bug: case-insensitivity incomplete — builtins + function calls still case-sensitive

• Type: bug (Track A — parser / symbol resolution)
• Status: done
• Found: 2026-06-23, differential probe vs FPC (Track B)
• Closed: 2026-06-23
• Severity: medium-high (breaks mixed-case FPC source broadly)

Resolution (2026-06-23)

Front-end/resolution only, no codegen.

1. Unit/RTL function calls (inttostr vs IntToStr): unqualified MatchProcCall compared Procs[i].Name = name exactly in every overload phase. Added ProcNameMatches(idx, name) (exact, plus case-insensitive for a non-external, non-case-sensitive proc — mirrors the FindProc fallback and the already-CI MatchProcCallInUnit) and routed all phases + the 2c interface phase + the mismatch diagnostic through it. External C imports stay exact (printf <> Printf; relax only under {$LAZYCASING ON}).
2. Builtins matched by name string: SetLength, New, Dispose, ReallocMem, Str, Val, LoadFile were (name='X') or (name='x') (two spellings only) — now CaseEqual(name, 'X'). (Length/High/Low/Inc/Dec/ Ord/Chr/Copy/Trunc/Round/UpCase are keyword tokens, already CI via the lexer; the nilpy int/str stay exact — Python-cased.)

Verified mixed-case: SETLENGTH/LENGTH/HIGH/LOW/INC/DEC/ORD/CHR/COPY/TRUNC/ROUND/ UPCASE and unit funcs inttostr/uppercase/lowercase/trim/strtoint/max/min — all byte-identical to FPC. Gate: make test (self-host byte-identical — resolution only) + FPC oracle. Closes bug-case-insensitive-incomplete-builtins-funcs.

• Relation: continues bug-keywords-case-sensitive (DONE 7d5b18d) and bug-builtin-write-case-sensitive (DONE 3de5d05) — those fixed keywords and Write/Read/WriteLn/ReadLn; the rest of the builtins and all unit-function calls were not converted.

Symptom

pascal26 is meant to be case-insensitive for user code (defs.inc "standard case-insensitive Pascal"); variables and type names already are (Foo/foo/FOO resolve, INTEGER works). But two classes of identifier still match case-sensitively:

1. Builtin intrinsics other than Write/Read

var s: string; begin s := 'hi'; writeln(Length(s)); end.   { ok: 2 }
var s: string; begin s := 'hi'; writeln(LENGTH(s)); end.   { error: undefined variable }

Likely affects SetLength, High, Low, Inc, Dec, Copy, Ord, Chr, Trunc, Round, … — matched by hardcoded exact-case string compares rather than CaseEqual. Concrete locus, e.g. compiler/parser.inc:6973:

else if (name = 'SetLength') or (name = 'setlength') then   { only two spellings }

so SETLENGTH / SetLENGTH fall through.

2. Unit / RTL function calls

uses sysutils; begin writeln(IntToStr(123)); end.   { ok: 123 }
uses sysutils; begin writeln(inttostr(123)); end.   { error: no overload of inttostr matches }

Same for UpperCase / LowerCase / Trim / StrToInt (sysutils) and Sqrt / Min / Max / Power (math): the exact-case spelling resolves, any other case fails. Unit function symbols are looked up case-sensitively even though local variables are not.

(Probed with -Fulib/rtl and the proper-case control passing, so this is name resolution, not a missing unit/function.)

Expected

All identifier resolution — builtins, unit functions, methods — uses the same case-insensitive matcher as variables (respecting {$CASESENSITIVE ON}, under which the compiler's own source still matches exactly for byte-identical self-host). Route the builtin string compares through CaseEqual and make imported-symbol lookup case-insensitive.

Repro / regression

tools/fpc_diff_probe.sh — proper-case probes pass, mixed-case fail. Keyword mixed-case (BEGIN) also still fails against the pinned v38 (that fix, 7d5b18d, post-dates the pin → also wants a re-pin, see chore-repin-new-intrinsics).