Fixed detection of optional chains containing a reference by Andarist · Pull Request #64232 · microsoft/TypeScript

Mateusz Burzyński (Andarist) · 2026-09-10T16:53:54Z

fixes #56998
fixes #60855

recreates #59144

Copilot

🟡 Changes recommended

The operand reversal regresses narrowing when an optional-chain base is wrapped in a satisfies expression.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Fixes control-flow narrowing for references assigned within optional-chain bases.

Changes:

Reverses reference matching to recognize assignment targets.
Adds regression and negative narrowing tests with baselines.

File summaries

File	Description
`tsc/internal/checker/flow.go`	Updates optional-chain reference matching.
`tsc/testdata/tests/cases/conformance/controlFlow/controlFlowOptionalChain4.ts`	Adds regression cases.
`tsc/testdata/baselines/reference/conformance/controlFlowOptionalChain4.types`	Records inferred types.
`tsc/testdata/baselines/reference/conformance/controlFlowOptionalChain4.symbols`	Records resolved symbols.
`tsc/testdata/baselines/reference/conformance/controlFlowOptionalChain4.errors.txt`	Records expected diagnostics.

Review details

Files reviewed: 5/5 changed files
Comments generated: 1
Review effort level: Balanced

Copilot

🟢 Approval recommended

The focused checker correction is supported by comprehensive positive and negative regression baselines.

Review details

Files reviewed: 10/10 changed files
Comments generated: 0 new
Review effort level: Balanced

Jake Bailey (jakebailey) · 2026-09-15T17:55:04Z

TypeScript Bot (@typescript-bot) test it

typescript-automation · 2026-09-15T17:55:09Z

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
`test top400`	✅ Started	✅ Results
`user test this`	✅ Started	✅ Results
`run dt`	✅ Started
`perf test this faster`	✅ Started	👀 Results

typescript-automation · 2026-09-15T18:29:47Z

Jake Bailey (@jakebailey)
The results of the perf run you requested are in!

Here they are:

tsc

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-Unions - native}
_Errors	₄₁	₄₁	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_115,480	_115,480	_~	_~	_~	_{p=1.000 n=12}
_Types	_96,945	_96,945	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{148,628k (± 0.46%)}	_{148,126k (± 0.49%)}	_~	_146,707k	_150,362k	_{p=0.198 n=12}
_{Memory Allocs}	_{2,271,272 (± 0.00%)}	_{2,271,232 (± 0.01%)}	_~	_2,270,935	_2,271,445	_{p=0.887 n=12}
_{Config Time}	_{0.000s (±217.90%)}	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.051s (± 3.79%)}	_{0.051s (± 3.11%)}	_~	_0.046s	_0.054s	_{p=0.899 n=12}
_{Bind Time}	_{0.016s (±12.37%)}	_{0.016s (±11.92%)}	_~	_0.013s	_0.021s	_{p=0.925 n=12}
_{Check Time}	_{0.597s (± 0.98%)}	_{0.602s (± 0.73%)}	_~	_0.591s	_0.610s	_{p=0.103 n=12}
_{Emit Time}	_{0.329s (± 2.63%)}	_{0.328s (± 1.70%)}	_~	_0.312s	_0.339s	_{p=0.966 n=12}
_{Total Time}	_{1.000s (± 0.67%)}	_{1.004s (± 0.88%)}	_~	_0.982s	_1.029s	_{p=0.354 n=12}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_{847,422 (± 0.06%)}	_{847,765 (± 0.08%)}	_~	_844,736	_848,512	_{p=0.128 n=12}
_Types	_{249,851 (± 0.00%)}	_{249,851 (± 0.00%)}	_~	_249,849	_249,861	_{p=0.376 n=12}
_{Memory Used}	_{793,676k (± 0.08%)}	_{793,679k (± 0.06%)}	_~	_792,649k	_795,382k	_{p=0.843 n=12}
_{Memory Allocs}	_{12,954,108 (± 0.02%)}	_{12,956,530 (± 0.06%)}	_~	_12,948,452	_12,989,228	_{p=0.671 n=12}
_{Config Time}	_{0.020s (± 0.91%)}	_0.020s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.343s (± 3.00%)}	_{0.348s (± 2.28%)}	_~	_0.325s	_0.362s	_{p=0.434 n=12}
_{Bind Time}	_{0.082s (±17.71%)}	_{0.075s (± 5.33%)}	_~	_0.069s	_0.094s	_{p=0.280 n=12}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Emit Time}	_{1.968s (± 1.06%)}	_{1.958s (± 0.62%)}	_~	_1.936s	_2.007s	_{p=0.560 n=12}
_{Total Time}	_{2.431s (± 1.27%)}	_{2.418s (± 0.62%)}	_~	_2.391s	_2.481s	_{p=0.921 n=12}
_{mui-docs - native}
_Errors	_{11,315 (± 0.06%)}	_{11,319 (± 0.04%)}	_~	_11,299	_11,323	_{p=0.635 n=12}
_Symbols	_4,082,255	_4,082,255	_~	_~	_~	_{p=1.000 n=12}
_Types	_1,497,312	_1,497,312	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{4,079,435k (± 0.04%)}	_{4,079,616k (± 0.03%)}	_~	_4,076,745k	_4,083,511k	_{p=0.977 n=12}
_{Memory Allocs}	_{43,636,964 (± 0.05%)}	_{43,626,760 (± 0.03%)}	_~	_43,604,253	_43,667,329	_{p=0.590 n=12}
_{Config Time}	_0.019s	_{0.019s (± 0.95%)}	_~	_0.019s	_0.020s	_{p=1.000 n=12}
_{Parse Time}	_{0.670s (± 2.29%)}	_{0.680s (± 1.44%)}	_~	_0.654s	_0.702s	_{p=0.339 n=12}
_{Bind Time}	_{0.003s (±27.24%)}	_{0.002s (±13.40%)}	_~	_0.002s	_0.003s	_{p=1.000 n=12}
_{Check Time}	_{16.916s (± 0.27%)}	_{16.882s (± 0.39%)}	_~	_16.699s	_17.042s	_{p=0.319 n=12}
_{Emit Time}	_{0.543s (±10.70%)}	_{0.524s (± 2.56%)}	_~	_0.512s	_0.570s	_{p=0.502 n=12}
_{Total Time}	_{19.070s (± 0.23%)}	_{19.039s (± 0.12%)}	_~	_18.987s	_19.093s	_{p=0.193 n=12}
_{strada-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,394,252	_1,394,252	_~	_~	_~	_{p=1.000 n=12}
_Types	_443,418	_443,418	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,647,910k (± 0.33%)}	_{1,646,605k (± 0.37%)}	_~	_1,631,090k	_1,665,144k	_{p=0.799 n=12}
_{Memory Allocs}	_{97,049,303 (± 0.04%)}	_{97,065,456 (± 0.05%)}	_~	_96,937,094	_97,210,142	_{p=0.671 n=12}
_{Config Time}	_{0.004s (±12.88%)}	_{0.004s (±12.60%)}	_~	_0.003s	_0.006s	_{p=0.484 n=12}
_{Parse Time}	_{0.192s (± 2.42%)}	_{0.196s (± 2.50%)}	_~	_0.188s	_0.212s	_{p=0.147 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{1.808s (± 0.34%)}	_{1.811s (± 0.28%)}	_~	_1.799s	_1.828s	_{p=0.418 n=12}
_{Emit Time}	_{0.280s (± 4.94%)}	_{0.284s (± 4.17%)}	_~	_0.245s	_0.303s	_{p=0.600 n=12}
_{Total Time}	_{24.792s (± 0.53%)}	_{24.917s (± 0.50%)}	_~	_24.652s	_25.263s	_{p=0.178 n=12}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_337,531	_337,531	_~	_~	_~	_{p=1.000 n=12}
_Types	_198,830	_198,830	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{319,648k (± 0.08%)}	_{319,531k (± 0.07%)}	_~	_319,183k	_320,604k	_{p=0.143 n=12}
_{Memory Allocs}	_{4,673,076 (± 0.01%)}	_{4,672,821 (± 0.01%)}	_~	_4,671,098	_4,674,085	_{p=0.514 n=12}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.112s (± 4.39%)}	_{0.113s (± 3.72%)}	_~	_0.099s	_0.122s	_{p=0.765 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{1.054s (± 0.42%)}	_{1.052s (± 0.44%)}	_~	_1.039s	_1.061s	_{p=0.811 n=12}
_{Emit Time}	_{0.124s (±12.37%)}	_{0.140s (±11.90%)}	_~	_0.098s	_0.169s	_{p=0.117 n=12}
_{Total Time}	_{1.346s (± 1.01%)}	_{1.359s (± 1.15%)}	_~	_1.315s	_1.396s	_{p=0.173 n=12}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_305,179	_305,179	_~	_~	_~	_{p=1.000 n=12}
_Types	_181,876	_181,876	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{277,220k (± 0.01%)}	_{277,170k (± 0.02%)}	_~	_277,068k	_277,322k	_{p=0.114 n=12}
_{Memory Allocs}	_{1,641,789 (± 0.01%)}	_{1,641,872 (± 0.01%)}	_~	_1,641,460	_1,642,255	_{p=0.410 n=12}
_{Config Time}	_{0.001s (±65.70%)}	_{0.001s (±65.70%)}	_~	_0.000s	_0.001s	_{p=1.000 n=12}
_{Parse Time}	_{0.102s (± 3.59%)}	_{0.100s (± 4.22%)}	_~	_0.091s	_0.110s	_{p=0.449 n=12}
_{Bind Time}	_{0.038s (±12.40%)}	_{0.037s (±11.41%)}	_~	_0.027s	_0.052s	_{p=0.521 n=12}
_{Check Time}	_{0.836s (± 0.78%)}	_{0.841s (± 0.42%)}	_~	_0.828s	_0.849s	_{p=0.354 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{0.990s (± 0.81%)}	_{0.992s (± 0.70%)}	_~	_0.972s	_1.004s	_{p=0.504 n=12}
_{vscode - native}
_Errors	₃₅₁	₃₅₁	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_8,856,348	_8,856,348	_~	_~	_~	_{p=1.000 n=12}
_Types	_3,024,061	_3,024,061	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{5,925,595k (± 0.02%)}	_{5,925,222k (± 0.01%)}	_~	_5,923,689k	_5,926,474k	_{p=0.887 n=12}
_{Memory Allocs}	_{45,575,813 (± 0.02%)}	_{45,565,779 (± 0.01%)}	_~	_45,558,771	_45,580,204	_{p=0.052 n=12}
_{Config Time}	_{0.053s (± 0.34%)}	_{0.053s (± 0.34%)}	_~	_0.052s	_0.053s	_{p=1.000 n=12}
_{Parse Time}	_{1.336s (± 2.85%)}	_{1.359s (± 2.59%)}	_~	_1.286s	_1.458s	_{p=0.224 n=12}
_{Bind Time}	_{0.414s (±13.23%)}	_{0.370s (±15.22%)}	_~	_0.302s	_0.530s	_{p=0.263 n=12}
_{Check Time}	_{9.175s (± 1.27%)}	_{9.273s (± 1.40%)}	_~	_9.012s	_9.544s	_{p=0.325 n=12}
_{Emit Time}	_{3.957s (± 9.22%)}	_{3.514s (±11.09%)}	_~	_2.782s	_4.431s	_{p=0.068 n=12}
_{Total Time}	_{15.030s (± 1.81%)}	_{14.658s (± 1.98%)}	_{-0.372s (- 2.48%)}	_14.088s	_15.419s	_{p=0.040 n=12}
_{webpack - native}
_Errors	₈₃₇	₈₃₇	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,125,807	_1,125,807	_~	_~	_~	_{p=1.000 n=12}
_Types	_480,798	_480,798	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{814,023k (± 0.02%)}	_{813,931k (± 0.02%)}	_~	_813,308k	_814,308k	_{p=0.319 n=12}
_{Memory Allocs}	_{5,145,772 (± 0.03%)}	_{5,146,027 (± 0.04%)}	_~	_5,143,713	_5,154,767	_{p=0.843 n=12}
_{Config Time}	_0.007s	_0.007s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.189s (± 3.80%)}	_{0.189s (± 2.21%)}	_~	_0.177s	_0.203s	_{p=0.921 n=12}
_{Bind Time}	_{0.053s (±20.84%)}	_{0.050s (±16.55%)}	_~	_0.038s	_0.073s	_{p=0.679 n=12}
_{Check Time}	_{1.362s (± 0.31%)}	_{1.367s (± 0.69%)}	_~	_1.331s	_1.391s	_{p=0.309 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.640s (± 0.56%)}	_{1.642s (± 0.88%)}	_~	_1.603s	_1.679s	_{p=1.000 n=12}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,045,691	_1,045,691	_~	_~	_~	_{p=1.000 n=12}
_Types	_381,854	_381,854	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{611,084k (± 0.01%)}	_{611,177k (± 0.02%)}	_~	_610,861k	_611,426k	_{p=0.132 n=12}
_{Memory Allocs}	_{4,827,173 (± 0.05%)}	_{4,826,257 (± 0.06%)}	_~	_4,822,651	_4,835,877	_{p=0.347 n=12}
_{Config Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.115s (± 3.79%)}	_{0.118s (± 3.57%)}	_~	_0.105s	_0.128s	_{p=0.368 n=12}
_{Bind Time}	_{0.036s (±20.15%)}	_{0.033s (±19.42%)}	_~	_0.024s	_0.059s	_{p=0.463 n=12}
_{Check Time}	_{0.989s (± 0.58%)}	_{0.987s (± 0.71%)}	_~	_0.973s	_1.010s	_{p=0.599 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.151s (± 0.78%)}	_{1.148s (± 0.74%)}	_~	_1.129s	_1.166s	_{p=0.640 n=12}

System info unknown

Hosts

native

Scenarios

Compiler-Unions - native
angular-1 - native
mui-docs - native
strada-build-src - native
strada-compiler - native
ts-pre-modules - native
vscode - native
webpack - native
xstate-main - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

Developer Information:

Download Benchmarks

typescript-automation · 2026-09-15T19:10:59Z

Jake Bailey (@jakebailey) Here are the results of running the user tests with tsc comparing main and refs/pull/64232/merge:

There were infrastructure failures potentially unrelated to your change:

2 instances of "Package install failed"
1 instance of "Git clone failed"

Otherwise...

Everything looks good!

typescript-automation · 2026-09-15T19:40:31Z

Jake Bailey (@jakebailey) Here are the results of running the top 400 repos with tsc comparing main and refs/pull/64232/merge:

Everything looks good!

Mateusz Burzyński (Andarist) added 2 commits September 10, 2026 17:44

Fixed detection of optional chains containing a reference

9326b60

Add negative optional chain narrowing tests

4d66eb7

Copilot AI balanced review requested due to automatic review settings September 10, 2026 16:53

github-project-automation Bot added this to PR Backlog Sep 10, 2026

github-project-automation Bot moved this to Not started in PR Backlog Sep 10, 2026

typescript-automation Bot added the For Backlog Bug PRs that fix a backlog bug label Sep 10, 2026

Copilot started reviewing on behalf of Mateusz Burzyński (Andarist) September 10, 2026 16:54 View session

Copilot AI reviewed Sep 10, 2026

View reviewed changes

Comment thread tsc/internal/checker/flow.go

Handle satisfies expressions when matching references

20fc192

Mateusz Burzyński (Andarist) force-pushed the port-59144-optional-chain-reference branch from c228f27 to 20fc192 Compare September 10, 2026 18:38

Jake Bailey (jakebailey) requested a balanced review from Copilot September 15, 2026 16:40

Copilot started reviewing on behalf of Jake Bailey (jakebailey) September 15, 2026 16:40 View session

Copilot AI reviewed Sep 15, 2026

View reviewed changes

Jake Bailey (jakebailey) approved these changes Sep 15, 2026

View reviewed changes

github-project-automation Bot moved this from Not started to Needs merge in PR Backlog Sep 15, 2026

Jake Bailey (jakebailey) added this pull request to the merge queue Sep 15, 2026

Jake Bailey (jakebailey) removed this pull request from the merge queue due to a manual request Sep 15, 2026

Navigation Menu

Fixed detection of optional chains containing a reference - #64232

Fixed detection of optional chains containing a reference#64232
Mateusz Burzyński (Andarist) wants to merge 3 commits into
microsoft:mainfrom
Andarist:port-59144-optional-chain-reference

Mateusz Burzyński (Andarist) commented Sep 10, 2026

Uh oh!

Copilot AI left a comment

Uh oh!

Uh oh!

Copilot AI left a comment

Uh oh!

Jake Bailey (jakebailey) commented Sep 15, 2026

Uh oh!

typescript-automation Bot commented Sep 15, 2026 •

edited

Loading

Uh oh!

typescript-automation Bot commented Sep 15, 2026

tsc

Uh oh!

typescript-automation Bot commented Sep 15, 2026

Uh oh!

typescript-automation Bot commented Sep 15, 2026

Uh oh!

This branch has not been deployed

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

Conversation

Mateusz Burzyński (Andarist) commented Sep 10, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

🟡 Changes recommended

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

🟢 Approval recommended

Uh oh!

Jake Bailey (jakebailey) commented Sep 15, 2026

Uh oh!

typescript-automation Bot commented Sep 15, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

typescript-automation Bot commented Sep 15, 2026

tsc

Uh oh!

typescript-automation Bot commented Sep 15, 2026

Uh oh!

typescript-automation Bot commented Sep 15, 2026

Uh oh!

This branch has not been deployed

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

3 participants

typescript-automation Bot commented Sep 15, 2026 •

edited

Loading