trans_put 'non-exhaustive match failure' in non-iter fn

```
fn foo() { put() }
fn main() { foo(); }
```

rt: 0790:main:main:                   upcall fail 'non-exhaustive match failure', ../src/comp/middle/trans.rs:5523
rt: 0790:main:                        domain main @0x2008c0c root task failed

Should have been rejected prior to trans, I think.
