It was fixed by 2.11.0 final (because I discovered it here) but as of -M8 that expression without an ascribed type did not compile.
```
[info] Compiling 10 Scala sources to /mirror/forks/gll-combinators/target/scala-2.11.0-M8/test-classes...
[error] type mismatch;
[error]  found   : => Any
[error]  required: AnyRef
[error] Note that <byname> extends Any, not AnyRef.
[error] Such types can participate in value classes, but instances
[error] cannot appear in singleton types or in reference comparisons.
[error] one error found
[error] (test:compile) Compilation failed
[error] Total time: 24 s, completed Apr 26, 2014 2:46:28 PM
```