Ord() / Chr() / Length() / Succ() are not folded in constant expressions

• Type: compat — Track P (Pascal frontend; constant-expression evaluation in the shared parser.inc, so it lands under Track A's gate).
• Status: done
• Found by: Track E, building examples/mandelbrot/mandelbrot_gui.pas ([[feature-demo-mandelbrot-gui-threaded]]) — case KeyCode of Ord('q'): ... is the natural way to write a key handler and it does not compile.

Symptom

program Ck;
const K = Ord('q');
begin writeln(K); end.

pascal26:2: error: not a constant ()
  near: program Ck  const K  >>> Ord  q

Same in a case label (case KeyCode of Ord('q'): ... → case label must be constant), which is where it actually bites.

Survey (what folds today)

So arithmetic/bit operators and High already go through the const evaluator; the ordinal/character builtins were never wired into it. FPC and Delphi fold all of the above — Ord and Chr in particular are ubiquitous in key handlers, lookup tables and set of Char construction.

Pred was not tested but is presumably in the same bucket; Low presumably works like High. Worth sweeping the whole builtin list while in there rather than adding them one at a time.

Secondary: the diagnostic dumps internal lexer state

The failing compile prints, before the error:

  Token 12: Line = 3 Kind = 1 SOffset = 22 SLen = 1

Internal token debugging leaking to stderr on this path. Should not ship; worth removing while fixing, or filing separately if it is a broader debug-output leak.

Workaround in the meantime

Numeric literals with a comment (113, { 'q' }), which is what the demo does.

Acceptance

• All six rows of the table above compile and produce the right value.
• The same expressions work as case labels, array bounds, and subrange bounds.
• A conformance test (test/test_const_expr_builtins.pas) covering Ord/Chr/Length/Succ/Pred/Low/High in a const, a case label and an array-bound position.
• No stray token dump on the failing path.
• Gate: make test + self-host byte-identical (shared parser.inc).

Links

[[feature-demo-mandelbrot-gui-threaded]] (where it turned up) · compiler/parser.inc (constant-expression evaluation).

Log

• 2026-07-20 — Filed from Track E with the folding survey above.
• 2026-08-01 — resolved, commit e4995a457.