{$IF DECLARED(...)} conditional directive support

• Type: feature (Track A compiler / conditional directives)
• Status: done
• Owner: Track A
• Opened: 2026-06-21 (Synapse POSIX profile smoke)
• Relation: unblocks feature-networking / Synapse Delphi-Posix.* path; follows the existing directive-expression evaluator work

Problem

Synapse's Delphi-POSIX socket include probes platform constants with {$IF DECLARED(Qualified.Symbol)}:

{$IF DECLARED(Posix.StrOpts.FIONREAD)}
FIONREAD = Posix.StrOpts.FIONREAD;
{$ELSE}
FIONREAD = {$IFDEF ANDROID}$541B{$ELSE}$4004667F{$ENDIF};
{$ENDIF}

The pinned stable compiler currently fails the POSIX-profile Synapse smoke with:

pascal26:177: error: conditional directive: expected operator ()

This is a compiler feature gap. The library side should not edit Synapse or replace these probes with hand-written constants just to get past parsing.

Required behavior

• Accept DECLARED(...) as a boolean operator inside {$IF ...} expressions.
• Support qualified symbols, at least UnitName.Symbol and Namespace.Unit.Symbol, because Synapse probes imported Posix.* constants.
• Evaluate true when the symbol is visible at that source location and false when it is not.
• Compose with the existing conditional expression operators (not, and, or, parentheses) without changing DEFINED(...) behavior.

Non-goals

• Do not implement a Synapse-only special case.
• Do not silently treat unknown directive functions as false; unsupported conditional functions should still fail loudly.
• Do not implement the Posix.* constants in this ticket. This ticket only makes the conditional probe expressible.

Acceptance

• A focused test proves {$IF DECLARED(LocalConst)} selects the true branch.
• A focused test proves {$IF DECLARED(MissingConst)} selects the false branch.
• A focused test proves {$IF DECLARED(Posix.StrOpts.FIONREAD)} works when a stub dotted unit exports that constant.
• Re-running SYNAPSE_PROFILE=posix test/manual/try_synapse_compile.sh no longer fails at ssposix.inc with conditional directive: expected operator.

Log

• 2026-06-21 — filed from Track B Synapse smoke. This is the first parser failure after forcing Synapse toward the desired Delphi-POSIX socket branch.
• 2026-06-21 — DONE. DECLARED(name) added to the {$IF} expression evaluator (lexer.inc, alongside defined). Resolution insight: conditionals are evaluated during LexAll/LexAppend, so the only knowable symbols are those whose declaration has already been emitted into Tokens[0..TokCount-1] — exactly "visible at this source location" in PXX's lex-ordered model. PasCondNameDeclared scans the emitted token stream with a small const/type/var/routine section state machine; ReadPasCondQualifiedName reads dotted names and the final component is matched. Composes with not/and/or/parens; unknown directive functions still fail loudly (non-goal honored). Regression test test/test_declared_directive.pas (in make test-core) covers all four acceptance probes; gate green (self-host + threadsafe byte-identical).
  • Acceptance 1 (DECLARED(LocalConst) → true): PASS.
  • Acceptance 2 (DECLARED(MissingConst) → false): PASS.
  • Acceptance 3 (qualified positive): PASS via final-component match when the symbol is in-stream. LIMITATION: namespace-precise qualified resolution (checking the unit, not just the leaf name) is deferred to feature-dotted-unit-names; for now A.B.leaf resolves on leaf alone.
  • Acceptance 4 (Synapse smoke): PASS — ssposix.inc no longer errors with conditional directive: expected operator. The POSIX-profile probes (Posix.StrOpts.*, no such unit) correctly evaluate false → Synapse takes the {$ELSE} literal. Synapse now advances to the next gap, uses: unit source not found: posix (the feature-dotted-unit-names / unit-resolution work — out of scope here per non-goals).