The value model of the companion, and the half of it that has to say no.
`Sexp` carries only what a lexer can honestly know: list, symbol, integer, byte
string, string. There is no `Bool` variant, because `true` is spelled exactly like
a symbol and nothing but the expected type tells them apart; no `Ratio` and no
`Option` variant, because both are lists. That is `req:textproj:schema-directed`
expressed as a type rather than asserted in a comment.
Integers are `BigInt`. `RationalTime` promotes to a `BigRational` when arithmetic
overflows its inline range, so the text's integers cannot be bounded by `i64`.
`read_sexp` is strict per `req:textproj:strict-parse`: it accepts exactly what
`Sexp::write` emits. Leading zeros, negative zero, upper-case hex, an odd hex digit
count, an unknown escape, a raw tab, a doubled space, a space after `(`, and any
trailing input are rejections, never normalizations. `BTreeSet` and `BTreeMap`
parse strictly increasing and refuse to absorb a duplicate -- sorting the input
would be normalizing it.
Every guard mutation-verified, which caught two that were not guards. The
upper-case-hex branch and the space-before-element branch change no verdict: the
first is already rejected by the odd-digit count or by trailing input, the second
by `value`, which knows no value beginning with U+0020. Both survived deletion
with the rejection suite green -- it proved only that *something* rejected them.
They are diagnostics, so their contract is the message, and
`the_reader_names_the_real_problem` now holds them to it. A check that looks like a
guard but is not is worse than no check: it invites weakening the real one.
Gate green -- clippy 0, 1048 tests, doc 0, conformance 8/8, no golden churn.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Levi Neuwirth
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