option_option: split part of diagnostic message into help message

Author: ada4a

clippy_lints/src/types/option_option.rs

@@ -1,6 +1,7 @@
-use clippy_utils::diagnostics::span_lint;
+use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::qpath_generic_tys;
 use clippy_utils::res::MaybeResPath;
+use clippy_utils::source::snippet;
 use rustc_hir::def_id::DefId;
 use rustc_hir::{self as hir, QPath};
 use rustc_lint::LateContext;
@@ -13,12 +14,21 @@ pub(super) fn check(cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>, qpath: &QPath<'_
         && let Some(arg) = qpath_generic_tys(qpath).next()
         && arg.basic_res().opt_def_id() == Some(def_id)
     {
-        span_lint(
+        span_lint_and_then(
             cx,
             OPTION_OPTION,
             hir_ty.span,
-            "consider using `Option<T>` instead of `Option<Option<T>>` or a custom \
-                                 enum if you need to distinguish all 3 cases",
+            // use just `T` here, as the inner type is not what's problematic
+            "use of `Option<Option<T>>`",
+            |diag| {
+                // but use the specific type here, as:
+                // - this is kind of a suggestion
+                // - it's printed right after the linted type
+                let inner_opt = snippet(cx, arg.span, "_");
+                diag.help(format!(
+                    "consider using `{inner_opt}`, or a custom enum if you need to distinguish all 3 cases"
+                ));
+            },
         );
         true
     } else {

tests/ui/option_option.stderr

@@ -1,77 +1,100 @@
-error: consider using `Option<T>` instead of `Option<Option<T>>` or a custom enum if you need to distinguish all 3 cases
+error: use of `Option<Option<T>>`
   --> tests/ui/option_option.rs:4:10
    |
 LL | const C: Option<Option<i32>> = None;
    |          ^^^^^^^^^^^^^^^^^^^
    |
+   = help: consider using `Option<i32>`, or a custom enum if you need to distinguish all 3 cases
    = note: `-D clippy::option-option` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::option_option)]`
 
-error: consider using `Option<T>` instead of `Option<Option<T>>` or a custom enum if you need to distinguish all 3 cases
+error: use of `Option<Option<T>>`
   --> tests/ui/option_option.rs:6:11
    |
 LL | static S: Option<Option<i32>> = None;
    |           ^^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using `Option<i32>`, or a custom enum if you need to distinguish all 3 cases
 
-error: consider using `Option<T>` instead of `Option<Option<T>>` or a custom enum if you need to distinguish all 3 cases
+error: use of `Option<Option<T>>`
   --> tests/ui/option_option.rs:9:13
    |
 LL | fn input(_: Option<Option<u8>>) {}
    |             ^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using `Option<u8>`, or a custom enum if you need to distinguish all 3 cases
 
-error: consider using `Option<T>` instead of `Option<Option<T>>` or a custom enum if you need to distinguish all 3 cases
+error: use of `Option<Option<T>>`
   --> tests/ui/option_option.rs:12:16
    |
 LL | fn output() -> Option<Option<u8>> {
    |                ^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using `Option<u8>`, or a custom enum if you need to distinguish all 3 cases
 
-error: consider using `Option<T>` instead of `Option<Option<T>>` or a custom enum if you need to distinguish all 3 cases
+error: use of `Option<Option<T>>`
   --> tests/ui/option_option.rs:17:27
    |
 LL | fn output_nested() -> Vec<Option<Option<u8>>> {
    |                           ^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using `Option<u8>`, or a custom enum if you need to distinguish all 3 cases
 
-error: consider using `Option<T>` instead of `Option<Option<T>>` or a custom enum if you need to distinguish all 3 cases
+error: use of `Option<Option<T>>`
   --> tests/ui/option_option.rs:23:30
    |
 LL | fn output_nested_nested() -> Option<Option<Option<u8>>> {
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using `Option<Option<u8>>`, or a custom enum if you need to distinguish all 3 cases
 
-error: consider using `Option<T>` instead of `Option<Option<T>>` or a custom enum if you need to distinguish all 3 cases
+error: use of `Option<Option<T>>`
   --> tests/ui/option_option.rs:29:8
    |
 LL |     x: Option<Option<u8>>,
    |        ^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using `Option<u8>`, or a custom enum if you need to distinguish all 3 cases
 
-error: consider using `Option<T>` instead of `Option<Option<T>>` or a custom enum if you need to distinguish all 3 cases
+error: use of `Option<Option<T>>`
   --> tests/ui/option_option.rs:34:23
    |
 LL |     fn struct_fn() -> Option<Option<u8>> {
    |                       ^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using `Option<u8>`, or a custom enum if you need to distinguish all 3 cases
 
-error: consider using `Option<T>` instead of `Option<Option<T>>` or a custom enum if you need to distinguish all 3 cases
+error: use of `Option<Option<T>>`
   --> tests/ui/option_option.rs:41:22
    |
 LL |     fn trait_fn() -> Option<Option<u8>>;
    |                      ^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using `Option<u8>`, or a custom enum if you need to distinguish all 3 cases
 
-error: consider using `Option<T>` instead of `Option<Option<T>>` or a custom enum if you need to distinguish all 3 cases
+error: use of `Option<Option<T>>`
   --> tests/ui/option_option.rs:46:11
    |
 LL |     Tuple(Option<Option<u8>>),
    |           ^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using `Option<u8>`, or a custom enum if you need to distinguish all 3 cases
 
-error: consider using `Option<T>` instead of `Option<Option<T>>` or a custom enum if you need to distinguish all 3 cases
+error: use of `Option<Option<T>>`
   --> tests/ui/option_option.rs:48:17
    |
 LL |     Struct { x: Option<Option<u8>> },
    |                 ^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using `Option<u8>`, or a custom enum if you need to distinguish all 3 cases
 
-error: consider using `Option<T>` instead of `Option<Option<T>>` or a custom enum if you need to distinguish all 3 cases
+error: use of `Option<Option<T>>`
   --> tests/ui/option_option.rs:90:14
    |
 LL |         foo: Option<Option<Cow<'a, str>>>,
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = help: consider using `Option<Cow<'a, str>>`, or a custom enum if you need to distinguish all 3 cases
 
 error: aborting due to 12 previous errors