after `HashSet::contains`",
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|diag| {
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diag.note("`HashSet::insert` returns whether it was inserted")
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.span_help(contains_expr.span, "remove the `HashSet::contains` call");
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},
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);
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}
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}
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}
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struct ContainsExpr<'tcx> {
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receiver: &'tcx Expr<'tcx>,
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value: &'tcx Expr<'tcx>,
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span: Span,
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}
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fn try_parse_contains<'tcx>(cx: &LateContext<'_>, expr: &'tcx Expr<'_>) -> Option<ContainsExpr<'tcx>> {
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let expr = peel_hir_expr_while(expr, |e| {
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if let ExprKind::Unary(UnOp::Not, e) = e.kind {
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Some(e)
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} else {
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None
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}
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});
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if let ExprKind::MethodCall(path, receiver, [value], span) = expr.kind {
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let value = value.peel_borrows();
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let receiver = receiver.peel_borrows();
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let receiver_ty = cx.typeck_results().expr_ty(receiver).peel_refs();
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if value.span.eq_ctxt(expr.span)
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&& is_type_diagnostic_item(cx, receiver_ty, sym::HashSet)
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&& path.ident.name == sym!(contains)
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{
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return Some(ContainsExpr { receiver, value, span });
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}
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}
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None
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}
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struct InsertExpr<'tcx> {
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receiver: &'tcx Expr<'tcx>,
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value: &'tcx Expr<'tcx>,
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}
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fn try_parse_insert<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<InsertExpr<'tcx>> {
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if let ExprKind::MethodCall(path, receiver, [value], _) = expr.kind {
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let value = value.peel_borrows();
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let value = peel_hir_expr_while(value, |e| {
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if let ExprKind::Unary(UnOp::Deref, e) = e.kind {
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Some(e)
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} else {
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None
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}
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});
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let receiver_ty = cx.typeck_results().expr_ty(receiver).peel_refs();
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if is_type_diagnostic_item(cx, receiver_ty, sym::HashSet) && path.ident.name == sym!(insert) {
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Some(InsertExpr { receiver, value })
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} else {
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None
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}
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} else {
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None
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}
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}
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fn find_insert_calls<'tcx>(cx: &LateContext<'tcx>, contains_expr: &ContainsExpr<'tcx>, expr: &'tcx Expr<'_>) -> bool {
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for_each_expr(expr, |e| {
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if let Some(insert_expr) = try_parse_insert(cx, e)
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&& SpanlessEq::new(cx).eq_expr(contains_expr.receiver, insert_expr.receiver)
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&& SpanlessEq::new(cx).eq_expr(contains_expr.value, insert_expr.value)
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{
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ControlFlow::Break(())
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} else {
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ControlFlow::Continue(())
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}
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})
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.is_some()
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}

‎clippy_lints/src/lib.rs

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@@ -149,6 +149,7 @@ mod from_raw_with_void_ptr;
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mod from_str_radix_10;
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mod functions;
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mod future_not_send;
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mod hashset_insert_after_contains;
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mod if_let_mutex;
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mod if_not_else;
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mod if_then_some_else_none;
@@ -1165,6 +1166,7 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
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..Default::default()
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})
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});
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store.register_late_pass(|_| Box::new(hashset_insert_after_contains::HashsetInsertAfterContains));
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// add lints here, do not remove this comment, it's used in `new_lint`
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}
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‎tests/ui/hashset_insert_after_contains.rs

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#![allow(unused)]
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#![allow(clippy::nonminimal_bool)]
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#![allow(clippy::needless_borrow)]
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#![warn(clippy::hashset_insert_after_contains)]
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use std::collections::HashSet;
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fn main() {
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should_warn_cases();
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should_not_warn_cases();
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}
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fn should_warn_cases() {
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let mut set = HashSet::new();
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let value = 5;
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if !set.contains(&value) {
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set.insert(value);
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println!("Just a comment");
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}
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if set.contains(&value) {
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set.insert(value);
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println!("Just a comment");
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}
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if !set.contains(&value) {
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set.insert(value);
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}
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if !!set.contains(&value) {
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set.insert(value);
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println!("Just a comment");
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}
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if (&set).contains(&value) {
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set.insert(value);
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}
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let borrow_value = &6;
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if !set.contains(borrow_value) {
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set.insert(*borrow_value);
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}
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let borrow_set = &mut set;
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if !borrow_set.contains(&value) {
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borrow_set.insert(value);
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}
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}
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fn should_not_warn_cases() {
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let mut set = HashSet::new();
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let value = 5;
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let another_value = 6;
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if !set.contains(&value) {
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set.insert(another_value);
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}
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if !set.contains(&value) {
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println!("Just a comment");
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}
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if simply_true() {
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set.insert(value);
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}
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if !set.contains(&value) {
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set.replace(value); //it is not insert
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println!("Just a comment");
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}
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}
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fn simply_true() -> bool {
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true
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}

‎tests/ui/hashset_insert_after_contains.stderr

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error: usage of `HashSet::insert` after `HashSet::contains`
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--> tests/ui/hashset_insert_after_contains.rs:18:5
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|
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LL | / if !set.contains(&value) {
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LL | | set.insert(value);
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LL | | println!("Just a comment");
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LL | | }
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| |_____^
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|
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= note: `HashSet::insert` returns whether it was inserted
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help: remove the `HashSet::contains` call
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--> tests/ui/hashset_insert_after_contains.rs:18:13
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|
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LL | if !set.contains(&value) {
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| ^^^^^^^^^^^^^^^^
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= note: `-D clippy::hashset-insert-after-contains` implied by `-D warnings`
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= help: to override `-D warnings` add `#[allow(clippy::hashset_insert_after_contains)]`
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error: usage of `HashSet::insert` after `HashSet::contains`
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--> tests/ui/hashset_insert_after_contains.rs:23:5
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|
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LL | / if set.contains(&value) {
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LL | | set.insert(value);
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LL | | println!("Just a comment");
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LL | | }
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| |_____^
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|
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= note: `HashSet::insert` returns whether it was inserted
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help: remove the `HashSet::contains` call
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--> tests/ui/hashset_insert_after_contains.rs:23:12
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|
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LL | if set.contains(&value) {
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| ^^^^^^^^^^^^^^^^
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error: usage of `HashSet::insert` after `HashSet::contains`
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--> tests/ui/hashset_insert_after_contains.rs:28:5
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|
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LL | / if !set.contains(&value) {
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LL | | set.insert(value);
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LL | | }
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| |_____^
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|
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= note: `HashSet::insert` returns whether it was inserted
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help: remove the `HashSet::contains` call
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--> tests/ui/hashset_insert_after_contains.rs:28:13
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|
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LL | if !set.contains(&value) {
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| ^^^^^^^^^^^^^^^^
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error: usage of `HashSet::insert` after `HashSet::contains`
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--> tests/ui/hashset_insert_after_contains.rs:32:5
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|
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LL | / if !!set.contains(&value) {
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LL | | set.insert(value);
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LL | | println!("Just a comment");
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LL | | }
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| |_____^
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|
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= note: `HashSet::insert` returns whether it was inserted
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help: remove the `HashSet::contains` call
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--> tests/ui/hashset_insert_after_contains.rs:32:14
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|
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LL | if !!set.contains(&value) {
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| ^^^^^^^^^^^^^^^^
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error: usage of `HashSet::insert` after `HashSet::contains`
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--> tests/ui/hashset_insert_after_contains.rs:37:5
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|
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LL | / if (&set).contains(&value) {
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LL | | set.insert(value);
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LL | | }
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| |_____^
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|
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= note: `HashSet::insert` returns whether it was inserted
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help: remove the `HashSet::contains` call
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--> tests/ui/hashset_insert_after_contains.rs:37:15
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|
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LL | if (&set).contains(&value) {
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| ^^^^^^^^^^^^^^^^
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error: usage of `HashSet::insert` after `HashSet::contains`
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--> tests/ui/hashset_insert_after_contains.rs:42:5
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|
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LL | / if !set.contains(borrow_value) {
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LL | | set.insert(*borrow_value);
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LL | | }
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| |_____^
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|
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= note: `HashSet::insert` returns whether it was inserted
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help: remove the `HashSet::contains` call
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--> tests/ui/hashset_insert_after_contains.rs:42:13
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|
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LL | if !set.contains(borrow_value) {
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| ^^^^^^^^^^^^^^^^^^^^^^
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error: usage of `HashSet::insert` after `HashSet::contains`
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--> tests/ui/hashset_insert_after_contains.rs:47:5
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|
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LL | / if !borrow_set.contains(&value) {
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LL | | borrow_set.insert(value);
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LL | | }
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| |_____^
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|
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= note: `HashSet::insert` returns whether it was inserted
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help: remove the `HashSet::contains` call
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--> tests/ui/hashset_insert_after_contains.rs:47:20
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|
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LL | if !borrow_set.contains(&value) {
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| ^^^^^^^^^^^^^^^^
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error: aborting due to 7 previous errors
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