Delete StringId's relational operators so handle order and name order stop being the same character (fixes #185, #183, #184)

[typeless]

StringId is enum class : uint32_t, so < on it was the built-in enum comparison — interning order. Whether a site meant "handle order, because this is a set" or "name order, because this order is observable" was untyped, unstated, and spelled with the same character. Four bugs came out of that confusion: #171, #175, and the two live ones this fixes — and the two live ones were audited and wrongly cleared in PR #176's own description.

The change

auto operator<(StringId, StringId) -> bool = delete;   // + >, <=, >=

inline constexpr auto handle_less = [](StringId a, StringId b) {
    return to_underlying(a) < to_underlying(b);
};

A user-declared deleted operator wins overload resolution over the built-in candidate for a scoped enum, so this does not require making StringId a class type. Equality, casts, and to_underlying are untouched.

What the compiler found

21 sites. Eighteen were genuine set structures — dedup, membership, binary search against a handle-keyed range — and now say handle_less out loud. Every sort/search pair was checked to agree.

Three were ordering bugs:

site	defect
src/exec/scheduler.cpp:62 (#183)	env cache sorted by handle, lower_bound-searched by name at :44. Precondition violated, lookups miss present entries, prepare_job_launch omits the variable, and base_child_env contributes only PATH= — so it is absent from the child entirely.
src/cli/context.cpp:677 (#184)	cached_env_vars sorted by handle, searched by name at builder.cpp:1305. A missed lookup falls through to an empty value, changing rendered command text and therefore command identity.
src/parser/var_tracking.cpp:21	group_by_name ordered by handle despite its name, and show var prints it. Now name-ordered — this changes that command's output order.

Reproduced before and after

export ZVAR / export MVAR / export AVAR    before: 0 of 3 in child env    after: 3 of 3
import Z/M/A, rebuild with env unset       before: A= M= Z=               after: A=aaa M=mmm Z=zzz

Both are pinned by new tests, each observed failing first: a three-variable section in test/unit/test_exec.cpp (the existing test used one variable, and lower_bound over a one-element range cannot be wrong), and an import_order e2e fixture that builds with the variables set and rebuilds with them unset.

Notes

• src/core/layout.cpp:221 is fixed here too, because it will not compile otherwise. That is the same one-line change as Order discovered variants by name, not by interning order (fixes #175) #176, which can land before or after this — expect a trivial conflict if Order discovered variants by name, not by interning order (fixes #175) #176 goes first.
• No INDEX_VERSION bump. No persisted format change and no deliberate identity-semantics change; commands whose identity was computed from a wrongly-empty env value re-run once, which is the repair. Flagging it explicitly since Order glob matches by path, not by interning order (fixes #171) #174 and Merge filesystem and generated glob matches into one path-ordered list (fixes #177, fixes #178) #180 both bumped.
• Cost: one word at 18 sites. There are no std::map/std::set keyed on StringId, and SortedIdVec/SortedPairVec take raw uint32_t, so they were unaffected.

make test green (142317 assertions, 617 cases, 32 e2e shards); make tidy and make iwyu clean; bootstrap scripts unchanged.

🤖 Generated with Claude Code

https://claude.ai/code/session_01TLob4Ef3qyMd3Dnp9q3XmA

[github-actions]

PR metrics

Performance (gcc example, Linux)

Workload	Instructions	CPU time	Page faults	D1 miss	LL miss	Wall	Peak RSS
parse	1075 M	0.55 s	14.1 k	0.8%	0.1%	0.54 s	30.7 MB (-0.1MB)
dry-run	1793 M (+0.1%)	0.65 s	16.6 k	0.9%	0.1%	0.628 s	40 MB (-0.1MB)

Deterministic signals: instructions (cachegrind-simulated instruction reads — exact across runs, no PMU needed), page faults, peak RSS, and the cachegrind D1/LL miss rates. CPU time is user+sys from time(1).

Internal statistics (gcc example, up-to-date dry run)

Metric	Value
Tupfiles parsed	24
Commands	3545
Commands scheduled	0
Files checked	5818
Files changed	0
Files in index	6087
Graph edges	367913
Index size (bytes)	7264970
Implicit deps	330624
Hash computations	0
Hashes skipped (stat cache)	5818
Stat calls	5869
Parse time (ms)	520.4 (+2.8%)
Total time (ms)	621.3 (+2.8%)
Runner CPU	AMD EPYC 7763 64-Core Processor

Counters from putup -n --stat on the fully-built gcc example (up-to-date dry run): deterministic work measures — a jump in commands scheduled, hash computations, or stat calls is a real behavior change, not noise. Timings are the minimum over repeated runs, compared only against a baseline from the same CPU model; the counters are the regression signal.

Binary size (Linux)

Binary	.text	.data	.bss	File
putup	504.9 KB (+0.6%)	1.6 KB	98.7 KB	596.8 KB (+0.5%)

Test coverage (lines)

Overall	Median file	Min file	Max file
86.6%	94.9%	0.0% src/platform/path-posix.cpp	100.0% include/pup/core/arena.hpp

103 files · 15008/17335 lines covered

Deltas vs main@59ff72962.

Updated for eecf318