Avoid subtype reduction when creating a union result in `discriminateTypeByDiscriminableItems` #54052

Andarist · 2023-04-28T10:04:01Z

fixes #54048 (which is a recent regression from https://github.com/microsoft/TypeScript/pull/53709/files , cc @ahejlsberg )

…TypeByDiscriminableItems`

jakebailey · 2023-04-28T17:48:49Z

@typescript-bot test this
@typescript-bot test top100
@typescript-bot user test this
@typescript-bot run dt
@typescript-bot perf test this faster
@typescript-bot pack this

typescript-bot · 2023-04-28T17:49:09Z

Heya @jakebailey, I've started to run the extended test suite on this PR at 1ef6b24. You can monitor the build here.

typescript-bot · 2023-04-28T17:49:09Z

Heya @jakebailey, I've started to run the abridged perf test suite on this PR at 1ef6b24. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-04-28T17:49:09Z

Heya @jakebailey, I've started to run the tarball bundle task on this PR at 1ef6b24. You can monitor the build here.

typescript-bot · 2023-04-28T17:49:09Z

Heya @jakebailey, I've started to run the diff-based user code test suite on this PR at 1ef6b24. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-04-28T17:49:09Z

Heya @jakebailey, I've started to run the parallelized Definitely Typed test suite on this PR at 1ef6b24. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-04-28T17:49:09Z

Heya @jakebailey, I've started to run the diff-based top-repos suite on this PR at 1ef6b24. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-04-28T17:51:13Z

Hey @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/153488/artifacts?artifactName=tgz&fileId=58624324DE8EC1191EA9F435313E02981A83B8D982B7E34D31A749096E3A7DCE02&fileName=/typescript-5.1.0-insiders.20230428.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/[email protected]".;

typescript-bot · 2023-04-28T18:01:10Z

@jakebailey Here are the results of running the user test suite comparing main and refs/pull/54052/merge:

There were infrastructure failures potentially unrelated to your change:

1 instance of "Package install failed"

Otherwise...

Everything looks good!

typescript-bot · 2023-04-28T18:26:25Z

@jakebailey
The results of the perf run you requested are in!

Here they are:

Comparison Report - main..54052

_Metric	_main	₅₄₀₅₂	_Delta	_Best	_Worst	_p-value
_{Angular - node (v16.17.1, x64)}
_{Memory used}	_{365,294k (± 0.01%)}	_{365,345k (± 0.01%)}	_{+51k (+ 0.01%)}	_365,270k	_365,399k	_{p=0.045 n=6}
_{Parse Time}	_{3.55s (± 0.48%)}	_{3.54s (± 0.46%)}	_~	_3.52s	_3.56s	_{p=0.684 n=6}
_{Bind Time}	_{1.17s (± 0.47%)}	_{1.17s (± 0.35%)}	_~	_1.17s	_1.18s	_{p=0.282 n=6}
_{Check Time}	_{9.56s (± 0.33%)}	_{9.59s (± 0.50%)}	_~	_9.51s	_9.65s	_{p=0.295 n=6}
_{Emit Time}	_{7.89s (± 0.41%)}	_{7.96s (± 0.78%)}	_{+0.08s (+ 0.95%)}	_7.85s	_8.03s	_{p=0.045 n=6}
_{Total Time}	_{22.18s (± 0.22%)}	_{22.27s (± 0.50%)}	_~	_22.06s	_22.40s	_{p=0.065 n=6}
_{Compiler-Unions - node (v16.17.1, x64)}
_{Memory used}	_{193,803k (± 0.90%)}	_{192,728k (± 0.03%)}	_~	_192,639k	_192,812k	_{p=1.000 n=6}
_{Parse Time}	_{1.60s (± 0.51%)}	_{1.60s (± 0.86%)}	_~	_1.57s	_1.61s	_{p=1.000 n=6}
_{Bind Time}	_{0.82s (± 0.63%)}	_{0.82s (± 0.00%)}	_~	_0.82s	_0.82s	_{p=0.174 n=6}
_{Check Time}	_{10.22s (± 0.49%)}	_{10.30s (± 0.63%)}	_~	_10.22s	_10.38s	_{p=0.065 n=6}
_{Emit Time}	_{3.00s (± 1.32%)}	_{3.04s (± 1.64%)}	_~	_2.99s	_3.12s	_{p=0.147 n=6}
_{Total Time}	_{15.64s (± 0.30%)}	_{15.76s (± 0.61%)}	_{+0.11s (+ 0.71%)}	_15.61s	_15.88s	_{p=0.045 n=6}
_{Monaco - node (v16.17.1, x64)}
_{Memory used}	_{345,853k (± 0.00%)}	_{345,864k (± 0.01%)}	_~	_345,842k	_345,897k	_{p=0.422 n=6}
_{Parse Time}	_{2.72s (± 0.43%)}	_{2.72s (± 0.23%)}	_~	_2.71s	_2.73s	_{p=1.000 n=6}
_{Bind Time}	_{1.09s (± 0.75%)}	_{1.08s (± 0.38%)}	_{-0.01s (- 0.77%)}	_1.07s	_1.08s	_{p=0.038 n=6}
_{Check Time}	_{7.89s (± 0.57%)}	_{7.90s (± 0.62%)}	_~	_7.83s	_7.97s	_{p=0.686 n=6}
_{Emit Time}	_{4.49s (± 0.81%)}	_{4.50s (± 0.71%)}	_~	_4.46s	_4.55s	_{p=0.517 n=6}
_{Total Time}	_{16.18s (± 0.54%)}	_{16.21s (± 0.43%)}	_~	_16.09s	_16.28s	_{p=0.575 n=6}
_{TFS - node (v16.17.1, x64)}
_{Memory used}	_{300,100k (± 0.01%)}	_{300,101k (± 0.01%)}	_~	_300,062k	_300,136k	_{p=1.000 n=6}
_{Parse Time}	_{2.15s (± 0.54%)}	_{2.15s (± 0.54%)}	_~	_2.14s	_2.17s	_{p=1.000 n=6}
_{Bind Time}	_{1.23s (± 0.61%)}	_{1.24s (± 0.33%)}	_~	_1.23s	_1.24s	_{p=0.100 n=6}
_{Check Time}	_{7.29s (± 0.27%)}	_{7.30s (± 0.23%)}	_~	_7.27s	_7.32s	_{p=0.195 n=6}
_{Emit Time}	_{4.39s (± 0.81%)}	_{4.38s (± 0.89%)}	_~	_4.33s	_4.43s	_{p=0.468 n=6}
_{Total Time}	_{15.06s (± 0.30%)}	_{15.06s (± 0.42%)}	_~	_14.97s	_15.14s	_{p=1.000 n=6}
_{material-ui - node (v16.17.1, x64)}
_{Memory used}	_{481,600k (± 0.00%)}	_{481,692k (± 0.01%)}	_{+92k (+ 0.02%)}	_481,654k	_481,753k	_{p=0.005 n=6}
_{Parse Time}	_{3.22s (± 0.25%)}	_{3.24s (± 0.30%)}	_{+0.02s (+ 0.47%)}	_3.23s	_3.25s	_{p=0.026 n=6}
_{Bind Time}	_{0.94s (± 0.80%)}	_{0.93s (± 0.55%)}	_~	_0.93s	_0.94s	_{p=0.247 n=6}
_{Check Time}	_{17.90s (± 0.49%)}	_{18.41s (± 1.24%)}	_{+0.51s (+ 2.83%)}	_18.17s	_18.83s	_{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}	_{22.06s (± 0.39%)}	_{22.58s (± 0.97%)}	_{+0.52s (+ 2.35%)}	_22.36s	_22.98s	_{p=0.005 n=6}
_{xstate - node (v16.17.1, x64)}
_{Memory used}	_{560,694k (± 0.02%)}	_{560,660k (± 0.02%)}	_~	_560,538k	_560,879k	_{p=0.471 n=6}
_{Parse Time}	_{3.97s (± 0.35%)}	_{3.99s (± 0.47%)}	_~	_3.97s	_4.02s	_{p=0.243 n=6}
_{Bind Time}	_{1.76s (± 0.56%)}	_{1.76s (± 0.47%)}	_~	_1.76s	_1.78s	_{p=0.273 n=6}
_{Check Time}	_{3.05s (± 0.13%)}	_{3.06s (± 0.27%)}	_{+0.01s (+ 0.49%)}	_3.05s	_3.07s	_{p=0.010 n=6}
_{Emit Time}	_{0.09s (± 0.00%)}	_{0.09s (± 0.00%)}	_~	_0.09s	_0.09s	_{p=1.000 n=6}
_{Total Time}	_{8.88s (± 0.22%)}	_{8.90s (± 0.15%)}	_{+0.03s (+ 0.30%)}	_8.88s	_8.92s	_{p=0.042 n=6}

System

_{Machine Name}	_ts-ci-ubuntu
_Platform	_{linux 5.4.0-148-generic}
_Architecture	_x64
_{Available Memory}	_{16 GB}
_{Available Memory}	_{15 GB}
_CPUs	_{4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz}

Hosts

node (v16.17.1, x64)

Scenarios

Angular - node (v16.17.1, x64)
Compiler-Unions - node (v16.17.1, x64)
Monaco - node (v16.17.1, x64)
TFS - node (v16.17.1, x64)
material-ui - node (v16.17.1, x64)
xstate - node (v16.17.1, x64)

_Benchmark	_Name	_Iterations
_Current	₅₄₀₅₂	₆
_Baseline	_main	₆

Developer Information:

Download Benchmark

jakebailey · 2023-04-28T18:57:58Z

@typescript-bot perf test this faster

typescript-bot · 2023-04-28T18:58:01Z

Heya @jakebailey, I've started to run the abridged perf test suite on this PR at 1ef6b24. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-04-28T19:13:30Z

@jakebailey
The results of the perf run you requested are in!

Here they are:

Comparison Report - main..54052

_Metric	_main	₅₄₀₅₂	_Delta	_Best	_Worst	_p-value
_{Angular - node (v16.17.1, x64)}
_{Memory used}	_{365,294k (± 0.01%)}	_{365,333k (± 0.00%)}	_{+39k (+ 0.01%)}	_365,315k	_365,350k	_{p=0.016 n=6}
_{Parse Time}	_{3.55s (± 0.48%)}	_{3.53s (± 0.76%)}	_~	_3.51s	_3.58s	_{p=0.145 n=6}
_{Bind Time}	_{1.17s (± 0.47%)}	_{1.17s (± 0.44%)}	_~	_1.17s	_1.18s	_{p=0.640 n=6}
_{Check Time}	_{9.56s (± 0.33%)}	_{9.59s (± 0.29%)}	_~	_9.57s	_9.64s	_{p=0.293 n=6}
_{Emit Time}	_{7.89s (± 0.41%)}	_{7.96s (± 0.84%)}	_~	_7.87s	_8.04s	_{p=0.108 n=6}
_{Total Time}	_{22.18s (± 0.22%)}	_{22.25s (± 0.24%)}	_{+0.07s (+ 0.33%)}	_22.16s	_22.30s	_{p=0.037 n=6}
_{Compiler-Unions - node (v16.17.1, x64)}
_{Memory used}	_{193,803k (± 0.90%)}	_{192,698k (± 0.02%)}	_~	_192,645k	_192,774k	_{p=0.689 n=6}
_{Parse Time}	_{1.60s (± 0.51%)}	_{1.59s (± 0.95%)}	_~	_1.57s	_1.60s	_{p=0.213 n=6}
_{Bind Time}	_{0.82s (± 0.63%)}	_{0.82s (± 0.66%)}	_~	_0.82s	_0.83s	_{p=0.640 n=6}
_{Check Time}	_{10.22s (± 0.49%)}	_{10.33s (± 0.58%)}	_{+0.11s (+ 1.06%)}	_10.25s	_10.40s	_{p=0.013 n=6}
_{Emit Time}	_{3.00s (± 1.32%)}	_{3.02s (± 1.35%)}	_~	_2.98s	_3.08s	_{p=0.423 n=6}
_{Total Time}	_{15.64s (± 0.30%)}	_{15.77s (± 0.58%)}	_{+0.12s (+ 0.78%)}	_15.62s	_15.88s	_{p=0.045 n=6}
_{Monaco - node (v16.17.1, x64)}
_{Memory used}	_{345,853k (± 0.00%)}	_{345,856k (± 0.00%)}	_~	_345,844k	_345,871k	_{p=0.936 n=6}
_{Parse Time}	_{2.72s (± 0.43%)}	_{2.73s (± 0.61%)}	_~	_2.71s	_2.75s	_{p=0.410 n=6}
_{Bind Time}	_{1.09s (± 0.75%)}	_{1.08s (± 0.59%)}	_~	_1.07s	_1.09s	_{p=0.097 n=6}
_{Check Time}	_{7.89s (± 0.57%)}	_{7.91s (± 0.37%)}	_~	_7.87s	_7.94s	_{p=0.373 n=6}
_{Emit Time}	_{4.49s (± 0.81%)}	_{4.50s (± 0.54%)}	_~	_4.47s	_4.53s	_{p=1.000 n=6}
_{Total Time}	_{16.18s (± 0.54%)}	_{16.22s (± 0.35%)}	_~	_16.15s	_16.31s	_{p=0.469 n=6}
_{TFS - node (v16.17.1, x64)}
_{Memory used}	_{300,100k (± 0.01%)}	_{300,113k (± 0.01%)}	_~	_300,089k	_300,132k	_{p=0.378 n=6}
_{Parse Time}	_{2.15s (± 0.54%)}	_{2.16s (± 0.63%)}	_~	_2.14s	_2.17s	_{p=0.562 n=6}
_{Bind Time}	_{1.23s (± 0.61%)}	_{1.24s (± 0.83%)}	_~	_1.22s	_1.25s	_{p=0.351 n=6}
_{Check Time}	_{7.29s (± 0.27%)}	_{7.26s (± 0.54%)}	_~	_7.23s	_7.32s	_{p=0.259 n=6}
_{Emit Time}	_{4.39s (± 0.81%)}	_{4.39s (± 1.01%)}	_~	_4.34s	_4.44s	_{p=0.936 n=6}
_{Total Time}	_{15.06s (± 0.30%)}	_{15.05s (± 0.56%)}	_~	_14.96s	_15.17s	_{p=0.872 n=6}
_{material-ui - node (v16.17.1, x64)}
_{Memory used}	_{481,600k (± 0.00%)}	_{481,688k (± 0.02%)}	_{+88k (+ 0.02%)}	_481,629k	_481,870k	_{p=0.008 n=6}
_{Parse Time}	_{3.22s (± 0.25%)}	_{3.24s (± 0.23%)}	_{+0.02s (+ 0.47%)}	_3.23s	_3.25s	_{p=0.015 n=6}
_{Bind Time}	_{0.94s (± 0.80%)}	_{0.93s (± 0.81%)}	_~	_0.92s	_0.94s	_{p=0.195 n=6}
_{Check Time}	_{17.90s (± 0.49%)}	_{18.15s (± 0.56%)}	_{+0.25s (+ 1.40%)}	_18.05s	_18.29s	_{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}	_{22.06s (± 0.39%)}	_{22.32s (± 0.46%)}	_{+0.26s (+ 1.19%)}	_22.22s	_22.47s	_{p=0.005 n=6}
_{xstate - node (v16.17.1, x64)}
_{Memory used}	_{560,694k (± 0.02%)}	_{560,739k (± 0.02%)}	_~	_560,598k	_560,867k	_{p=0.575 n=6}
_{Parse Time}	_{3.97s (± 0.35%)}	_{3.97s (± 0.19%)}	_~	_3.96s	_3.98s	_{p=0.389 n=6}
_{Bind Time}	_{1.76s (± 0.56%)}	_{1.76s (± 0.43%)}	_~	_1.75s	_1.77s	_{p=0.554 n=6}
_{Check Time}	_{3.05s (± 0.13%)}	_{3.07s (± 0.39%)}	_{+0.02s (+ 0.60%)}	_3.05s	_3.08s	_{p=0.010 n=6}
_{Emit Time}	_{0.09s (± 0.00%)}	_{0.09s (± 0.00%)}	_~	_0.09s	_0.09s	_{p=1.000 n=6}
_{Total Time}	_{8.88s (± 0.22%)}	_{8.89s (± 0.20%)}	_~	_8.86s	_8.91s	_{p=0.258 n=6}

System

_{Machine Name}	_ts-ci-ubuntu
_Platform	_{linux 5.4.0-148-generic}
_Architecture	_x64
_{Available Memory}	_{16 GB}
_{Available Memory}	_{15 GB}
_CPUs	_{4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz}

Hosts

node (v16.17.1, x64)

Scenarios

Angular - node (v16.17.1, x64)
Compiler-Unions - node (v16.17.1, x64)
Monaco - node (v16.17.1, x64)
TFS - node (v16.17.1, x64)
material-ui - node (v16.17.1, x64)
xstate - node (v16.17.1, x64)

_Benchmark	_Name	_Iterations
_Current	₅₄₀₅₂	₆
_Baseline	_main	₆

Developer Information:

Download Benchmark

typescript-bot · 2023-04-28T19:55:11Z

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

typescript-bot · 2023-04-28T20:07:03Z

@jakebailey Here are the results of running the top-repos suite comparing main and refs/pull/54052/merge:

Everything looks good!

Andarist · 2023-05-26T21:32:56Z

this is for 5.1 regression, is there any chance to get some eyes on it before the stable release?

DanielRosenwasser · 2023-05-26T22:17:04Z

@typescript-bot test this
@typescript-bot test top100
@typescript-bot user test this
@typescript-bot run dt
@typescript-bot perf test this faster
@typescript-bot pack this

typescript-bot · 2023-05-26T22:17:07Z

Heya @DanielRosenwasser, I've started to run the parallelized Definitely Typed test suite on this PR at 1ef6b24. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-05-26T22:17:07Z

Heya @DanielRosenwasser, I've started to run the diff-based top-repos suite on this PR at 1ef6b24. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-05-26T22:17:07Z

Heya @DanielRosenwasser, I've started to run the tarball bundle task on this PR at 1ef6b24. You can monitor the build here.

typescript-bot · 2023-05-26T22:17:07Z

Heya @DanielRosenwasser, I've started to run the extended test suite on this PR at 1ef6b24. You can monitor the build here.

typescript-bot · 2023-05-26T22:17:07Z

Heya @DanielRosenwasser, I've started to run the abridged perf test suite on this PR at 1ef6b24. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-05-26T22:17:07Z

Heya @DanielRosenwasser, I've started to run the diff-based user code test suite on this PR at 1ef6b24. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-05-26T22:18:56Z

Hey @DanielRosenwasser, 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/155020/artifacts?artifactName=tgz&fileId=371BFA1AE731F4CD85C993428125E1F040D1F3F411588EDE7261519EA824D12602&fileName=/typescript-5.2.0-insiders.20230526.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/[email protected]".;

ahejlsberg · 2023-05-26T22:24:18Z

In general I think this is a good change, we really shouldn't be subtype reducing contextual types (elsewhere we specifically avoid it). Seems like there's a slight performance regression in material-ui, but may just be that we're giving back the slight gain we got in #53709. Plus, TBH I'm not sure what we're really measuring with that old snapshot at this point.

typescript-bot · 2023-05-26T22:32:55Z

@DanielRosenwasser
The results of the perf run you requested are in!

Here they are:

Comparison Report - main..54052

_Metric	_main	₅₄₀₅₂	_Delta	_Best	_Worst	_p-value
_{Angular - node (v16.17.1, x64)}
_{Memory used}	_{365,242k (± 0.01%)}	_{365,247k (± 0.01%)}	_~	_365,187k	_365,303k	_{p=0.936 n=6}
_{Parse Time}	_{3.56s (± 0.49%)}	_{3.57s (± 0.46%)}	_~	_3.54s	_3.58s	_{p=0.744 n=6}
_{Bind Time}	_{1.18s (± 1.15%)}	_{1.19s (± 0.34%)}	_~	_1.19s	_1.20s	_{p=0.275 n=6}
_{Check Time}	_{9.55s (± 0.58%)}	_{9.62s (± 0.80%)}	_~	_9.52s	_9.71s	_{p=0.108 n=6}
_{Emit Time}	_{7.88s (± 0.46%)}	_{7.96s (± 1.01%)}	_~	_7.86s	_8.07s	_{p=0.064 n=6}
_{Total Time}	_{22.18s (± 0.41%)}	_{22.34s (± 0.63%)}	_~	_22.15s	_22.47s	_{p=0.053 n=6}
_{Compiler-Unions - node (v16.17.1, x64)}
_{Memory used}	_{193,524k (± 0.71%)}	_{192,919k (± 0.03%)}	_~	_192,836k	_192,986k	_{p=0.375 n=6}
_{Parse Time}	_{1.59s (± 1.52%)}	_{1.60s (± 1.16%)}	_~	_1.57s	_1.62s	_{p=0.511 n=6}
_{Bind Time}	_{0.82s (± 0.50%)}	_{0.83s (± 0.49%)}	_{+0.01s (+ 1.22%)}	_0.83s	_0.84s	_{p=0.008 n=6}
_{Check Time}	_{10.13s (± 0.70%)}	_{10.22s (± 0.62%)}	_{+0.09s (+ 0.90%)}	_10.13s	_10.30s	_{p=0.045 n=6}
_{Emit Time}	_{3.00s (± 0.88%)}	_{3.01s (± 0.66%)}	_~	_2.98s	_3.03s	_{p=0.406 n=6}
_{Total Time}	_{15.55s (± 0.53%)}	_{15.67s (± 0.43%)}	_{+0.12s (+ 0.75%)}	_15.56s	_15.75s	_{p=0.030 n=6}
_{Monaco - node (v16.17.1, x64)}
_{Memory used}	_{345,891k (± 0.00%)}	_{345,891k (± 0.00%)}	_~	_345,876k	_345,916k	_{p=0.935 n=6}
_{Parse Time}	_{2.73s (± 0.97%)}	_{2.74s (± 0.43%)}	_~	_2.73s	_2.76s	_{p=0.370 n=6}
_{Bind Time}	_{1.08s (± 0.48%)}	_{1.09s (± 0.37%)}	_~	_1.08s	_1.09s	_{p=0.112 n=6}
_{Check Time}	_{7.85s (± 0.23%)}	_{7.87s (± 0.36%)}	_~	_7.84s	_7.90s	_{p=0.368 n=6}
_{Emit Time}	_{4.46s (± 0.93%)}	_{4.49s (± 0.64%)}	_~	_4.46s	_4.53s	_{p=0.261 n=6}
_{Total Time}	_{16.12s (± 0.47%)}	_{16.19s (± 0.30%)}	_~	_16.14s	_16.25s	_{p=0.170 n=6}
_{TFS - node (v16.17.1, x64)}
_{Memory used}	_{299,951k (± 0.01%)}	_{299,965k (± 0.01%)}	_~	_299,947k	_299,994k	_{p=0.423 n=6}
_{Parse Time}	_{2.16s (± 0.35%)}	_{2.18s (± 0.84%)}	_~	_2.16s	_2.21s	_{p=0.063 n=6}
_{Bind Time}	_{1.24s (± 0.42%)}	_{1.24s (± 0.61%)}	_~	_1.23s	_1.25s	_{p=0.241 n=6}
_{Check Time}	_{7.27s (± 0.20%)}	_{7.28s (± 0.45%)}	_~	_7.24s	_7.32s	_{p=0.872 n=6}
_{Emit Time}	_{4.33s (± 0.72%)}	_{4.34s (± 0.56%)}	_~	_4.30s	_4.37s	_{p=0.413 n=6}
_{Total Time}	_{15.00s (± 0.28%)}	_{15.04s (± 0.23%)}	_~	_15.02s	_15.11s	_{p=0.089 n=6}
_{material-ui - node (v16.17.1, x64)}
_{Memory used}	_{480,988k (± 0.00%)}	_{481,071k (± 0.01%)}	_{+83k (+ 0.02%)}	_481,010k	_481,179k	_{p=0.013 n=6}
_{Parse Time}	_{3.25s (± 0.34%)}	_{3.26s (± 0.32%)}	_~	_3.24s	_3.27s	_{p=0.281 n=6}
_{Bind Time}	_{0.94s (± 0.55%)}	_{0.94s (± 0.43%)}	_~	_0.94s	_0.95s	_{p=0.114 n=6}
_{Check Time}	_{17.80s (± 0.30%)}	_{18.35s (± 0.60%)}	_{+0.55s (+ 3.10%)}	_18.16s	_18.45s	_{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}	_{21.98s (± 0.23%)}	_{22.55s (± 0.48%)}	_{+0.57s (+ 2.58%)}	_22.37s	_22.67s	_{p=0.005 n=6}
_{xstate - node (v16.17.1, x64)}
_{Memory used}	_{560,637k (± 0.01%)}	_{560,571k (± 0.02%)}	_~	_560,488k	_560,710k	_{p=0.173 n=6}
_{Parse Time}	_{4.00s (± 0.44%)}	_{4.01s (± 0.60%)}	_~	_3.99s	_4.06s	_{p=0.732 n=6}
_{Bind Time}	_{1.77s (± 0.29%)}	_{1.76s (± 0.59%)}	_~	_1.75s	_1.78s	_{p=0.437 n=6}
_{Check Time}	_{3.06s (± 0.74%)}	_{3.08s (± 0.70%)}	_~	_3.04s	_3.09s	_{p=0.249 n=6}
_{Emit Time}	_{0.09s (± 0.00%)}	_{0.09s (± 0.00%)}	_~	_0.09s	_0.09s	_{p=1.000 n=6}
_{Total Time}	_{8.91s (± 0.38%)}	_{8.94s (± 0.41%)}	_~	_8.91s	_9.01s	_{p=0.125 n=6}

System

_{Machine Name}	_ts-ci-ubuntu
_Platform	_{linux 5.4.0-148-generic}
_Architecture	_x64
_{Available Memory}	_{16 GB}
_{Available Memory}	_{15 GB}
_CPUs	_{4 × Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz}

Hosts

node (v16.17.1, x64)

Scenarios

Angular - node (v16.17.1, x64)
Compiler-Unions - node (v16.17.1, x64)
Monaco - node (v16.17.1, x64)
TFS - node (v16.17.1, x64)
material-ui - node (v16.17.1, x64)
xstate - node (v16.17.1, x64)

_Benchmark	_Name	_Iterations
_Current	₅₄₀₅₂	₆
_Baseline	_main	₆

Developer Information:

Download Benchmark

typescript-bot · 2023-05-26T22:44:32Z

@DanielRosenwasser Here are the results of running the user test suite comparing main and refs/pull/54052/merge:

There were infrastructure failures potentially unrelated to your change:

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

Otherwise...

Everything looks good!

typescript-bot · 2023-05-26T23:52:32Z

Hey @DanielRosenwasser, the results of running the DT tests are ready.
Everything looks the same!
You can check the log here.

typescript-bot · 2023-05-27T00:10:58Z

@DanielRosenwasser Here are the results of running the top-repos suite comparing main and refs/pull/54052/merge:

Everything looks good!

Andarist · 2023-05-31T09:10:30Z

It seems that this PR got preliminary approval from @ahejlsberg . I wonder if it could land before 5.1 (and be cherry-picked into it) since its due date was supposed to be... yesterday 😅 (according to the 5.1 iteration plan)

…on-on-discriminated-items

DanielRosenwasser · 2023-06-27T18:48:25Z

It seems that this PR got preliminary approval from @ahejlsberg .

Sorry, can you link back to where? @weswigham can you take a look?

Andarist · 2023-06-27T18:52:02Z

@DanielRosenwasser here:

In general I think this is a good change, we really shouldn't be subtype reducing contextual types (elsewhere we specifically avoid it)

I called it preliminary since it didnt come with a more formal ✅ :P

DanielRosenwasser · 2023-07-18T21:40:50Z

Just documenting this one as a consistent 0.3-0.4 second regression.

jakebailey · 2023-07-18T21:42:32Z

Original PR which this PR fixes up shows an improvement, so it may be a wash maybe but not entirely :\

Avoid subtype reduction when creating a union result in `discriminate…

1ef6b24

…TypeByDiscriminableItems`

typescript-bot added the For Uncommitted Bug PR for untriaged, rejected, closed or missing bug label Apr 28, 2023

sandersn requested review from ahejlsberg and weswigham May 24, 2023 22:17

sandersn assigned ahejlsberg May 24, 2023

jakebailey added this to the TypeScript 5.1.4 milestone Jun 6, 2023

typescript-bot added For Milestone Bug PRs that fix a bug with a specific milestone and removed For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Jun 6, 2023

Merge remote-tracking branch 'origin/main' into avoid-subtype-reducti…

ab02254

…on-on-discriminated-items

DanielRosenwasser merged commit a3773ec into microsoft:main Jun 27, 2023

Andarist deleted the avoid-subtype-reduction-on-discriminated-items branch June 27, 2023 19:04

This was referenced Dec 17, 2023

chore: set noPropertyAccessFromIndexSignature to true in tsconfig (on next-branch) trpc/trpc#5175

Closed

bug: TRPCClientError.ts compilation error due to typescript 5.1.3 type narrowing regression trpc/trpc#5176

Closed

microsoft locked as resolved and limited conversation to collaborators Oct 22, 2025

Avoid subtype reduction when creating a union result in discriminateTypeByDiscriminableItems #54052

Avoid subtype reduction when creating a union result in discriminateTypeByDiscriminableItems #54052

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Andarist commented May 31, 2023

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Avoid subtype reduction when creating a union result in `discriminateTypeByDiscriminableItems` #54052

Avoid subtype reduction when creating a union result in `discriminateTypeByDiscriminableItems` #54052

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