Do not make incomplete or invalid suggestions (#14487)

The `unnecessary_filter_map` and `unnecessary_find_map` lints were
making partial suggestions, proposing to replace the whole expression by
only the method name, or a subexpression which contained explicit
placeholders.

Since even `MaybeIncorrect` suggestions must generate code that
compiles, this changes those lints to recommandation lints with no code
suggestion.

Fixes #14486

changelog: [`unnecessary_find_map`, `unnecessary_filter_map`]: do not
make suggestions that will not compile

Author: Manishearth

Diff for: clippy_lints/src/methods/unnecessary_filter_map.rs

@@ -1,11 +1,10 @@
 use super::utils::clone_or_copy_needed;
-use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::diagnostics::span_lint;
 use clippy_utils::ty::is_copy;
 use clippy_utils::usage::mutated_variables;
 use clippy_utils::visitors::{Descend, for_each_expr_without_closures};
 use clippy_utils::{is_res_lang_ctor, is_trait_method, path_res, path_to_local_id};
 use core::ops::ControlFlow;
-use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_hir::LangItem::{OptionNone, OptionSome};
 use rustc_lint::LateContext;
@@ -45,41 +44,40 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>, a
                 && is_res_lang_ctor(cx, path_res(cx, expr), OptionSome)
                 && let hir::ExprKind::Path(_) = args[0].kind
             {
-                span_lint_and_sugg(
+                span_lint(
                     cx,
                     UNNECESSARY_FILTER_MAP,
                     expr.span,
-                    format!("{name} is unnecessary"),
-                    "try removing the filter_map",
-                    String::new(),
-                    Applicability::MaybeIncorrect,
+                    String::from("this call to `.filter_map(..)` is unnecessary"),
                 );
+                return;
+            }
+            if name == "filter_map" {
+                "map(..)"
+            } else {
+                "map(..).next()"
             }
-            if name == "filter_map" { "map" } else { "map(..).next()" }
         } else if !found_mapping && !mutates_arg && (!clone_or_copy_needed || is_copy(cx, in_ty)) {
             match cx.typeck_results().expr_ty(body.value).kind() {
                 ty::Adt(adt, subst)
                     if cx.tcx.is_diagnostic_item(sym::Option, adt.did()) && in_ty == subst.type_at(0) =>
                 {
-                    if name == "filter_map" { "filter" } else { "find" }
+                    if name == "filter_map" { "filter(..)" } else { "find(..)" }
                 },
                 _ => return,
             }
         } else {
             return;
         };
-        span_lint_and_sugg(
+        span_lint(
             cx,
             if name == "filter_map" {
                 UNNECESSARY_FILTER_MAP
             } else {
                 UNNECESSARY_FIND_MAP
             },
             expr.span,
-            format!("this `.{name}` can be written more simply"),
-            "try instead",
-            sugg.to_string(),
-            Applicability::MaybeIncorrect,
+            format!("this `.{name}(..)` can be written more simply using `.{sugg}`"),
         );
     }
 }

Diff for: tests/ui/unnecessary_filter_map.rs

@@ -1,5 +1,4 @@
-//@no-rustfix
-#![allow(dead_code)]
+#![allow(clippy::redundant_closure)]
 
 fn main() {
     let _ = (0..4).filter_map(|x| if x > 1 { Some(x) } else { None });
@@ -27,9 +26,7 @@ fn main() {
     let _ = (0..4).filter_map(Some);
 
     let _ = vec![Some(10), None].into_iter().filter_map(|x| Some(x));
-    //~^ redundant_closure
-    //~| unnecessary_filter_map
-    //~| unnecessary_filter_map
+    //~^ unnecessary_filter_map
 }
 
 fn filter_map_none_changes_item_type() -> impl Iterator<Item = bool> {

Diff for: tests/ui/unnecessary_filter_map.stderr

@@ -1,14 +1,14 @@
-error: this `.filter_map` can be written more simply
-  --> tests/ui/unnecessary_filter_map.rs:5:13
+error: this `.filter_map(..)` can be written more simply using `.filter(..)`
+  --> tests/ui/unnecessary_filter_map.rs:4:13
    |
 LL |     let _ = (0..4).filter_map(|x| if x > 1 { Some(x) } else { None });
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try instead: `filter`
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::unnecessary-filter-map` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::unnecessary_filter_map)]`
 
-error: this `.filter_map` can be written more simply
-  --> tests/ui/unnecessary_filter_map.rs:8:13
+error: this `.filter_map(..)` can be written more simply using `.filter(..)`
+  --> tests/ui/unnecessary_filter_map.rs:7:13
    |
 LL |       let _ = (0..4).filter_map(|x| {
    |  _____________^
@@ -18,51 +18,36 @@ LL | |         if x > 1 {
 ...  |
 LL | |         None
 LL | |     });
-   | |______^ help: try instead: `filter`
+   | |______^
 
-error: this `.filter_map` can be written more simply
-  --> tests/ui/unnecessary_filter_map.rs:16:13
+error: this `.filter_map(..)` can be written more simply using `.filter(..)`
+  --> tests/ui/unnecessary_filter_map.rs:15:13
    |
 LL |       let _ = (0..4).filter_map(|x| match x {
    |  _____________^
 LL | |
 LL | |         0 | 1 => None,
 LL | |         _ => Some(x),
 LL | |     });
-   | |______^ help: try instead: `filter`
+   | |______^
 
-error: this `.filter_map` can be written more simply
-  --> tests/ui/unnecessary_filter_map.rs:22:13
+error: this `.filter_map(..)` can be written more simply using `.map(..)`
+  --> tests/ui/unnecessary_filter_map.rs:21:13
    |
 LL |     let _ = (0..4).filter_map(|x| Some(x + 1));
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try instead: `map`
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: redundant closure
-  --> tests/ui/unnecessary_filter_map.rs:29:57
+error: this call to `.filter_map(..)` is unnecessary
+  --> tests/ui/unnecessary_filter_map.rs:28:61
    |
 LL |     let _ = vec![Some(10), None].into_iter().filter_map(|x| Some(x));
-   |                                                         ^^^^^^^^^^^ help: replace the closure with the function itself: `Some`
-   |
-   = note: `-D clippy::redundant-closure` implied by `-D warnings`
-   = help: to override `-D warnings` add `#[allow(clippy::redundant_closure)]`
-
-error: filter_map is unnecessary
-  --> tests/ui/unnecessary_filter_map.rs:29:61
-   |
-LL |     let _ = vec![Some(10), None].into_iter().filter_map(|x| Some(x));
-   |                                                             ^^^^ help: try removing the filter_map
-
-error: this `.filter_map` can be written more simply
-  --> tests/ui/unnecessary_filter_map.rs:29:13
-   |
-LL |     let _ = vec![Some(10), None].into_iter().filter_map(|x| Some(x));
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try instead: `map`
+   |                                                             ^^^^
 
-error: this `.filter_map` can be written more simply
-  --> tests/ui/unnecessary_filter_map.rs:169:14
+error: this `.filter_map(..)` can be written more simply using `.filter(..)`
+  --> tests/ui/unnecessary_filter_map.rs:166:14
    |
 LL |     let _x = std::iter::once(1).filter_map(|n| (n > 1).then_some(n));
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try instead: `filter`
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 8 previous errors
+error: aborting due to 6 previous errors
 

Diff for: tests/ui/unnecessary_find_map.rs

@@ -1,4 +1,3 @@
-//@no-rustfix
 #![allow(dead_code)]
 
 fn main() {

Diff for: tests/ui/unnecessary_find_map.stderr

@@ -1,14 +1,14 @@
-error: this `.find_map` can be written more simply
-  --> tests/ui/unnecessary_find_map.rs:5:13
+error: this `.find_map(..)` can be written more simply using `.find(..)`
+  --> tests/ui/unnecessary_find_map.rs:4:13
    |
 LL |     let _ = (0..4).find_map(|x| if x > 1 { Some(x) } else { None });
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try instead: `find`
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::unnecessary-find-map` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::unnecessary_find_map)]`
 
-error: this `.find_map` can be written more simply
-  --> tests/ui/unnecessary_find_map.rs:8:13
+error: this `.find_map(..)` can be written more simply using `.find(..)`
+  --> tests/ui/unnecessary_find_map.rs:7:13
    |
 LL |       let _ = (0..4).find_map(|x| {
    |  _____________^
@@ -18,30 +18,30 @@ LL | |         if x > 1 {
 ...  |
 LL | |         None
 LL | |     });
-   | |______^ help: try instead: `find`
+   | |______^
 
-error: this `.find_map` can be written more simply
-  --> tests/ui/unnecessary_find_map.rs:16:13
+error: this `.find_map(..)` can be written more simply using `.find(..)`
+  --> tests/ui/unnecessary_find_map.rs:15:13
    |
 LL |       let _ = (0..4).find_map(|x| match x {
    |  _____________^
 LL | |
 LL | |         0 | 1 => None,
 LL | |         _ => Some(x),
 LL | |     });
-   | |______^ help: try instead: `find`
+   | |______^
 
-error: this `.find_map` can be written more simply
-  --> tests/ui/unnecessary_find_map.rs:22:13
+error: this `.find_map(..)` can be written more simply using `.map(..).next()`
+  --> tests/ui/unnecessary_find_map.rs:21:13
    |
 LL |     let _ = (0..4).find_map(|x| Some(x + 1));
-   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try instead: `map(..).next()`
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: this `.find_map` can be written more simply
-  --> tests/ui/unnecessary_find_map.rs:34:14
+error: this `.find_map(..)` can be written more simply using `.find(..)`
+  --> tests/ui/unnecessary_find_map.rs:33:14
    |
 LL |     let _x = std::iter::once(1).find_map(|n| (n > 1).then_some(n));
-   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try instead: `find`
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 5 previous errors