Improve detection of cases where subtype reduction is unnecessary #53435

ahejlsberg · 2023-03-22T15:25:14Z

ahejlsberg · 2023-03-22T15:26:20Z

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

typescript-bot · 2023-03-22T15:26:23Z

Heya @ahejlsberg, I've started to run the diff-based user code test suite on this PR at aab1be6. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-03-22T15:26:23Z

Heya @ahejlsberg, I've started to run the abridged perf test suite on this PR at aab1be6. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-03-22T15:26:23Z

Heya @ahejlsberg, I've started to run the extended test suite on this PR at aab1be6. You can monitor the build here.

typescript-bot · 2023-03-22T15:26:23Z

Heya @ahejlsberg, I've started to run the parallelized Definitely Typed test suite on this PR at aab1be6. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-03-22T15:26:24Z

Heya @ahejlsberg, I've started to run the diff-based top-repos suite on this PR at aab1be6. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-03-22T15:38:51Z

@ahejlsberg Here are the results of running the user test suite comparing main and refs/pull/53435/merge:

Everything looks good!

typescript-bot · 2023-03-22T15:42:00Z

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

Here they are:

Comparison Report - main..53435

_Metric	_main	₅₃₄₃₅	_Delta	_Best	_Worst	_p-value
_{Angular - node (v16.17.1, x64)}
_{Memory used}	_{361,412k (± 0.01%)}	_{361,413k (± 0.01%)}	_~	_361,349k	_361,472k	_{p=1.000 n=6}
_{Parse Time}	_{3.53s (± 0.81%)}	_{3.51s (± 1.02%)}	_~	_3.47s	_3.56s	_{p=0.377 n=6}
_{Bind Time}	_{1.18s (± 0.44%)}	_{1.19s (± 0.69%)}	_~	_1.18s	_1.20s	_{p=0.523 n=6}
_{Check Time}	_{9.54s (± 0.69%)}	_{9.53s (± 0.25%)}	_~	_9.51s	_9.57s	_{p=0.872 n=6}
_{Emit Time}	_{7.97s (± 0.55%)}	_{7.93s (± 0.41%)}	_~	_7.90s	_7.99s	_{p=0.120 n=6}
_{Total Time}	_{22.22s (± 0.42%)}	_{22.16s (± 0.15%)}	_~	_22.12s	_22.21s	_{p=0.374 n=6}
_{Compiler-Unions - node (v16.17.1, x64)}
_{Memory used}	_{193,117k (± 0.71%)}	_{193,501k (± 0.80%)}	_~	_192,493k	_195,888k	_{p=1.000 n=6}
_{Parse Time}	_{1.60s (± 0.61%)}	_{1.58s (± 1.24%)}	_~	_1.56s	_1.60s	_{p=0.128 n=6}
_{Bind Time}	_{0.82s (± 0.63%)}	_{0.82s (± 0.63%)}	_~	_0.82s	_0.83s	_{p=1.000 n=6}
_{Check Time}	_{10.12s (± 0.34%)}	_{10.14s (± 0.59%)}	_~	_10.07s	_10.23s	_{p=0.807 n=6}
_{Emit Time}	_{2.99s (± 0.85%)}	_{3.01s (± 0.68%)}	_~	_2.99s	_3.05s	_{p=0.118 n=6}
_{Total Time}	_{15.53s (± 0.40%)}	_{15.56s (± 0.46%)}	_~	_15.50s	_15.67s	_{p=0.810 n=6}
_{Monaco - node (v16.17.1, x64)}
_{Memory used}	_{345,578k (± 0.01%)}	_{345,562k (± 0.00%)}	_~	_345,542k	_345,578k	_{p=0.378 n=6}
_{Parse Time}	_{2.73s (± 0.68%)}	_{2.72s (± 0.49%)}	_~	_2.70s	_2.74s	_{p=0.112 n=6}
_{Bind Time}	_{1.09s (± 0.37%)}	_{1.08s (± 0.50%)}	_~	_1.08s	_1.09s	_{p=0.282 n=6}
_{Check Time}	_{7.76s (± 0.30%)}	_{7.75s (± 0.27%)}	_~	_7.72s	_7.77s	_{p=0.406 n=6}
_{Emit Time}	_{4.48s (± 0.73%)}	_{4.47s (± 1.07%)}	_~	_4.42s	_4.53s	_{p=0.573 n=6}
_{Total Time}	_{16.06s (± 0.26%)}	_{16.01s (± 0.33%)}	_~	_15.94s	_16.08s	_{p=0.172 n=6}
_{TFS - node (v16.17.1, x64)}
_{Memory used}	_{299,820k (± 0.01%)}	_{299,833k (± 0.01%)}	_~	_299,798k	_299,874k	_{p=0.575 n=6}
_{Parse Time}	_{2.16s (± 0.35%)}	_{2.17s (± 0.39%)}	_~	_2.16s	_2.18s	_{p=0.652 n=6}
_{Bind Time}	_{1.25s (± 0.44%)}	_{1.24s (± 1.14%)}	_~	_1.22s	_1.26s	_{p=0.498 n=6}
_{Check Time}	_{7.21s (± 0.38%)}	_{7.21s (± 0.36%)}	_~	_7.18s	_7.25s	_{p=1.000 n=6}
_{Emit Time}	_{4.34s (± 0.54%)}	_{4.34s (± 0.52%)}	_~	_4.32s	_4.38s	_{p=0.568 n=6}
_{Total Time}	_{14.96s (± 0.30%)}	_{14.96s (± 0.16%)}	_~	_14.93s	_14.99s	_{p=0.936 n=6}
_{material-ui - node (v16.17.1, x64)}
_{Memory used}	_{476,418k (± 0.00%)}	_{476,441k (± 0.00%)}	_~	_476,418k	_476,475k	_{p=0.065 n=6}
_{Parse Time}	_{3.21s (± 0.23%)}	_{3.21s (± 0.51%)}	_~	_3.19s	_3.23s	_{p=0.805 n=6}
_{Bind Time}	_{0.96s (± 0.54%)}	_{0.96s (± 0.85%)}	_~	_0.95s	_0.97s	_{p=0.929 n=6}
_{Check Time}	_{18.16s (± 0.77%)}	_{18.22s (± 0.30%)}	_~	_18.16s	_18.30s	_{p=0.228 n=6}
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_~	_0.00s	_0.00s	_{p=1.000 n=6}
_{Total Time}	_{22.33s (± 0.59%)}	_{22.39s (± 0.27%)}	_~	_22.30s	_22.47s	_{p=0.229 n=6}
_{xstate - node (v16.17.1, x64)}
_{Memory used}	_{550,540k (± 0.03%)}	_{550,481k (± 0.01%)}	_~	_550,430k	_550,599k	_{p=0.689 n=6}
_{Parse Time}	_{3.95s (± 0.69%)}	_{3.94s (± 0.25%)}	_~	_3.92s	_3.95s	_{p=0.871 n=6}
_{Bind Time}	_{1.79s (± 0.91%)}	_{1.79s (± 0.91%)}	_~	_1.77s	_1.82s	_{p=1.000 n=6}
_{Check Time}	_{3.04s (± 0.87%)}	_{3.04s (± 0.82%)}	_~	_3.00s	_3.07s	_{p=0.746 n=6}
_{Emit Time}	_{0.09s (± 0.00%)}	_{0.09s (± 4.45%)}	_~	_0.09s	_0.10s	_{p=0.405 n=6}
_{Total Time}	_{8.86s (± 0.44%)}	_{8.86s (± 0.45%)}	_~	_8.81s	_8.92s	_{p=0.936 n=6}

System

_{Machine Name}	_ts-ci-ubuntu
_Platform	_{linux 5.4.0-135-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	₅₃₄₃₅	₆
_Baseline	_main	₆

Developer Information:

Download Benchmark

typescript-bot · 2023-03-22T17:09:08Z

@ahejlsberg Here are the results of running the top-repos suite comparing main and refs/pull/53435/merge:

Something interesting changed - please have a look.

Details

microsoft/vscode

4 of 53 projects failed to build with the old tsc and were ignored

src/tsconfig.tsec.json

error TS2454: Variable 'r' is used before being assigned.
- src/vs/workbench/contrib/testing/common/testItemCollection.ts#L565

refined-github/refined-github

tsconfig.json

error TS2454: Variable 'result' is used before being assigned.
- source/feature-manager.tsx#L186

jakebailey · 2023-03-22T17:13:05Z

The new errors above actually seem... good?

RyanCavanaugh · 2023-03-22T17:14:09Z

Looks like people who declared something with

let x: void | number;
if (maybe) {
  x = 32;
}
x;

now get an error, which they absolutely should have.

typescript-bot · 2023-03-22T17:31:30Z

Hey @ahejlsberg, it looks like the DT test run failed. Please check the log for more details.
You can check the log here.

jakebailey · 2023-03-22T17:38:32Z

@typescript-bot run dt

typescript-bot · 2023-03-22T17:38:34Z

Heya @jakebailey, I've started to run the parallelized Definitely Typed test suite on this PR at aab1be6. You can monitor the build here.

Update: The results are in!

ahejlsberg · 2023-03-22T17:53:06Z

@jakebailey @RyanCavanaugh I think the new errors are better. They're caused by the change to use initialType in the calls to isTypeSubsetOf but aren't actually necessary to fix the original issue. Previously, the undefined we inject in the initial type to catch missing initialization situations was seen as a "foreign" type because it isn't part of the declared type. That would then cause us to perform subtype reduction, in which void would eat the undefined, leaving us with the declared type. That in turn would make it look like all code paths initialized the variable and we wouldn't report the error.

typescript-bot · 2023-03-22T19:44:53Z

Hey @jakebailey, it looks like the DT test run failed. Please check the log for more details.
You can check the log here.

fatcerberus · 2023-03-22T21:33:17Z

To be fair, nobody should be declaring things as T | void anyway. void !== undefined. #42709 FTW 😉

ahejlsberg added 2 commits March 22, 2023 08:20

Improve detection of cases where subtype reduction is unnecessary

613b0f1

Add regression test

aab1be6

typescript-bot assigned ahejlsberg Mar 22, 2023

typescript-bot added Author: Team For Milestone Bug PRs that fix a bug with a specific milestone labels Mar 22, 2023

RyanCavanaugh approved these changes Mar 22, 2023

View reviewed changes

RyanCavanaugh added the Breaking Change Would introduce errors in existing code label Mar 22, 2023

ahejlsberg merged commit 511921e into main Mar 23, 2023

ahejlsberg deleted the fix53425 branch March 23, 2023 14:09

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Improve detection of cases where subtype reduction is unnecessary #53435

Improve detection of cases where subtype reduction is unnecessary #53435

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microsoft/vscode

src/tsconfig.tsec.json

refined-github/refined-github

tsconfig.json

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Improve detection of cases where subtype reduction is unnecessary #53435

Improve detection of cases where subtype reduction is unnecessary #53435

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microsoft/vscode

src/tsconfig.tsec.json

refined-github/refined-github

tsconfig.json

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