test: add a test and bless tests

Author: Kcang-gna

tests/ui/lint/dropping_copy_types-issue-125189-can-not-fixed.stderr

@@ -6,7 +6,7 @@ LL |         0 => drop(y),
    |                   |
    |                   argument has type `i32`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+   = note: use `let _ = y` simply to ignore the expression or result
 note: the lint level is defined here
   --> $DIR/dropping_copy_types-issue-125189-can-not-fixed.rs:3:9
    |
@@ -21,7 +21,7 @@ LL |         1 => drop(z),
    |                   |
    |                   argument has type `i32`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+   = note: use `let _ = z` simply to ignore the expression or result
 
 error: calls to `std::mem::drop` with a value that implements `Copy` does nothing
   --> $DIR/dropping_copy_types-issue-125189-can-not-fixed.rs:11:14
@@ -31,7 +31,7 @@ LL |         2 => drop(3),
    |                   |
    |                   argument has type `i32`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+   = note: use `let _ = 3` simply to ignore the expression or result
 
 error: aborting due to 3 previous errors
 

tests/ui/lint/dropping_copy_types-issue-125189.stderr

@@ -11,7 +11,7 @@ note: the lint level is defined here
    |
 LL | #![deny(dropping_copy_types)]
    |         ^^^^^^^^^^^^^^^^^^^
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = 3.2` simply to ignore the expression or result
    |
 LL -     drop(3.2);
 LL +     let _ = 3.2;
@@ -25,7 +25,7 @@ LL |     drop(y);
    |          |
    |          argument has type `i32`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = y` simply to ignore the expression or result
    |
 LL -     drop(y);
 LL +     let _ = y;

tests/ui/lint/dropping_copy_types-macros.stderr

@@ -11,7 +11,7 @@ note: the lint level is defined here
    |
 LL | #![deny(dropping_copy_types)]
    |         ^^^^^^^^^^^^^^^^^^^
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = writeln!(&mut msg, "test")` simply to ignore the expression or result
    |
 LL -     drop(writeln!(&mut msg, "test"));
 LL +     let _ = writeln!(&mut msg, "test");
@@ -25,7 +25,7 @@ LL |     drop(format_args!("a"));
    |          |
    |          argument has type `Arguments<'_>`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = format_args!("a")` simply to ignore the expression or result
    |
 LL -     drop(format_args!("a"));
 LL +     let _ = format_args!("a");

tests/ui/lint/dropping_copy_types.stderr

@@ -11,7 +11,7 @@ note: the lint level is defined here
    |
 LL | #![warn(dropping_copy_types)]
    |         ^^^^^^^^^^^^^^^^^^^
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = s1` simply to ignore the expression or result
    |
 LL -     drop(s1);
 LL +     let _ = s1;
@@ -25,13 +25,13 @@ LL |     drop(s2);
    |          |
    |          argument has type `SomeStruct`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = s2` simply to ignore the expression or result
    |
 LL -     drop(s2);
 LL +     let _ = s2;
    |
 
-warning: calls to `std::mem::drop` with a reference instead of an owned value does nothing
+warning: calls to `std::mem::drop` with a reference does not drop the underline value
   --> $DIR/dropping_copy_types.rs:36:5
    |
 LL |     drop(s3);
@@ -40,7 +40,7 @@ LL |     drop(s3);
    |          argument has type `&SomeStruct`
    |
    = note: `#[warn(dropping_references)]` on by default
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = s3` simply to ignore the expression or result
    |
 LL -     drop(s3);
 LL +     let _ = s3;
@@ -54,49 +54,49 @@ LL |     drop(s4);
    |          |
    |          argument has type `SomeStruct`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = s4` simply to ignore the expression or result
    |
 LL -     drop(s4);
 LL +     let _ = s4;
    |
 
-warning: calls to `std::mem::drop` with a reference instead of an owned value does nothing
+warning: calls to `std::mem::drop` with a reference does not drop the underline value
   --> $DIR/dropping_copy_types.rs:38:5
    |
 LL |     drop(s5);
    |     ^^^^^--^
    |          |
    |          argument has type `&SomeStruct`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = s5` simply to ignore the expression or result
    |
 LL -     drop(s5);
 LL +     let _ = s5;
    |
 
-warning: calls to `std::mem::drop` with a reference instead of an owned value does nothing
+warning: calls to `std::mem::drop` with a reference does not drop the underline value
   --> $DIR/dropping_copy_types.rs:50:5
    |
 LL |     drop(a2);
    |     ^^^^^--^
    |          |
    |          argument has type `&AnotherStruct`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = a2` simply to ignore the expression or result
    |
 LL -     drop(a2);
 LL +     let _ = a2;
    |
 
-warning: calls to `std::mem::drop` with a reference instead of an owned value does nothing
+warning: calls to `std::mem::drop` with a reference does not drop the underline value
   --> $DIR/dropping_copy_types.rs:52:5
    |
 LL |     drop(a4);
    |     ^^^^^--^
    |          |
    |          argument has type `&AnotherStruct`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = a4` simply to ignore the expression or result
    |
 LL -     drop(a4);
 LL +     let _ = a4;
@@ -110,7 +110,7 @@ LL |             drop(println_and(13));
    |                  |
    |                  argument has type `i32`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = println_and(13)` simply to ignore the expression or result
    |
 LL -             drop(println_and(13));
 LL +             let _ = println_and(13);
@@ -124,7 +124,7 @@ LL |         3 if drop(println_and(14)) == () => (),
    |                   |
    |                   argument has type `i32`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+   = note: use `let _ = println_and(14)` simply to ignore the expression or result
 
 warning: calls to `std::mem::drop` with a value that implements `Copy` does nothing
   --> $DIR/dropping_copy_types.rs:76:14
@@ -134,7 +134,7 @@ LL |         4 => drop(2),
    |                   |
    |                   argument has type `i32`
    |
-   = note: use `let _ = ...` to ignore the expression or result
+   = note: use `let _ = 2` simply to ignore the expression or result
 
 warning: 10 warnings emitted
 

tests/ui/lint/dropping_references-can-fixed.stderr

@@ -1,4 +1,4 @@
-error: calls to `std::mem::drop` with a reference instead of an owned value does nothing
+error: calls to `std::mem::drop` with a reference does not drop the underline value
   --> $DIR/dropping_references-can-fixed.rs:9:5
    |
 LL |     drop(&SomeStruct);
@@ -11,105 +11,105 @@ note: the lint level is defined here
    |
 LL | #![deny(dropping_references)]
    |         ^^^^^^^^^^^^^^^^^^^
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = &SomeStruct` simply to ignore the expression or result
    |
 LL -     drop(&SomeStruct);
 LL +     let _ = &SomeStruct;
    |
 
-error: calls to `std::mem::drop` with a reference instead of an owned value does nothing
+error: calls to `std::mem::drop` with a reference does not drop the underline value
   --> $DIR/dropping_references-can-fixed.rs:12:5
    |
 LL |     drop(&owned1);
    |     ^^^^^-------^
    |          |
    |          argument has type `&SomeStruct`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = &owned1` simply to ignore the expression or result
    |
 LL -     drop(&owned1);
 LL +     let _ = &owned1;
    |
 
-error: calls to `std::mem::drop` with a reference instead of an owned value does nothing
+error: calls to `std::mem::drop` with a reference does not drop the underline value
   --> $DIR/dropping_references-can-fixed.rs:13:5
    |
 LL |     drop(&&owned1);
    |     ^^^^^--------^
    |          |
    |          argument has type `&&SomeStruct`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = &&owned1` simply to ignore the expression or result
    |
 LL -     drop(&&owned1);
 LL +     let _ = &&owned1;
    |
 
-error: calls to `std::mem::drop` with a reference instead of an owned value does nothing
+error: calls to `std::mem::drop` with a reference does not drop the underline value
   --> $DIR/dropping_references-can-fixed.rs:14:5
    |
 LL |     drop(&mut owned1);
    |     ^^^^^-----------^
    |          |
    |          argument has type `&mut SomeStruct`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = &mut owned1` simply to ignore the expression or result
    |
 LL -     drop(&mut owned1);
 LL +     let _ = &mut owned1;
    |
 
-error: calls to `std::mem::drop` with a reference instead of an owned value does nothing
+error: calls to `std::mem::drop` with a reference does not drop the underline value
   --> $DIR/dropping_references-can-fixed.rs:18:5
    |
 LL |     drop(reference1);
    |     ^^^^^----------^
    |          |
    |          argument has type `&SomeStruct`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = reference1` simply to ignore the expression or result
    |
 LL -     drop(reference1);
 LL +     let _ = reference1;
    |
 
-error: calls to `std::mem::drop` with a reference instead of an owned value does nothing
+error: calls to `std::mem::drop` with a reference does not drop the underline value
   --> $DIR/dropping_references-can-fixed.rs:21:5
    |
 LL |     drop(reference2);
    |     ^^^^^----------^
    |          |
    |          argument has type `&mut SomeStruct`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = reference2` simply to ignore the expression or result
    |
 LL -     drop(reference2);
 LL +     let _ = reference2;
    |
 
-error: calls to `std::mem::drop` with a reference instead of an owned value does nothing
+error: calls to `std::mem::drop` with a reference does not drop the underline value
   --> $DIR/dropping_references-can-fixed.rs:24:5
    |
 LL |     drop(reference3);
    |     ^^^^^----------^
    |          |
    |          argument has type `&SomeStruct`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = reference3` simply to ignore the expression or result
    |
 LL -     drop(reference3);
 LL +     let _ = reference3;
    |
 
-error: calls to `std::mem::drop` with a reference instead of an owned value does nothing
+error: calls to `std::mem::drop` with a reference does not drop the underline value
   --> $DIR/dropping_references-can-fixed.rs:29:5
    |
 LL |     drop(&val);
    |     ^^^^^----^
    |          |
    |          argument has type `&T`
    |
-help: use `let _ = ...` to ignore the expression or result
+help: use `let _ = &val` simply to ignore the expression or result
    |
 LL -     drop(&val);
 LL +     let _ = &val;

tests/ui/lint/dropping_references.rs

@@ -116,3 +116,7 @@ fn issue112653() {
         Ok(())
     }
 }
+
+fn issue155895() {
+    let _ = drop(&SomeStruct); //~ WARN calls to `std::mem::drop`
+}