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

CHANGELOG.md

@@ -5455,6 +5455,7 @@ Released 2018-09-13
 [`comparison_to_empty`]: https://rust-lang.github.io/rust-clippy/master/index.html#comparison_to_empty
 [`const_is_empty`]: https://rust-lang.github.io/rust-clippy/master/index.html#const_is_empty
 [`const_static_lifetime`]: https://rust-lang.github.io/rust-clippy/master/index.html#const_static_lifetime
+[`contains_for_slice`]: https://rust-lang.github.io/rust-clippy/master/index.html#contains_for_slice
 [`copy_iterator`]: https://rust-lang.github.io/rust-clippy/master/index.html#copy_iterator
 [`crate_in_macro_def`]: https://rust-lang.github.io/rust-clippy/master/index.html#crate_in_macro_def
 [`create_dir`]: https://rust-lang.github.io/rust-clippy/master/index.html#create_dir

clippy_lints/src/declared_lints.rs

@@ -371,6 +371,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
     crate::methods::CLONE_ON_REF_PTR_INFO,
     crate::methods::COLLAPSIBLE_STR_REPLACE_INFO,
     crate::methods::CONST_IS_EMPTY_INFO,
+    crate::methods::CONTAINS_FOR_SLICE_INFO,
     crate::methods::DRAIN_COLLECT_INFO,
     crate::methods::ERR_EXPECT_INFO,
     crate::methods::EXPECT_FUN_CALL_INFO,

clippy_lints/src/methods/contains_for_slice.rs

@@ -0,0 +1,42 @@
+use clippy_utils::diagnostics::span_lint;
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::LateContext;
+use rustc_middle::ty::{self};
+
+use super::{CONTAINS_FOR_SLICE, 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"
+    {
+        // check if the receiver is a u8/i8 slice
+        let ref_type = cx.typeck_results().expr_ty(recv);
+
+        match ref_type.kind() {
+            ty::Ref(_, inner_type, _)
+                if inner_type.is_slice()
+                    && let ty::Slice(slice_type) = inner_type.kind()
+                    && (slice_type.to_string() == "u8" || slice_type.to_string() == "i8") =>
+            {
+                span_lint(
+                    cx,
+                    CONTAINS_FOR_SLICE,
+                    expr.span,
+                    "using `contains()` instead of `iter().any()` on u8/i8 slices is more efficient",
+                );
+            },
+            _ => {},
+        }
+    }
+}

clippy_lints/src/methods/mod.rs

@@ -14,6 +14,7 @@ mod clone_on_copy;
 mod clone_on_ref_ptr;
 mod cloned_instead_of_copied;
 mod collapsible_str_replace;
+mod contains_for_slice;
 mod drain_collect;
 mod err_expect;
 mod expect_fun_call;
@@ -4284,6 +4285,31 @@ 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` or `i8` and suggests using `contains()` instead.
+    ///
+    /// ### Why is this bad?
+    /// `iter().any()` on slices of `u8` or `i8` is optimized to use `memchr`.
+    ///
+    /// ### 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 CONTAINS_FOR_SLICE,
+    perf,
+    "using `contains()` instead of `iter().any()` on u8/i8 slices is more efficient"
+}
+
 pub struct Methods {
     avoid_breaking_exported_api: bool,
     msrv: Msrv,
@@ -4449,6 +4475,7 @@ impl_lint_pass!(Methods => [
     MAP_ALL_ANY_IDENTITY,
     MAP_WITH_UNUSED_ARGUMENT_OVER_RANGES,
     UNNECESSARY_MAP_OR,
+    CONTAINS_FOR_SLICE,
 ]);
 
 /// Extracts a method call name, args, and `Span` of the method name.
@@ -4683,6 +4710,7 @@ impl Methods {
                 ("any", [arg]) => {
                     unused_enumerate_index::check(cx, expr, recv, arg);
                     needless_character_iteration::check(cx, expr, recv, arg, false);
+                    contains_for_slice::check(cx, expr);
                     match method_call(recv) {
                         Some(("cloned", recv2, [], _, _)) => iter_overeager_cloned::check(
                             cx,

tests/ui/contains_for_slice.rs

@@ -0,0 +1,36 @@
+#![warn(clippy::contains_for_slice)]
+
+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);
+    // no error, because it's not a slice of u8/i8
+
+    let values: [u8; 6] = [3, 14, 15, 92, 6, 5];
+    let _ = values.iter().any(|&v| v == 10);
+    // no error, because it's an array
+
+    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)
+    // no error, because it's an array
+}

tests/ui/contains_for_slice.stderr

@@ -0,0 +1,17 @@
+error: using `contains()` instead of `iter().any()` on u8/i8 slices is more efficient
+  --> tests/ui/contains_for_slice.rs:6:13
+   |
+LL |     let _ = values.iter().any(|&v| v == 4);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: `-D clippy::contains-for-slice` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::contains_for_slice)]`
+
+error: using `contains()` instead of `iter().any()` on u8/i8 slices is more efficient
+  --> tests/ui/contains_for_slice.rs:29:5
+   |
+LL |     values.iter().any(|&v| v == 10)
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+