thread tighter span for closures around

Track the span corresponding to the `|...|` part of the closure.

2 files changed, 37 insertions, 13 deletions

diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index a4e5b68277d..8ebf4863af5 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -194,10 +194,14 @@ pub trait AstBuilder {
                cond: P<ast::Expr>, then: P<ast::Expr>, els: Option<P<ast::Expr>>) -> P<ast::Expr>;
     fn expr_loop(&self, span: Span, block: P<ast::Block>) -> P<ast::Expr>;
 
-    fn lambda_fn_decl(&self, span: Span,
-                      fn_decl: P<ast::FnDecl>, blk: P<ast::Block>) -> P<ast::Expr>;
+    fn lambda_fn_decl(&self,
+                      span: Span,
+                      fn_decl: P<ast::FnDecl>,
+                      blk: P<ast::Block>,
+                      fn_decl_span: Span)
+                      -> P<ast::Expr>;
 
-    fn lambda(&self, span: Span, ids: Vec<ast::Ident> , blk: P<ast::Block>) -> P<ast::Expr>;
+    fn lambda(&self, span: Span, ids: Vec<ast::Ident>, blk: P<ast::Block>) -> P<ast::Expr>;
     fn lambda0(&self, span: Span, blk: P<ast::Block>) -> P<ast::Expr>;
     fn lambda1(&self, span: Span, blk: P<ast::Block>, ident: ast::Ident) -> P<ast::Expr>;
 
@@ -894,17 +898,34 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
         self.expr(span, ast::ExprKind::Loop(block, None))
     }
 
-    fn lambda_fn_decl(&self, span: Span,
-                      fn_decl: P<ast::FnDecl>, blk: P<ast::Block>) -> P<ast::Expr> {
-        self.expr(span, ast::ExprKind::Closure(ast::CaptureBy::Ref, fn_decl, blk))
+    fn lambda_fn_decl(&self,
+                      span: Span,
+                      fn_decl: P<ast::FnDecl>,
+                      blk: P<ast::Block>,
+                      fn_decl_span: Span) // span of the `|...|` part
+                      -> P<ast::Expr> {
+        self.expr(span, ast::ExprKind::Closure(ast::CaptureBy::Ref,
+                                               fn_decl,
+                                               blk,
+                                               fn_decl_span))
     }
-    fn lambda(&self, span: Span, ids: Vec<ast::Ident>, blk: P<ast::Block>) -> P<ast::Expr> {
+
+    fn lambda(&self,
+              span: Span,
+              ids: Vec<ast::Ident>,
+              blk: P<ast::Block>)
+              -> P<ast::Expr> {
         let fn_decl = self.fn_decl(
             ids.iter().map(|id| self.arg(span, *id, self.ty_infer(span))).collect(),
             self.ty_infer(span));
 
-        self.expr(span, ast::ExprKind::Closure(ast::CaptureBy::Ref, fn_decl, blk))
+        // FIXME -- We are using `span` as the span of the `|...|`
+        // part of the lambda, but it probably (maybe?) corresponds to
+        // the entire lambda body. Probably we should extend the API
+        // here, but that's not entirely clear.
+        self.expr(span, ast::ExprKind::Closure(ast::CaptureBy::Ref, fn_decl, blk, span))
     }
+
     fn lambda0(&self, span: Span, blk: P<ast::Block>) -> P<ast::Expr> {
         self.lambda(span, Vec::new(), blk)
     }
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index cd7b0fcfb00..38132eb42ee 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -149,14 +149,17 @@ pub fn expand_expr(e: P<ast::Expr>, fld: &mut MacroExpander) -> P<ast::Expr> {
             fld.cx.expr(span, il).with_attrs(fold_thin_attrs(attrs, fld))
         }
 
-        ast::ExprKind::Closure(capture_clause, fn_decl, block) => {
+        ast::ExprKind::Closure(capture_clause, fn_decl, block, fn_decl_span) => {
             let (rewritten_fn_decl, rewritten_block)
                 = expand_and_rename_fn_decl_and_block(fn_decl, block, fld);
             let new_node = ast::ExprKind::Closure(capture_clause,
-                                            rewritten_fn_decl,
-                                            rewritten_block);
-            P(ast::Expr{id:id, node: new_node, span: fld.new_span(span),
-                        attrs: fold_thin_attrs(attrs, fld)})
+                                                  rewritten_fn_decl,
+                                                  rewritten_block,
+                                                  fld.new_span(fn_decl_span));
+            P(ast::Expr{ id:id,
+                         node: new_node,
+                         span: fld.new_span(span),
+                         attrs: fold_thin_attrs(attrs, fld) })
         }
 
         _ => {