Args.roc has always been in a broken state, relying on particular
hand-holding of the compiler to operate. With recent changes to type
emplacement, Args.roc now shows off compiler bugs that cannot be papered
over and need to be addressed head-on. These are problems that I do not
think can be directly solved via eliminating type emplacement; I think
they are a combination of constraining and mono bugs, and will be
investigated separately.
For now, turn off attempts to build Args, and instead just test that
`roc check` continues to behave well.
Prior to this commit, we emplace type variables into `Index<TypeTag>`
only for translated top-level types. However, we need to be careful to
do this emplacement for nested types as well! This patch ensures we do,
but immediately emplacing the destination variable of a type when we
allocate a variable for it.
This materially improves performance for programs that are
recursion-heavy (as most Roc programs will likely be).
```
$ hyperfine '/tmp/roc-old check examples/cli/cli-platform/Arg.roc' '/tmp/roc-new check examples/cli/cli-platform/Arg.roc' --warmup 10
Benchmark 1: /tmp/roc-old check examples/cli/cli-platform/Arg.roc
Time (mean ± σ): 53.8 ms ± 1.3 ms [User: 87.3 ms, System: 10.8 ms]
Range (min … max): 52.2 ms … 60.4 ms 51 runs
Benchmark 2: /tmp/roc-new check examples/cli/cli-platform/Arg.roc
Time (mean ± σ): 45.0 ms ± 1.6 ms [User: 59.4 ms, System: 11.3 ms]
Range (min … max): 42.6 ms … 49.8 ms 60 runs
Summary
'/tmp/roc-new check examples/cli/cli-platform/Arg.roc' ran
1.20 ± 0.05 times faster than '/tmp/roc-old check examples/cli/cli-platform/Arg.roc'
```
The time spent in `occurs` during checking for `Arg` drops from 50% to 23%.
