Fix sign-only integer unpacking

[dduan]

Summary

• Reject sign-only integer tokens before reading past the token bounds.
• Add regression coverage for x = +.

Validation

• Not run in this split branch per instruction; this commit was already verified before PR splitting.

[github-actions]

�[33mWarning: running with the Swift runtime interposer on Linux to avoid the Swift 6.3 runtime hook crash. See https://github.com/ordo-one/benchmark/issues/349�[0m

Comparing results between 'main' and 'pull_request'

Host 'runnervm5mmn9' with 4 'x86_64' processors with 15 GB memory, running:
#18~24.04.1-Ubuntu SMP Thu May 28 16:39:11 UTC 2026

TOMLDecoderBenchmarks

Decode toml.io example metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (μs) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	62	63	63	64	68	87	136	7341
pull_request	62	63	64	71	89	105	211	6918
Δ	0	0	1	7	21	18	75	-423
Improvement %	0	0	-2	-11	-31	-21	-55	-423

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	765	765	765	765	765	765	765	7341
pull_request	765	765	765	765	765	765	765	6918
Δ	0	0	0	0	0	0	0	-423
Improvement %	0	0	0	0	0	0	0	-423

Parse toml.io example metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ns) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	5050	5199	5231	5283	5351	6863	30307	10000
pull_request	5029	5131	5159	5191	5263	8551	41688	10000
Δ	-21	-68	-72	-92	-88	1688	11381	0
Improvement %	0	1	1	2	2	-25	-38	0

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	31	31	31	31	31	31	31	10000
pull_request	31	31	31	31	31	31	31	10000
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

decode canada.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	252	252	253	254	256	256	256	4
pull_request	248	248	249	250	260	260	260	4
Δ	-4	-4	-4	-4	4	4	4	0
Improvement %	2	2	2	2	-2	-2	-2	0

Retains: results within specified thresholds, fold down for details.

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	1286	1286	1286	1286	1286	1286	1286	4
pull_request	1286	1286	1286	1286	1286	1286	1286	4
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

decode twitter.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (μs) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	8720	9568	9609	9683	9757	9855	10658	103
pull_request	8703	9462	9486	9535	9576	9760	9760	105
Δ	-17	-106	-123	-148	-181	-95	-898	2
Improvement %	0	1	1	2	2	1	8	2

Retains: results within specified thresholds, fold down for details.

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	113	113	113	113	113	113	113	103
pull_request	113	113	113	113	113	113	113	105
Δ	0	0	0	0	0	0	0	2
Improvement %	0	0	0	0	0	0	0	2

parse GitHub events archive metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	125	125	126	128	136	136	136	8
pull_request	122	123	124	128	134	134	134	8
Δ	-3	-2	-2	0	-2	-2	-2	0
Improvement %	2	2	2	0	1	1	1	0

Retains: results within specified thresholds, fold down for details.

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	394	394	394	394	394	394	394	8
pull_request	394	394	394	394	394	394	394	8
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

parse canada.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	15	16	16	16	16	23	23	63
pull_request	15	15	15	16	16	23	23	65
Δ	0	-1	-1	0	0	0	0	2
Improvement %	0	6	6	0	0	0	0	2

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	47	47	47	47	47	47	47	63
pull_request	47	47	47	47	47	47	47	65
Δ	0	0	0	0	0	0	0	2
Improvement %	0	0	0	0	0	0	0	2

parse twitter.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (μs) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	2260	2284	2292	2302	2314	2404	3383	425
pull_request	2253	2267	2275	2288	2304	2458	3336	428
Δ	-7	-17	-17	-14	-10	54	-47	3
Improvement %	0	1	1	1	0	-2	1	3

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	7736	7736	7736	7736	7736	7736	7736	425
pull_request	7736	7736	7736	7736	7736	7736	7736	428
Δ	0	0	0	0	0	0	0	3
Improvement %	0	0	0	0	0	0	0	3