Span debugger

src/librustc/driver/driver.rs

@@ -518,6 +518,10 @@ pub fn compile_input(sess: Session, cfg: ast::CrateConfig, input: &Input,
     let (outputs, trans) = {
         let (expanded_crate, ast_map) = {
             let crate = phase_1_parse_input(sess, cfg, input);
+            if sess.show_span() {
+                front::show_span::run(sess, &crate);
+                return;
+            }
             if stop_after_phase_1(sess) { return; }
             let loader = &mut Loader::new(sess);
             phase_2_configure_and_expand(sess, loader, crate)

src/librustc/driver/session.rs

@@ -60,6 +60,7 @@ debugging_opts!(
         BORROWCK_STATS,
         NO_LANDING_PADS,
         DEBUG_LLVM,
+        SHOW_SPAN,
         COUNT_TYPE_SIZES,
         META_STATS,
         NO_OPT,
@@ -95,6 +96,7 @@ pub fn debugging_opts_map() -> ~[(&'static str, &'static str, u64)] {
      ("no-landing-pads", "omit landing pads for unwinding",
       NO_LANDING_PADS),
      ("debug-llvm", "enable debug output from LLVM", DEBUG_LLVM),
+     ("show-span", "show spans", SHOW_SPAN),
      ("count-type-sizes", "count the sizes of aggregate types",
       COUNT_TYPE_SIZES),
      ("meta-stats", "gather metadata statistics", META_STATS),
@@ -351,6 +353,9 @@ impl Session_ {
     pub fn no_landing_pads(&self) -> bool {
         self.debugging_opt(NO_LANDING_PADS)
     }
+    pub fn show_span(&self) -> bool {
+        self.debugging_opt(SHOW_SPAN)
+    }
 
     // DEPRECATED. This function results in a lot of allocations when they
     // are not necessary.

src/librustc/front/show_span.rs

@@ -0,0 +1,31 @@
+// Copyright 2014 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.
+
+use syntax::ast;
+use syntax::visit;
+use syntax::visit::Visitor;
+
+use driver::session::Session;
+
+struct ShowSpanVisitor {
+    sess: Session
+}
+
+impl Visitor<()> for ShowSpanVisitor {
+    fn visit_expr(&mut self, e: &ast::Expr, _: ()) {
+        self.sess.span_note(e.span, "expression");
+        visit::walk_expr(self, e, ());
+    }
+}
+
+pub fn run(sess: Session, crate: &ast::Crate) {
+    let mut v = ShowSpanVisitor { sess: sess };
+    visit::walk_crate(&mut v, crate, ());
+}

src/librustc/lib.rs

@@ -97,6 +97,7 @@ pub mod front {
     pub mod std_inject;
     pub mod assign_node_ids_and_map;
     pub mod feature_gate;
+    pub mod show_span;
 }
 
 pub mod back {