Move special treatment of `derive(Copy, PartialEq, Eq)` from expansion infrastructure to elsewhere

4 files changed, 26 insertions, 51 deletions

diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index bb7834a133f..5e1cc70784e 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -595,6 +595,8 @@ pub struct SyntaxExtension {
     /// Built-in macros have a couple of special properties (meaning of `$crate`,
     /// availability in `#[no_implicit_prelude]` modules), so we have to keep this flag.
     pub is_builtin: bool,
+    /// We have to identify macros providing a `Copy` impl early for compatibility reasons.
+    pub is_derive_copy: bool,
 }
 
 impl SyntaxExtensionKind {
@@ -640,6 +642,7 @@ impl SyntaxExtension {
             helper_attrs: Vec::new(),
             edition,
             is_builtin: false,
+            is_derive_copy: false,
             kind,
         }
     }
@@ -683,6 +686,16 @@ pub type NamedSyntaxExtension = (Name, SyntaxExtension);
 /// Error type that denotes indeterminacy.
 pub struct Indeterminate;
 
+bitflags::bitflags! {
+    /// Built-in derives that need some extra tracking beyond the usual macro functionality.
+    #[derive(Default)]
+    pub struct SpecialDerives: u8 {
+        const PARTIAL_EQ = 1 << 0;
+        const EQ         = 1 << 1;
+        const COPY       = 1 << 2;
+    }
+}
+
 pub trait Resolver {
     fn next_node_id(&mut self) -> ast::NodeId;
 
@@ -699,6 +712,9 @@ pub trait Resolver {
                                 -> Result<Option<Lrc<SyntaxExtension>>, Indeterminate>;
 
     fn check_unused_macros(&self);
+
+    fn has_derives(&self, expn_id: ExpnId, derives: SpecialDerives) -> bool;
+    fn add_derives(&mut self, expn_id: ExpnId, derives: SpecialDerives);
 }
 
 #[derive(Clone)]
@@ -725,7 +741,6 @@ pub struct ExtCtxt<'a> {
     pub resolver: &'a mut dyn Resolver,
     pub current_expansion: ExpansionData,
     pub expansions: FxHashMap<Span, Vec<String>>,
-    pub allow_derive_markers: Lrc<[Symbol]>,
 }
 
 impl<'a> ExtCtxt<'a> {
@@ -745,7 +760,6 @@ impl<'a> ExtCtxt<'a> {
                 directory_ownership: DirectoryOwnership::Owned { relative: None },
             },
             expansions: FxHashMap::default(),
-            allow_derive_markers: [sym::rustc_attrs, sym::structural_match][..].into(),
         }
     }
 
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 1e9e16d72f8..c16e772d1cc 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -4,7 +4,7 @@ use crate::attr::{self, HasAttrs};
 use crate::source_map::{dummy_spanned, respan};
 use crate::config::StripUnconfigured;
 use crate::ext::base::*;
-use crate::ext::proc_macro::{add_derived_markers, collect_derives};
+use crate::ext::proc_macro::collect_derives;
 use crate::ext::hygiene::{ExpnId, SyntaxContext, ExpnInfo, ExpnKind};
 use crate::ext::placeholders::{placeholder, PlaceholderExpander};
 use crate::feature_gate::{self, Features, GateIssue, is_builtin_attr, emit_feature_err};
@@ -209,7 +209,6 @@ pub enum InvocationKind {
     Derive {
         path: Path,
         item: Annotatable,
-        item_with_markers: Annotatable,
     },
     /// "Invocation" that contains all derives from an item,
     /// broken into multiple `Derive` invocations when expanded.
@@ -360,8 +359,6 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
 
                 let mut item = self.fully_configure(item);
                 item.visit_attrs(|attrs| attrs.retain(|a| a.path != sym::derive));
-                let mut item_with_markers = item.clone();
-                add_derived_markers(&mut self.cx, item.span(), &traits, &mut item_with_markers);
                 let derives = derives.entry(invoc.expansion_data.id).or_default();
 
                 derives.reserve(traits.len());
@@ -370,11 +367,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                     let expn_id = ExpnId::fresh(self.cx.current_expansion.id, None);
                     derives.push(expn_id);
                     invocations.push(Invocation {
-                        kind: InvocationKind::Derive {
-                            path,
-                            item: item.clone(),
-                            item_with_markers: item_with_markers.clone(),
-                        },
+                        kind: InvocationKind::Derive { path, item: item.clone() },
                         fragment_kind: invoc.fragment_kind,
                         expansion_data: ExpansionData {
                             id: expn_id,
@@ -383,7 +376,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                     });
                 }
                 let fragment = invoc.fragment_kind
-                    .expect_from_annotatables(::std::iter::once(item_with_markers));
+                    .expect_from_annotatables(::std::iter::once(item));
                 self.collect_invocations(fragment, derives)
             } else {
                 unreachable!()
@@ -569,13 +562,9 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                 }
                 _ => unreachable!()
             }
-            InvocationKind::Derive { path, item, item_with_markers } => match ext {
+            InvocationKind::Derive { path, item } => match ext {
                 SyntaxExtensionKind::Derive(expander) |
                 SyntaxExtensionKind::LegacyDerive(expander) => {
-                    let (path, item) = match ext {
-                        SyntaxExtensionKind::LegacyDerive(..) => (path, item_with_markers),
-                        _ => (path, item),
-                    };
                     if !item.derive_allowed() {
                         return fragment_kind.dummy(span);
                     }
diff --git a/src/libsyntax/ext/proc_macro.rs b/src/libsyntax/ext/proc_macro.rs
index ec708994fad..c17b6f6b424 100644
--- a/src/libsyntax/ext/proc_macro.rs
+++ b/src/libsyntax/ext/proc_macro.rs
@@ -1,17 +1,15 @@
 use crate::ast::{self, ItemKind, Attribute, Mac};
-use crate::attr::{mark_used, mark_known, HasAttrs};
+use crate::attr::{mark_used, mark_known};
 use crate::errors::{Applicability, FatalError};
 use crate::ext::base::{self, *};
 use crate::ext::proc_macro_server;
 use crate::parse::{self, token};
 use crate::parse::parser::PathStyle;
-use crate::symbol::{sym, Symbol};
+use crate::symbol::sym;
 use crate::tokenstream::{self, TokenStream};
 use crate::visit::Visitor;
 
-use rustc_data_structures::fx::FxHashSet;
 use rustc_data_structures::sync::Lrc;
-use syntax_pos::hygiene::{ExpnInfo, ExpnKind};
 use syntax_pos::{Span, DUMMY_SP};
 
 const EXEC_STRATEGY: proc_macro::bridge::server::SameThread =
@@ -217,32 +215,3 @@ crate fn collect_derives(cx: &mut ExtCtxt<'_>, attrs: &mut Vec<ast::Attribute>)
     });
     result
 }
-
-crate fn add_derived_markers<T: HasAttrs>(
-    cx: &mut ExtCtxt<'_>, span: Span, traits: &[ast::Path], item: &mut T
-) {
-    let (mut names, mut pretty_name) = (FxHashSet::default(), String::new());
-    for (i, path) in traits.iter().enumerate() {
-        if i > 0 {
-            pretty_name.push_str(", ");
-        }
-        pretty_name.push_str(&path.to_string());
-        names.insert(unwrap_or!(path.segments.get(0), continue).ident.name);
-    }
-
-    let span = span.fresh_expansion(cx.current_expansion.id, ExpnInfo::allow_unstable(
-        ExpnKind::Macro(MacroKind::Derive, Symbol::intern(&pretty_name)), span,
-        cx.parse_sess.edition, cx.allow_derive_markers.clone(),
-    ));
-
-    item.visit_attrs(|attrs| {
-        if names.contains(&sym::Eq) && names.contains(&sym::PartialEq) {
-            let meta = cx.meta_word(span, sym::structural_match);
-            attrs.push(cx.attribute(meta));
-        }
-        if names.contains(&sym::Copy) {
-            let meta = cx.meta_word(span, sym::rustc_copy_clone_marker);
-            attrs.push(cx.attribute(meta));
-        }
-    });
-}
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index ce695df7775..4ca2971dbbc 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -429,6 +429,8 @@ pub fn compile(
         }
     }
 
+    let is_builtin = attr::contains_name(&def.attrs, sym::rustc_builtin_macro);
+
     SyntaxExtension {
         kind: SyntaxExtensionKind::LegacyBang(expander),
         span: def.span,
@@ -440,7 +442,8 @@ pub fn compile(
         deprecation: attr::find_deprecation(&sess, &def.attrs, def.span),
         helper_attrs: Vec::new(),
         edition,
-        is_builtin: attr::contains_name(&def.attrs, sym::rustc_builtin_macro),
+        is_builtin,
+        is_derive_copy: is_builtin && def.ident.name == sym::Copy,
     }
 }