Add fallback when both co- and contra-variant inference candidates exist by ahejlsberg · Pull Request #54072 · microsoft/TypeScript

Anders Hejlsberg (ahejlsberg) · 2023-04-30T15:32:38Z

In cases where both co- and contra-variant inference candidates exist, this PR adds the ability to fall back to the secondary inference when the constraint check fails for the primary inference.

Fixes#54005.

Anders Hejlsberg (ahejlsberg) · 2023-04-30T15:33:27Z

TypeScript Bot (@typescript-bot) test this
TypeScript Bot (@typescript-bot) user test this inline
TypeScript Bot (@typescript-bot) run dt
TypeScript Bot (@typescript-bot) perf test faster
TypeScript Bot (@typescript-bot) test top100

TypeScript Bot (typescript-bot) · 2023-04-30T15:33:31Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the diff-based top-repos suite on this PR at f0f477e. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-04-30T15:33:31Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the diff-based user code test suite on this PR at f0f477e. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-04-30T15:33:31Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the abridged perf test suite on this PR at f0f477e. You can monitor the build here.

TypeScript Bot (typescript-bot) · 2023-04-30T15:33:31Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the parallelized Definitely Typed test suite on this PR at f0f477e. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-04-30T15:33:31Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the extended test suite on this PR at f0f477e. You can monitor the build here.

TypeScript Bot (typescript-bot) · 2023-04-30T15:45:18Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the user test suite comparing main and refs/pull/54072/merge:

There were infrastructure failures potentially unrelated to your change:

1 instance of "Package install failed"

Otherwise...

Everything looks good!

TypeScript Bot (typescript-bot) · 2023-04-30T17:19:23Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the top-repos suite comparing main and refs/pull/54072/merge:

Everything looks good!

TypeScript Bot (typescript-bot) · 2023-04-30T17:35:19Z

Hey Anders Hejlsberg (@ahejlsberg), the results of running the DT tests are ready.
Everything looks the same!
You can check the log here.

Jake Bailey (jakebailey) · 2023-05-01T18:58:28Z

TypeScript Bot (@typescript-bot) pack this

TypeScript Bot (typescript-bot) · 2023-05-01T18:58:30Z

Heya Jake Bailey (@jakebailey), I've started to run the tarball bundle task on this PR at f0f477e. You can monitor the build here.

TypeScript Bot (typescript-bot) · 2023-05-01T19:00:34Z

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/153602/artifacts?artifactName=tgz&fileId=F183196F0EFF7B9788739321E9D293638E4A21829C7352033326EE52B01E173002&fileName=/typescript-5.1.0-insiders.20230501.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@5.1.0-pr-54072-11".;

Jake Bailey (jakebailey) · 2023-05-01T19:00:43Z

+ every(context.inferences, other => other === inference ||
+ getConstraintOfTypeParameter(other.typeParameter) !== inference.typeParameter ||


Part of #52180 was motivated by noticing that when we treat the "current" inference as special, we incur some order-dependent behavior. Where this came up (if my memory was correct) was when I was editing the strictFunctionTypes PR, where I could edit the file and see errors change around non-deterministically.
I tested restoring the change from #52180 and this PR still passes (i.e. putting back other !== inference && getConstraintOfTypeParameter(other.typeParameter) !== inference.typeParameter), which makes me feel like reverting it back to the state in #52123 that skips over other === inference will bring back that oddity (and we just don't have a test for it).
I'll try and see if I can make it break again like I did the first time.

It turns out we deleted the code where I was able to reproduce this, so, I guess I don't really know anymore.

Looking carefully at the code you had in #52180 and the original code plus the line I added here, I've convinced myself they're just two ways of saying the same thing. So I'll restore the change from #52180.

Oh! You're right, I missed that new line.

In that case, I'm happy with whichever is more performant or clearer. They're definitely equivalent now that I think closely.

Anders Hejlsberg (ahejlsberg) · 2023-05-02T01:17:20Z

TypeScript Bot (@typescript-bot) test this
TypeScript Bot (@typescript-bot) user test this inline
TypeScript Bot (@typescript-bot) run dt
TypeScript Bot (@typescript-bot) perf test faster
TypeScript Bot (@typescript-bot) test top100

TypeScript Bot (typescript-bot) · 2023-05-02T01:17:23Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the extended test suite on this PR at c377c44. You can monitor the build here.

TypeScript Bot (typescript-bot) · 2023-05-02T01:17:23Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the parallelized Definitely Typed test suite on this PR at c377c44. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-05-02T01:17:23Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the diff-based user code test suite on this PR at c377c44. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-05-02T01:17:23Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the abridged perf test suite on this PR at c377c44. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-05-02T01:17:23Z

Heya Anders Hejlsberg (@ahejlsberg), I've started to run the diff-based top-repos suite on this PR at c377c44. You can monitor the build here.

Update: The results are in!

TypeScript Bot (typescript-bot) · 2023-05-02T01:28:05Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the user test suite comparing main and refs/pull/54072/merge:

There were infrastructure failures potentially unrelated to your change:

1 instance of "Package install failed"

Otherwise...

Everything looks good!

TypeScript Bot (typescript-bot) · 2023-05-02T01:32:38Z

Anders Hejlsberg (@ahejlsberg)
The results of the perf run you requested are in!

Here they are:

Comparison Report - main..54072

_Metric	_main	₅₄₀₇₂	_Delta	_Best	_Worst	_p-value
_{Angular - node (v16.17.1, x64)}
_{Memory used}	_{365,246k (± 0.01%)}	_{365,264k (± 0.00%)}	_~	_365,246k	_365,293k	_{p=0.229 n=6}
_{Parse Time}	_{3.55s (± 0.75%)}	_{3.54s (± 0.39%)}	_~	_3.52s	_3.55s	_{p=0.563 n=6}
_{Bind Time}	_{1.17s (± 0.00%)}	_{1.17s (± 0.35%)}	_~	_1.17s	_1.18s	_{p=0.405 n=6}
_{Check Time}	_{9.56s (± 0.29%)}	_{9.56s (± 0.40%)}	_~	_9.50s	_9.60s	_{p=0.936 n=6}
_{Emit Time}	_{7.90s (± 0.50%)}	_{7.93s (± 0.60%)}	_~	_7.87s	_7.99s	_{p=0.376 n=6}
_{Total Time}	_{22.19s (± 0.12%)}	_{22.20s (± 0.24%)}	_~	_22.14s	_22.29s	_{p=0.744 n=6}
_{Compiler-Unions - node (v16.17.1, x64)}
_{Memory used}	_{192,765k (± 0.04%)}	_{192,717k (± 0.04%)}	_~	_192,654k	_192,851k	_{p=0.298 n=6}
_{Parse Time}	_{1.59s (± 0.34%)}	_{1.59s (± 0.40%)}	_~	_1.58s	_1.60s	_{p=0.201 n=6}
_{Bind Time}	_{0.82s (± 0.50%)}	_{0.83s (± 1.01%)}	_~	_0.82s	_0.84s	_{p=0.527 n=6}
_{Check Time}	_{10.30s (± 0.58%)}	_{10.32s (± 0.82%)}	_~	_10.20s	_10.43s	_{p=0.936 n=6}
_{Emit Time}	_{3.02s (± 0.44%)}	_{3.02s (± 1.37%)}	_~	_2.98s	_3.08s	_{p=0.935 n=6}
_{Total Time}	_{15.74s (± 0.45%)}	_{15.76s (± 0.76%)}	_~	_15.58s	_15.92s	_{p=0.873 n=6}
_{Monaco - node (v16.17.1, x64)}
_{Memory used}	_{345,849k (± 0.01%)}	_{345,854k (± 0.00%)}	_~	_345,825k	_345,871k	_{p=0.872 n=6}
_{Parse Time}	_{2.72s (± 0.45%)}	_{2.71s (± 0.28%)}	_~	_2.70s	_2.72s	_{p=0.240 n=6}
_{Bind Time}	_{1.08s (± 0.70%)}	_{1.08s (± 0.48%)}	_~	_1.08s	_1.09s	_{p=0.784 n=6}
_{Check Time}	_{7.90s (± 0.19%)}	_{7.88s (± 0.22%)}	_~	_7.85s	_7.90s	_{p=0.321 n=6}
_{Emit Time}	_{4.46s (± 0.98%)}	_{4.48s (± 0.76%)}	_~	_4.44s	_4.54s	_{p=0.332 n=6}
_{Total Time}	_{16.16s (± 0.38%)}	_{16.15s (± 0.26%)}	_~	_16.09s	_16.21s	_{p=0.872 n=6}
_{TFS - node (v16.17.1, x64)}
_{Memory used}	_{300,107k (± 0.01%)}	_{300,097k (± 0.01%)}	_~	_300,055k	_300,136k	_{p=0.748 n=6}
_{Parse Time}	_{2.15s (± 0.54%)}	_{2.15s (± 0.87%)}	_~	_2.13s	_2.18s	_{p=0.461 n=6}
_{Bind Time}	_{1.24s (± 0.97%)}	_{1.24s (± 0.88%)}	_~	_1.23s	_1.25s	_{p=0.666 n=6}
_{Check Time}	_{7.29s (± 0.36%)}	_{7.26s (± 0.27%)}	_~	_7.23s	_7.28s	_{p=0.125 n=6}
_{Emit Time}	_{4.38s (± 0.80%)}	_{4.37s (± 0.57%)}	_~	_4.34s	_4.40s	_{p=0.808 n=6}
_{Total Time}	_{15.06s (± 0.42%)}	_{15.01s (± 0.14%)}	_~	_14.97s	_15.03s	_{p=0.570 n=6}
_{material-ui - node (v16.17.1, x64)}
_{Memory used}	_{481,593k (± 0.00%)}	_{481,624k (± 0.00%)}	_{+31k (+ 0.01%)}	_481,607k	_481,644k	_{p=0.025 n=6}
_{Parse Time}	_{3.24s (± 0.34%)}	_{3.24s (± 0.48%)}	_~	_3.21s	_3.25s	_{p=0.863 n=6}
_{Bind Time}	_{0.94s (± 1.42%)}	_{0.93s (± 0.00%)}	_~	_0.93s	_0.93s	_{p=0.176 n=6}
_{Check Time}	_{17.88s (± 0.73%)}	_{17.89s (± 0.36%)}	_~	_17.78s	_17.95s	_{p=1.000 n=6}
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_~	_0.00s	_0.00s	_{p=1.000 n=6}
_{Total Time}	_{22.07s (± 0.64%)}	_{22.06s (± 0.31%)}	_~	_21.96s	_22.12s	_{p=0.936 n=6}
_{xstate - node (v16.17.1, x64)}
_{Memory used}	_{560,355k (± 0.01%)}	_{560,380k (± 0.01%)}	_~	_560,296k	_560,450k	_{p=0.575 n=6}
_{Parse Time}	_{3.98s (± 0.31%)}	_{3.98s (± 0.19%)}	_~	_3.97s	_3.99s	_{p=0.505 n=6}
_{Bind Time}	_{1.76s (± 0.46%)}	_{1.76s (± 0.29%)}	_~	_1.75s	_1.76s	_{p=0.929 n=6}
_{Check Time}	_{3.06s (± 0.52%)}	_{3.07s (± 0.74%)}	_~	_3.05s	_3.11s	_{p=0.304 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 (± 0.20%)}	_{8.89s (± 0.26%)}	_~	_8.87s	_8.93s	_{p=0.460 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	₅₄₀₇₂	₆
_Baseline	_main	₆

Developer Information:

Download Benchmark

TypeScript Bot (typescript-bot) · 2023-05-02T02:57:35Z

Anders Hejlsberg (@ahejlsberg) Here are the results of running the top-repos suite comparing main and refs/pull/54072/merge:

Everything looks good!

TypeScript Bot (typescript-bot) · 2023-05-02T03:16:23Z

Hey Anders Hejlsberg (@ahejlsberg), the results of running the DT tests are ready.
Everything looks the same!
You can check the log here.

Anders Hejlsberg (ahejlsberg) added 2 commits April 30, 2023 08:21

Add fallback when both co- and contra-variant inferences exist
966a5a8

Add regression test
f0f477e

TypeScript Bot (typescript-bot) assigned Anders Hejlsberg (ahejlsberg)Apr 30, 2023

TypeScript Bot (typescript-bot) added Author: Team For Milestone Bug PRs that fix a bug with a specific milestone labels Apr 30, 2023

Anders Hejlsberg (ahejlsberg) requested review from Ryan Cavanaugh (RyanCavanaugh) and Jake Bailey (jakebailey)April 30, 2023 15:33

Jake Bailey (jakebailey) reviewed May 1, 2023
View reviewed changes

Jake Bailey (jakebailey) approved these changes May 1, 2023
View reviewed changes

Restore code from#52180
c377c44

Anders Hejlsberg (ahejlsberg) merged commit ae6393e into mainMay 2, 2023

Anders Hejlsberg (ahejlsberg) deleted the fix54005 branch May 2, 2023 13:39

Mateusz Burzyński (Andarist) mentioned this pull request Mar 22, 2024
Improve logic that chooses co- vs. contra-variant inferences #57909
Merged

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

		every(context.inferences, other => other === inference \|\|
		getConstraintOfTypeParameter(other.typeParameter) !== inference.typeParameter \|\|

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