Fix uninit() intrinsic when used with empty types

src/librustc/middle/trans/intrinsic.rs

@@ -317,7 +317,7 @@ pub fn trans_intrinsic(ccx: @CrateContext,
         "uninit" => {
             // Do nothing, this is effectively a no-op
             let retty = substs.tys[0];
-            if type_is_immediate(ccx, retty) && !ty::type_is_nil(retty) {
+            if type_is_immediate(ccx, retty) && !type_is_voidish(ccx, retty) {
                 unsafe {
                     Ret(bcx, lib::llvm::llvm::LLVMGetUndef(type_of(ccx, retty).to_ref()));
                 }

src/test/run-pass/uninit-empty-types.rs

@@ -0,0 +1,24 @@
+// Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Test the uninit() construct returning various empty types.
+
+use std::vec;
+use std::unstable::intrinsics;
+
+#[deriving(Clone)]
+struct Foo;
+
+fn main() {
+    unsafe {
+        let _x: Foo = intrinsics::uninit();
+        let _x: [Foo, ..2] = intrinsics::uninit();
+    }
+}