fix: new_without_default misses where clause in new

clippy_lints/src/new_without_default.rs

@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint_hir_and_then;
 use clippy_utils::return_ty;
-use clippy_utils::source::snippet_with_applicability;
+use clippy_utils::source::{indent_of, reindent_multiline, snippet_with_applicability};
 use clippy_utils::sugg::DiagExt;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
@@ -57,6 +57,7 @@ pub struct NewWithoutDefault {
 impl_lint_pass!(NewWithoutDefault => [NEW_WITHOUT_DEFAULT]);
 
 impl<'tcx> LateLintPass<'tcx> for NewWithoutDefault {
+    #[expect(clippy::too_many_lines)]
     fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
         let hir::ItemKind::Impl(hir::Impl {
             of_trait: None,
@@ -140,10 +141,29 @@ impl<'tcx> LateLintPass<'tcx> for NewWithoutDefault {
                 };
                 let generics_sugg = snippet_with_applicability(cx, generics.span, "", &mut app);
                 let where_clause_sugg = if generics.has_where_clause_predicates {
-                    format!(
-                        "\n{}\n",
-                        snippet_with_applicability(cx, generics.where_clause_span, "", &mut app)
-                    )
+                    let where_clause_sugg =
+                        snippet_with_applicability(cx, generics.where_clause_span, "", &mut app).to_string();
+                    let mut where_clause_sugg = reindent_multiline(&where_clause_sugg, true, Some(4));
+                    if impl_item.generics.has_where_clause_predicates {
+                        if !where_clause_sugg.ends_with(',') {
+                            where_clause_sugg.push(',');
+                        }
+
+                        let additional_where_preds =
+                            snippet_with_applicability(cx, impl_item.generics.where_clause_span, "", &mut app);
+                        let ident = indent_of(cx, generics.where_clause_span).unwrap_or(0);
+                        // Remove the leading `where ` keyword
+                        let additional_where_preds = additional_where_preds.trim_start_matches("where").trim_start();
+                        where_clause_sugg.push('\n');
+                        where_clause_sugg.extend(std::iter::repeat_n(' ', ident));
+                        where_clause_sugg.push_str(additional_where_preds);
+                    }
+                    format!("\n{where_clause_sugg}\n")
+                } else if impl_item.generics.has_where_clause_predicates {
+                    let where_clause_sugg =
+                        snippet_with_applicability(cx, impl_item.generics.where_clause_span, "", &mut app);
+                    let where_clause_sugg = reindent_multiline(&where_clause_sugg, true, Some(4));
+                    format!("\n{}\n", where_clause_sugg.trim_start())
                 } else {
                     String::new()
                 };

tests/ui/new_without_default.fixed

@@ -409,3 +409,58 @@ mod issue15778 {
         }
     }
 }
+
+pub mod issue16255 {
+    use std::fmt::Display;
+    use std::marker::PhantomData;
+
+    pub struct Foo<T> {
+        marker: PhantomData<T>,
+    }
+
+    impl<T> Default for Foo<T>
+    where
+        T: Display,
+        T: Clone,
+     {
+        fn default() -> Self {
+            Self::new()
+        }
+    }
+
+    impl<T> Foo<T>
+    where
+        T: Display,
+    {
+        pub fn new() -> Self
+        //~^ new_without_default
+        where
+            T: Clone,
+        {
+            Self { marker: PhantomData }
+        }
+    }
+
+    pub struct Bar<T> {
+        marker: PhantomData<T>,
+    }
+
+    impl<T> Default for Bar<T>
+    where
+        T: Clone,
+     {
+        fn default() -> Self {
+            Self::new()
+        }
+    }
+
+    impl<T> Bar<T> {
+        pub fn new() -> Self
+        //~^ new_without_default
+        where
+            T: Clone,
+        {
+            Self { marker: PhantomData }
+        }
+    }
+}

tests/ui/new_without_default.rs

@@ -324,3 +324,39 @@ mod issue15778 {
         }
     }
 }
+
+pub mod issue16255 {
+    use std::fmt::Display;
+    use std::marker::PhantomData;
+
+    pub struct Foo<T> {
+        marker: PhantomData<T>,
+    }
+
+    impl<T> Foo<T>
+    where
+        T: Display,
+    {
+        pub fn new() -> Self
+        //~^ new_without_default
+        where
+            T: Clone,
+        {
+            Self { marker: PhantomData }
+        }
+    }
+
+    pub struct Bar<T> {
+        marker: PhantomData<T>,
+    }
+
+    impl<T> Bar<T> {
+        pub fn new() -> Self
+        //~^ new_without_default
+        where
+            T: Clone,
+        {
+            Self { marker: PhantomData }
+        }
+    }
+}

tests/ui/new_without_default.stderr

@@ -250,5 +250,58 @@ LL +     }
 LL + }
    |
 
-error: aborting due to 13 previous errors
+error: you should consider adding a `Default` implementation for `Foo<T>`
+  --> tests/ui/new_without_default.rs:340:9
+   |
+LL | /         pub fn new() -> Self
+LL | |
+LL | |         where
+LL | |             T: Clone,
+LL | |         {
+LL | |             Self { marker: PhantomData }
+LL | |         }
+   | |_________^
+   |
+help: try adding this
+   |
+LL ~     impl<T> Default for Foo<T>
+LL +     where
+LL +         T: Display,
+LL +         T: Clone,
+LL +      {
+LL +         fn default() -> Self {
+LL +             Self::new()
+LL +         }
+LL +     }
+LL + 
+LL ~     impl<T> Foo<T>
+   |
+
+error: you should consider adding a `Default` implementation for `Bar<T>`
+  --> tests/ui/new_without_default.rs:354:9
+   |
+LL | /         pub fn new() -> Self
+LL | |
+LL | |         where
+LL | |             T: Clone,
+LL | |         {
+LL | |             Self { marker: PhantomData }
+LL | |         }
+   | |_________^
+   |
+help: try adding this
+   |
+LL ~     impl<T> Default for Bar<T>
+LL +     where
+LL +         T: Clone,
+LL +      {
+LL +         fn default() -> Self {
+LL +             Self::new()
+LL +         }
+LL +     }
+LL + 
+LL ~     impl<T> Bar<T> {
+   |
+
+error: aborting due to 15 previous errors