rustc: Handle valueless ret expressions as block results. Closes #521

Author: brson

src/comp/front/parser.rs

@@ -891,6 +891,8 @@ fn parse_bottom_expr(&parser p) -> @ast::expr {
     } else if (eat_word(p, "ret")) {
         alt (p.peek()) {
             case (token::SEMI) { ex = ast::expr_ret(none); }
+            // Handle ret as the block result expression
+            case (token::RBRACE) { ex = ast::expr_ret(none); }
             case (_) {
                 auto e = parse_expr(p);
                 hi = e.span.hi;

src/test/run-pass/expr-empty-ret.rs

@@ -0,0 +1,11 @@
+// xfail-stage0
+// Issue #521
+
+fn f() {
+  auto x = alt (true) {
+    case (true) { 10 }
+    case (false) { ret }
+  };
+}
+
+fn main() { }