add manual_repeat_n lint

tests/ui/from_iter_instead_of_collect.fixed

@@ -1,6 +1,6 @@
 #![warn(clippy::from_iter_instead_of_collect)]
 #![allow(unused_imports)]
-#![allow(clippy::useless_vec)]
+#![allow(clippy::useless_vec, clippy::manual_repeat_n)]
 
 use std::collections::{BTreeMap, BTreeSet, HashMap, VecDeque};
 

tests/ui/from_iter_instead_of_collect.rs

@@ -1,6 +1,6 @@
 #![warn(clippy::from_iter_instead_of_collect)]
 #![allow(unused_imports)]
-#![allow(clippy::useless_vec)]
+#![allow(clippy::useless_vec, clippy::manual_repeat_n)]
 
 use std::collections::{BTreeMap, BTreeSet, HashMap, VecDeque};
 

tests/ui/manual_repeat_n.fixed

@@ -0,0 +1,30 @@
+#![warn(clippy::manual_repeat_n)]
+
+use std::iter::repeat;
+
+fn main() {
+    let _ = std::iter::repeat_n(10, 3);
+
+    let _ = std::iter::repeat_n(String::from("foo"), 4);
+
+    for value in std::iter::repeat_n(5, 3) {}
+
+    let _: Vec<_> = std::iter::repeat_n(String::from("bar"), 10).collect();
+
+    let _ = std::iter::repeat_n(vec![1, 2], 2);
+}
+
+mod foo_lib {
+    pub fn iter() -> std::iter::Take<std::iter::Repeat<&'static [u8]>> {
+        todo!()
+    }
+}
+
+fn foo() {
+    let _ = match 1 {
+        1 => foo_lib::iter(),
+        // Shouldn't lint because `external_lib::iter` doesn't return `std::iter::RepeatN`.
+        2 => std::iter::repeat([1, 2].as_slice()).take(2),
+        _ => todo!(),
+    };
+}

tests/ui/manual_repeat_n.rs

@@ -0,0 +1,30 @@
+#![warn(clippy::manual_repeat_n)]
+
+use std::iter::repeat;
+
+fn main() {
+    let _ = repeat(10).take(3);
+
+    let _ = repeat(String::from("foo")).take(4);
+
+    for value in std::iter::repeat(5).take(3) {}
+
+    let _: Vec<_> = std::iter::repeat(String::from("bar")).take(10).collect();
+
+    let _ = repeat(vec![1, 2]).take(2);
+}
+
+mod foo_lib {
+    pub fn iter() -> std::iter::Take<std::iter::Repeat<&'static [u8]>> {
+        todo!()
+    }
+}
+
+fn foo() {
+    let _ = match 1 {
+        1 => foo_lib::iter(),
+        // Shouldn't lint because `external_lib::iter` doesn't return `std::iter::RepeatN`.
+        2 => std::iter::repeat([1, 2].as_slice()).take(2),
+        _ => todo!(),
+    };
+}

tests/ui/manual_repeat_n.stderr

@@ -0,0 +1,35 @@
+error: this `repeat().take()` can be written more concisely
+  --> tests/ui/manual_repeat_n.rs:6:13
+   |
+LL |     let _ = repeat(10).take(3);
+   |             ^^^^^^^^^^^^^^^^^^ help: consider using `repeat_n()` instead: `std::iter::repeat_n(10, 3)`
+   |
+   = note: `-D clippy::manual-repeat-n` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(clippy::manual_repeat_n)]`
+
+error: this `repeat().take()` can be written more concisely
+  --> tests/ui/manual_repeat_n.rs:8:13
+   |
+LL |     let _ = repeat(String::from("foo")).take(4);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `repeat_n()` instead: `std::iter::repeat_n(String::from("foo"), 4)`
+
+error: this `repeat().take()` can be written more concisely
+  --> tests/ui/manual_repeat_n.rs:10:18
+   |
+LL |     for value in std::iter::repeat(5).take(3) {}
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `repeat_n()` instead: `std::iter::repeat_n(5, 3)`
+
+error: this `repeat().take()` can be written more concisely
+  --> tests/ui/manual_repeat_n.rs:12:21
+   |
+LL |     let _: Vec<_> = std::iter::repeat(String::from("bar")).take(10).collect();
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `repeat_n()` instead: `std::iter::repeat_n(String::from("bar"), 10)`
+
+error: this `repeat().take()` can be written more concisely
+  --> tests/ui/manual_repeat_n.rs:14:13
+   |
+LL |     let _ = repeat(vec![1, 2]).take(2);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider using `repeat_n()` instead: `std::iter::repeat_n(vec![1, 2], 2)`
+
+error: aborting due to 5 previous errors
+

tests/ui/manual_str_repeat.fixed

@@ -1,4 +1,4 @@
-#![allow(non_local_definitions)]
+#![allow(non_local_definitions, clippy::manual_repeat_n)]
 #![warn(clippy::manual_str_repeat)]
 
 use std::borrow::Cow;

tests/ui/manual_str_repeat.rs

@@ -1,4 +1,4 @@
-#![allow(non_local_definitions)]
+#![allow(non_local_definitions, clippy::manual_repeat_n)]
 #![warn(clippy::manual_str_repeat)]
 
 use std::borrow::Cow;

tests/ui/slow_vector_initialization.fixed

@@ -1,4 +1,5 @@
-#![allow(clippy::useless_vec)]
+#![allow(clippy::useless_vec, clippy::manual_repeat_n)]
+
 use std::iter::repeat;
 fn main() {
     resize_vector();

tests/ui/slow_vector_initialization.rs

@@ -1,4 +1,5 @@
-#![allow(clippy::useless_vec)]
+#![allow(clippy::useless_vec, clippy::manual_repeat_n)]
+
 use std::iter::repeat;
 fn main() {
     resize_vector();

tests/ui/slow_vector_initialization.stderr

@@ -1,5 +1,5 @@
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:13:20
+  --> tests/ui/slow_vector_initialization.rs:14:20
    |
 LL |       let mut vec1 = Vec::with_capacity(len);
    |  ____________________^
@@ -11,7 +11,7 @@ LL | |     vec1.extend(repeat(0).take(len));
    = help: to override `-D warnings` add `#[allow(clippy::slow_vector_initialization)]`
 
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:19:20
+  --> tests/ui/slow_vector_initialization.rs:20:20
    |
 LL |       let mut vec2 = Vec::with_capacity(len - 10);
    |  ____________________^
@@ -20,7 +20,7 @@ LL | |     vec2.extend(repeat(0).take(len - 10));
    | |_________________________________________^ help: consider replacing this with: `vec![0; len - 10]`
 
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:27:20
+  --> tests/ui/slow_vector_initialization.rs:28:20
    |
 LL |       let mut vec4 = Vec::with_capacity(len);
    |  ____________________^
@@ -29,7 +29,7 @@ LL | |     vec4.extend(repeat(0).take(vec4.capacity()));
    | |________________________________________________^ help: consider replacing this with: `vec![0; len]`
 
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:38:27
+  --> tests/ui/slow_vector_initialization.rs:39:27
    |
 LL |       let mut resized_vec = Vec::with_capacity(30);
    |  ___________________________^
@@ -38,7 +38,7 @@ LL | |     resized_vec.resize(30, 0);
    | |_____________________________^ help: consider replacing this with: `vec![0; 30]`
 
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:42:26
+  --> tests/ui/slow_vector_initialization.rs:43:26
    |
 LL |       let mut extend_vec = Vec::with_capacity(30);
    |  __________________________^
@@ -47,7 +47,7 @@ LL | |     extend_vec.extend(repeat(0).take(30));
    | |_________________________________________^ help: consider replacing this with: `vec![0; 30]`
 
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:50:20
+  --> tests/ui/slow_vector_initialization.rs:51:20
    |
 LL |       let mut vec1 = Vec::with_capacity(len);
    |  ____________________^
@@ -56,7 +56,7 @@ LL | |     vec1.resize(len, 0);
    | |_______________________^ help: consider replacing this with: `vec![0; len]`
 
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:59:20
+  --> tests/ui/slow_vector_initialization.rs:60:20
    |
 LL |       let mut vec3 = Vec::with_capacity(len - 10);
    |  ____________________^
@@ -65,7 +65,7 @@ LL | |     vec3.resize(len - 10, 0);
    | |____________________________^ help: consider replacing this with: `vec![0; len - 10]`
 
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:63:20
+  --> tests/ui/slow_vector_initialization.rs:64:20
    |
 LL |       let mut vec4 = Vec::with_capacity(len);
    |  ____________________^
@@ -74,7 +74,7 @@ LL | |     vec4.resize(vec4.capacity(), 0);
    | |___________________________________^ help: consider replacing this with: `vec![0; len]`
 
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:68:12
+  --> tests/ui/slow_vector_initialization.rs:69:12
    |
 LL |       vec1 = Vec::with_capacity(10);
    |  ____________^
@@ -83,7 +83,7 @@ LL | |     vec1.resize(10, 0);
    | |______________________^ help: consider replacing this with: `vec![0; 10]`
 
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:76:20
+  --> tests/ui/slow_vector_initialization.rs:77:20
    |
 LL |       let mut vec1 = Vec::new();
    |  ____________________^
@@ -92,7 +92,7 @@ LL | |     vec1.resize(len, 0);
    | |_______________________^ help: consider replacing this with: `vec![0; len]`
 
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:81:20
+  --> tests/ui/slow_vector_initialization.rs:82:20
    |
 LL |       let mut vec3 = Vec::new();
    |  ____________________^
@@ -101,7 +101,7 @@ LL | |     vec3.resize(len - 10, 0);
    | |____________________________^ help: consider replacing this with: `vec![0; len - 10]`
 
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:86:12
+  --> tests/ui/slow_vector_initialization.rs:87:12
    |
 LL |       vec1 = Vec::new();
    |  ____________^
@@ -110,7 +110,7 @@ LL | |     vec1.resize(10, 0);
    | |______________________^ help: consider replacing this with: `vec![0; 10]`
 
 error: slow zero-filling initialization
-  --> tests/ui/slow_vector_initialization.rs:90:12
+  --> tests/ui/slow_vector_initialization.rs:91:12
    |
 LL |       vec1 = vec![];
    |  ____________^