Auto merge of rust-lang#13241 - alex-semenyuk:fix_double_must_use, r=xFrednet

Fix confusing message in double_must_use lint

Close rust-lang#13003
As mentioned at rust-lang#13003 it isn't quite clear what it means "an empty `#[must_use]` attribute" so clarify it

changelog: [none]

Author: bors

clippy_lints/src/functions/must_use.rs

@@ -129,9 +129,9 @@ fn check_needless_must_use(
             cx,
             DOUBLE_MUST_USE,
             fn_header_span,
-            "this function has an empty `#[must_use]` attribute, but returns a type already marked as `#[must_use]`",
+            "this function has a `#[must_use]` attribute with no message, but returns a type already marked as `#[must_use]`",
             None,
-            "either add some descriptive text or remove the attribute",
+            "either add some descriptive message or remove the attribute",
         );
     }
 }

tests/ui/double_must_use.rs

@@ -3,19 +3,19 @@
 
 #[must_use]
 pub fn must_use_result() -> Result<(), ()> {
-    //~^ ERROR: this function has an empty `#[must_use]` attribute, but returns a type already
+    //~^ ERROR: this function has a `#[must_use]` attribute with no message, but returns a type already
     unimplemented!();
 }
 
 #[must_use]
 pub fn must_use_tuple() -> (Result<(), ()>, u8) {
-    //~^ ERROR: this function has an empty `#[must_use]` attribute, but returns a type already
+    //~^ ERROR: this function has a `#[must_use]` attribute with no message, but returns a type already
     unimplemented!();
 }
 
 #[must_use]
 pub fn must_use_array() -> [Result<(), ()>; 1] {
-    //~^ ERROR: this function has an empty `#[must_use]` attribute, but returns a type already
+    //~^ ERROR: this function has a `#[must_use]` attribute with no message, but returns a type already
     unimplemented!();
 }
 
@@ -32,7 +32,7 @@ async fn async_must_use() -> usize {
 
 #[must_use]
 async fn async_must_use_result() -> Result<(), ()> {
-    //~^ ERROR: this function has an empty `#[must_use]` attribute, but returns a type already
+    //~^ ERROR: this function has a `#[must_use]` attribute with no message, but returns a type already
     Ok(())
 }
 

tests/ui/double_must_use.stderr

@@ -1,36 +1,36 @@
-error: this function has an empty `#[must_use]` attribute, but returns a type already marked as `#[must_use]`
+error: this function has a `#[must_use]` attribute with no message, but returns a type already marked as `#[must_use]`
   --> tests/ui/double_must_use.rs:5:1
    |
 LL | pub fn must_use_result() -> Result<(), ()> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: either add some descriptive text or remove the attribute
+   = help: either add some descriptive message or remove the attribute
    = note: `-D clippy::double-must-use` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::double_must_use)]`
 
-error: this function has an empty `#[must_use]` attribute, but returns a type already marked as `#[must_use]`
+error: this function has a `#[must_use]` attribute with no message, but returns a type already marked as `#[must_use]`
   --> tests/ui/double_must_use.rs:11:1
    |
 LL | pub fn must_use_tuple() -> (Result<(), ()>, u8) {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: either add some descriptive text or remove the attribute
+   = help: either add some descriptive message or remove the attribute
 
-error: this function has an empty `#[must_use]` attribute, but returns a type already marked as `#[must_use]`
+error: this function has a `#[must_use]` attribute with no message, but returns a type already marked as `#[must_use]`
   --> tests/ui/double_must_use.rs:17:1
    |
 LL | pub fn must_use_array() -> [Result<(), ()>; 1] {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: either add some descriptive text or remove the attribute
+   = help: either add some descriptive message or remove the attribute
 
-error: this function has an empty `#[must_use]` attribute, but returns a type already marked as `#[must_use]`
+error: this function has a `#[must_use]` attribute with no message, but returns a type already marked as `#[must_use]`
   --> tests/ui/double_must_use.rs:34:1
    |
 LL | async fn async_must_use_result() -> Result<(), ()> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = help: either add some descriptive text or remove the attribute
+   = help: either add some descriptive message or remove the attribute
 
 error: aborting due to 4 previous errors