checker,cgen,type_resolver: prevent stale type cast on comptime for, …

[dy-tea]

Fixes #25781.

I really hope I fixed all the issues with comptime for at this point. There was some issues with stale type references being used in assignment inside comptime for, value != none was also not casting value to a some type and $if v is string would evaluate to true on all iterations inside the loop in the test (due to the stale reference).

I added multiple cases of the below code snippet:

mut idx_str := comptime_branch_context_str + '|id=${branch.id}|'
if c.comptime.inside_comptime_for && c.comptime.comptime_for_field_var != '' {
	idx_str += '|field_type=${c.comptime.comptime_for_field_type}|'
}

Maybe might want to make it into a function.

[spytheman]

A method on comptime will be best imho, to avoid passing in .inside_comptime_for. .comptime_for_field_var and .comptime_for_field_type.

[spytheman]

Excellent work, thanks @dy-tea 🙇🏻 .

[jorgeluismireles]

Thanks a lot @dy-tea this last PR permits to process the unwrapped option values finally. I had to call inside my encoder a process function where inside update a values map and now is working. If instead I reused a process function didn't work. I think is too complex the validation inside those comptime code to request any further. Thanks also for your fix for comptime struct fields as fixed array they are working too. Your fixes were necessary though not sufficient for json2 as is to include fields as options and fixed array but is another thing to look next. Thanks.