From c7e3f88c93883ecbb27dcdfb7d8ec6e263b126b0 Mon Sep 17 00:00:00 2001
From: Brian Anderson <andersrb@gmail.com>
Date: Mon, 30 May 2011 23:39:20 -0400
Subject: [PATCH] rustc: Pushdown type params for tag patterns. Closes #363

---
 src/comp/middle/typeck.rs                      | 18 ++++++++++++++----
 .../run-pass/alt-pattern-no-type-params.rs     | 15 +++++++++++++++
 2 files changed, 29 insertions(+), 4 deletions(-)
 create mode 100644 src/test/run-pass/alt-pattern-no-type-params.rs

diff --git a/src/comp/middle/typeck.rs b/src/comp/middle/typeck.rs
index c5433a2b7524..552d0bdddc54 100644
--- a/src/comp/middle/typeck.rs
+++ b/src/comp/middle/typeck.rs
@@ -1171,10 +1171,20 @@ mod pushdown {
                 let ty_param_substs_and_ty res_t = demand::full(scx, pat.span,
                       expected, tt, tps, NO_AUTODEREF);
 
-                // TODO: push down type from "expected".
-                write::ty_fixup(scx, ann.id,
-                    ty::ann_to_ty_param_substs_opt_and_ty
-                        (scx.fcx.ccx.tcx.node_types, ann));
+                auto ty_params_subst = ty::ann_to_ty_param_substs_opt_and_ty
+                    (scx.fcx.ccx.tcx.node_types, ann);
+
+                auto ty_params_opt;
+                alt (ty_params_subst._0) {
+                    case (none[vec[ty::t]]) {
+                        ty_params_opt = none[vec[ty::t]];
+                    }
+                    case (some[vec[ty::t]](?tps)) {
+                        ty_params_opt = some[vec[ty::t]](tag_tps);
+                    }
+                }
+
+                write::ty_fixup(scx, ann.id, tup(ty_params_opt, tt));
             }
         }
     }
diff --git a/src/test/run-pass/alt-pattern-no-type-params.rs b/src/test/run-pass/alt-pattern-no-type-params.rs
new file mode 100644
index 000000000000..1836b2b75fec
--- /dev/null
+++ b/src/test/run-pass/alt-pattern-no-type-params.rs
@@ -0,0 +1,15 @@
+// xfail-stage0
+
+tag maybe[T] {
+  nothing;
+  just(T);
+}
+
+fn foo(maybe[int] x) {
+  alt (x) {
+    case (nothing) {log_err "A";}
+    case (just(?a)) {log_err "B";}
+  }
+}
+
+fn main() {}