`map_identity` Add tests for needless `.map_err`

3 files changed, 11 insertions, 1 deletions

diff --git a/tests/ui/map_identity.fixed b/tests/ui/map_identity.fixed
index 4a1452b25f3..2256e51f2d0 100644
--- a/tests/ui/map_identity.fixed
+++ b/tests/ui/map_identity.fixed
@@ -16,6 +16,8 @@ fn main() {
     let _: Result<i8, f32> = Err(2.3).map(|x: i8| {
         return x + 3;
     });
+    let _: Result<u32, u32> = Ok(1);
+    let _: Result<u32, u32> = Ok(1).map_err(|a: u32| a * 42);
 }
 
 fn not_identity(x: &u16) -> u16 {
diff --git a/tests/ui/map_identity.rs b/tests/ui/map_identity.rs
index 65c7e6e1ea5..ccfdc9ea76d 100644
--- a/tests/ui/map_identity.rs
+++ b/tests/ui/map_identity.rs
@@ -18,6 +18,8 @@ fn main() {
     let _: Result<i8, f32> = Err(2.3).map(|x: i8| {
         return x + 3;
     });
+    let _: Result<u32, u32> = Ok(1).map_err(|a| a);
+    let _: Result<u32, u32> = Ok(1).map_err(|a: u32| a * 42);
 }
 
 fn not_identity(x: &u16) -> u16 {
diff --git a/tests/ui/map_identity.stderr b/tests/ui/map_identity.stderr
index e4a0320cbda..b6a77281f6d 100644
--- a/tests/ui/map_identity.stderr
+++ b/tests/ui/map_identity.stderr
@@ -33,5 +33,11 @@ LL | |         return x;
 LL | |     });
    | |______^ help: remove the call to `map`
 
-error: aborting due to 5 previous errors
+error: unnecessary map of the identity function
+  --> $DIR/map_identity.rs:21:36
+   |
+LL |     let _: Result<u32, u32> = Ok(1).map_err(|a| a);
+   |                                    ^^^^^^^^^^^^^^^ help: remove the call to `map_err`
+
+error: aborting due to 6 previous errors