---

yaml
---
r: 273360
b: refs/heads/beta
c: 5abacd3
h: refs/heads/master

Author: nikomatsakis

[refs]

@@ -23,7 +23,7 @@ refs/tags/0.9: 36870b185fc5f5486636d4515f0e22677493f225
 refs/tags/0.10: ac33f2b15782272ae348dbd7b14b8257b2148b5a
 refs/tags/0.11.0: e1247cb1d0d681be034adb4b558b5a0c0d5720f9
 refs/tags/0.12.0: f0c419429ef30723ceaf6b42f9b5a2aeb5d2e2d1
-refs/heads/beta: 7f8d24590fa9b381eb38e2b007c88a446cf99479
+refs/heads/beta: 5abacd36f0149a9106d7ee04e97eadba4e523bb4
 refs/tags/1.0.0-alpha: e42bd6d93a1d3433c486200587f8f9e12590a4d7
 refs/heads/tmp: e06d2ad9fcd5027bcaac5b08fc9aa39a49d0ecd3
 refs/tags/1.0.0-alpha.2: 4c705f6bc559886632d3871b04f58aab093bfa2f

branches/beta/src/librustc_typeck/check/coercion.rs

@@ -278,6 +278,14 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
             //   want to use that target type region (`'b`) because --
             //   for the program to type-check -- it must be the
             //   smaller of the two.
+            //   - One fine point. It may be surprising that we can
+            //     use `'b` without relating `'a` and `'b`. The reason
+            //     that this is ok is that what we produce is
+            //     effectively a `&'b *x` expression (if you could
+            //     annotate the region of a borrow), and regionck has
+            //     code that adds edges from the region of a borrow
+            //     (`'b`, here) into the regions in the borrowed
+            //     expression (`*x`, here).  (Search for "link".)
             // - if in lub mode, things can get fairly complicated. The
             //   easiest thing is just to make a fresh
             //   region variable [4], which effectively means we defer