Keep getting errors in the build ruby example on
Json, and it doesn't tell me the name of the
symbol, just the IdentId, which makes this
really hard to track down.
This approach works fine, it'll just be harder
to debug the next time we run into a special
case like ElemWalker.
e.g. in the scenario of `[ A Str, B, C, D ]`, rather than having one tag be nullable, we want
to store the tag id in the pointer. This generally saves 8 bytes for
every allocation, and prevents an allocations for all tags except A.
Previously, we would drop uninhabited captures from lambda sets' runtime
representations, which meant sets like
```
[L1 {a: Str}, L2 {a: []}]
```
had runtime representation
```
{Str}
```
rather than
```
Union({Str}, {[]})
```
if we drop unreachable lambdas from the representation, then the
reachable lambdas are somewhat more efficient to compile (as there are
less material tag options), but the compiler complexity increases
because we must represent voided capture sets in the lambda set.
Even if a lambda has voided captures, we must specialize it, because
failing to do so opens us up to losing relevant specializations needed
later on. See 2f7020aa31 for a
previous occurence of that.
As such, simply keep voided layouts in place during lambda set
compilation. The optimizer should elide them anyway.
previously the dev backend did not take into account lambda name information to generate function names. This could cause the same function name to be defined twice
