Proxy-pass #[allow]/#[expect] attributes in Constructor derive (#477, #397)

Resolves #397

## Synopsis

Clippy emits a `too_many_arguments` warning for the new method generated
by the `Constructor` derive.
Clippy attributes currently have no effect in this context.

## Solution

Proxy-pass `#[allow(clippy::too_many_arguments)]` to the generated `impl` to
suppress the warning.

Co-authored-by: Kai Ren <tyranron@gmail.com>

Author: Cheban1996

CHANGELOG.md

@@ -21,6 +21,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
   ([#469](https://github.com/JelteF/derive_more/pull/469))
 - Add `PartialEq` derive similar to `std`'s one, but considering generics correctly.
   ([#473](https://github.com/JelteF/derive_more/pull/473))
+- Proxy-pass `#[allow]`/`#[expect]` attributes of the type in `Constructor` derive.
+  ([#477](https://github.com/JelteF/derive_more/pull/477))
 
 ### Changed
 

impl/src/constructor.rs

@@ -23,11 +23,19 @@ pub fn expand(input: &DeriveInput, _: &str) -> TokenStream {
         },
         _ => panic!("Only structs can derive a constructor"),
     };
+
+    let inherited_lint_attrs = input.attrs.iter().filter(|attr| {
+        attr.path()
+            .get_ident()
+            .is_some_and(|name| name == "allow" || name == "expect")
+    });
+
     let original_types = &get_field_types(&fields);
     quote! {
-        #[allow(deprecated)] // omit warnings on deprecated fields/variants
+        #[allow(deprecated)]       // omit warnings on deprecated fields/variants
         #[allow(missing_docs)]
         #[allow(unreachable_code)] // omit warnings for `!` and other unreachable types
+        #(#inherited_lint_attrs)*  // proxy-pass any `#[allow]`/`#[expect]` attributes
         #[automatically_derived]
         impl #impl_generics #input_type #ty_generics #where_clause {
             #[inline]

tests/constructor.rs

@@ -68,3 +68,38 @@ mod deprecated {
         field: i32,
     }
 }
+
+mod proxy_lint_attr {
+    #![deny(non_snake_case, clippy::too_many_arguments)]
+
+    use super::*;
+
+    #[allow(clippy::too_many_arguments)]
+    #[derive(Constructor)]
+    struct ManyArguments(
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+        u8,
+    );
+
+    #[expect(non_snake_case)]
+    #[derive(Constructor)]
+    struct User {
+        Num: i32,
+    }
+}