Nested routines: capture of fixed-size array locals not supported

• Type: feature gap (frontend/codegen — nested-routine uplevel access) — Track A
• Status: backlog
• Opened: 2026-07-11, filed from Track B (feature-dns-resolver-library) while writing DnsParseIpv6 in lib/rtl/dns_config.pas.

Symptom

A nested routine that reads or writes a fixed-size array local of its enclosing routine fails to compile:

pascal26:144: error: nested routine: capture of fixed-size array 'rightG' not yet supported ()

Repro shape (rejected):

function Outer: Boolean;
var
  leftG, rightG: array[0..7] of Integer;
  leftN, rightN: Integer;
  onRight: Boolean;

  function AddGroup(v: Integer): Boolean;
  begin
    AddGroup := False;
    if leftN + rightN >= 8 then Exit;
    if onRight then begin rightG[rightN] := v; rightN := rightN + 1; end
    else begin leftG[leftN] := v; leftN := leftN + 1; end;
    AddGroup := True;
  end;

begin
  ...
end;

Scalar captures (leftN, onRight) work; the fixed-size array locals are the missing case. FPC accepts this.

Workaround used

Flattened the helper into the enclosing routine (single g[0..7] array + index bookkeeping inline) — see DnsParseIpv6 in lib/rtl/dns_config.pas.

Acceptance

• Nested routine can read and write a fixed-size array local (and array parameter) of any enclosing routine, at any nesting depth.
• Works for element access, whole-array passing to further calls, and for-loop iteration over the captured array.
• Self-host stays byte-identical; a compile-run test in the nested-routines test family covers array capture.