dcast() error fails opaquely if 'x' is a long expression

```r
tibble(a = c(1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7), b = c(1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2), c = c(9, 8, 7, 6, 5, 4, 3, 2, 1, 0, 10,
11, 12, 13)) |> dcast(a ~ b, value.var = 'c')
# Error in signal(obj) : bad error message
```

The problem is we use `deparse()` where `deparse1()` is appropriate.