extract suggestion out of the main message

1. In the singe-line case, we switch to verbose suggestions, otherwise
   the suggestion line gets too long due to the longer message.
2. In the multi-line case, we use span-less help, otherwise the whole
   multiline span gets highlighted the second time.
3. Also make the suggestion message more concise.

Author: ada4a

clippy_lints/src/methods/filter_map_next.rs

@@ -16,18 +16,21 @@ pub(super) fn check(cx: &LateContext<'_>, expr: &Expr<'_>, recv: &Expr<'_>, arg:
             cx,
             FILTER_MAP_NEXT,
             expr.span,
-            "called `filter_map(..).next()` on an `Iterator`. \
-            This is more succinctly expressed by calling `.find_map(..)` instead",
+            "called `filter_map(..).next()` on an `Iterator`",
             |diag| {
+                let sugg_msg = "use `.find_map(..)` instead";
+
                 let filter_snippet = snippet(cx, arg.span, "..");
                 if filter_snippet.lines().count() <= 1 {
                     let iter_snippet = snippet(cx, recv.span, "..");
-                    diag.span_suggestion(
+                    diag.span_suggestion_verbose(
                         expr.span,
-                        "try",
+                        sugg_msg,
                         format!("{iter_snippet}.find_map({filter_snippet})"),
                         Applicability::MachineApplicable,
                     );
+                } else {
+                    diag.help(sugg_msg);
                 }
             },
         );

tests/ui/filter_map_next.stderr

@@ -1,17 +1,28 @@
-error: called `filter_map(..).next()` on an `Iterator`. This is more succinctly expressed by calling `.find_map(..)` instead
+error: called `filter_map(..).next()` on an `Iterator`
   --> tests/ui/filter_map_next.rs:6:32
    |
 LL |     let element: Option<i32> = a.iter().filter_map(|s| s.parse().ok()).next();
-   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `a.iter().find_map(|s| s.parse().ok())`
+   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::filter-map-next` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::filter_map_next)]`
+help: use `.find_map(..)` instead
+   |
+LL -     let element: Option<i32> = a.iter().filter_map(|s| s.parse().ok()).next();
+LL +     let element: Option<i32> = a.iter().find_map(|s| s.parse().ok());
+   |
 
-error: called `filter_map(..).next()` on an `Iterator`. This is more succinctly expressed by calling `.find_map(..)` instead
+error: called `filter_map(..).next()` on an `Iterator`
   --> tests/ui/filter_map_next.rs:20:26
    |
 LL |     let _: Option<i32> = a.iter().filter_map(|s| s.parse().ok()).next();
-   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `a.iter().find_map(|s| s.parse().ok())`
+   |                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+help: use `.find_map(..)` instead
+   |
+LL -     let _: Option<i32> = a.iter().filter_map(|s| s.parse().ok()).next();
+LL +     let _: Option<i32> = a.iter().find_map(|s| s.parse().ok());
+   |
 
 error: aborting due to 2 previous errors
 

tests/ui/filter_map_next_unfixable.stderr

@@ -1,4 +1,4 @@
-error: called `filter_map(..).next()` on an `Iterator`. This is more succinctly expressed by calling `.find_map(..)` instead
+error: called `filter_map(..).next()` on an `Iterator`
   --> tests/ui/filter_map_next_unfixable.rs:7:26
    |
 LL |       let _: Option<u32> = vec![1, 2, 3, 4, 5, 6]
@@ -8,6 +8,7 @@ LL | |         })
 LL | |         .next();
    | |_______________^
    |
+   = help: use `.find_map(..)` instead
    = note: `-D clippy::filter-map-next` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::filter_map_next)]`