Move complex parameter lists of async function into downlevel generator body #56296

rbuckton · 2023-11-02T22:22:39Z

This modifies our down-level emit for async functions when they contain non-trivial parameter lists that may potentially throw when bound. Prior to this change, the following would throw immediately when it should instead produce a rejected promise:

// @target: es2015
// @lib: esnext
async function f(x, y = doesNotExist) {}
f();

The reason for this is that we eagerly evaluate the parameter list in the down-level emit:

function f(x, y = doesNotExist) {
  return __awaiter(this, void 0, void 0, function*() {});
}

To address this, this PR repurposes the second parameter to __awaiter, which was previously only used to bind a lexically-captured arguments, to instead be used to forward arguments for the function to the down-level generator body, producing the following emit instead:

function f(x_1) {
  return __awaiter(this, arguments, void 0, function*(x, y = doesNotExist) {});
}

When the transformed function is not an arrow function, we merely forward the function's arguments and emit placeholders for each fixed parameter to preserve the function's length, as can be seen with x_1 above.

Arrow functions, however, do not have their own arguments. In that case, we instead capture all fixed arguments, followed by a rest parameter that holds any additional arguments.

Thus,

const f = async (x, y = doesNotExist) => {};

now transforms to

const f = (x_1, ...args_1) => __awaiter(this, [x_1, ...args_1], void 0, function*(x, y = doesNotExist) {});

This change means that we can no longer rely on the previous mechanism for lexical arguments capturing (i.e., just passing it along as the second parameter to __awaiter), and instead must manually capture a lexical arguments binding.

Thus,

function f() {
  return async (x, y = doesNotExist) => arguments.length;
}

now transforms to

function f() {
  return (x_1, ...args_1) => {
    var arguments_1 = arguments;
    return __awaiter(this, [x_1, ...args_1], void 0, function* (x, y = doesNotExist) {
      return arguments_1.length;
    });
  };
}

Aside from the change to lexical arguments capturing, a function with a trivial parameter list does not undergo this transformation.

Thus,

async function f(x, y) {}

still transforms to

function f(x, y) { return __awaiter(this, void 0, void 0, function*() {}); }

in an effort to limit the complexity of the down-level emit when it is unwarranted.

It should also be noted that this PR applies a similar change to async generators as well.

Fixes #40410

…el generator body

jakebailey · 2023-11-02T23:32:16Z

Just to understand, is this backwards compatible for tslib helpers? Given they aren't changing, I think yes?

rbuckton · 2023-11-03T00:10:44Z

Just to understand, is this backwards compatible for tslib helpers? Given they aren't changing, I think yes?

That's correct. No change needs to be made to the helpers, so this is backwards compatible with existing tslib versions.

rbuckton · 2023-11-03T13:43:40Z

@typescript-bot perf test

typescript-bot · 2023-11-03T13:43:43Z

Heya @rbuckton, I've started to run the regular perf test suite on this PR at b783f61. You can monitor the build here.

Update: The results are in!

rbuckton · 2023-11-03T13:44:01Z

@typescript-bot test this
@typescript-bot user test this

typescript-bot · 2023-11-03T13:44:03Z

Heya @rbuckton, I've started to run the diff-based user code test suite on this PR at b783f61. You can monitor the build here.

Update: The results are in!

typescript-bot · 2023-11-03T13:59:34Z

@rbuckton Here are the results of running the user test suite comparing main and refs/pull/56296/merge:

There were infrastructure failures potentially unrelated to your change:

3 instances of "Package install failed"

Otherwise...

Everything looks good!

typescript-bot · 2023-11-03T14:05:26Z

@rbuckton
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}	_{295,092k (± 0.01%)}	_{295,122k (± 0.02%)}	_~	_295,072k	_295,199k	_{p=0.297 n=6}
_{Parse Time}	_{2.62s (± 0.45%)}	_{2.62s (± 0.39%)}	_~	_2.60s	_2.63s	_{p=0.801 n=6}
_{Bind Time}	_{0.84s (± 1.17%)}	_{0.83s (± 0.62%)}	_~	_0.83s	_0.84s	_{p=0.417 n=6}
_{Check Time}	_{8.05s (± 0.23%)}	_{8.05s (± 0.19%)}	_~	_8.03s	_8.06s	_{p=0.928 n=6}
_{Emit Time}	_{7.08s (± 0.21%)}	_{7.09s (± 0.40%)}	_~	_7.06s	_7.14s	_{p=0.514 n=6}
_{Total Time}	_{18.59s (± 0.14%)}	_{18.59s (± 0.12%)}	_~	_18.57s	_18.63s	_{p=0.627 n=6}
_{Compiler-Unions - node (v18.15.0, x64)}
_{Memory used}	_{191,102k (± 0.56%)}	_{190,710k (± 0.02%)}	_~	_190,678k	_190,761k	_{p=0.128 n=6}
_{Parse Time}	_{1.35s (± 1.05%)}	_{1.36s (± 0.60%)}	_~	_1.35s	_1.37s	_{p=0.402 n=6}
_{Bind Time}	_{0.73s (± 0.00%)}	_{0.73s (± 0.00%)}	_~	_0.73s	_0.73s	_{p=1.000 n=6}
_{Check Time}	_{9.13s (± 0.38%)}	_{9.15s (± 0.35%)}	_~	_9.11s	_9.20s	_{p=0.170 n=6}
_{Emit Time}	_{2.63s (± 0.52%)}	_{2.63s (± 0.52%)}	_~	_2.61s	_2.64s	_{p=0.933 n=6}
_{Total Time}	_{13.84s (± 0.35%)}	_{13.87s (± 0.28%)}	_~	_13.83s	_13.92s	_{p=0.145 n=6}
_{Monaco - node (v18.15.0, x64)}
_{Memory used}	_{347,358k (± 0.01%)}	_{347,374k (± 0.01%)}	_~	_347,353k	_347,406k	_{p=0.336 n=6}
_{Parse Time}	_{2.46s (± 0.67%)}	_{2.46s (± 0.21%)}	_~	_2.45s	_2.46s	_{p=0.797 n=6}
_{Bind Time}	_{0.94s (± 0.55%)}	_{0.94s (± 0.00%)}	_~	_0.94s	_0.94s	_{p=0.174 n=6}
_{Check Time}	_{6.94s (± 0.53%)}	_{6.94s (± 0.26%)}	_~	_6.92s	_6.97s	_{p=0.807 n=6}
_{Emit Time}	_{4.05s (± 0.25%)}	_{4.06s (± 0.34%)}	_~	_4.04s	_4.07s	_{p=0.934 n=6}
_{Total Time}	_{14.39s (± 0.29%)}	_{14.39s (± 0.20%)}	_~	_14.35s	_14.43s	_{p=0.568 n=6}
_{TFS - node (v18.15.0, x64)}
_{Memory used}	_{302,599k (± 0.01%)}	_{302,606k (± 0.01%)}	_~	_302,562k	_302,653k	_{p=0.936 n=6}
_{Parse Time}	_{1.99s (± 1.36%)}	_{1.99s (± 1.21%)}	_~	_1.95s	_2.02s	_{p=1.000 n=6}
_{Bind Time}	_{1.00s (± 0.54%)}	_{1.01s (± 0.81%)}	_~	_1.00s	_1.02s	_{p=0.859 n=6}
_{Check Time}	_{6.25s (± 0.34%)}	_{6.26s (± 0.47%)}	_~	_6.22s	_6.30s	_{p=0.808 n=6}
_{Emit Time}	_{3.57s (± 0.31%)}	_{3.58s (± 0.25%)}	_~	_3.57s	_3.59s	_{p=0.149 n=6}
_{Total Time}	_{12.82s (± 0.21%)}	_{12.84s (± 0.33%)}	_~	_12.79s	_12.89s	_{p=0.375 n=6}
_{material-ui - node (v18.15.0, x64)}
_{Memory used}	_{470,531k (± 0.01%)}	_{470,521k (± 0.00%)}	_~	_470,488k	_470,548k	_{p=0.936 n=6}
_{Parse Time}	_{2.58s (± 0.80%)}	_{2.57s (± 0.53%)}	_~	_2.55s	_2.59s	_{p=0.869 n=6}
_{Bind Time}	_{0.99s (± 0.76%)}	_{0.99s (± 0.76%)}	_~	_0.98s	_1.00s	_{p=0.487 n=6}
_{Check Time}	_{16.63s (± 0.33%)}	_{16.62s (± 0.24%)}	_~	_16.57s	_16.67s	_{p=0.936 n=6}
_{Emit Time}	_{0.00s (± 0.00%)}	_{0.00s (± 0.00%)}	_~	_0.00s	_0.00s	_{p=1.000 n=6}
_{Total Time}	_{20.20s (± 0.34%)}	_{20.19s (± 0.20%)}	_~	_20.13s	_20.23s	_{p=0.872 n=6}
_{xstate - node (v18.15.0, x64)}
_{Memory used}	_{512,630k (± 0.01%)}	_{512,684k (± 0.00%)}	_{+54k (+ 0.01%)}	_512,668k	_512,703k	_{p=0.016 n=6}
_{Parse Time}	_{3.26s (± 0.36%)}	_{3.27s (± 0.16%)}	_{+0.01s (+ 0.36%)}	_3.27s	_3.28s	_{p=0.039 n=6}
_{Bind Time}	_{1.55s (± 0.00%)}	_{1.54s (± 0.54%)}	_~	_1.54s	_1.56s	_{p=0.121 n=6}
_{Check Time}	_{2.85s (± 1.07%)}	_{2.85s (± 0.82%)}	_~	_2.81s	_2.88s	_{p=0.628 n=6}
_{Emit Time}	_{0.08s (± 0.00%)}	_{0.08s (± 0.00%)}	_~	_0.08s	_0.08s	_{p=1.000 n=6}
_{Total Time}	_{7.74s (± 0.41%)}	_{7.74s (± 0.23%)}	_~	_7.72s	_7.77s	_{p=0.870 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}	_{2,371ms (± 0.61%)}	_{2,390ms (± 1.11%)}	_~	_2,349ms	_2,431ms	_{p=0.173 n=6}
_{Req 2 - geterr}	_{5,413ms (± 1.33%)}	_{5,347ms (± 1.10%)}	_~	_5,294ms	_5,460ms	_{p=0.199 n=6}
_{Req 3 - references}	_{326ms (± 0.36%)}	_{328ms (± 1.28%)}	_~	_323ms	_334ms	_{p=0.357 n=6}
_{Req 4 - navto}	_{276ms (± 1.27%)}	_{279ms (± 1.03%)}	_~	_273ms	_281ms	_{p=0.244 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}	_{85ms (± 8.46%)}	_{80ms (± 7.30%)}	_~	_74ms	_90ms	_{p=0.203 n=6}
_{CompilerTSServer - node (v18.15.0, x64)}
_{Req 1 - updateOpen}	_{2,478ms (± 0.96%)}	_{2,489ms (± 0.85%)}	_~	_2,455ms	_2,517ms	_{p=0.748 n=6}
_{Req 2 - geterr}	_{4,112ms (± 1.99%)}	_{4,141ms (± 1.83%)}	_~	_4,034ms	_4,199ms	_{p=0.378 n=6}
_{Req 3 - references}	_{338ms (± 1.51%)}	_{336ms (± 1.57%)}	_~	_332ms	_344ms	_{p=0.459 n=6}
_{Req 4 - navto}	_{282ms (± 0.27%)}	_{282ms (± 0.43%)}	_~	_280ms	_283ms	_{p=0.867 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}	_{83ms (± 7.69%)}	_{81ms (± 7.31%)}	_~	_77ms	_89ms	_{p=0.798 n=6}
_{xstateTSServer - node (v18.15.0, x64)}
_{Req 1 - updateOpen}	_{2,587ms (± 0.64%)}	_{2,599ms (± 0.48%)}	_~	_2,584ms	_2,620ms	_{p=0.296 n=6}
_{Req 2 - geterr}	_{1,699ms (± 2.59%)}	_{1,691ms (± 1.51%)}	_~	_1,654ms	_1,716ms	_{p=1.000 n=6}
_{Req 3 - references}	_{122ms (± 6.96%)}	_{113ms (± 9.74%)}	_~	_105ms	_128ms	_{p=0.514 n=6}
_{Req 4 - navto}	_{367ms (± 1.88%)}	_{365ms (± 0.22%)}	_~	_364ms	_366ms	_{p=0.282 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}	_{307ms (± 1.29%)}	_{305ms (± 1.26%)}	_~	_299ms	_308ms	_{p=0.261 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}	_{152.44ms (± 0.21%)}	_{152.52ms (± 0.18%)}	_{+0.08ms (+ 0.05%)}	_151.48ms	_155.52ms	_{p=0.001 n=600}
_{tsserver-startup - node (v18.15.0, x64)}
_{Execution time}	_{227.56ms (± 0.17%)}	_{227.40ms (± 0.16%)}	_{-0.16ms (- 0.07%)}	_226.07ms	_232.17ms	_{p=0.000 n=600}
_{tsserverlibrary-startup - node (v18.15.0, x64)}
_{Execution time}	_{228.92ms (± 0.18%)}	_{229.11ms (± 0.19%)}	_{+0.19ms (+ 0.08%)}	_227.16ms	_236.33ms	_{p=0.000 n=600}
_{typescript-startup - node (v18.15.0, x64)}
_{Execution time}	_{228.62ms (± 0.15%)}	_{228.86ms (± 0.18%)}	_{+0.24ms (+ 0.10%)}	_227.23ms	_234.76ms	_{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:

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rbuckton added 4 commits November 2, 2023 11:41

track argument capturing upwards through all arrows to outer function

ef8530e

Capture arguments for async functions using variable

58396cb

Move complex parameter lists of async function into downlevel generator

8466d66

Move complex parameter lists of async generator function into downlev…

48639e3

…el generator body

rbuckton requested review from sandersn, weswigham and jakebailey November 2, 2023 22:22

typescript-bot assigned rbuckton Nov 2, 2023

typescript-bot added Author: Team For Milestone Bug PRs that fix a bug with a specific milestone labels Nov 2, 2023

Run formatter

b783f61

jakebailey approved these changes Nov 3, 2023

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rbuckton merged commit 10db652 into main Nov 3, 2023

rbuckton deleted the fix-40410 branch November 3, 2023 16:57

iclanton mentioned this pull request Mar 21, 2024

A shadowed variable is generated in a an async function with a default parameter declared as a static property of a class when targeting ES5. #57897

Closed

julienp mentioned this pull request Mar 25, 2024

Make function serialization work on typescript 4 and 5 pulumi/pulumi#15761

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Move complex parameter lists of async function into downlevel generator body #56296

Move complex parameter lists of async function into downlevel generator body #56296

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Compiler

tsserver

Startup

Move complex parameter lists of async function into downlevel generator body #56296

Move complex parameter lists of async function into downlevel generator body #56296

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Compiler

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Startup

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