Revert "Try detecting mixed derive/derivative with Clone and Copy"

This reverts commit 4117fff.

As of rust 1.17, proc-macros don't get attributes other than their own
in the token stream they're fed.
See rust-lang/rust#39572

Author: glandium

src/attr.rs

@@ -49,17 +49,13 @@ pub struct InputClone {
     bounds: Option<Vec<syn::WherePredicate>>,
     /// Whether the implementation should have an explicit `clone_from`.
     pub clone_from: bool,
-    /// Whether the `rustc_copy_clone_marker` was found.
-    pub rustc_copy_clone_marker: bool,
 }
 
 #[derive(Debug, Default)]
 /// Represent the `derivative(Clone(…))` attributes on an input.
 pub struct InputCopy {
     /// The `bound` attribute if present and the corresponding bounds.
     bounds: Option<Vec<syn::WherePredicate>>,
-    /// Whether the input also derive `Clone` (ie. `derive(Clone)`, but not `derivative(Clone)`)
-    derives_clone: bool,
 }
 
 #[derive(Debug, Default)]
@@ -215,50 +211,21 @@ impl Input {
         for_all_attr! {
             for (name, values) in attrs;
             "Clone" => {
-                let mut clone = input.clone.take().unwrap_or_default();
-
-                clone.rustc_copy_clone_marker = attrs
-                    .iter()
-                    .filter_map(|attr| attr.parse_meta().ok())
-                    .any(|meta| meta.name().to_string() == "rustc_copy_clone_marker");
-
                 match_attributes! {
+                    let Some(clone) = input.clone;
                     for value in values;
                     "bound" => try!(parse_bound(&mut clone.bounds, opt_string_to_str!(value))),
                     "clone_from" => {
                         clone.clone_from = try!(parse_boolean_meta_item(&opt_string_to_str!(value), true, "clone_from"));
                     }
                 }
-
-                input.clone = Some(clone);
             }
             "Copy" => {
-                let mut copy = input.copy.take().unwrap_or_default();
-
-                for attr in attrs {
-                    if let Ok(syn::Meta::List(syn::MetaList{
-                        ident: ref name,
-                        nested: ref traits,
-                        ..
-                    })) = attr.parse_meta() {
-                        fn is_clone(elem: &syn::NestedMeta) -> bool {
-                            match *elem {
-                                syn::NestedMeta::Meta(ref mi) => mi.name() == "Clone",
-                                syn::NestedMeta::Literal(..) => false,
-                            }
-                        }
-                        if name == "derive" && traits.iter().any(is_clone) {
-                            copy.derives_clone = true;
-                        }
-                    }
-                }
-
                 match_attributes! {
+                    let Some(copy) = input.copy;
                     for value in values;
                     "bound" => try!(parse_bound(&mut copy.bounds, opt_string_to_str!(value))),
                 }
-
-                input.copy = Some(copy);
             }
             "Debug" => {
                 match_attributes! {
@@ -325,10 +292,6 @@ impl Input {
             .map_or(None, |d| d.bounds.as_ref().map(Vec::as_slice))
     }
 
-    pub fn derives_clone(&self) -> bool {
-        self.copy.as_ref().map_or(false, |d| d.derives_clone)
-    }
-
     pub fn debug_bound(&self) -> Option<&[syn::WherePredicate]> {
         self.debug
             .as_ref()
@@ -357,12 +320,6 @@ impl Input {
             .map_or(None, |d| d.bounds.as_ref().map(Vec::as_slice))
     }
 
-    pub fn rustc_copy_clone_marker(&self) -> bool {
-        self.clone
-            .as_ref()
-            .map_or(false, |d| d.rustc_copy_clone_marker)
-    }
-
     pub fn partial_eq_bound(&self) -> Option<&[syn::WherePredicate]> {
         self.partial_eq
             .as_ref()

src/clone.rs

@@ -7,13 +7,9 @@ use syn;
 use utils;
 
 /// Derive `Copy` for `input`.
-pub fn derive_copy(input: &ast::Input) -> Result<proc_macro2::TokenStream, String> {
+pub fn derive_copy(input: &ast::Input) -> proc_macro2::TokenStream {
     let name = &input.ident;
 
-    if input.attrs.derives_clone() {
-        return Err("`#[derivative(Copy)]` can't be used with `#[derive(Clone)]`".into());
-    }
-
     let copy_trait_path = copy_trait_path();
     let generics = utils::build_impl_generics(
         input,
@@ -24,10 +20,10 @@ pub fn derive_copy(input: &ast::Input) -> Result<proc_macro2::TokenStream, Strin
     );
     let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
 
-    Ok(quote! {
+    quote! {
         #[allow(unused_qualifications)]
         impl #impl_generics #copy_trait_path for #name #ty_generics #where_clause {}
-    })
+    }
 }
 
 /// Derive `Clone` for `input`.
@@ -44,7 +40,7 @@ pub fn derive_clone(input: &ast::Input) -> proc_macro2::TokenStream {
     );
     let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
 
-    let is_copy = input.attrs.rustc_copy_clone_marker() || input.attrs.copy.is_some();
+    let is_copy = input.attrs.copy.is_some();
     if is_copy && input.generics.type_params().count() == 0 {
         quote! {
             #[allow(unused_qualifications)]

src/lib.rs

@@ -26,7 +26,7 @@ fn derive_impls(input: &ast::Input) -> Result<proc_macro2::TokenStream, String>
         tokens.extend(clone::derive_clone(input));
     }
     if input.attrs.copy.is_some() {
-        tokens.extend(clone::derive_copy(input)?);
+        tokens.extend(clone::derive_copy(input));
     }
     if input.attrs.debug.is_some() {
         tokens.extend(debug::derive(input));

tests/compile-fail/derive-copy-clone.rs

@@ -44,15 +44,6 @@ struct OurOur1(Liar);
 #[derivative(Clone, Copy)]
 struct OurOur2(Liar);
 
-#[derive(Copy)]
-#[derive(Derivative)]
-#[derivative(Clone)]
-struct TheirOur1(Liar);
-#[derive(Copy)]
-#[derive(Derivative)]
-#[derivative(Clone)]
-struct TheirOur2(Liar);
-
 #[test]
 fn main() {
     let _ = TheirTheir(Liar).clone();
@@ -62,12 +53,4 @@ fn main() {
     assert!(!CLONED.load(Ordering::SeqCst), "OurOur1");
     let _ = OurOur2(Liar).clone();
     assert!(!CLONED.load(Ordering::SeqCst), "OurOur2");
-
-    // Ideally this would work the same, just testing that the behaviour does not change:
-    CLONED.store(false, Ordering::SeqCst);
-    let _ = TheirOur1(Liar).clone();
-    assert!(CLONED.load(Ordering::SeqCst), "TheirOur1");
-    CLONED.store(false, Ordering::SeqCst);
-    let _ = TheirOur2(Liar).clone();
-    assert!(CLONED.load(Ordering::SeqCst), "TheirOur2");
 }