1 files changed, 47 insertions, 3 deletions
diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs
index f61bb3a6bf4..098d3fca9b2 100644
--- a/clippy_lints/src/methods/mod.rs
+++ b/clippy_lints/src/methods/mod.rs
@@ -111,6 +111,7 @@ mod uninit_assumed_init;
 mod unit_hash;
 mod unnecessary_fallible_conversions;
 mod unnecessary_filter_map;
+mod unnecessary_first_then_check;
 mod unnecessary_fold;
 mod unnecessary_get_then_check;
 mod unnecessary_iter_cloned;
@@ -441,6 +442,17 @@ declare_clippy_lint! {
     ///     }
     /// }
     /// ```
+    ///
+    /// Use instead:
+    /// ```no_run
+    /// # struct X;
+    /// impl X {
+    ///     fn as_str(&self) -> &'static str {
+    ///         // ..
+    /// # ""
+    ///     }
+    /// }
+    /// ```
     #[clippy::version = "pre 1.29.0"]
     pub WRONG_SELF_CONVENTION,
     style,
@@ -3964,7 +3976,7 @@ declare_clippy_lint! {
     /// ```no_run
     /// let _ = 0;
     /// ```
-    #[clippy::version = "1.78.0"]
+    #[clippy::version = "1.81.0"]
     pub UNNECESSARY_MIN_OR_MAX,
     complexity,
     "using 'min()/max()' when there is no need for it"
@@ -4025,7 +4037,7 @@ declare_clippy_lint! {
     /// ```
     #[clippy::version = "1.78.0"]
     pub MANUAL_C_STR_LITERALS,
-    pedantic,
+    complexity,
     r#"creating a `CStr` through functions when `c""` literals can be used"#
 }
 
@@ -4099,7 +4111,7 @@ declare_clippy_lint! {
     /// ```no_run
     /// "foo".is_ascii();
     /// ```
-    #[clippy::version = "1.80.0"]
+    #[clippy::version = "1.81.0"]
     pub NEEDLESS_CHARACTER_ITERATION,
     suspicious,
     "is_ascii() called on a char iterator"
@@ -4126,6 +4138,34 @@ declare_clippy_lint! {
     "use of `map` returning the original item"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks the usage of `.first().is_some()` or `.first().is_none()` to check if a slice is
+    /// empty.
+    ///
+    /// ### Why is this bad?
+    /// Using `.is_empty()` is shorter and better communicates the intention.
+    ///
+    /// ### Example
+    /// ```no_run
+    /// let v = vec![1, 2, 3];
+    /// if v.first().is_none() {
+    ///     // The vector is empty...
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```no_run
+    /// let v = vec![1, 2, 3];
+    /// if v.is_empty() {
+    ///     // The vector is empty...
+    /// }
+    /// ```
+    #[clippy::version = "1.83.0"]
+    pub UNNECESSARY_FIRST_THEN_CHECK,
+    complexity,
+    "calling `.first().is_some()` or `.first().is_none()` instead of `.is_empty()`"
+}
+
 pub struct Methods {
     avoid_breaking_exported_api: bool,
     msrv: Msrv,
@@ -4283,6 +4323,7 @@ impl_lint_pass!(Methods => [
     UNNECESSARY_RESULT_MAP_OR_ELSE,
     MANUAL_C_STR_LITERALS,
     UNNECESSARY_GET_THEN_CHECK,
+    UNNECESSARY_FIRST_THEN_CHECK,
     NEEDLESS_CHARACTER_ITERATION,
     MANUAL_INSPECT,
     UNNECESSARY_MIN_OR_MAX,
@@ -5055,6 +5096,9 @@ fn check_is_some_is_none(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>,
         Some(("get", f_recv, [arg], _, _)) => {
             unnecessary_get_then_check::check(cx, call_span, recv, f_recv, arg, is_some);
         },
+        Some(("first", f_recv, [], _, _)) => {
+            unnecessary_first_then_check::check(cx, call_span, recv, f_recv, is_some);
+        },
         _ => {},
     }
 }