Short-circuit isTypeVarSame subtype checks

[Bill Schnurr (bschnurr)]

Summary

• Fixes allSubtypes so union checks return callback results.
• Delegates directly to Array.every for allocation-free early termination.
• Uses allSubtypes in isTypeVarSame to stop at the first incompatible subtype instead of walking the remaining union entries with no-op callbacks.
• Preserves someSubtypes and adds direct unit coverage for both helpers.

This is the safe typeUtils portion split from #11419. It intentionally excludes the literal, tuple, derivesFromAnyOrUnknown, and NoReturn early exits that produced mypy_primer differences.

Validation

• pnpm exec jest typeUtils.test --forceExit
• pnpm run build
• pnpm run check:prettier
• pnpm run check:eslint
• full hosted validation: 16 checks passed
• exact-head mypy_primer rerun: all eight diff artifacts empty

[Bill Schnurr (bschnurr)]

/benchmark

[Rich Chiodo (rchiodo)]

🔒 Automated review in progress — Rich Chiodo (@rchiodo) is auto-reviewing this PR.

[Rich Chiodo (rchiodo)]

Verification: The relevant tests could not be fully run in the isolated environment; this review is not fully verified.

[Rich Chiodo (rchiodo)]

Approved via Review Center.

[Rich Chiodo (rchiodo)]

Verification: The relevant tests could not be fully run in the isolated environment; this review is not fully verified.

[Rich Chiodo (rchiodo)]

Verification: The relevant tests could not be fully run in the isolated environment; this review is not fully verified.

[Bill Schnurr (bschnurr)]

/benchmark

[Rich Chiodo (rchiodo)]

Verification: The relevant tests could not be fully run in the isolated environment; this review is not fully verified.

Result: could-not-verify

Summary: Verification could not run because no trusted `microsoft/pyright` sandbox image was configured and local execution was unauthorized. The PR adds focused coverage for union short-circuiting and non-union callbacks in `allSubtypes` and `someSubtypes`. No meaningful test execution occurred, so the verdict is **could-not-verify**.

Test runs: 1 not run

• ⚠️ Not run | typeUtils unit tests | pnpm exec jest typeUtils.test --runInBand

⚠️ typeUtils unit tests diagnostic output

Container verification could not start: no trusted sandbox image is configured for microsoft/pyright; local execution was not authorized for this PR HEAD.

[Bill Schnurr (bschnurr)]

/benchmark

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[Bill Schnurr (bschnurr)]

/benchmark

[github-actions]

Type checker benchmark

🟢 No performance regressions detected.

Regression threshold: 20.0%
Variance guard: >1.0s time and >100.0 MB memory

Package	Checker	Files checked	Time	Time delta	Peak memory	Memory delta	Status
ansible	pyright	583	18.951s	-12.5%	1168.3 MB	+5.2%	🟢 Pass
click	pyright	17	2.706s	-6.9%	361.7 MB	+0.2%	🟢 Pass
homeassistant	pyright	9850	137.064s	-13.4%	6196.9 MB	+0.1%	🟢 Pass
numpy	pyright	356	37.361s	-14.0%	1847.0 MB	-0.2%	🟢 Pass
pandas	pyright	1459	866.065s	-12.4%	4451.5 MB	+0.4%	🟢 Pass
pytest	pyright	243	11.420s	-9.2%	891.8 MB	-4.2%	🟢 Pass
requests	pyright	19	2.155s	-6.3%	343.7 MB	-1.0%	🟢 Pass
torch	pyright	2400	136.841s	-11.0%	5182.0 MB	+5.9%	🟢 Pass
transformers	pyright	2901	113.567s	-15.6%	5250.5 MB	+2.3%	🟢 Pass

Pyright stats

Package	Parsed/bound	Checked	Find	Read	Tokenize	Parse	Imports	Bind	Check	Cycles
ansible	989	583	0.030s	0.100s	0.450s	0.650s	0.220s	0.860s	16.130s	0.000s
click	111	17	0.000s	0.020s	0.120s	0.160s	0.030s	0.230s	1.840s	0.000s
homeassistant	11138	9850	0.330s	0.900s	3.020s	4.280s	2.080s	6.270s	117.340s	0.000s
numpy	603	356	0.010s	0.070s	0.400s	0.620s	0.230s	0.780s	34.760s	0.000s
pandas	1895	1459	0.050s	0.270s	1.200s	1.850s	0.290s	2.220s	859.110s	0.000s
pytest	542	243	0.010s	0.070s	0.360s	0.440s	0.090s	0.630s	9.420s	0.000s
requests	168	19	0.000s	0.020s	0.110s	0.180s	0.050s	0.240s	1.280s	0.000s
torch	3076	2400	0.110s	0.560s	2.840s	3.100s	0.580s	4.410s	123.890s	0.000s
transformers	3534	2901	0.100s	0.430s	2.680s	3.180s	0.990s	8.650s	98.000s	0.000s

[Heejae Chang (heejaechang)]

✅ Pyright CLI QA — c49ce2fb — verdict: green

Automated CLI checks compared this change with its base revision.
4 focused check(s) completed.

No new behavior difference was detected by the completed CLI checks.