map_identity Add tests for needless .map_err

rust-lang · Mar 1, 2022 · 3d1f83e · 3d1f83e
1 parent 35b1453
commit 3d1f83e
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diff --git 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
@@ -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
@@ -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