Allow local definition in comprehension syntax

[oconnorr]

For example I could replace the expression

{ [k]: processedField[k]
for field in std.objectFields(feature)
for processedField in [processFeature(field)]
for k in std.objectFields(processedField) }

with

{ [k]: processedField[k]
  for field in std.objectFields(feature)
  local processedField = processFeature(field)
  for k in std.objectFields(processedField) }

which is a bit more clear syntactically.

[sparkprime]

Yeah this seems like a good idea.

[hausdorff]

@sparkprime Is there still appetite for this? This is useful enough that I think (assuming our POC goes well) we could devote some attention to it.

[sparkprime]

Heh I didn't see your comment until now. Yeah it would be nice, and it's probably no harder than tweaking the desugaring rule for comprehensions

[zxc122333]

Any update on this?

[sparkprime]

No update. The problem with doing language changes now is that they need to be done in both the Go and C++ branch. Anyone is welcome to do it though.