slice seq, or maybe not bug
please note that the last statement, i.e. `a[..3]` outputs 3 lines of result
```
nim> var a = @[3, 1]
nim> a[0..1]
@[3, 1] == type int
nim> a.add 4
nim> a[0..2]
@[3, 1, 4] == type int
nim> a.add 1
nim> a[..3]
@[3, 1] == type int
@[3, 1, 4] == type int
@[3, 1, 4, 1] == type seq[int]
```

but 
```
nim> var a = @[3, 1]
nim> a[0..1]
@[3, 1] == type int
nim> a.add 4
nim> a[0..2]
@[3, 1, 4] == type int
nim> a.add 1
nim> a[0..3]
@[3, 1, 4, 1] == type int
```

we know that `nim` says `Warning: replace `..b` with `0..b`; .. is deprecated [Deprecated]` on `a[..3]`, but why `inim` outputs
```
@[3, 1] == type int
@[3, 1, 4] == type int
@[3, 1, 4, 1] == type seq[int]
```
 
