M2compiler-V3/docs/wip/local-array-bug.mod

MODULE local_array_bug;
(* MISDIAGNOSED (2026-10-05).  The original report said a local ARRAY
   inside a PROCEDURE was miscompiled.  The actual cause was the module
   *name*: this grammar's scanner did not accept `_` in identifiers
   (`ident = letter { letter | digit }`), so `local_array_bug` lexed as
   `local` + `_array_bug` and the module body was silently dropped
   (empty `main`).

   FIXED: `M2.atg`'s ident rule now includes "_"
   (`ident = letter { letter | digit | "_" }`), per ISO Modula-2.
   Regression: compiler/tests/t_under.mod.

   Local arrays themselves compile correctly; e.g. with a camelCase
   module name this same program exits 60.  See also
   tests/t_lower5arr.mod for local arrays of records and open-array
   arguments. *)

VAR ExitCode : INTEGER;

PROCEDURE P;
  VAR a : ARRAY [0..3] OF INTEGER; i : INTEGER;
BEGIN
  i := 0;
  WHILE i < 4 DO a[i] := i * 10; INC(i) END;
  ExitCode := a[0] + a[1] + a[2] + a[3]   (* 0+10+20+30 = 60 *)
END P;

BEGIN P END local_array_bug.