Extract function types from function and arrow expressions. by dragomirtitian · Pull Request #60234 · microsoft/TypeScript

Titian Cernicova-Dragomir (dragomirtitian) · 2024-10-15T15:57:47Z

This PR brings TS emit closer to what an external tool could emit without type information.

TypeScript Bot (typescript-bot) · 2024-10-15T15:57:50Z

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) · 2024-10-25T19:10:25Z

TypeScript Bot (@typescript-bot) test it

TypeScript Bot (typescript-bot) · 2024-10-25T19:10:30Z

Starting jobs; this comment will be updated as builds start and complete.

Command	Status	Results
`test top400`	✅ Started	✅ Results
`user test this`	✅ Started	✅ Results
`run dt`	✅ Started	✅ Results
`perf test this faster`	✅ Started	👀 Results

TypeScript Bot (typescript-bot) · 2024-10-25T19:28:31Z

Jake Bailey (@jakebailey) Here are the results of running the user tests with tsc comparing main and refs/pull/60234/merge:

Everything looks good!

TypeScript Bot (typescript-bot) · 2024-10-25T19:30:32Z

Hey Jake Bailey (@jakebailey), the results of running the DT tests are ready.

Everything looks the same!

You can check the log here.

TypeScript Bot (typescript-bot) · 2024-10-25T19:52:58Z

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

Here they are:

tsc

Comparison Report - baseline..pr

_Metric	_baseline	_pr	_Delta	_Best	_Worst	_p-value
_{Compiler-Unions - node (v18.15.0, x64)}
_Errors	₃₁	₃₁	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_62,340	_62,340	_~	_~	_~	_{p=1.000 n=6}
_Types	_50,379	_50,379	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{192,861k (± 0.06%)}	_{193,971k (± 0.93%)}	_~	_192,784k	_196,309k	_{p=0.689 n=6}
_{Parse Time}	_{1.32s (± 0.48%)}	_{1.31s (± 0.48%)}	_{-0.01s (- 0.76%)}	_1.30s	_1.32s	_{p=0.031 n=6}
_{Bind Time}	_0.72s	_0.72s	_~	_~	_~	_{p=1.000 n=6}
_{Check Time}	_{9.73s (± 0.36%)}	_{9.73s (± 0.24%)}	_~	_9.70s	_9.77s	_{p=1.000 n=6}
_{Emit Time}	_{2.72s (± 0.36%)}	_{2.73s (± 0.38%)}	_~	_2.72s	_2.74s	_{p=0.557 n=6}
_{Total Time}	_{14.49s (± 0.20%)}	_{14.49s (± 0.20%)}	_~	_14.44s	_14.52s	_{p=0.935 n=6}
_{angular-1 - node (v18.15.0, x64)}
_Errors	₃₃	₃₃	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_947,886	_947,886	_~	_~	_~	_{p=1.000 n=6}
_Types	_410,840	_410,840	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{1,224,631k (± 0.00%)}	_{1,224,538k (± 0.00%)}	_{-93k (- 0.01%)}	_1,224,504k	_1,224,603k	_{p=0.008 n=6}
_{Parse Time}	_{6.65s (± 0.66%)}	_{6.64s (± 0.69%)}	_~	_6.58s	_6.71s	_{p=0.628 n=6}
_{Bind Time}	_{1.88s (± 0.34%)}	_{1.88s (± 0.43%)}	_~	_1.87s	_1.89s	_{p=0.432 n=6}
_{Check Time}	_{31.87s (± 0.56%)}	_{31.81s (± 0.58%)}	_~	_31.61s	_32.05s	_{p=0.378 n=6}
_{Emit Time}	_{15.23s (± 0.51%)}	_{15.23s (± 0.30%)}	_~	_15.16s	_15.27s	_{p=1.000 n=6}
_{Total Time}	_{55.63s (± 0.38%)}	_{55.56s (± 0.32%)}	_~	_55.30s	_55.79s	_{p=0.630 n=6}
_{mui-docs - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,494,500	_2,494,500	_~	_~	_~	_{p=1.000 n=6}
_Types	_908,298	_908,298	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,307,127k (± 0.00%)}	_{2,307,056k (± 0.00%)}	_{-71k (- 0.00%)}	_2,307,014k	_2,307,101k	_{p=0.031 n=6}
_{Parse Time}	_{9.34s (± 0.37%)}	_{9.31s (± 0.25%)}	_~	_9.28s	_9.35s	_{p=0.217 n=6}
_{Bind Time}	_{2.15s (± 0.35%)}	_{2.13s (± 0.26%)}	_{-0.01s (- 0.62%)}	_2.13s	_2.14s	_{p=0.015 n=6}
_{Check Time}	_{75.10s (± 0.40%)}	_{74.97s (± 0.65%)}	_~	_74.13s	_75.57s	_{p=0.936 n=6}
_{Emit Time}	_{0.28s (± 3.04%)}	_{0.28s (± 3.91%)}	_~	_0.27s	_0.29s	_{p=0.465 n=6}
_{Total Time}	_{86.85s (± 0.37%)}	_{86.70s (± 0.54%)}	_~	_85.87s	_87.27s	_{p=0.748 n=6}
_{self-build-src - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,258,044	_1,258,045	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_266,229	_266,229	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,422,307k (± 0.03%)}	_{2,422,555k (± 0.02%)}	_~	_2,422,050k	_2,423,069k	_{p=0.575 n=6}
_{Parse Time}	_{5.17s (± 0.83%)}	_{5.22s (± 1.06%)}	_~	_5.15s	_5.29s	_{p=0.128 n=6}
_{Bind Time}	_{1.93s (± 0.51%)}	_{1.93s (± 0.33%)}	_~	_1.92s	_1.94s	_{p=0.733 n=6}
_{Check Time}	_{35.55s (± 0.36%)}	_{35.50s (± 0.39%)}	_~	_35.36s	_35.74s	_{p=0.378 n=6}
_{Emit Time}	_{3.09s (± 5.47%)}	_{3.00s (± 1.61%)}	_~	_2.94s	_3.08s	_{p=0.199 n=6}
_{Total Time}	_{45.74s (± 0.54%)}	_{45.65s (± 0.26%)}	_~	_45.50s	_45.80s	_{p=0.689 n=6}
_{self-build-src-public-api - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,258,044	_1,258,045	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_266,229	_266,229	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,619,089k (±11.20%)}	_{2,499,028k (± 0.03%)}	_~	_2,497,849k	_2,500,129k	_{p=0.575 n=6}
_{Parse Time}	_{6.64s (± 2.54%)}	_{6.56s (± 0.79%)}	_~	_6.51s	_6.63s	_{p=0.423 n=6}
_{Bind Time}	_{2.16s (± 2.21%)}	_{2.14s (± 1.86%)}	_~	_2.11s	_2.22s	_{p=0.574 n=6}
_{Check Time}	_{43.30s (± 0.60%)}	_{43.45s (± 0.57%)}	_~	_43.16s	_43.91s	_{p=0.229 n=6}
_{Emit Time}	_{3.60s (± 2.81%)}	_{3.57s (± 2.72%)}	_~	_3.44s	_3.72s	_{p=0.471 n=6}
_{Total Time}	_{55.69s (± 0.56%)}	_{55.73s (± 0.51%)}	_~	_55.42s	_56.27s	_{p=0.575 n=6}
_{self-compiler - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_261,754	_261,755	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_106,477	_106,477	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{438,854k (± 0.01%)}	_{438,781k (± 0.02%)}	_{-74k (- 0.02%)}	_438,634k	_438,843k	_{p=0.013 n=6}
_{Parse Time}	_{3.54s (± 0.73%)}	_{3.54s (± 0.73%)}	_~	_3.50s	_3.57s	_{p=0.809 n=6}
_{Bind Time}	_{1.30s (± 1.43%)}	_{1.30s (± 1.26%)}	_~	_1.28s	_1.32s	_{p=1.000 n=6}
_{Check Time}	_{18.89s (± 0.62%)}	_{18.84s (± 0.41%)}	_~	_18.78s	_18.98s	_{p=0.470 n=6}
_{Emit Time}	_{1.54s (± 0.82%)}	_{1.53s (± 1.41%)}	_~	_1.50s	_1.56s	_{p=0.677 n=6}
_{Total Time}	_{25.28s (± 0.33%)}	_{25.21s (± 0.35%)}	_~	_25.14s	_25.38s	_{p=0.092 n=6}
_{ts-pre-modules - node (v18.15.0, x64)}
_Errors	₆₈	₆₈	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_225,919	_225,919	_~	_~	_~	_{p=1.000 n=6}
_Types	_94,415	_94,415	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{371,092k (± 0.01%)}	_{371,084k (± 0.01%)}	_~	_371,015k	_371,128k	_{p=1.000 n=6}
_{Parse Time}	_{2.89s (± 1.11%)}	_{2.89s (± 1.50%)}	_~	_2.83s	_2.95s	_{p=1.000 n=6}
_{Bind Time}	_{1.58s (± 0.95%)}	_{1.60s (± 1.02%)}	_~	_1.57s	_1.61s	_{p=0.069 n=6}
_{Check Time}	_{16.38s (± 0.19%)}	_{16.41s (± 0.38%)}	_~	_16.33s	_16.49s	_{p=0.332 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{20.85s (± 0.09%)}	_{20.89s (± 0.49%)}	_~	_20.75s	_21.06s	_{p=0.170 n=6}
_{vscode - node (v18.15.0, x64)}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_3,127,992	_3,127,992	_~	_~	_~	_{p=1.000 n=6}
_Types	_1,078,245	_1,078,245	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{3,220,297k (± 0.01%)}	_{3,220,271k (± 0.02%)}	_~	_3,219,491k	_3,220,844k	_{p=0.936 n=6}
_{Parse Time}	_{14.15s (± 0.54%)}	_{14.13s (± 0.57%)}	_~	_14.02s	_14.26s	_{p=0.809 n=6}
_{Bind Time}	_{4.46s (± 0.27%)}	_{4.45s (± 0.54%)}	_~	_4.42s	_4.48s	_{p=0.253 n=6}
_{Check Time}	_{86.96s (± 3.43%)}	_{85.67s (± 1.65%)}	_~	_84.54s	_88.50s	_{p=0.471 n=6}
_{Emit Time}	_{26.53s (± 6.88%)}	_{27.53s (± 1.70%)}	_~	_27.00s	_28.29s	_{p=0.230 n=6}
_{Total Time}	_{132.11s (± 1.44%)}	_{131.78s (± 0.94%)}	_~	_130.39s	_133.98s	_{p=1.000 n=6}
_{webpack - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_286,866	_286,866	_~	_~	_~	_{p=1.000 n=6}
_Types	_116,245	_116,245	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{437,881k (± 0.04%)}	_{437,812k (± 0.03%)}	_~	_437,690k	_438,055k	_{p=0.575 n=6}
_{Parse Time}	_{4.99s (± 0.24%)}	_{4.99s (± 0.54%)}	_~	_4.95s	_5.03s	_{p=0.803 n=6}
_{Bind Time}	_{2.17s (± 0.86%)}	_{2.16s (± 0.99%)}	_~	_2.12s	_2.18s	_{p=0.746 n=6}
_{Check Time}	_{23.10s (± 1.66%)}	_{22.95s (± 0.65%)}	_~	_22.79s	_23.20s	_{p=0.810 n=6}
_{Emit Time}	_{0.00s (±244.70%)}	_0.00s	_~	_~	_~	_{p=0.405 n=6}
_{Total Time}	_{30.25s (± 1.28%)}	_{30.11s (± 0.52%)}	_~	_29.93s	_30.35s	_{p=0.810 n=6}
_{xstate-main - node (v18.15.0, x64)}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_543,130	_543,130	_~	_~	_~	_{p=1.000 n=6}
_Types	_181,889	_181,889	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{485,484k (± 0.03%)}	_{485,537k (± 0.01%)}	_~	_485,507k	_485,599k	_{p=1.000 n=6}
_{Parse Time}	_{4.17s (± 0.64%)}	_{4.18s (± 0.71%)}	_~	_4.14s	_4.22s	_{p=0.809 n=6}
_{Bind Time}	_{1.46s (± 0.84%)}	_{1.45s (± 0.94%)}	_~	_1.44s	_1.47s	_{p=0.798 n=6}
_{Check Time}	_{23.84s (± 0.90%)}	_{23.78s (± 0.46%)}	_~	_23.65s	_23.91s	_{p=0.746 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{29.47s (± 0.77%)}	_{29.41s (± 0.49%)}	_~	_29.24s	_29.57s	_{p=0.936 n=6}

System info unknown

Hosts

node (v18.15.0, x64)

Scenarios

Compiler-Unions - node (v18.15.0, x64)
angular-1 - node (v18.15.0, x64)
mui-docs - node (v18.15.0, x64)
self-build-src - node (v18.15.0, x64)
self-build-src-public-api - node (v18.15.0, x64)
self-compiler - node (v18.15.0, x64)
ts-pre-modules - node (v18.15.0, x64)
vscode - node (v18.15.0, x64)
webpack - node (v18.15.0, x64)
xstate-main - node (v18.15.0, x64)

_Benchmark	_Name	_Iterations
_Current	_pr	₆
_Baseline	_baseline	₆

Developer Information:

Download Benchmarks

TypeScript Bot (typescript-bot) · 2024-10-25T21:07:23Z

Jake Bailey (@jakebailey) Here are the results of running the top 400 repos with tsc comparing main and refs/pull/60234/merge:

Everything looks good!

Jake Bailey (jakebailey) · 2024-10-28T17:43:14Z

+declare var foo3: () => () => /*elided*/ any;
+declare var x: () => () => /*elided*/ any;


Do you know why this is changing? It seems a little awkward for this self referential type to be printed one level deep like this rather than the single elided any (which would cause fewer downstream errors)

The base cause is that at the root level syntactic printing is now always given a try. And in this case the parameter list can be copied, it's just the return type that needs to fallback on type printing. I think I can revert this behavior.

I looked into it and I don't think I can easily revert to the old behavior. The type checked printer only knows a type is too recursive to represent when it tries to print it. So when I see the function expression, I try to reuse types from the expression. When doing so, I discover the missing return type and fallback to type checker printing which then discovers the type is recursive.
What specifically is the worry in this case ? () => any and () => () => any are both bad, they both allow calling the function, so I don't really think the types are worse.

Moreso if someone actually calls it and uses the result, that result will not be any and may cause follow-on errors. But I think this particular case is exceeding rare and weird anyway. Like, the function is clearly returning a function, so maybe that safety is better.

Jake Bailey (jakebailey)

In general, this seems fine to me, though I am unsure if we want to sneak this in before the 5.7 RC. Wesley Wigham (@weswigham)Daniel Rosenwasser (@DanielRosenwasser) do you have an opinion here?

Jake Bailey (jakebailey) · 2024-11-11T18:14:03Z

5.7 is cut, main is open for 5.8; I'm just going to merge this now. I don't think we need this for 5.7 or anything.

Extract function types from function and arrow expressions.
b248c5c

TypeScript Bot (typescript-bot) added the For Uncommitted Bug PR for untriaged, rejected, closed or missing bug label Oct 15, 2024

Jake Bailey (jakebailey) reviewed Oct 15, 2024
View reviewed changes

Comment threadsrc/compiler/checker.ts Outdated

Removed option to expand parameters from enterNewScope
cbb36c4

Jake Bailey (jakebailey) reviewed Oct 28, 2024
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Jake Bailey (jakebailey) approved these changes Oct 31, 2024
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Jake Bailey (jakebailey) requested review from Daniel Rosenwasser (DanielRosenwasser) and Wesley Wigham (weswigham)October 31, 2024 22:53

Jake Bailey (jakebailey) merged commit b58ac4a into microsoft:mainNov 11, 2024

Mateusz Burzyński (Andarist) mentioned this pull request Mar 3, 2025
5.8.2 generates incorrect d.ts for generics in static method #61334
Closed

Nathan Shively-Sanders (sandersn) removed this from PR Backlog Apr 22, 2025

CopilotAI mentioned this pull request Oct 9, 2025
Port PR#60234: Use signature.parameters directly instead of getExpandedParameters microsoft/typescript-go#1861
Closed

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

		declare var foo3: () => () => /elided/ any;
		declare var x: () => () => /elided/ any;

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Titian Cernicova-Dragomir (dragomirtitian) commented Oct 15, 2024

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tsc

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TypeScript Bot (typescript-bot) commented Oct 25, 2024•
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