---

yaml
---
r: 22451
b: refs/heads/master
c: 9b094c0
h: refs/heads/master
i:
  22449: ce9a0b5
  22447: f9bf538
v: v3

Author: nikomatsakis

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: 668285b9c85bebc5d1a4e8d346e99b580420be8e
+refs/heads/master: 9b094c0baf4fa758c80fb9db8cc172f03789adbb
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: cd6f24f9d14ac90d167386a56e7a6ac1f0318195
 refs/heads/try: ffbe0e0e00374358b789b0037bcb3a577cd218be

trunk/src/rustc/driver/session.rs

@@ -37,6 +37,7 @@ const trace: uint = 128u;
 const no_rt: uint = 256u;
 const coherence: uint = 512u;
 const borrowck_stats: uint = 1024u;
+const borrowck_note_pure: uint = 2048;
 
 fn debugging_opts_map() -> ~[(str, str, uint)] {
     ~[("ppregions", "prettyprint regions with \
@@ -51,7 +52,9 @@ fn debugging_opts_map() -> ~[(str, str, uint)] {
      ("trace", "emit trace logs", trace),
      ("no-rt", "do not link to the runtime", no_rt),
      ("coherence", "perform coherence checking", coherence),
-     ("borrowck-stats", "gather borrowck statistics",  borrowck_stats)
+     ("borrowck-stats", "gather borrowck statistics",  borrowck_stats),
+     ("borrowck-note-pure", "note where purity is req'd",
+      borrowck_note_pure)
     ]
 }
 
@@ -168,6 +171,7 @@ impl session for session {
     fn trace() -> bool { self.debugging_opt(trace) }
     fn coherence() -> bool { self.debugging_opt(coherence) }
     fn borrowck_stats() -> bool { self.debugging_opt(borrowck_stats) }
+    fn borrowck_note_pure() -> bool { self.debugging_opt(borrowck_note_pure) }
 }
 
 /// Some reasonable defaults

trunk/src/rustc/middle/borrowck/gather_loans.rs

@@ -246,6 +246,12 @@ impl methods for gather_loan_ctxt {
                   some(scope_id) {
                     self.req_maps.pure_map.insert(scope_id, e);
                     self.bccx.req_pure_paths += 1;
+
+                    if self.tcx().sess.borrowck_note_pure() {
+                        self.bccx.span_note(
+                            cmt.span,
+                            #fmt["purity required"]);
+                    }
                   }
                   none {
                     // otherwise, fine, I give up.