Move RepeatOnce into Methods lint pass

clippy_lints/src/methods/mod.rs

@@ -65,6 +65,7 @@ mod or_fun_call;
 mod or_then_unwrap;
 mod path_buf_push_overwrite;
 mod range_zip_with_len;
+mod repeat_once;
 mod search_is_some;
 mod single_char_add_str;
 mod single_char_insert_string;
@@ -2760,6 +2761,38 @@ declare_clippy_lint! {
     "zipping iterator with a range when `enumerate()` would do"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for usage of `.repeat(1)` and suggest the following method for each types.
+    /// - `.to_string()` for `str`
+    /// - `.clone()` for `String`
+    /// - `.to_vec()` for `slice`
+    ///
+    /// The lint will evaluate constant expressions and values as arguments of `.repeat(..)` and emit a message if
+    /// they are equivalent to `1`. (Related discussion in [rust-clippy#7306](https://github.com/rust-lang/rust-clippy/issues/7306))
+    ///
+    /// ### Why is this bad?
+    /// For example, `String.repeat(1)` is equivalent to `.clone()`. If cloning
+    /// the string is the intention behind this, `clone()` should be used.
+    ///
+    /// ### Example
+    /// ```rust
+    /// fn main() {
+    ///     let x = String::from("hello world").repeat(1);
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// fn main() {
+    ///     let x = String::from("hello world").clone();
+    /// }
+    /// ```
+    #[clippy::version = "1.47.0"]
+    pub REPEAT_ONCE,
+    complexity,
+    "using `.repeat(1)` instead of `String.clone()`, `str.to_string()` or `slice.to_vec()` "
+}
+
 pub struct Methods {
     avoid_breaking_exported_api: bool,
     msrv: Option<RustcVersion>,
@@ -2875,6 +2908,7 @@ impl_lint_pass!(Methods => [
     NONSENSICAL_OPEN_OPTIONS,
     PATH_BUF_PUSH_OVERWRITE,
     RANGE_ZIP_WITH_LEN,
+    REPEAT_ONCE,
 ]);
 
 /// Extracts a method call name, args, and `Span` of the method name.
@@ -3263,6 +3297,9 @@ impl Methods {
                 ("push", [arg]) => {
                     path_buf_push_overwrite::check(cx, expr, arg);
                 },
+                ("repeat", [arg]) => {
+                    repeat_once::check(cx, expr, recv, arg);
+                },
                 ("splitn" | "rsplitn", [count_arg, pat_arg]) => {
                     if let Some((Constant::Int(count), _)) = constant(cx, cx.typeck_results(), count_arg) {
                         suspicious_splitn::check(cx, name, expr, recv, count);