Add -Zinput-stats

Emits loc, and node count - before and after expansion.

E.g.,

```
rustc: x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore
Lines of code:             32060
Pre-expansion node count:  120205
Post-expansion node count: 482749
```

3 files changed, 174 insertions, 1 deletions

diff --git a/src/libsyntax/codemap.rs b/src/libsyntax/codemap.rs
index a73fd4534c9..db011265c73 100644
--- a/src/libsyntax/codemap.rs
+++ b/src/libsyntax/codemap.rs
@@ -559,6 +559,10 @@ impl FileMap {
     pub fn is_imported(&self) -> bool {
         self.src.is_none()
     }
+
+    fn count_lines(&self) -> usize {
+        self.lines.borrow().len()
+    }
 }
 
 /// An abstraction over the fs operations used by the Parser.
@@ -1021,6 +1025,10 @@ impl CodeMap {
         debug!("span_allows_unstable? {}", allows_unstable);
         allows_unstable
     }
+
+    pub fn count_lines(&self) -> usize {
+        self.files.borrow().iter().fold(0, |a, f| a + f.count_lines())
+    }
 }
 
 // _____________________________________________________________________________
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index 8b001f2419c..524ac655d88 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -62,10 +62,11 @@ macro_rules! panictry {
 
 pub mod util {
     pub mod interner;
+    pub mod node_count;
+    pub mod parser;
     #[cfg(test)]
     pub mod parser_testing;
     pub mod small_vector;
-    pub mod parser;
 }
 
 pub mod diagnostics {
diff --git a/src/libsyntax/util/node_count.rs b/src/libsyntax/util/node_count.rs
new file mode 100644
index 00000000000..e692ec4452c
--- /dev/null
+++ b/src/libsyntax/util/node_count.rs
@@ -0,0 +1,164 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Simply gives a rought count of the number of nodes in an AST.
+
+use visit::*;
+use ast::*;
+use codemap::Span;
+
+pub struct NodeCounter {
+    pub count: usize,
+}
+
+impl NodeCounter {
+    pub fn new() -> NodeCounter {
+        NodeCounter {
+            count: 0,
+        }
+    }
+}
+
+impl<'v> Visitor<'v> for NodeCounter {
+    fn visit_ident(&mut self, span: Span, ident: Ident) {
+        self.count += 1;
+        walk_ident(self, span, ident);
+    }
+    fn visit_mod(&mut self, m: &'v Mod, _s: Span, _n: NodeId) {
+        self.count += 1;
+        walk_mod(self, m)
+    }
+    fn visit_foreign_item(&mut self, i: &'v ForeignItem) {
+        self.count += 1;
+        walk_foreign_item(self, i)
+    }
+    fn visit_item(&mut self, i: &'v Item) {
+        self.count += 1;
+        walk_item(self, i)
+    }
+    fn visit_local(&mut self, l: &'v Local) {
+        self.count += 1;
+        walk_local(self, l)
+    }
+    fn visit_block(&mut self, b: &'v Block) {
+        self.count += 1;
+        walk_block(self, b)
+    }
+    fn visit_stmt(&mut self, s: &'v Stmt) {
+        self.count += 1;
+        walk_stmt(self, s)
+    }
+    fn visit_arm(&mut self, a: &'v Arm) {
+        self.count += 1;
+        walk_arm(self, a)
+    }
+    fn visit_pat(&mut self, p: &'v Pat) {
+        self.count += 1;
+        walk_pat(self, p)
+    }
+    fn visit_decl(&mut self, d: &'v Decl) {
+        self.count += 1;
+        walk_decl(self, d)
+    }
+    fn visit_expr(&mut self, ex: &'v Expr) {
+        self.count += 1;
+        walk_expr(self, ex)
+    }
+    fn visit_ty(&mut self, t: &'v Ty) {
+        self.count += 1;
+        walk_ty(self, t)
+    }
+    fn visit_generics(&mut self, g: &'v Generics) {
+        self.count += 1;
+        walk_generics(self, g)
+    }
+    fn visit_fn(&mut self, fk: FnKind<'v>, fd: &'v FnDecl, b: &'v Block, s: Span, _: NodeId) {
+        self.count += 1;
+        walk_fn(self, fk, fd, b, s)
+    }
+    fn visit_trait_item(&mut self, ti: &'v TraitItem) {
+        self.count += 1;
+        walk_trait_item(self, ti)
+    }
+    fn visit_impl_item(&mut self, ii: &'v ImplItem) {
+        self.count += 1;
+        walk_impl_item(self, ii)
+    }
+    fn visit_trait_ref(&mut self, t: &'v TraitRef) {
+        self.count += 1;
+        walk_trait_ref(self, t)
+    }
+    fn visit_ty_param_bound(&mut self, bounds: &'v TyParamBound) {
+        self.count += 1;
+        walk_ty_param_bound(self, bounds)
+    }
+    fn visit_poly_trait_ref(&mut self, t: &'v PolyTraitRef, m: &'v TraitBoundModifier) {
+        self.count += 1;
+        walk_poly_trait_ref(self, t, m)
+    }
+    fn visit_variant_data(&mut self, s: &'v VariantData, _: Ident,
+                        _: &'v Generics, _: NodeId, _: Span) {
+        self.count += 1;
+        walk_struct_def(self, s)
+    }
+    fn visit_struct_field(&mut self, s: &'v StructField) {
+        self.count += 1;
+        walk_struct_field(self, s)
+    }
+    fn visit_enum_def(&mut self, enum_definition: &'v EnumDef,
+                      generics: &'v Generics, item_id: NodeId, _: Span) {
+        self.count += 1;
+        walk_enum_def(self, enum_definition, generics, item_id)
+    }
+    fn visit_variant(&mut self, v: &'v Variant, g: &'v Generics, item_id: NodeId) {
+        self.count += 1;
+        walk_variant(self, v, g, item_id)
+    }
+    fn visit_lifetime(&mut self, lifetime: &'v Lifetime) {
+        self.count += 1;
+        walk_lifetime(self, lifetime)
+    }
+    fn visit_lifetime_def(&mut self, lifetime: &'v LifetimeDef) {
+        self.count += 1;
+        walk_lifetime_def(self, lifetime)
+    }
+    fn visit_explicit_self(&mut self, es: &'v ExplicitSelf) {
+        self.count += 1;
+        walk_explicit_self(self, es)
+    }
+    fn visit_mac(&mut self, _mac: &'v Mac) {
+        self.count += 1;
+        walk_mac(self, _mac)
+    }
+    fn visit_path(&mut self, path: &'v Path, _id: NodeId) {
+        self.count += 1;
+        walk_path(self, path)
+    }
+    fn visit_path_list_item(&mut self, prefix: &'v Path, item: &'v PathListItem) {
+        self.count += 1;
+        walk_path_list_item(self, prefix, item)
+    }
+    fn visit_path_parameters(&mut self, path_span: Span, path_parameters: &'v PathParameters) {
+        self.count += 1;
+        walk_path_parameters(self, path_span, path_parameters)
+    }
+    fn visit_assoc_type_binding(&mut self, type_binding: &'v TypeBinding) {
+        self.count += 1;
+        walk_assoc_type_binding(self, type_binding)
+    }
+    fn visit_attribute(&mut self, _attr: &'v Attribute) {
+        self.count += 1;
+    }
+    fn visit_macro_def(&mut self, macro_def: &'v MacroDef) {
+        self.count += 1;
+        walk_macro_def(self, macro_def)
+    }
+
+}