Do not narrow using JSDoc type assertion nodes by Andarist · Pull Request #56048 · microsoft/TypeScript

Mateusz Burzyński (Andarist) · 2023-10-09T21:54:38Z

spotted by Jake Bailey (@jakebailey) here

TypeScript Bot (typescript-bot) · 2023-10-09T21:54:42Z

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

Jake Bailey (jakebailey) · 2023-10-09T21:59:30Z

Just to further describe things, switch (value as "a" | "b") or switch (value satisfies "a" | "b") don't allow narrowing to work today, but switch (/** @type {"a" | "b"} */ (value)) does, because the existing code thinks it can skip parens safely. But, that type assertion in JS should behave just like as/satisfies.

Jake Bailey (jakebailey) · 2023-10-09T22:00:12Z

TypeScript Bot (@typescript-bot) test top200
TypeScript Bot (@typescript-bot) user test this
TypeScript Bot (@typescript-bot) run dt
TypeScript Bot (@typescript-bot) perf test this
TypeScript Bot (@typescript-bot) pack this

TypeScript Bot (typescript-bot) · 2023-10-09T22:00:14Z

Heya Jake Bailey (@jakebailey), I've started to run the diff-based top-repos suite on this PR at 5b057c5. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-10-09T22:00:14Z

Heya Jake Bailey (@jakebailey), I've started to run the parallelized Definitely Typed test suite on this PR at 5b057c5. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-10-09T22:00:14Z

Heya Jake Bailey (@jakebailey), I've started to run the tarball bundle task on this PR at 5b057c5. You can monitor the build here.

TypeScript Bot (typescript-bot) · 2023-10-09T22:00:14Z

Heya Jake Bailey (@jakebailey), I've started to run the diff-based user code test suite on this PR at 5b057c5. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-10-09T22:00:14Z

Heya Jake Bailey (@jakebailey), I've started to run the regular perf test suite on this PR at 5b057c5. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-10-09T22:02:13Z

Hey Jake Bailey (@jakebailey), I've packed this into an installable tgz. You can install it for testing by referencing it in your package.json like so:

{
    "devDependencies": {
        "typescript": "https://typescript.visualstudio.com/cf7ac146-d525-443c-b23c-0d58337efebc/_apis/build/builds/158160/artifacts?artifactName=tgz&fileId=FB1C5B46B9F616011551E5F144FFFC008199B2D8886F8501653DA59FB616AAA302&fileName=/typescript-5.3.0-insiders.20231009.tgz"
    }
}

and then running npm install.

There is also a playground for this build and an npm module you can use via "typescript": "npm:@typescript-deploys/pr-build@5.3.0-pr-56048-8".;

TypeScript Bot (typescript-bot) · 2023-10-09T22:18:29Z

Jake Bailey (@jakebailey) Here are the results of running the user test suite comparing main and refs/pull/56048/merge:

There were infrastructure failures potentially unrelated to your change:

3 instances of "Package install failed"
1 instance of "Unknown failure"

Otherwise...

Everything looks good!

TypeScript Bot (typescript-bot) · 2023-10-09T22:20:06Z

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

Here they are:

Compiler

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Angular - node (v18.15.0, x64)}
_{Memory used}	_{295,127k (± 0.01%)}	_{295,102k (± 0.02%)}	_~	_295,003k	_295,150k	_{p=0.336 n=6}
_{Parse Time}	_{2.64s (± 0.32%)}	_{2.64s (± 0.44%)}	_~	_2.63s	_2.66s	_{p=1.000 n=6}
_{Bind Time}	_{0.83s (± 0.66%)}	_{0.84s (± 1.06%)}	_~	_0.83s	_0.85s	_{p=0.341 n=6}
_{Check Time}	_{8.08s (± 0.25%)}	_{8.07s (± 0.44%)}	_~	_8.03s	_8.12s	_{p=0.808 n=6}
_{Emit Time}	_{7.06s (± 0.28%)}	_{7.07s (± 0.21%)}	_~	_7.05s	_7.09s	_{p=0.330 n=6}
_{Total Time}	_{18.61s (± 0.12%)}	_{18.62s (± 0.27%)}	_~	_18.57s	_18.70s	_{p=1.000 n=6}
_{Compiler-Unions - node (v18.15.0, x64)}
_{Memory used}	_{192,062k (± 1.27%)}	_{190,610k (± 0.01%)}	_~	_190,597k	_190,638k	_{p=0.199 n=6}
_{Parse Time}	_{1.34s (± 0.87%)}	_{1.34s (± 0.78%)}	_~	_1.33s	_1.36s	_{p=0.800 n=6}
_{Bind Time}	_{0.73s (± 0.00%)}	_{0.73s (± 0.00%)}	_~	_0.73s	_0.73s	_{p=1.000 n=6}
_{Check Time}	_{9.11s (± 0.14%)}	_{9.10s (± 0.35%)}	_~	_9.05s	_9.14s	_{p=0.624 n=6}
_{Emit Time}	_{2.63s (± 0.56%)}	_{2.63s (± 0.62%)}	_~	_2.61s	_2.65s	_{p=0.624 n=6}
_{Total Time}	_{13.81s (± 0.19%)}	_{13.80s (± 0.34%)}	_~	_13.73s	_13.85s	_{p=0.934 n=6}
_{Monaco - node (v18.15.0, x64)}
_{Memory used}	_{347,302k (± 0.00%)}	_{347,304k (± 0.00%)}	_~	_347,288k	_347,318k	_{p=0.936 n=6}
_{Parse Time}	_{2.46s (± 0.21%)}	_{2.46s (± 0.33%)}	_~	_2.45s	_2.47s	_{p=0.140 n=6}
_{Bind Time}	_{0.94s (± 0.00%)}	_{0.95s (± 0.54%)}	_{+0.01s (+ 0.71%)}	_0.94s	_0.95s	_{p=0.025 n=6}
_{Check Time}	_{6.89s (± 0.44%)}	_{6.89s (± 0.41%)}	_~	_6.86s	_6.94s	_{p=1.000 n=6}
_{Emit Time}	_{4.01s (± 0.34%)}	_{4.02s (± 0.59%)}	_~	_3.99s	_4.06s	_{p=0.681 n=6}
_{Total Time}	_{14.30s (± 0.27%)}	_{14.32s (± 0.35%)}	_~	_14.27s	_14.41s	_{p=0.520 n=6}
_{TFS - node (v18.15.0, x64)}
_{Memory used}	_{302,590k (± 0.01%)}	_{302,591k (± 0.01%)}	_~	_302,539k	_302,618k	_{p=1.000 n=6}
_{Parse Time}	_{1.99s (± 0.63%)}	_{1.99s (± 1.07%)}	_~	_1.96s	_2.02s	_{p=0.805 n=6}
_{Bind Time}	_{1.01s (± 1.58%)}	_{1.00s (± 0.41%)}	_~	_1.00s	_1.01s	_{p=0.227 n=6}
_{Check Time}	_{6.27s (± 0.37%)}	_{6.27s (± 0.33%)}	_~	_6.24s	_6.29s	_{p=1.000 n=6}
_{Emit Time}	_{3.57s (± 0.51%)}	_{3.56s (± 0.52%)}	_~	_3.54s	_3.59s	_{p=0.568 n=6}
_{Total Time}	_{12.84s (± 0.26%)}	_{12.82s (± 0.15%)}	_~	_12.80s	_12.85s	_{p=0.421 n=6}
_{material-ui - node (v18.15.0, x64)}
_{Memory used}	_{470,495k (± 0.00%)}	_{470,481k (± 0.00%)}	_~	_470,454k	_470,502k	_{p=0.298 n=6}
_{Parse Time}	_{2.57s (± 0.53%)}	_{2.58s (± 0.29%)}	_~	_2.57s	_2.59s	_{p=0.611 n=6}
_{Bind Time}	_{1.00s (± 0.41%)}	_{0.99s (± 0.76%)}	_{-0.01s (- 1.33%)}	_0.98s	_1.00s	_{p=0.010 n=6}
_{Check Time}	_{16.70s (± 0.37%)}	_{16.59s (± 0.22%)}	_{-0.11s (- 0.68%)}	_16.54s	_16.62s	_{p=0.005 n=6}
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_~	_0.00s	_0.00s	_{p=1.000 n=6}
_{Total Time}	_{20.27s (± 0.37%)}	_{20.16s (± 0.18%)}	_{-0.12s (- 0.57%)}	_20.11s	_20.19s	_{p=0.005 n=6}
_{xstate - node (v18.15.0, x64)}
_{Memory used}	_{512,660k (± 0.02%)}	_{512,621k (± 0.01%)}	_~	_512,528k	_512,718k	_{p=0.574 n=6}
_{Parse Time}	_{3.26s (± 0.42%)}	_{3.27s (± 0.36%)}	_~	_3.25s	_3.28s	_{p=0.244 n=6}
_{Bind Time}	_{1.55s (± 0.33%)}	_{1.56s (± 0.33%)}	_~	_1.55s	_1.56s	_{p=0.311 n=6}
_{Check Time}	_{2.87s (± 1.52%)}	_{2.89s (± 1.04%)}	_~	_2.85s	_2.93s	_{p=0.421 n=6}
_{Emit Time}	_{0.08s (± 4.99%)}	_{0.09s (± 6.44%)}	_~	_0.08s	_0.09s	_{p=0.282 n=6}
_{Total Time}	_{7.75s (± 0.70%)}	_{7.79s (± 0.45%)}	_~	_7.75s	_7.85s	_{p=0.261 n=6}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

Angular - node (v18.15.0, x64)
Compiler-Unions - node (v18.15.0, x64)
Monaco - node (v18.15.0, x64)
TFS - node (v18.15.0, x64)
material-ui - node (v18.15.0, x64)
xstate - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

tsserver

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-UnionsTSServer - node (v18.15.0, x64)}
_{Req 1 - updateOpen}	_{2,381ms (± 1.72%)}	_{2,383ms (± 1.35%)}	_~	_2,326ms	_2,414ms	_{p=0.936 n=6}
_{Req 2 - geterr}	_{5,355ms (± 1.60%)}	_{5,332ms (± 1.57%)}	_~	_5,284ms	_5,502ms	_{p=0.873 n=6}
_{Req 3 - references}	_{327ms (± 1.26%)}	_{330ms (± 1.41%)}	_~	_324ms	_334ms	_{p=0.373 n=6}
_{Req 4 - navto}	_{278ms (± 1.11%)}	_{280ms (± 1.14%)}	_~	_274ms	_283ms	_{p=0.277 n=6}
_{Req 5 - completionInfo count}	_{1,356 (± 0.00%)}	_{1,356 (± 0.00%)}	_~	_1,356	_1,356	_{p=1.000 n=6}
_{Req 5 - completionInfo}	_{82ms (± 8.11%)}	_{78ms (± 7.94%)}	_~	_74ms	_90ms	_{p=0.117 n=6}
_{CompilerTSServer - node (v18.15.0, x64)}
_{Req 1 - updateOpen}	_{2,494ms (± 0.54%)}	_{2,477ms (± 1.17%)}	_~	_2,438ms	_2,528ms	_{p=0.229 n=6}
_{Req 2 - geterr}	_{4,064ms (± 0.27%)}	_{4,134ms (± 1.91%)}	_~	_4,051ms	_4,210ms	_{p=0.230 n=6}
_{Req 3 - references}	_{344ms (± 0.40%)}	_{338ms (± 1.62%)}	_~	_332ms	_345ms	_{p=0.061 n=6}
_{Req 4 - navto}	_{285ms (± 0.29%)}	_{284ms (± 0.62%)}	_~	_280ms	_285ms	_{p=0.177 n=6}
_{Req 5 - completionInfo count}	_{1,518 (± 0.00%)}	_{1,518 (± 0.00%)}	_~	_1,518	_1,518	_{p=1.000 n=6}
_{Req 5 - completionInfo}	_{87ms (± 0.86%)}	_{82ms (± 7.61%)}	_~	_76ms	_88ms	_{p=0.206 n=6}
_{xstateTSServer - node (v18.15.0, x64)}
_{Req 1 - updateOpen}	_{2,587ms (± 0.53%)}	_{2,602ms (± 0.50%)}	_~	_2,585ms	_2,624ms	_{p=0.149 n=6}
_{Req 2 - geterr}	_{1,717ms (± 2.14%)}	_{1,675ms (± 1.69%)}	_~	_1,649ms	_1,727ms	_{p=0.066 n=6}
_{Req 3 - references}	_{114ms (± 8.64%)}	_{113ms (± 9.29%)}	_~	_106ms	_128ms	_{p=0.868 n=6}
_{Req 4 - navto}	_{360ms (± 0.58%)}	_{358ms (± 0.43%)}	_~	_355ms	_359ms	_{p=0.078 n=6}
_{Req 5 - completionInfo count}	_{2,073 (± 0.00%)}	_{2,073 (± 0.00%)}	_~	_2,073	_2,073	_{p=1.000 n=6}
_{Req 5 - completionInfo}	_{310ms (± 1.59%)}	_{301ms (± 2.02%)}	_{🟩-9ms (- 3.01%)}	_295ms	_309ms	_{p=0.044 n=6}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

CompilerTSServer - node (v18.15.0, x64)
Compiler-UnionsTSServer - node (v18.15.0, x64)
xstateTSServer - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

Startup

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{tsc-startup - node (v18.15.0, x64)}
_{Execution time}	_{152.42ms (± 0.21%)}	_{152.21ms (± 0.16%)}	_{-0.22ms (- 0.14%)}	_151.18ms	_154.21ms	_{p=0.000 n=600}
_{tsserver-startup - node (v18.15.0, x64)}
_{Execution time}	_{227.84ms (± 0.15%)}	_{227.85ms (± 0.19%)}	_~	_226.42ms	_235.86ms	_{p=0.145 n=600}
_{tsserverlibrary-startup - node (v18.15.0, x64)}
_{Execution time}	_{229.03ms (± 0.16%)}	_{229.10ms (± 0.18%)}	_~	_227.51ms	_235.78ms	_{p=0.241 n=600}
_{typescript-startup - node (v18.15.0, x64)}
_{Execution time}	_{228.47ms (± 0.15%)}	_{228.61ms (± 0.16%)}	_{+0.14ms (+ 0.06%)}	_227.09ms	_231.91ms	_{p=0.000 n=600}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

tsc-startup - node (v18.15.0, x64)
tsserver-startup - node (v18.15.0, x64)
tsserverlibrary-startup - node (v18.15.0, x64)
typescript-startup - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

Developer Information:

Download Benchmarks

TypeScript Bot (typescript-bot) · 2023-10-09T23:31:01Z

Hey Jake Bailey (@jakebailey), the results of running the DT tests are ready.
Everything looks the same!
You can check the log here.

Jake Bailey (jakebailey)

This seems correct to me. Technically a breaking change but not one I expect anyone has ever encountered.

TypeScript Bot (typescript-bot) · 2023-10-10T00:01:25Z

Jake Bailey (@jakebailey) Here are the results of running the top-repos suite comparing main and refs/pull/56048/merge:

Everything looks good!

Do not narrow using JSDoc type assertion nodes

5b057c5

TypeScript Bot (typescript-bot) added the For Uncommitted Bug PR for untriaged, rejected, closed or missing bug label Oct 9, 2023

Jake Bailey (jakebailey) approved these changes Oct 9, 2023

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Nathan Shively-Sanders (sandersn) approved these changes Nov 3, 2023

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Nathan Shively-Sanders (sandersn) merged commit 6a9bc38 into microsoft:main Nov 3, 2023

Microsoft (microsoft) locked as resolved and limited conversation to collaborators Oct 16, 2025

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Compiler

tsserver

Startup

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