This code was failing to compile with `Error: unhandled exception:
semmagic.nim(247, 5) operand.kind == tyTuple tyAlias [AssertionDefect]`
```nim
import std/typetraits
type
Bar[T] = T
Foo = Bar[tuple[a: int]]
echo Foo.tupleLen
```
Fix was just making `tupleLen` skip alias types also
(cherry picked from commit 91d51923b9)
34e61d5ae6