Stop using Eq::assert_receiver_is_total_eq()

Author: daxpedda

CHANGELOG.md

@@ -12,7 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   `Drop` but instead only asserts that every field implements `ZeroizeOnDrop`.
 
 ### Fixed
-- Stop depending on unstable APIs of `zeroize` to implement `ZeroizeOnDrop`.
+- Stop depending on unstable APIs for `Eq` for `ZeroizeOnDrop`.
 
 ## [1.4.0] - 2025-05-01
 

src/test/basic.rs

@@ -45,16 +45,23 @@ fn struct_() -> Result<()> {
 				}
 			}
 
-			#[automatically_derived]
-			impl<T> ::core::cmp::Eq for Test<T> {
-				#[inline]
-				fn assert_receiver_is_total_eq(&self) {
-					struct __AssertEq<__T: ::core::cmp::Eq + ?::core::marker::Sized>(::core::marker::PhantomData<__T>);
+			const _: () = {
+				trait DeriveWhereAssertEq {
+					fn assert(&self);
+				}
 
-					// For some reason the comparison fails without the extra space at the end.
-					let _: __AssertEq<std::marker::PhantomData<T> >;
+				impl<T> DeriveWhereAssertEq for Test<T> {
+					fn assert(&self) {
+						struct __AssertEq<__T: ::core::cmp::Eq + ?::core::marker::Sized>(::core::marker::PhantomData<__T>);
+
+						// For some reason the comparison fails without the extra space at the end.
+						let _: __AssertEq<std::marker::PhantomData<T> >;
+					}
 				}
-			}
+			};
+
+			#[automatically_derived]
+			impl<T> ::core::cmp::Eq for Test<T> { }
 
 			#[automatically_derived]
 			impl<T> ::core::hash::Hash for Test<T> {
@@ -141,16 +148,23 @@ fn tuple() -> Result<()> {
 				}
 			}
 
-			#[automatically_derived]
-			impl<T> ::core::cmp::Eq for Test<T> {
-				#[inline]
-				fn assert_receiver_is_total_eq(&self) {
-					struct __AssertEq<__T: ::core::cmp::Eq + ?::core::marker::Sized>(::core::marker::PhantomData<__T>);
+			const _: () = {
+				trait DeriveWhereAssertEq {
+					fn assert(&self);
+				}
+
+				impl<T> DeriveWhereAssertEq for Test<T> {
+					fn assert(&self) {
+						struct __AssertEq<__T: ::core::cmp::Eq + ?::core::marker::Sized>(::core::marker::PhantomData<__T>);
 
-					// For some reason the comparison fails without the extra space at the end.
-					let _: __AssertEq<std::marker::PhantomData<T> >;
+						// For some reason the comparison fails without the extra space at the end.
+						let _: __AssertEq<std::marker::PhantomData<T> >;
+					}
 				}
-			}
+			};
+
+			#[automatically_derived]
+			impl<T> ::core::cmp::Eq for Test<T> { }
 
 			#[automatically_derived]
 			impl<T> ::core::hash::Hash for Test<T> {
@@ -287,17 +301,24 @@ fn enum_() -> Result<()> {
 				}
 			}
 
-			#[automatically_derived]
-			impl<T> ::core::cmp::Eq for Test<T> {
-				#[inline]
-				fn assert_receiver_is_total_eq(&self) {
-					struct __AssertEq<__T: ::core::cmp::Eq + ?::core::marker::Sized>(::core::marker::PhantomData<__T>);
+			const _: () = {
+				trait DeriveWhereAssertEq {
+					fn assert(&self);
+				}
+
+				impl<T> DeriveWhereAssertEq for Test<T> {
+					fn assert(&self) {
+						struct __AssertEq<__T: ::core::cmp::Eq + ?::core::marker::Sized>(::core::marker::PhantomData<__T>);
 
-					// For some reason the comparison fails without the extra space at the end.
-					let _: __AssertEq<std::marker::PhantomData<T> >;
-					let _: __AssertEq<std::marker::PhantomData<T> >;
+						// For some reason the comparison fails without the extra space at the end.
+						let _: __AssertEq<std::marker::PhantomData<T> >;
+						let _: __AssertEq<std::marker::PhantomData<T> >;
+					}
 				}
-			}
+			};
+
+			#[automatically_derived]
+			impl<T> ::core::cmp::Eq for Test<T> { }
 
 			#[automatically_derived]
 			impl<T> ::core::hash::Hash for Test<T> {

src/test/bound.rs

@@ -235,19 +235,28 @@ fn check_trait_bounds() -> Result<()> {
 				}
 			}
 
+			const _: () = {
+				trait DeriveWhereAssertEq {
+					fn assert(&self);
+				}
+
+				impl<T, U> DeriveWhereAssertEq for Test<T, U>
+				where T: ::core::cmp::Eq
+				{
+					fn assert(&self) {
+						struct __AssertEq<__T: ::core::cmp::Eq + ?::core::marker::Sized>(::core::marker::PhantomData<__T>);
+
+						// For some reason the comparison fails without the extra space at the end.
+						let _: __AssertEq<T >;
+						let _: __AssertEq<std::marker::PhantomData<U> >;
+					}
+				}
+			};
+
 			#[automatically_derived]
 			impl<T, U> ::core::cmp::Eq for Test<T, U>
 			where T: ::core::cmp::Eq
-			{
-				#[inline]
-				fn assert_receiver_is_total_eq(&self) {
-					struct __AssertEq<__T: ::core::cmp::Eq + ?::core::marker::Sized>(::core::marker::PhantomData<__T>);
-
-					// For some reason the comparison fails without the extra space at the end.
-					let _: __AssertEq<T >;
-					let _: __AssertEq<std::marker::PhantomData<U> >;
-				}
-			}
+			{ }
 
 			#[automatically_derived]
 			impl<T, U> ::core::hash::Hash for Test<T, U>
@@ -377,21 +386,32 @@ fn check_multiple_trait_bounds() -> Result<()> {
 				}
 			}
 
+			const _: () = {
+				trait DeriveWhereAssertEq {
+					fn assert(&self);
+				}
+
+				impl<T, U, V> DeriveWhereAssertEq for Test<T, U, V>
+				where
+					T: ::core::cmp::Eq,
+					U: ::core::cmp::Eq
+				{
+					fn assert(&self) {
+						struct __AssertEq<__T: ::core::cmp::Eq + ?::core::marker::Sized>(::core::marker::PhantomData<__T>);
+
+						// For some reason the comparison fails without the extra space at the end.
+						let _: __AssertEq<T >;
+						let _: __AssertEq<std::marker::PhantomData<(U, V)> >;
+					}
+				}
+			};
+
 			#[automatically_derived]
 			impl<T, U, V> ::core::cmp::Eq for Test<T, U, V>
 			where
 				T: ::core::cmp::Eq,
 				U: ::core::cmp::Eq
-			{
-				#[inline]
-				fn assert_receiver_is_total_eq(&self) {
-					struct __AssertEq<__T: ::core::cmp::Eq + ?::core::marker::Sized>(::core::marker::PhantomData<__T>);
-
-					// For some reason the comparison fails without the extra space at the end.
-					let _: __AssertEq<T >;
-					let _: __AssertEq<std::marker::PhantomData<(U, V)> >;
-				}
-			}
+			{ }
 
 			#[automatically_derived]
 			impl<T, U, V> ::core::hash::Hash for Test<T, U, V>

src/trait_.rs

@@ -292,8 +292,8 @@ pub trait TraitImpl: Deref<Target = Trait> {
 		None
 	}
 
-	/// Trait to implement. Only used for [`ZeroizeOnDrop`](https://docs.rs/zeroize/latest/zeroize/trait.ZeroizeOnDrop.html)
-	/// because it implements [`Drop`] and not itself.
+	/// Trait to implement. Only used by [`Eq`] and
+	/// [`ZeroizeOnDrop`](https://docs.rs/zeroize/latest/zeroize/trait.ZeroizeOnDrop.html).
 	fn impl_item(
 		&self,
 		imp: &ImplGenerics<'_>,

src/trait_/eq.rs

@@ -1,9 +1,10 @@
 //! [`Eq`](trait@std::cmp::Eq) implementation.
 
-use std::ops::Deref;
+use std::{borrow::Cow, ops::Deref};
 
 use proc_macro2::TokenStream;
 use quote::quote;
+use syn::{Ident, ImplGenerics, Path, TypeGenerics, WhereClause};
 
 use crate::{util, Data, DeriveTrait, DeriveWhere, Item, SplitGenerics, Trait, TraitImpl};
 
@@ -19,10 +20,37 @@ impl TraitImpl for Eq {
 		DeriveTrait::Eq
 	}
 
-	fn path(&self) -> syn::Path {
+	fn path(&self) -> Path {
 		util::path_from_strs(&["core", "cmp", "Eq"])
 	}
 
+	fn additional_impl(&self) -> Option<(Path, TokenStream)> {
+		Some((self.path(), quote! {}))
+	}
+
+	fn impl_item(
+		&self,
+		imp: &ImplGenerics<'_>,
+		ident: &Ident,
+		ty: &TypeGenerics<'_>,
+		where_clause: &Option<Cow<'_, WhereClause>>,
+		body: TokenStream,
+	) -> TokenStream {
+		quote! {
+			const _: () = {
+				trait DeriveWhereAssertEq {
+					fn assert(&self);
+				}
+
+				impl #imp DeriveWhereAssertEq for #ident #ty
+				#where_clause
+				{
+					#body
+				}
+			};
+		}
+	}
+
 	fn build_signature(
 		&self,
 		_derive_where: &DeriveWhere,
@@ -31,8 +59,7 @@ impl TraitImpl for Eq {
 		body: &TokenStream,
 	) -> TokenStream {
 		quote! {
-			#[inline]
-			fn assert_receiver_is_total_eq(&self) {
+			fn assert(&self) {
 				struct __AssertEq<__T: ::core::cmp::Eq + ?::core::marker::Sized>(::core::marker::PhantomData<__T>);
 
 				#body