swift234

Improve some diagnostics around invalid calls to ClosureExprs and random values of function type,
fixing:
<rdar://problem/20789423> Unclear diagnostic for multi-statement closure with no return type
<rdar://problem/21829141> BOGUS: unexpected trailing closure
<rdar://problem/21784170> Incongruous `unexpected trailing closure` error in `init` function which is cast and called without trailing closure.



Swift SVN r30443