Add tests to ensure that map_clone is not emitted if as_ref().clone() is present

Author: GuillaumeGomez

tests/ui/map_clone.fixed

@@ -5,6 +5,7 @@
     clippy::many_single_char_names,
     clippy::redundant_clone,
     clippy::redundant_closure,
+    clippy::useless_asref,
     clippy::useless_vec
 )]
 
@@ -76,4 +77,11 @@ fn main() {
     let x = x.as_ref(); // We do this to prevent triggering the `useless_asref` lint.
     let y = x.cloned();
     //~^ ERROR: you are explicitly cloning with `.map()`
+    let y = x.cloned();
+
+    // We ensure that no warning is emitted here because `useless_asref` is taking over.
+    let x = Some(String::new());
+    let y = x.as_ref().map(|x| String::clone(x));
+    let x: Result<String, ()> = Ok(String::new());
+    let y = x.as_ref().map(|x| String::clone(x));
 }

tests/ui/map_clone.rs

@@ -5,6 +5,7 @@
     clippy::many_single_char_names,
     clippy::redundant_clone,
     clippy::redundant_closure,
+    clippy::useless_asref,
     clippy::useless_vec
 )]
 
@@ -76,4 +77,11 @@ fn main() {
     let x = x.as_ref(); // We do this to prevent triggering the `useless_asref` lint.
     let y = x.map(|x| String::clone(x));
     //~^ ERROR: you are explicitly cloning with `.map()`
+    let y = x.map(|x| String::clone(x));
+
+    // We ensure that no warning is emitted here because `useless_asref` is taking over.
+    let x = Some(String::new());
+    let y = x.as_ref().map(|x| String::clone(x));
+    let x: Result<String, ()> = Ok(String::new());
+    let y = x.as_ref().map(|x| String::clone(x));
 }

tests/ui/map_clone.stderr

@@ -1,5 +1,5 @@
 error: you are using an explicit closure for copying elements
-  --> $DIR/map_clone.rs:12:22
+  --> $DIR/map_clone.rs:13:22
    |
 LL |     let _: Vec<i8> = vec![5_i8; 6].iter().map(|x| *x).collect();
    |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider calling the dedicated `copied` method: `vec![5_i8; 6].iter().copied()`
@@ -8,58 +8,64 @@ LL |     let _: Vec<i8> = vec![5_i8; 6].iter().map(|x| *x).collect();
    = help: to override `-D warnings` add `#[allow(clippy::map_clone)]`
 
 error: you are using an explicit closure for cloning elements
-  --> $DIR/map_clone.rs:13:26
+  --> $DIR/map_clone.rs:14:26
    |
 LL |     let _: Vec<String> = vec![String::new()].iter().map(|x| x.clone()).collect();
    |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider calling the dedicated `cloned` method: `vec![String::new()].iter().cloned()`
 
 error: you are using an explicit closure for copying elements
-  --> $DIR/map_clone.rs:14:23
+  --> $DIR/map_clone.rs:15:23
    |
 LL |     let _: Vec<u32> = vec![42, 43].iter().map(|&x| x).collect();
    |                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider calling the dedicated `copied` method: `vec![42, 43].iter().copied()`
 
 error: you are using an explicit closure for copying elements
-  --> $DIR/map_clone.rs:16:26
+  --> $DIR/map_clone.rs:17:26
    |
 LL |     let _: Option<u64> = Some(&16).map(|b| *b);
    |                          ^^^^^^^^^^^^^^^^^^^^^ help: consider calling the dedicated `copied` method: `Some(&16).copied()`
 
 error: you are using an explicit closure for copying elements
-  --> $DIR/map_clone.rs:17:25
+  --> $DIR/map_clone.rs:18:25
    |
 LL |     let _: Option<u8> = Some(&1).map(|x| x.clone());
    |                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider calling the dedicated `copied` method: `Some(&1).copied()`
 
 error: you are needlessly cloning iterator elements
-  --> $DIR/map_clone.rs:28:29
+  --> $DIR/map_clone.rs:29:29
    |
 LL |     let _ = std::env::args().map(|v| v.clone());
    |                             ^^^^^^^^^^^^^^^^^^^ help: remove the `map` call
 
 error: you are explicitly cloning with `.map()`
-  --> $DIR/map_clone.rs:67:13
+  --> $DIR/map_clone.rs:68:13
    |
 LL |     let y = x.map(|x| String::clone(x));
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider calling the dedicated `cloned` method: `x.cloned()`
 
 error: you are explicitly cloning with `.map()`
-  --> $DIR/map_clone.rs:69:13
+  --> $DIR/map_clone.rs:70:13
    |
 LL |     let y = x.map(Clone::clone);
    |             ^^^^^^^^^^^^^^^^^^^ help: consider calling the dedicated `cloned` method: `x.cloned()`
 
 error: you are explicitly cloning with `.map()`
-  --> $DIR/map_clone.rs:71:13
+  --> $DIR/map_clone.rs:72:13
    |
 LL |     let y = x.map(String::clone);
    |             ^^^^^^^^^^^^^^^^^^^^ help: consider calling the dedicated `cloned` method: `x.cloned()`
 
 error: you are explicitly cloning with `.map()`
-  --> $DIR/map_clone.rs:77:13
+  --> $DIR/map_clone.rs:78:13
    |
 LL |     let y = x.map(|x| String::clone(x));
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider calling the dedicated `cloned` method: `x.cloned()`
 
-error: aborting due to 10 previous errors
+error: you are explicitly cloning with `.map()`
+  --> $DIR/map_clone.rs:80:13
+   |
+LL |     let y = x.map(|x| String::clone(x));
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider calling the dedicated `cloned` method: `x.cloned()`
+
+error: aborting due to 11 previous errors