Improve `Eq` deriving

2 files changed, 37 insertions, 33 deletions

diff --git a/src/libsyntax_ext/deriving/clone.rs b/src/libsyntax_ext/deriving/clone.rs
index aa7c2c301dd..d7bc2a6faee 100644
--- a/src/libsyntax_ext/deriving/clone.rs
+++ b/src/libsyntax_ext/deriving/clone.rs
@@ -115,20 +115,7 @@ fn cs_clone_shallow(name: &str,
         let assert_path = cx.path_all(span, true,
                                         cx.std_path(&["clone", helper_name]),
                                         vec![], vec![ty], vec![]);
-        let local = P(ast::Local {
-            pat: cx.pat_wild(span),
-            ty: Some(cx.ty_path(assert_path)),
-            init: None,
-            id: ast::DUMMY_NODE_ID,
-            span: span,
-            attrs: ast::ThinVec::new(),
-        });
-        let stmt = ast::Stmt {
-            id: ast::DUMMY_NODE_ID,
-            node: ast::StmtKind::Local(local),
-            span: span,
-        };
-        stmts.push(stmt);
+        stmts.push(cx.stmt_let_type_only(span, cx.ty_path(assert_path)));
     }
     fn process_variant(cx: &mut ExtCtxt, stmts: &mut Vec<ast::Stmt>, variant: &VariantData) {
         for field in variant.fields() {
diff --git a/src/libsyntax_ext/deriving/cmp/eq.rs b/src/libsyntax_ext/deriving/cmp/eq.rs
index 425a47a991b..fa0fb2492c5 100644
--- a/src/libsyntax_ext/deriving/cmp/eq.rs
+++ b/src/libsyntax_ext/deriving/cmp/eq.rs
@@ -11,7 +11,7 @@
 use deriving::generic::*;
 use deriving::generic::ty::*;
 
-use syntax::ast::{Expr, MetaItem};
+use syntax::ast::{self, Expr, MetaItem};
 use syntax::ext::base::{Annotatable, ExtCtxt};
 use syntax::ext::build::AstBuilder;
 use syntax::parse::token::InternedString;
@@ -23,22 +23,6 @@ pub fn expand_deriving_eq(cx: &mut ExtCtxt,
                           mitem: &MetaItem,
                           item: &Annotatable,
                           push: &mut FnMut(Annotatable)) {
-    fn cs_total_eq_assert(cx: &mut ExtCtxt, span: Span, substr: &Substructure) -> P<Expr> {
-        cs_same_method(|cx, span, exprs| {
-            // create `a.<method>(); b.<method>(); c.<method>(); ...`
-            // (where method is `assert_receiver_is_total_eq`)
-            let stmts = exprs.into_iter().map(|e| cx.stmt_expr(e)).collect();
-            let block = cx.block(span, stmts);
-            cx.expr_block(block)
-        },
-                       Box::new(|cx, sp, _, _| {
-                           cx.span_bug(sp, "non matching enums in derive(Eq)?")
-                       }),
-                       cx,
-                       span,
-                       substr)
-    }
-
     let inline = cx.meta_word(span, InternedString::new("inline"));
     let hidden = cx.meta_list_item_word(span, InternedString::new("hidden"));
     let doc = cx.meta_list(span, InternedString::new("doc"), vec![hidden]);
@@ -50,7 +34,7 @@ pub fn expand_deriving_eq(cx: &mut ExtCtxt,
         additional_bounds: Vec::new(),
         generics: LifetimeBounds::empty(),
         is_unsafe: false,
-        supports_unions: false,
+        supports_unions: true,
         methods: vec![MethodDef {
                           name: "assert_receiver_is_total_eq",
                           generics: LifetimeBounds::empty(),
@@ -66,5 +50,38 @@ pub fn expand_deriving_eq(cx: &mut ExtCtxt,
                       }],
         associated_types: Vec::new(),
     };
-    trait_def.expand(cx, mitem, item, push)
+    trait_def.expand_ext(cx, mitem, item, push, true)
+}
+
+fn cs_total_eq_assert(cx: &mut ExtCtxt, trait_span: Span, substr: &Substructure) -> P<Expr> {
+    fn assert_ty_bounds(cx: &mut ExtCtxt, stmts: &mut Vec<ast::Stmt>,
+                        ty: P<ast::Ty>, span: Span, helper_name: &str) {
+        // Generate statement `let _: helper_name<ty>;`,
+        // set the expn ID so we can use the unstable struct.
+        let span = super::allow_unstable(cx, span, "derive(Eq)");
+        let assert_path = cx.path_all(span, true,
+                                        cx.std_path(&["cmp", helper_name]),
+                                        vec![], vec![ty], vec![]);
+        stmts.push(cx.stmt_let_type_only(span, cx.ty_path(assert_path)));
+    }
+    fn process_variant(cx: &mut ExtCtxt, stmts: &mut Vec<ast::Stmt>, variant: &ast::VariantData) {
+        for field in variant.fields() {
+            // let _: AssertParamIsEq<FieldTy>;
+            assert_ty_bounds(cx, stmts, field.ty.clone(), field.span, "AssertParamIsEq");
+        }
+    }
+
+    let mut stmts = Vec::new();
+    match *substr.fields {
+        StaticStruct(vdata, ..) => {
+            process_variant(cx, &mut stmts, vdata);
+        }
+        StaticEnum(enum_def, ..) => {
+            for variant in &enum_def.variants {
+                process_variant(cx, &mut stmts, &variant.node.data);
+            }
+        }
+        _ => cx.span_bug(trait_span, "unexpected substructure in `derive(Eq)`")
+    }
+    cx.expr_block(cx.block(trait_span, stmts))
 }