Unit-qualified constant reference Unit.Const is not resolved

• Type: bug (parser / name resolution)
• Status: urgent (Track A)
• Owner: — (Track A — compiler/**)
• Opened: 2026-06-24
• Found-by: [[feature-synapse-compile-check]] — ssfpc.inc re-exports FIONREAD = termio.FIONREAD; (and FIONBIO/FIOASYNC).

Symptom

Referencing a constant qualified by its unit name fails everywhere:

const X = termio.FIONREAD;     { ConstEval error: SVal = termio }
...
x := termio.FIONREAD;          { error: undefined variable (termio) }

Qualified types (sockets.TInetSockAddr, BaseUnix.ptimeval) and qualified function calls (dynlibs.LoadLibrary, SysUtils.StrLCopy) both resolve fine — synafpc compiles using them. Only a qualified constant is not found: the parser treats the unit name as an undefined identifier instead of looking up the constant in that unit's scope.

Impact

Blocks Synapse's synsock/blcksock (and the protocol units httpsend/ ftpsend/smtpsend that pull them): ssfpc.inc does FIONREAD = termio.FIONREAD; to re-export ioctl constants, which is standard FPC. Any Unit.Const reference is affected.

Fix

In name resolution for a qualified A.B where A is a used unit, look up B as a constant in that unit's interface (the same lookup that already finds types and functions there), in both constant-expression and ordinary-expression context.

Done when

• const X = termio.FIONREAD; and x := termio.FIONREAD; both compile and yield the constant's value.
• synsock gets past the ssfpc const block (next gap: the netdb / sockets address-string surface, RTL — Track B).
• Regression test under make test; self-host fixedpoint byte-identical.

Resolution (2026-06-25, v58)

The ordinary-expression path (x := Unit.Const) already resolved (via ConsumeUnitQualifier + FindSymInUnit in ParseFactor). Only the const- expression evaluator ConstEvalFactor was missing it: its tkIdent branch did a bare FindSym(CurTok.SVal) and never recognised a Unit.Const qualifier, so const X = termio.FIONREAD; failed with "not a constant" (it saw termio).

Fix (parser.inc, ConstEvalFactor): reuse ConsumeUnitQualifier (leaves the parser on the member name, yields the unit index) and resolve via FindSymInUnit when qualified, else FindSym as before. Same lookup that already serves qualified types and function calls.

Regression: test/test_qualified_units.pas extended with a qualified const (qualified_a.SharedConst) used in both a const expression and an ordinary expression. Self-host byte-identical; pinned v58.