class consts are unscoped globals — silent name-collision miscompiles

• Type: bug (SILENT wrong values on valid FPC code — not a conformance nicety). Track P.
• History: filed 2026-07-15 as the low-prio visibility residual split from [[bug-pascal-member-visibility-unenforced]]; UPGRADED same day after the user flagged the collision hazard and both shapes reproduced as silent-wrong (compat escape rule: silent wrong behavior = real bug ticket, not parity).

Repro 1 — cross-class clobber

type
  TA = class private const Max = 5;  public function GetMax: Integer; end;
  TB = class private const Max = 99; public function GetMax: Integer; end;
function TA.GetMax: Integer; begin Result := Max; end;
function TB.GetMax: Integer; begin Result := Max; end;

FPC: 5 / 99. pxx: 99 / 99 — the later decl wins the global const table, so TA's methods silently read TB's value.

Repro 2 — class const clobbers a GLOBAL

const Size = 10;
type TA = class private const Size = 777; public function GetSize: Integer; end;

FPC: writeln(Size) in main = 10, a.GetSize = 777. pxx: 777 / 777 — main's Size silently reads the class const.

Any codebase where two classes use the same private const name (Max, Size, DefaultCapacity, BufSize...) — i.e. exactly what private invites — miscompiles silently.

Root

The class-body const section parses into the ordinary GLOBAL constant tables (scalar Syms skConst / StrConst), keyed by bare name: no owning class, no shadowing, later registration overwrites. TFoo.MaxItems qualified access resolves the same global by name (parser ~3595 fallbacks).

Fix direction

Scope them for real (this is name RESOLUTION, not just visibility):

1. Registry: ClassConstCi/NOff/NLen/Vis (+ value or backing global sym idx), stamped in the class-body const parse; STOP registering the bare name in the global tables (or register a mangled name, e.g. TA.Max).
2. Resolution inside a method body: bare Max looks up the enclosing class chain FIRST (own -> ancestors), then unit globals — FPC scoping order. Repro 2's main-body Size then finds only the global.
3. Qualified TClass.Const resolves via the registry (the existing ~3595 class-qualified fallback becomes a registry hit).
4. Visibility: with the registry carrying Vis, EnforceMemberVis slots in for free at both access paths — burns tclass12b (strict private const from a descendant) under --strict-visibility/--mimic-fpc.
5. Typed/string class consts: StrConst table needs the same ownership or mangling treatment.

Acceptance

Repro 1 prints 5/99 and repro 2 prints 10/777 (FPC-differential identical); inherited class consts resolve up the parent chain; tclass12b rejected under --strict-visibility; fpjson/Synapse/fgl + conformance pass-set stay green (regression sweep — the resolution-order change is the risky part).

Log

• 2026-07-15 — resolved, commit 9122d8cc.