(#14301) Selectors cannot return hash literals

Selectors can return any `rvalue` as defined by the grammer. Hash literals fall
under the category of `expressions` and are rejected by the parser when used as
the return value of a selector.
Merge pull request #173 from Sharpie/14301-Selectors-cannot-return-hash-literals

(#14301) Selectors cannot return hash literals