Incorrect behaviour when capturing var and changing it in a loop

[asterite]

Crystal 0.24.1

def capture(&block)
  block
end

x = 1
3.times do
  p x
  capture do
    x = "hello"
  end.call
end

Output:

1
194613232
194613232

The problem is that we only bind the variable to the metavariable if it's a closured var on a first pass, but the first read of x happens before we determine it's a closure.

I found this while thinking about how to fix #4359

[SlayerShadow]

It works correctly with

def capture
  yield
end

And doesn't work with block.call...
Crystal version: 0.28.0-dev [d1cdab2]

[straight-shoota]

@SlayerShadow Yes, that's to be expected because yield essentially inlines the block directly. With capturing + block.call it's indirected through a Proc and that seems to have a bug somewhere, probably in code generation.

[asterite]

The problem is actually in the semantic phase.

[miketheman]

#CodeTriage
The behavior today emits the following output:

1
-1334769312
-1334769312

So it's still incorrect. The referenced linked PR #8588 appears to try and get this working, however that has yet to be merged, and there's further discussion that can be followed over there.