"Type aliases" like `X{T} = Y{T, S}` are not handled

It seems that "type aliases" are not handled correctly at the moment:

```julia
julia> solve(:(X{T} = Y{T, S}))
:((@global X){@global T} = (@global Y){@global T, @global S})
```

I suppose the result should be

```julia
:((@global X){@T} = (@global Y){@T, @global S})
```

?