Fix: Compilation of continue labels no longer crashing in Go

[MikaelMayer]

This PR fixes #3978
Our compiler hit the problem stated there: golang/go#27165
I haven't tested if this problem is fixed in a more recent version of the Go compiler, but a workaround I found is to wrap the labelled code with curly braces, so that the goto escape the scope when jumping to the label, hence Go does not complain anymore about jumping over variable declaration

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

[MikaelMayer]

@robin-aws your script required me to change my test for the Go compiler to every compiler. Nice job!

[RustanLeino]

Instead of explicitly adding the open and close curly braces, change the var w = wr.Fork(); line to

var w = wr.NewBlock(open: BlockStyle.Brace);

[MikaelMayer]

I can't because we need to add a label right after the final closing brace (line 1843), unless you have another suggestion?

[RustanLeino]

I don't see that the label after the closing brace is a problem, but I now see that the goto between the fork point and the closing curly is. So, the Fork is necessary, after all. My bad.

However, when I now look at that, it seems that both the forked w and the goto ... are not indented inside the curly braces. The best way to fix that is to use a NewBlock.

In summary, would the following body of CreateLabeledCode work for you?

var wBody = wr.NewBlock(open: BlockStyle.Brace);
var w = wBody.Fork();
var prefix = createContinueLabel ? "C" : "L";
wBody.WriteLine($"goto {prefix}{label};");
wr.Fork(-1).WriteLine($"{prefix}{label}:");
return w;

[RustanLeino]

I see this is how the bug report showed the code. Still, I would suggest renaming v_int_7 and v_int_93 to something like x and y.

[RustanLeino]

Remove returns ()

[RustanLeino]

I don't see that the label after the closing brace is a problem, but I now see that the goto between the fork point and the closing curly is. So, the Fork is necessary, after all. My bad.

However, when I now look at that, it seems that both the forked w and the goto ... are not indented inside the curly braces. The best way to fix that is to use a NewBlock.

In summary, would the following body of CreateLabeledCode work for you?

var wBody = wr.NewBlock(open: BlockStyle.Brace);
var w = wBody.Fork();
var prefix = createContinueLabel ? "C" : "L";
wBody.WriteLine($"goto {prefix}{label};");
wr.Fork(-1).WriteLine($"{prefix}{label}:");
return w;