1 files changed, 90 insertions, 0 deletions
diff --git a/compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs b/compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs
new file mode 100644
index 000000000..4e798bf6a
--- /dev/null
+++ b/compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs
@@ -0,0 +1,90 @@
+use crate::deriving::generic::ty::*;
+use crate::deriving::generic::*;
+use crate::deriving::path_std;
+
+use rustc_ast::{self as ast, MetaItem};
+use rustc_data_structures::fx::FxHashSet;
+use rustc_expand::base::{Annotatable, ExtCtxt};
+use rustc_span::symbol::{sym, Ident};
+use rustc_span::Span;
+
+pub fn expand_deriving_eq(
+    cx: &mut ExtCtxt<'_>,
+    span: Span,
+    mitem: &MetaItem,
+    item: &Annotatable,
+    push: &mut dyn FnMut(Annotatable),
+) {
+    let span = cx.with_def_site_ctxt(span);
+    let inline = cx.meta_word(span, sym::inline);
+    let hidden = rustc_ast::attr::mk_nested_word_item(Ident::new(sym::hidden, span));
+    let doc = rustc_ast::attr::mk_list_item(Ident::new(sym::doc, span), vec![hidden]);
+    let no_coverage = cx.meta_word(span, sym::no_coverage);
+    let attrs = vec![cx.attribute(inline), cx.attribute(doc), cx.attribute(no_coverage)];
+    let trait_def = TraitDef {
+        span,
+        attributes: Vec::new(),
+        path: path_std!(cmp::Eq),
+        additional_bounds: Vec::new(),
+        generics: Bounds::empty(),
+        supports_unions: true,
+        methods: vec![MethodDef {
+            name: sym::assert_receiver_is_total_eq,
+            generics: Bounds::empty(),
+            explicit_self: true,
+            nonself_args: vec![],
+            ret_ty: Unit,
+            attributes: attrs,
+            unify_fieldless_variants: true,
+            combine_substructure: combine_substructure(Box::new(|a, b, c| {
+                cs_total_eq_assert(a, b, c)
+            })),
+        }],
+        associated_types: Vec::new(),
+    };
+
+    super::inject_impl_of_structural_trait(cx, span, item, path_std!(marker::StructuralEq), push);
+
+    trait_def.expand_ext(cx, mitem, item, push, true)
+}
+
+fn cs_total_eq_assert(
+    cx: &mut ExtCtxt<'_>,
+    trait_span: Span,
+    substr: &Substructure<'_>,
+) -> BlockOrExpr {
+    let mut stmts = Vec::new();
+    let mut seen_type_names = FxHashSet::default();
+    let mut process_variant = |variant: &ast::VariantData| {
+        for field in variant.fields() {
+            // This basic redundancy checking only prevents duplication of
+            // assertions like `AssertParamIsEq<Foo>` where the type is a
+            // simple name. That's enough to get a lot of cases, though.
+            if let Some(name) = field.ty.kind.is_simple_path() && !seen_type_names.insert(name) {
+                // Already produced an assertion for this type.
+            } else {
+                // let _: AssertParamIsEq<FieldTy>;
+                super::assert_ty_bounds(
+                    cx,
+                    &mut stmts,
+                    field.ty.clone(),
+                    field.span,
+                    &[sym::cmp, sym::AssertParamIsEq],
+                );
+            }
+        }
+    };
+
+    match *substr.fields {
+        StaticStruct(vdata, ..) => {
+            process_variant(vdata);
+        }
+        StaticEnum(enum_def, ..) => {
+            for variant in &enum_def.variants {
+                process_variant(&variant.data);
+            }
+        }
+        _ => cx.span_bug(trait_span, "unexpected substructure in `derive(Eq)`"),
+    }
+    BlockOrExpr::new_stmts(stmts)
+}