gen-c uses Trit 141 times and declares it zero times: the C backend does not follow "use" #5278

Re-filed from #2764. An attempt claimed that issue on 2026-09-24 and left an empty branch, and a dispatch row that has spent its retry ceiling keeps its issue for good - so no bee could take it again, however much the brief improved. The work below is carried over unchanged.

t27c corpus puts C last of the four backends — 157 of 559 accepted (24.2%), against Zig 217, rustc 214 and Verilog 378. The largest systematic cause is not a long tail.

The measurement

specs/vsa/ops.t27 opens with

use base::types;
use base::ops;

and Trit is declared in specs/base/types.t27. The generated C:

$ t27c gen-c specs/vsa/ops.t27 | grep -c Trit
141
$ t27c gen-c specs/vsa/ops.t27 | grep -cE '^typedef|^enum'
0

141 uses, zero declarations. The prelude emits only <stdint.h> <stdbool.h> <stddef.h> <assert.h> and nothing from the imported spec. cc reports unknown type name 'Trit' in 12 specs measured across the whole corpus.

What this is not

It is not a missing typedef Trit in the prelude. Trit is not a language built-in — it is declared in a spec, and other specs import it. Adding a typedef would paper over the actual gap and invent a representation the language never fixed.

The gap is that gen-c does not resolve use: it emits a standalone translation unit per spec and never emits, includes, or forward-declares anything the spec imported.

Rust has the same shape, C just fails louder

gen-rust on the same spec emits pub fn bind(a: Vec<Trit>, …) with no Trit in scope either. Zig drops the affected code entirely, so its number does not show the cost. Three backends, three different silences over one missing mechanism.

Why this is worth doing

Every other lever in the Rust column has now been pulled — the ruler (-o /dev/null, #2760), unconditional serde derives (#2760), and Vec<const T> — taking it from a false 0 to 214. C has had none of that, and this is the one cause that is systematic rather than per-spec: the first-error histogram is otherwise a long tail of user types appearing once each.

Effort is days, not minutes: it needs a decision about what an imported declaration becomes in C — a generated header per spec plus #include, or inlined declarations in dependency order — and the same decision then applies to Rust.

Boundary

• specs/base/types.t27
• specs/vsa/ops.t27

The instruments

Every one of these reads and prints; none of them writes. Run them from the repository root, with <spec> replaced by the file in ## Boundary:

.t27 is not Rust and not Zig, and a bee fluent in either writes one by
accident. Measured 2026-09-20: a bee filled eight bodies in
specs/file/watcher.t27 with return Ok(());, Err(FileError::WatcherNotFound)
and for i in 0..watchers.length. The parse ratchet refused the whole file --
Unexpected token in expression: RParen, line 123 -- and a spec that does not
parse generates nothing, so every test it already carried stopped running.

At the top level the parser accepts exactly these eight forms, with an optional
pub, and no others:

const   var   fn   enum   struct   test   invariant   bench

There is no trait, no impl, no type X = ..., no generics, no macro. What
a bee reaches for from another language, and what happens:

• Rust's result sugar (Ok(()), Err(E::V), ?) is not a construct here.
• Rust macros (println!, format!, vec!) are not constructs here.
• A range loop (for i in 0..n) is Rust and Zig, not this language.
• Zig builtins (catch unreachable, @intCast, @constCast) are not constructs here.
• Cross-module reuse (use other::fn;) parses and then generates a comment and an unqualified call, so the Zig fails with use of undeclared identifier (use a::b; generates no import, so no spec can reuse a function from another spec #4298). It does not work yet.

t27c parse <spec> answers in one line whether what you wrote is the language.
Run it before you report, every time.

• t27c spec-status <spec> - the compiler's one-word verdict: IMPLEMENTED, PARTIAL, UNWRITTEN, NOPARSE, NOFN. Exit code is 0 whatever it says, so read the word.
• t27c symbols <spec> - every name the file declares, with its kind. Answers "does this already exist here?" before you add it.
• t27c outline <spec> - per function: its locals, what it calls, what it returns. The contract you are implementing against.
• t27c coverage <spec> - which functions have a test and which do not. The issue asks for tests; this is how you check you wrote them.
• t27c lint <spec> - style and shape warnings. It OVER-REPORTS has no test or invariant: measured 2026-09-20 over 60 specs it printed 677 of those where coverage found 190 untested functions, disagreeing on 59 of the 60 - it warns about bit_to_trit_pair in specs/base/ternary_encoding.t27, which test bit_to_trit_pair_zero calls on line 249. Read it as a hint; coverage is the answer.
• t27c typecheck <spec> - types, before generation. Prints Typecheck OK (0 errors, 0 warnings) or the errors.
• t27c test-report <spec> - builds this spec and runs its own tests, which is what the oracle does. BLOCKED means the generated Zig does not compile, with the error beside it.
• python3 tools/dupe_scan.py --name <function> - where that function already lives, if it does. 576 of 4021 bodies here are byte-identical copies.

The rest of the toolbelt is in docs/BEE_TOOLBELT.md.