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Repro

program T;
function sysopen(const p: AnsiString; f: Integer): Integer;
begin sysopen := 0; end;
begin writeln(sysopen('x', 1)); end.



pascal26:2: error: expected name
  near: program T  function >>> sysopen  const

Why it happens

sysopen / syswrite / sysclose / sysfchmod are compiler intrinsics with their own token kinds (defs.inc:4510 — "sysopen/sysread/sysclose are compiler INTRINSICS (tkSysOpen &c)"). The lexer emits tkSysOpen rather than an identifier, so the declaration parser sees a token where a name belongs and says so, accurately but unhelpfully.

Which row of the compat table this is

Row 3, FPC accepts a form we reject, ranked by how much real code uses it — which is nearly none. It is not the "diagnostic differs" row: the program does not compile at all, so a program whose behaviour changes can be named, which is the line separating a low-prio ticket from a rejected/ one.

Suggested fix

Probably not un-reserving the names — they are deliberate intrinsics. A diagnostic naming the reservation would be enough:

error: 'sysopen' is a compiler intrinsic and cannot be redeclared

Provenance

Found while building the wasm Phase 1 self-test, which needed file output from a standalone program and first tried to declare these three as shims. The actual resolution was better — the intrinsics are callable from a standalone program without declaring them, which is what let the self-test exercise compiler/wasmenc.inc without including it into compiler.pas.

2026-09-05 (frankB) — this is the CALL side of a DECLARATION defect

Measured: the call never happens. procedure Write; / procedure SysOpen; is refused at the DECLARATION with expected name, so the user name cannot exist to be shadowed, and the call-site framing above is downstream of that.

Root cause and the whole cluster — nine spellings, one mechanism, with the blast radius enumerated — is [[bug-p-nine-intrinsic-spellings-are-hard-keywords-so-they-cannot-be-user-names]]. Work that one, not this one: a fix aimed at the call site is aimed at the wrong half, and fixing only the declaration would leave a routine that is declared and then silently never called, which is worse than today's refusal.

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