Auto merge of #21079 - huonw:chained-cmp-tweaks, r=pnkfelix

First commit is mindless groundwork for the second one, to make the spans (arguably) nicer.

### before

```
require-parens-for-chained-comparison.rs:14:20: 14:22 error: Chained comparison operators require parentheses
require-parens-for-chained-comparison.rs:14     false == false == false;
                                                               ^~
require-parens-for-chained-comparison.rs:17:16: 17:17 error: Chained comparison operators require parentheses
require-parens-for-chained-comparison.rs:17     false == 0 < 2;
                                                           ^
require-parens-for-chained-comparison.rs:20:8: 20:9 error: Chained comparison operators require parentheses
require-parens-for-chained-comparison.rs:20     f<X>();
                                                   ^
require-parens-for-chained-comparison.rs:20:8: 20:9 help: Use ::< instead of < if you meant to specify type arguments.
require-parens-for-chained-comparison.rs:20     f<X>();
                                                   ^
```

### after

```
require-parens-for-chained-comparison.rs:14:11: 14:22 error: chained comparison operators require parentheses
require-parens-for-chained-comparison.rs:14     false == false == false;
                                                      ^~~~~~~~~~~
require-parens-for-chained-comparison.rs:17:11: 17:17 error: chained comparison operators require parentheses
require-parens-for-chained-comparison.rs:17     false == 0 < 2;
                                                      ^~~~~~
require-parens-for-chained-comparison.rs:20:6: 20:9 error: chained comparison operators require parentheses
require-parens-for-chained-comparison.rs:20     f<X>();
                                                 ^~~
require-parens-for-chained-comparison.rs:20:6: 20:9 help: use `::<...>` instead of `<...>` if you meant to specify type arguments
require-parens-for-chained-comparison.rs:20     f<X>();
                                                 ^~~
```

2 files changed, 4 insertions, 4 deletions

diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index 92619cf42e4..2b3a7212683 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -106,7 +106,7 @@ pub trait AstBuilder {
     fn expr_ident(&self, span: Span, id: ast::Ident) -> P<ast::Expr>;
 
     fn expr_self(&self, span: Span) -> P<ast::Expr>;
-    fn expr_binary(&self, sp: Span, op: ast::BinOp,
+    fn expr_binary(&self, sp: Span, op: ast::BinOp_,
                    lhs: P<ast::Expr>, rhs: P<ast::Expr>) -> P<ast::Expr>;
     fn expr_deref(&self, sp: Span, e: P<ast::Expr>) -> P<ast::Expr>;
     fn expr_unary(&self, sp: Span, op: ast::UnOp, e: P<ast::Expr>) -> P<ast::Expr>;
@@ -561,9 +561,9 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
         self.expr_ident(span, special_idents::self_)
     }
 
-    fn expr_binary(&self, sp: Span, op: ast::BinOp,
+    fn expr_binary(&self, sp: Span, op: ast::BinOp_,
                    lhs: P<ast::Expr>, rhs: P<ast::Expr>) -> P<ast::Expr> {
-        self.expr(sp, ast::ExprBinary(op, lhs, rhs))
+        self.expr(sp, ast::ExprBinary(Spanned { node: op, span: sp }, lhs, rhs))
     }
 
     fn expr_deref(&self, sp: Span, e: P<ast::Expr>) -> P<ast::Expr> {
diff --git a/src/libsyntax/ext/deriving/generic/mod.rs b/src/libsyntax/ext/deriving/generic/mod.rs
index 272b0464010..f8812f4d28d 100644
--- a/src/libsyntax/ext/deriving/generic/mod.rs
+++ b/src/libsyntax/ext/deriving/generic/mod.rs
@@ -1449,7 +1449,7 @@ pub fn cs_same_method_fold<F>(use_foldl: bool,
 /// Use a given binop to combine the result of calling the derived method
 /// on all the fields.
 #[inline]
-pub fn cs_binop(binop: ast::BinOp, base: P<Expr>,
+pub fn cs_binop(binop: ast::BinOp_, base: P<Expr>,
                 enum_nonmatch_f: EnumNonMatchCollapsedFunc,
                 cx: &mut ExtCtxt, trait_span: Span,
                 substructure: &Substructure) -> P<Expr> {