flexcolumn calling-convention directive

• Type: feature
• Status: done
• Owner: Track A
• Opened: 2026-06-06 (from todo.md §4)

Motivation

The value:w:d formatting micro-grammar is today special-cased in write/writeln/Str. Generalize it into a declarable calling-convention directive so formatted routines can be ordinary library functions whose call args carry optional :w:d modifiers. Pays off when variadic write/writeln move to library code (see feature-writeln-as-library).

Scope

• A declarable directive marking a routine as accepting per-arg :w:d modifiers.
• Spec the per-arg modifier → formal mapping and variadic interplay.
• Resolve in the parser (it knows the callee's directive) — never the lexer.

Rationale: plan-pascal-syntax-issues.md §B1.

Acceptance

A library write-like routine declared with the directive accepts x:w:d call syntax and formats correctly; existing write/writeln/Str unchanged.

Spec (as implemented, 2026-07-03)

• Directive: flexcolumn; after a procedure/function header, in the same clause position as overload/cdecl (parser.inc header-directive loop). Stored as ProcFlexColumn[procIdx] (defs.inc), applied on all header resolution paths (register, forward/prescan, external).
• Call-site mapping: at a parenthesized call to a flexcolumn routine, each value argument may be followed by :width[:decimals]. Every value argument expands to three actuals — value, width, decimals — with defaults 0 / -1 when a modifier is absent (write's defaults). The routine therefore declares (v; w, d) triples and normal arity/overload/type checking runs on the expanded list. Width/decimals are full expressions, not just integer literals (they bind real formals).
• Resolved entirely in the parser (ParseFlexColumnTail, hooked into the two general call-argument loops: expression-call and statement-call). The lexer is untouched; write/writeln/Str keep their existing special cases.
• Variadic interplay: array of const arguments are not expanded (a [...] literal contains no : grammar); flexcolumn is for fixed-arity routines. Don't mix flexcolumn and non-flexcolumn overloads of one name — the syntax is enabled from the first name match.

Log

• 2026-06-06 — ticket opened from todo.md §4.
• 2026-06-28 — Removed chore-inc-to-units as a blocker after that refactor was rejected. This feature remains optional and should justify itself through a future library-backed formatted-output path, not through a broad compiler-file split.
• 2026-07-03 — Implemented (Track A). New ProcFlexColumn flag + ParseFlexColumnTail in the parser; regression test/test_flexcolumn.pas wired into make test (procedures, functions, multi-column, expression widths, defaults). Self-host byte-identical.