Capital `Write`/`WriteLn` rejected in some contexts (compiler self-build), works standalone

Type: bug (compiler / intrinsic name resolution) — Track A
Status: done
Owner: Codex
Found / Opened: 2026-06-27, while adding --dump-cpp to compiler.pas.
Relation: residual gap after [[bug-builtin-write-case-sensitive]] (marked done) — that fix made capital write/writeln resolve in normal programs, but a context-dependent hole remains.

Symptom

Adding if DumpCpp then begin Write(Source); Halt(0); end; to compiler.pas (Source: AnsiString) failed the self-build:

pascal26:64157: error: undefined variable (Write)

Lowercasing to write(Source) compiled fine. Only the capitalization changed.

But the same compiler binary accepts capital Write/WriteLn in a standalone program:

program wcase;
var s: AnsiString;
begin
  s := 'hi';
  Write(s); WriteLn('!');   { works: prints hi! }
  write('lower ok'); writeln;
end.

So capital write/writeln resolves in a small program but not in compiler.pas. Same binary, opposite result → context-dependent.

Why does it differ by context? Candidates to check:

The declaration pre-scan (compiler.pas is a large two-pass program; wcase.pas is trivial) — does prescan change how a tkIdent-spelled Write falls back to the write intrinsic?
A near-miss symbol: the compiler source has WriteExprIsFloat, writeShdr64, etc. Case-insensitive resolution of Write shouldn't match those (different names), but worth confirming the resolver isn't doing a prefix/partial match or being shadowed by a write-spelled enum/const.
Statement position / nesting depth in the big else if isC then … chain.
Whether the lexer only emits the write/writeln intrinsic token for the exact lowercase spelling, and capital Write always goes through the symbol-resolution fallback (which the standalone case happens to satisfy and the self-build does not).

Self-build: temporarily put Write(...) (capital) in compiler.pas and rebuild → fails. (Reverted; the shipped --dump-cpp uses lowercase write.)
Need a minimal program that reproduces the capital-Write rejection outside compiler.pas — wcase.pas above does NOT, so the trigger is still unknown.

Capital Write/WriteLn/Read/ReadLn resolve to the intrinsic in all contexts (statement + the compiler's own source), matching the documented case-insensitive default.
A minimal repro added to test/.
self-host byte-identical (the fix is name-resolution only).

2026-06-29 - Fixed by making only the four I/O intrinsic keyword matches (Read, ReadLn, Write, WriteLn) case-insensitive even while {$CASESENSITIVE ON} is active. Verified the original temporary Write(Source) self-build repro now succeeds, added a casesensitive-mode Read/Write regression, and make test-core passes.
2026-06-29 - Picked up on Track A. Reproduced the current compiler failing when compiler.pas temporarily changes the --dump-cpp branch from write(Source) to Write(Source): undefined variable (Write).
2026-06-27 - Found adding --dump-cpp. Capital Write rejected in compiler.pas, accepted standalone — same binary. Mechanism unknown; filed.