Reword suggestion messages.

Author: a2aaron

compiler/rustc_lint/src/let_underscore.rs

@@ -150,12 +150,12 @@ fn build_and_emit_lint(
     lint.build(msg)
         .span_suggestion_verbose(
             local.pat.span,
-            "consider binding to an unused variable",
+            "consider binding to an unused variable to avoid immediately dropping the value",
             "_unused",
             Applicability::MachineApplicable,
         )
         .multipart_suggestion(
-            "consider explicitly droping with `std::mem::drop`",
+            "consider immediately dropping the value",
             vec![
                 (init_span.shrink_to_lo(), "drop(".to_string()),
                 (init_span.shrink_to_hi(), ")".to_string()),

src/test/ui/lint/let_underscore/let_underscore_drop.stderr

@@ -5,11 +5,11 @@ LL |     let _ = NontrivialDrop;
    |     ^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: requested on the command line with `-W let-underscore-drop`
-help: consider binding to an unused variable
+help: consider binding to an unused variable to avoid immediately dropping the value
    |
 LL |     let _unused = NontrivialDrop;
    |         ~~~~~~~
-help: consider explicitly droping with `std::mem::drop`
+help: consider immediately dropping the value
    |
 LL |     let _ = drop(NontrivialDrop);
    |             +++++              +

src/test/ui/lint/let_underscore/let_underscore_lock.stderr

@@ -5,11 +5,11 @@ LL |     let _ = data.lock().unwrap();
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `#[deny(let_underscore_lock)]` on by default
-help: consider binding to an unused variable
+help: consider binding to an unused variable to avoid immediately dropping the value
    |
 LL |     let _unused = data.lock().unwrap();
    |         ~~~~~~~
-help: consider explicitly droping with `std::mem::drop`
+help: consider immediately dropping the value
    |
 LL |     let _ = drop(data.lock().unwrap());
    |             +++++                    +