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Auto merge of #12873 - lochetti:issue_11103, r=llogiq
Add new lint `hashset_insert_after_contains` This PR closes #11103. This is my first PR creating a new lint (and the second attempt of creating this PR, the first one I was not able to continue because of personal reasons). Thanks for the patience :) The idea of the lint is to find insert in hashmanps inside if staments that are checking if the hashmap contains the same value that is being inserted. This is not necessary since you could simply call the insert and check for the bool returned if you still need the if statement. changelog: new lint: [hashset_insert_after_contains]
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,125 @@ | ||
| use std::ops::ControlFlow; | ||
|
|
||
| use clippy_utils::diagnostics::span_lint; | ||
| use clippy_utils::ty::is_type_diagnostic_item; | ||
| use clippy_utils::visitors::for_each_expr; | ||
| use clippy_utils::{higher, peel_hir_expr_while, SpanlessEq}; | ||
| use rustc_hir::{Expr, ExprKind, UnOp}; | ||
| use rustc_lint::{LateContext, LateLintPass}; | ||
| use rustc_session::declare_lint_pass; | ||
| use rustc_span::symbol::Symbol; | ||
| use rustc_span::{sym, Span}; | ||
|
|
||
| declare_clippy_lint! { | ||
| /// ### What it does | ||
| /// Checks for usage of `contains` to see if a value is not | ||
| /// present on `HashSet` followed by a `insert`. | ||
| /// | ||
| /// ### Why is this bad? | ||
| /// Using just `insert` and checking the returned `bool` is more efficient. | ||
| /// | ||
| /// ### Known problems | ||
| /// In case the value that wants to be inserted is borrowed and also expensive or impossible | ||
| /// to clone. In such a scenario, the developer might want to check with `contains` before inserting, | ||
| /// to avoid the clone. In this case, it will report a false positive. | ||
| /// | ||
| /// ### Example | ||
| /// ```rust | ||
| /// use std::collections::HashSet; | ||
| /// let mut set = HashSet::new(); | ||
| /// let value = 5; | ||
| /// if !set.contains(&value) { | ||
| /// set.insert(value); | ||
| /// println!("inserted {value:?}"); | ||
| /// } | ||
| /// ``` | ||
| /// Use instead: | ||
| /// ```rust | ||
| /// use std::collections::HashSet; | ||
| /// let mut set = HashSet::new(); | ||
| /// let value = 5; | ||
| /// if set.insert(&value) { | ||
| /// println!("inserted {value:?}"); | ||
| /// } | ||
| /// ``` | ||
| #[clippy::version = "1.80.0"] | ||
| pub SET_CONTAINS_OR_INSERT, | ||
| nursery, | ||
| "call to `HashSet::contains` followed by `HashSet::insert`" | ||
| } | ||
|
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||
| declare_lint_pass!(HashsetInsertAfterContains => [SET_CONTAINS_OR_INSERT]); | ||
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||
| impl<'tcx> LateLintPass<'tcx> for HashsetInsertAfterContains { | ||
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { | ||
| if !expr.span.from_expansion() | ||
| && let Some(higher::If { | ||
| cond: cond_expr, | ||
| then: then_expr, | ||
| .. | ||
| }) = higher::If::hir(expr) | ||
| && let Some(contains_expr) = try_parse_op_call(cx, cond_expr, sym!(contains))//try_parse_contains(cx, cond_expr) | ||
| && let Some(insert_expr) = find_insert_calls(cx, &contains_expr, then_expr) | ||
| { | ||
| span_lint( | ||
| cx, | ||
| SET_CONTAINS_OR_INSERT, | ||
| vec![contains_expr.span, insert_expr.span], | ||
| "usage of `HashSet::insert` after `HashSet::contains`", | ||
| ); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| struct OpExpr<'tcx> { | ||
| receiver: &'tcx Expr<'tcx>, | ||
| value: &'tcx Expr<'tcx>, | ||
| span: Span, | ||
| } | ||
|
|
||
| fn try_parse_op_call<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, symbol: Symbol) -> Option<OpExpr<'tcx>> { | ||
| let expr = peel_hir_expr_while(expr, |e| { | ||
| if let ExprKind::Unary(UnOp::Not, e) = e.kind { | ||
| Some(e) | ||
| } else { | ||
| None | ||
| } | ||
| }); | ||
|
|
||
| if let ExprKind::MethodCall(path, receiver, [value], span) = expr.kind { | ||
| let value = value.peel_borrows(); | ||
| let value = peel_hir_expr_while(value, |e| { | ||
| if let ExprKind::Unary(UnOp::Deref, e) = e.kind { | ||
| Some(e) | ||
| } else { | ||
| None | ||
| } | ||
| }); | ||
| let receiver = receiver.peel_borrows(); | ||
| let receiver_ty = cx.typeck_results().expr_ty(receiver).peel_refs(); | ||
| if value.span.eq_ctxt(expr.span) | ||
| && is_type_diagnostic_item(cx, receiver_ty, sym::HashSet) | ||
| && path.ident.name == symbol | ||
| { | ||
| return Some(OpExpr { receiver, value, span }); | ||
| } | ||
| } | ||
| None | ||
| } | ||
|
|
||
| fn find_insert_calls<'tcx>( | ||
| cx: &LateContext<'tcx>, | ||
| contains_expr: &OpExpr<'tcx>, | ||
| expr: &'tcx Expr<'_>, | ||
| ) -> Option<OpExpr<'tcx>> { | ||
| for_each_expr(cx, expr, |e| { | ||
| if let Some(insert_expr) = try_parse_op_call(cx, e, sym!(insert)) | ||
| && SpanlessEq::new(cx).eq_expr(contains_expr.receiver, insert_expr.receiver) | ||
| && SpanlessEq::new(cx).eq_expr(contains_expr.value, insert_expr.value) | ||
| { | ||
| ControlFlow::Break(insert_expr) | ||
| } else { | ||
| ControlFlow::Continue(()) | ||
| } | ||
| }) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,83 @@ | ||
| #![allow(unused)] | ||
| #![allow(clippy::nonminimal_bool)] | ||
| #![allow(clippy::needless_borrow)] | ||
| #![warn(clippy::set_contains_or_insert)] | ||
|
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| use std::collections::HashSet; | ||
|
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||
| fn main() { | ||
| should_warn_cases(); | ||
|
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| should_not_warn_cases(); | ||
| } | ||
|
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| fn should_warn_cases() { | ||
| let mut set = HashSet::new(); | ||
| let value = 5; | ||
|
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| if !set.contains(&value) { | ||
| set.insert(value); | ||
| println!("Just a comment"); | ||
| } | ||
|
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| if set.contains(&value) { | ||
| set.insert(value); | ||
| println!("Just a comment"); | ||
| } | ||
|
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||
| if !set.contains(&value) { | ||
| set.insert(value); | ||
| } | ||
|
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| if !!set.contains(&value) { | ||
| set.insert(value); | ||
| println!("Just a comment"); | ||
| } | ||
|
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||
| if (&set).contains(&value) { | ||
| set.insert(value); | ||
| } | ||
|
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||
| let borrow_value = &6; | ||
| if !set.contains(borrow_value) { | ||
| set.insert(*borrow_value); | ||
| } | ||
|
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| let borrow_set = &mut set; | ||
| if !borrow_set.contains(&value) { | ||
| borrow_set.insert(value); | ||
| } | ||
| } | ||
|
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| fn should_not_warn_cases() { | ||
| let mut set = HashSet::new(); | ||
| let value = 5; | ||
| let another_value = 6; | ||
|
|
||
| if !set.contains(&value) { | ||
| set.insert(another_value); | ||
| } | ||
|
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||
| if !set.contains(&value) { | ||
| println!("Just a comment"); | ||
| } | ||
|
|
||
| if simply_true() { | ||
| set.insert(value); | ||
| } | ||
|
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||
| if !set.contains(&value) { | ||
| set.replace(value); //it is not insert | ||
| println!("Just a comment"); | ||
| } | ||
|
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| if set.contains(&value) { | ||
| println!("value is already in set"); | ||
| } else { | ||
| set.insert(value); | ||
| } | ||
| } | ||
|
|
||
| fn simply_true() -> bool { | ||
| true | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,61 @@ | ||
| error: usage of `HashSet::insert` after `HashSet::contains` | ||
| --> tests/ui/set_contains_or_insert.rs:18:13 | ||
| | | ||
| LL | if !set.contains(&value) { | ||
| | ^^^^^^^^^^^^^^^^ | ||
| LL | set.insert(value); | ||
| | ^^^^^^^^^^^^^ | ||
| | | ||
| = note: `-D clippy::set-contains-or-insert` implied by `-D warnings` | ||
| = help: to override `-D warnings` add `#[allow(clippy::set_contains_or_insert)]` | ||
|
|
||
| error: usage of `HashSet::insert` after `HashSet::contains` | ||
| --> tests/ui/set_contains_or_insert.rs:23:12 | ||
| | | ||
| LL | if set.contains(&value) { | ||
| | ^^^^^^^^^^^^^^^^ | ||
| LL | set.insert(value); | ||
| | ^^^^^^^^^^^^^ | ||
|
|
||
| error: usage of `HashSet::insert` after `HashSet::contains` | ||
| --> tests/ui/set_contains_or_insert.rs:28:13 | ||
| | | ||
| LL | if !set.contains(&value) { | ||
| | ^^^^^^^^^^^^^^^^ | ||
| LL | set.insert(value); | ||
| | ^^^^^^^^^^^^^ | ||
|
|
||
| error: usage of `HashSet::insert` after `HashSet::contains` | ||
| --> tests/ui/set_contains_or_insert.rs:32:14 | ||
| | | ||
| LL | if !!set.contains(&value) { | ||
| | ^^^^^^^^^^^^^^^^ | ||
| LL | set.insert(value); | ||
| | ^^^^^^^^^^^^^ | ||
|
|
||
| error: usage of `HashSet::insert` after `HashSet::contains` | ||
| --> tests/ui/set_contains_or_insert.rs:37:15 | ||
| | | ||
| LL | if (&set).contains(&value) { | ||
| | ^^^^^^^^^^^^^^^^ | ||
| LL | set.insert(value); | ||
| | ^^^^^^^^^^^^^ | ||
|
|
||
| error: usage of `HashSet::insert` after `HashSet::contains` | ||
| --> tests/ui/set_contains_or_insert.rs:42:13 | ||
| | | ||
| LL | if !set.contains(borrow_value) { | ||
| | ^^^^^^^^^^^^^^^^^^^^^^ | ||
| LL | set.insert(*borrow_value); | ||
| | ^^^^^^^^^^^^^^^^^^^^^ | ||
|
|
||
| error: usage of `HashSet::insert` after `HashSet::contains` | ||
| --> tests/ui/set_contains_or_insert.rs:47:20 | ||
| | | ||
| LL | if !borrow_set.contains(&value) { | ||
| | ^^^^^^^^^^^^^^^^ | ||
| LL | borrow_set.insert(value); | ||
| | ^^^^^^^^^^^^^ | ||
|
|
||
| error: aborting due to 7 previous errors | ||
|
|