new lint to detect inefficient iter().any()

CHANGELOG.md

@@ -6020,6 +6020,7 @@ Released 2018-09-13
 [`size_of_in_element_count`]: https://rust-lang.github.io/rust-clippy/master/index.html#size_of_in_element_count
 [`size_of_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#size_of_ref
 [`skip_while_next`]: https://rust-lang.github.io/rust-clippy/master/index.html#skip_while_next
+[`slice_iter_any`]: https://rust-lang.github.io/rust-clippy/master/index.html#slice_iter_any
 [`slow_vector_initialization`]: https://rust-lang.github.io/rust-clippy/master/index.html#slow_vector_initialization
 [`stable_sort_primitive`]: https://rust-lang.github.io/rust-clippy/master/index.html#stable_sort_primitive
 [`std_instead_of_alloc`]: https://rust-lang.github.io/rust-clippy/master/index.html#std_instead_of_alloc
@@ -6115,6 +6116,7 @@ Released 2018-09-13
 [`unnecessary_first_then_check`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_first_then_check
 [`unnecessary_fold`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_fold
 [`unnecessary_get_then_check`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_get_then_check
+[`unnecessary_iter_any`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_iter_any
 [`unnecessary_join`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_join
 [`unnecessary_lazy_evaluations`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_lazy_evaluations
 [`unnecessary_literal_bound`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_literal_bound

clippy_lints/src/declared_lints.rs

@@ -464,6 +464,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
     crate::methods::SHOULD_IMPLEMENT_TRAIT_INFO,
     crate::methods::SINGLE_CHAR_ADD_STR_INFO,
     crate::methods::SKIP_WHILE_NEXT_INFO,
+    crate::methods::SLICE_ITER_ANY_INFO,
     crate::methods::STABLE_SORT_PRIMITIVE_INFO,
     crate::methods::STRING_EXTEND_CHARS_INFO,
     crate::methods::STRING_LIT_CHARS_ANY_INFO,
@@ -482,6 +483,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
     crate::methods::UNNECESSARY_FIRST_THEN_CHECK_INFO,
     crate::methods::UNNECESSARY_FOLD_INFO,
     crate::methods::UNNECESSARY_GET_THEN_CHECK_INFO,
+    crate::methods::UNNECESSARY_ITER_ANY_INFO,
     crate::methods::UNNECESSARY_JOIN_INFO,
     crate::methods::UNNECESSARY_LAZY_EVALUATIONS_INFO,
     crate::methods::UNNECESSARY_LITERAL_UNWRAP_INFO,

clippy_lints/src/methods/iter_any.rs

@@ -0,0 +1,60 @@
+use clippy_utils::diagnostics::span_lint;
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::LateContext;
+use rustc_middle::ty::{self};
+
+use super::{SLICE_ITER_ANY, UNNECESSARY_ITER_ANY, method_call};
+
+pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>) {
+    if !expr.span.from_expansion()
+    // any()
+    && let Some((name, recv, args, _, _)) = method_call(expr)
+    && name == "any"
+    // check if the inner closure is a equality check
+    && args.len() == 1
+    && let ExprKind::Closure(closure) = args[0].kind
+    && let body = cx.tcx.hir().body(closure.body)
+    && let ExprKind::Binary(op, _, _) = body.value.kind
+    && op.node == rustc_ast::ast::BinOpKind::Eq
+    // iter()
+    && let Some((name, recv, _, _, _)) = method_call(recv)
+    && name == "iter"
+    {
+        let ref_type = cx.typeck_results().expr_ty(recv);
+
+        match ref_type.kind() {
+            ty::Ref(_, inner_type, _) if inner_type.is_slice() => {
+                // check if the receiver is a u8/i8 slice
+                if let ty::Slice(slice_type) = inner_type.kind()
+                    && (slice_type.to_string() == "u8" || slice_type.to_string() == "i8")
+                {
+                    span_lint(
+                        cx,
+                        SLICE_ITER_ANY,
+                        expr.span,
+                        "using `contains()` instead of `iter().any()` on u8/i8 slices is more efficient",
+                    );
+                } else if let ty::Slice(slice_type) = inner_type.kind()
+                    && slice_type.is_numeric()
+                {
+                    span_lint(
+                        cx,
+                        UNNECESSARY_ITER_ANY,
+                        expr.span,
+                        "using `contains()` instead of `iter().any()` is more readable",
+                    );
+                }
+            },
+            // if it's an array that uses `iter().any()` and its closure is an equality check, suggest using
+            // `contains()` (currently only for numeric arrays because of the difficulty in determining whether
+            // `contains()` can be replaced by `contains()` for arrays of general types)
+            ty::Array(array_type, _) if array_type.is_numeric() => span_lint(
+                cx,
+                UNNECESSARY_ITER_ANY,
+                expr.span,
+                "using `contains()` instead of `iter().any()` is more readable",
+            ),
+            _ => {},
+        }
+    }
+}

clippy_lints/src/methods/mod.rs

@@ -37,6 +37,7 @@ mod inspect_for_each;
 mod into_iter_on_ref;
 mod is_digit_ascii_radix;
 mod is_empty;
+mod iter_any;
 mod iter_cloned_collect;
 mod iter_count;
 mod iter_filter;
@@ -4284,6 +4285,54 @@ declare_clippy_lint! {
     "map of a trivial closure (not dependent on parameter) over a range"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for usage of `iter().any()` on slices of `u8`/`i8` when it can be replaced with `contains()` and suggests doing so.
+    ///
+    /// ### Why is this bad?
+    /// `contains()` on slices of `u8`/`i8` is faster than `iter().any()` in such cases.
+    ///
+    /// ### Example
+    /// ```no_run
+    /// fn foo(values: &[u8]) -> bool {
+    ///    values.iter().any(|&v| v == 10)
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```no_run
+    /// fn foo(values: &[u8]) -> bool {
+    ///    values.contains(&10)
+    /// }
+    /// ```
+    #[clippy::version = "1.85.0"]
+    pub SLICE_ITER_ANY,
+    perf,
+    "using `contains()` instead of `iter().any()` on `u8`/`i8` slices is more fast"
+}
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for usage of `iter().any()` when it can be replaced with `contains()` and suggests doing so.
+    ///
+    /// ### Why is this bad?
+    /// It makes the code less readable.
+    ///
+    /// ### Example
+    /// ```no_run
+    /// let values = &[1, 2, 3];
+    /// let _ = values.iter().any(|&v| v == 2);
+    /// ```
+    /// Use instead:
+    /// ```no_run
+    /// let values = &[1, 2, 3];
+    /// let _ = values.contains(&2);
+    /// ```
+    #[clippy::version = "1.85.0"]
+    pub UNNECESSARY_ITER_ANY,
+    style,
+    "using `contains()` instead of `iter().any()` is more readable"
+}
+
 pub struct Methods {
     avoid_breaking_exported_api: bool,
     msrv: Msrv,
@@ -4449,6 +4498,8 @@ impl_lint_pass!(Methods => [
     MAP_ALL_ANY_IDENTITY,
     MAP_WITH_UNUSED_ARGUMENT_OVER_RANGES,
     UNNECESSARY_MAP_OR,
+    SLICE_ITER_ANY,
+    UNNECESSARY_ITER_ANY,
 ]);
 
 /// Extracts a method call name, args, and `Span` of the method name.
@@ -4683,6 +4734,7 @@ impl Methods {
                 ("any", [arg]) => {
                     unused_enumerate_index::check(cx, expr, recv, arg);
                     needless_character_iteration::check(cx, expr, recv, arg, false);
+                    iter_any::check(cx, expr);
                     match method_call(recv) {
                         Some(("cloned", recv2, [], _, _)) => iter_overeager_cloned::check(
                             cx,

tests/ui/iter_any.rs

@@ -0,0 +1,36 @@
+#![warn(clippy::slice_iter_any)]
+
+fn main() {
+    let vec: Vec<u8> = vec![1, 2, 3, 4, 5, 6];
+    let values = &vec[..];
+    let _ = values.iter().any(|&v| v == 4);
+    //~^ ERROR: using `contains()` instead of `iter().any()` on u8/i8 slices is more efficient
+
+    let vec: Vec<u8> = vec![1, 2, 3, 4, 5, 6];
+    let values = &vec[..];
+    let _ = values.contains(&4);
+    // no error, because it uses `contains()`
+
+    let vec: Vec<u32> = vec![1, 2, 3, 4, 5, 6];
+    let values = &vec[..];
+    let _ = values.iter().any(|&v| v == 4);
+    //~^ ERROR: using `contains()` instead of `iter().any()` is more readable
+
+    let values: [u8; 6] = [3, 14, 15, 92, 6, 5];
+    let _ = values.iter().any(|&v| v == 10);
+    //~^ ERROR: using `contains()` instead of `iter().any()` is more readable
+
+    let values: [u8; 6] = [3, 14, 15, 92, 6, 5];
+    let _ = values.iter().any(|&v| v > 10);
+    // no error, because this `any()` is not for equality
+}
+
+fn foo(values: &[u8]) -> bool {
+    values.iter().any(|&v| v == 10)
+    //~^ ERROR: using `contains()` instead of `iter().any()` on u8/i8 slices is more efficient
+}
+
+fn bar(values: [u8; 3]) -> bool {
+    values.iter().any(|&v| v == 10)
+    //~^ ERROR: using `contains()` instead of `iter().any()` is more readable
+}

tests/ui/iter_any.stderr

@@ -0,0 +1,38 @@
+error: using `contains()` instead of `iter().any()` on u8/i8 slices is more efficient
+  --> tests/ui/iter_any.rs:6:13
+   |
+LL |     let _ = values.iter().any(|&v| v == 4);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::slice-iter-any` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::slice_iter_any)]`
+
+error: using `contains()` instead of `iter().any()` is more readable
+  --> tests/ui/iter_any.rs:16:13
+   |
+LL |     let _ = values.iter().any(|&v| v == 4);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::unnecessary-iter-any` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::unnecessary_iter_any)]`
+
+error: using `contains()` instead of `iter().any()` is more readable
+  --> tests/ui/iter_any.rs:20:13
+   |
+LL |     let _ = values.iter().any(|&v| v == 10);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: using `contains()` instead of `iter().any()` on u8/i8 slices is more efficient
+  --> tests/ui/iter_any.rs:29:5
+   |
+LL |     values.iter().any(|&v| v == 10)
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: using `contains()` instead of `iter().any()` is more readable
+  --> tests/ui/iter_any.rs:34:5
+   |
+LL |     values.iter().any(|&v| v == 10)
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 5 previous errors
+

tests/ui/needless_collect.fixed

@@ -3,7 +3,12 @@
 use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, LinkedList};
 
 #[warn(clippy::needless_collect)]
-#[allow(unused_variables, clippy::iter_cloned_collect, clippy::iter_next_slice)]
+#[allow(
+    unused_variables,
+    clippy::unnecessary_iter_any,
+    clippy::iter_cloned_collect,
+    clippy::iter_next_slice
+)]
 fn main() {
     let sample = [1; 5];
     let len = sample.iter().count();

tests/ui/needless_collect.rs

@@ -3,7 +3,12 @@
 use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, LinkedList};
 
 #[warn(clippy::needless_collect)]
-#[allow(unused_variables, clippy::iter_cloned_collect, clippy::iter_next_slice)]
+#[allow(
+    unused_variables,
+    clippy::unnecessary_iter_any,
+    clippy::iter_cloned_collect,
+    clippy::iter_next_slice
+)]
 fn main() {
     let sample = [1; 5];
     let len = sample.iter().collect::<Vec<_>>().len();