Add a test case for previous commit

src/test/run-pass/fat-arrow-alt.rs

@@ -0,0 +1,17 @@
+// -*- rust -*-
+// xfail-pretty
+
+enum color {
+    red,
+    green,
+    blue
+}
+
+fn main() {
+    log(error, alt red {
+        red => { 1 }
+        green => { 2 }
+        blue => { 3 }
+    });
+}
+