---

yaml
---
r: 14844
b: refs/heads/try
c: 1ed768b
h: refs/heads/master
v: v3

Author: pcwalton

[refs]

@@ -2,5 +2,5 @@
 refs/heads/master: 61b1875c16de39c166b0f4d54bba19f9c6777d1a
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: 4a81779abd786ff22d71434c6d9a5917ea4cdfff
-refs/heads/try: 1600be2c3b1054e2fce59778e2f85d7fa582657f
+refs/heads/try: 1ed768bc3b32f45626b1fb1c3dca83d4936bf33f
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105

branches/try/src/rustc/middle/typeck.rs

@@ -1933,8 +1933,8 @@ fn lookup_field_ty(cx: ty::ctxt, items:[@ast::class_item],
 
 /*
  * Returns the region that the value named by the given expression lives in.
- * If the expression is not an lvalue, reports an error and returns the block
- * region.
+ * The expression must have been typechecked. If the expression is not an
+ * lvalue, returns the block region.
  *
  * Note that borrowing is not detected here, because we would have to
  * immediately structurally resolve too many types otherwise. Thus the
@@ -1958,10 +1958,20 @@ fn region_of(fcx: @fn_ctxt, expr: @ast::expr) -> ty::region {
                 }
             }
         }
-        ast::expr_field(base, _, _) | ast::expr_index(base, _) |
-                ast::expr_unary(ast::deref, base) {
-            fcx.ccx.tcx.sess.span_unimpl(expr.span, "regions of field, " +
-                                         "index, or deref operations");
+        ast::expr_field(base, _, _) | ast::expr_index(base, _) {
+            fcx.ccx.tcx.sess.span_unimpl(expr.span, "regions of field or " +
+                                         "index operations");
+        }
+        ast::expr_unary(ast::deref, base) {
+            let expr_ty = ty::expr_ty(fcx.ccx.tcx, base);
+            let expr_ty = structurally_resolved_type(fcx, expr.span, expr_ty);
+            alt ty::get(expr_ty).struct {
+                ty::ty_rptr(region, _) { region }
+                ty::ty_box(_) | ty::ty_uniq(_) {
+                    fcx.ccx.tcx.sess.span_unimpl(expr.span, "borrowing");
+                }
+                _ { ret region_of(fcx, base); }
+            }
         }
         _ {
             let blk_id = fcx.ccx.tcx.region_map.rvalue_to_block.get(expr.id);