Use proper type parameter hosts in JS files by Andarist · Pull Request #61013 · microsoft/TypeScript

Mateusz Burzyński (Andarist) · 2025-01-22T10:17:18Z

fixes#60988 , it fixes a regression from #57403 that was not addressed by #58168 , cc Wesley Wigham (@weswigham)

…res in JS files

Jake Bailey (jakebailey) · 2025-01-22T18:40:12Z

TypeScript Bot (@typescript-bot) test it

TypeScript Bot (typescript-bot) · 2025-01-22T18:40:16Z

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) · 2025-01-22T19:01:21Z

Jake Bailey (@jakebailey) Here are the results of running the user tests with tsc comparing main and refs/pull/61013/merge:

Something interesting changed - please have a look.

Details

webpack

tsconfig.types.json

[NEW] error TS2345: Argument of type 'Children<T>' is not assignable to parameter of type 'any[]'.
- lib/stats/DefaultStatsFactoryPlugin.js#L1855

tsconfig.json

[NEW] error TS2345: Argument of type 'Children<T>' is not assignable to parameter of type 'any[]'.
- lib/stats/DefaultStatsFactoryPlugin.js#L1855

TypeScript Bot (typescript-bot) · 2025-01-22T19:01:22Z

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) · 2025-01-22T19:27:54Z

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	₃₄	₃₄	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_62,390	_62,390	_~	_~	_~	_{p=1.000 n=6}
_Types	_50,395	_50,395	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{196,755k (± 0.13%)}	_{195,667k (± 0.93%)}	_~	_193,315k	_196,979k	_{p=0.378 n=6}
_{Parse Time}	_{1.61s (± 1.22%)}	_{1.61s (± 0.82%)}	_~	_1.59s	_1.63s	_{p=0.741 n=6}
_{Bind Time}	_{0.88s (± 1.51%)}	_{0.88s (± 1.56%)}	_~	_0.86s	_0.90s	_{p=0.452 n=6}
_{Check Time}	_{11.83s (± 0.53%)}	_{11.78s (± 0.57%)}	_~	_11.67s	_11.88s	_{p=0.199 n=6}
_{Emit Time}	_{3.34s (± 2.72%)}	_{3.30s (± 0.74%)}	_~	_3.27s	_3.33s	_{p=0.624 n=6}
_{Total Time}	_{17.66s (± 0.71%)}	_{17.57s (± 0.37%)}	_~	_17.48s	_17.64s	_{p=0.226 n=6}
_{angular-1 - node (v18.15.0, x64)}
_Errors	₃₇	₃₇	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_948,492	_948,492	_~	_~	_~	_{p=1.000 n=6}
_Types	_411,004	_411,004	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{1,225,498k (± 0.00%)}	_{1,225,499k (± 0.01%)}	_~	_1,225,426k	_1,225,645k	_{p=0.936 n=6}
_{Parse Time}	_{8.02s (± 0.79%)}	_{8.02s (± 0.76%)}	_~	_7.94s	_8.10s	_{p=0.872 n=6}
_{Bind Time}	_{2.31s (± 0.42%)}	_{2.29s (± 0.53%)}	_{-0.02s (- 0.72%)}	_2.28s	_2.31s	_{p=0.048 n=6}
_{Check Time}	_{38.30s (± 0.54%)}	_{38.37s (± 0.50%)}	_~	_38.04s	_38.56s	_{p=0.378 n=6}
_{Emit Time}	_{18.23s (± 0.38%)}	_{18.32s (± 0.53%)}	_~	_18.16s	_18.42s	_{p=0.109 n=6}
_{Total Time}	_{66.86s (± 0.41%)}	_{67.01s (± 0.30%)}	_~	_66.64s	_67.20s	_{p=0.229 n=6}
_{mui-docs - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_2,444,910	_2,444,910	_~	_~	_~	_{p=1.000 n=6}
_Types	_896,791	_896,791	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{2,303,627k (± 0.00%)}	_{2,303,578k (± 0.01%)}	_~	_2,303,349k	_2,303,748k	_{p=0.810 n=6}
_{Parse Time}	_{10.77s (± 0.64%)}	_{10.78s (± 0.67%)}	_~	_10.64s	_10.84s	_{p=0.810 n=6}
_{Bind Time}	_{2.60s (± 0.94%)}	_{2.63s (± 0.57%)}	_~	_2.60s	_2.64s	_{p=0.050 n=6}
_{Check Time}	_{89.46s (± 1.94%)}	_{89.39s (± 1.73%)}	_~	_87.72s	_91.19s	_{p=1.000 n=6}
_{Emit Time}	_{0.35s (± 1.59%)}	_{0.69s (±121.40%)}	_~	_0.34s	_2.39s	_{p=0.476 n=6}
_{Total Time}	_{103.18s (± 1.63%)}	_{103.48s (± 1.33%)}	_~	_101.53s	_104.95s	_{p=0.689 n=6}
_{self-build-src - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,228,792	_1,228,793	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_266,906	_266,905	_{-1 (- 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{3,092,401k (± 0.01%)}	_{2,727,494k (±14.62%)}	_{🟩-364,907k (-11.80%)}	_2,362,288k	_3,092,514k	_{p=0.020 n=6}
_{Parse Time}	_{6.80s (± 0.83%)}	_{6.71s (± 1.57%)}	_~	_6.58s	_6.83s	_{p=0.230 n=6}
_{Bind Time}	_{2.12s (± 2.08%)}	_{2.17s (± 1.51%)}	_~	_2.11s	_2.20s	_{p=0.065 n=6}
_{Check Time}	_{42.99s (± 0.30%)}	_{42.72s (± 0.29%)}	_{-0.26s (- 0.61%)}	_42.55s	_42.90s	_{p=0.008 n=6}
_{Emit Time}	_{3.47s (± 1.59%)}	_{3.53s (± 2.29%)}	_~	_3.46s	_3.67s	_{p=0.230 n=6}
_{Total Time}	_{55.40s (± 0.26%)}	_{55.14s (± 0.28%)}	_{-0.26s (- 0.47%)}	_54.98s	_55.36s	_{p=0.016 n=6}
_{self-build-src-public-api - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_1,228,792	_1,228,793	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_266,906	_266,905	_{-1 (- 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{2,794,341k (±14.22%)}	_{3,037,093k (± 9.74%)}	_~	_2,432,790k	_3,158,401k	_{p=0.128 n=6}
_{Parse Time}	_{8.56s (± 1.52%)}	_{8.63s (± 0.96%)}	_~	_8.47s	_8.69s	_{p=0.336 n=6}
_{Bind Time}	_{2.66s (± 2.03%)}	_{2.65s (± 1.54%)}	_~	_2.58s	_2.70s	_{p=0.575 n=6}
_{Check Time}	_{53.02s (± 0.61%)}	_{53.16s (± 0.38%)}	_~	_52.94s	_53.45s	_{p=0.575 n=6}
_{Emit Time}	_{4.27s (± 2.34%)}	_{4.32s (± 2.52%)}	_~	_4.19s	_4.48s	_{p=0.471 n=6}
_{Total Time}	_{68.51s (± 0.61%)}	_{68.76s (± 0.47%)}	_~	_68.32s	_69.21s	_{p=0.298 n=6}
_{self-compiler - node (v18.15.0, x64)}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_262,659	_262,660	_{+1 (+ 0.00%)}	_~	_~	_{p=0.001 n=6}
_Types	_106,711	_106,710	_{-1 (- 0.00%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{440,865k (± 0.02%)}	_{440,873k (± 0.02%)}	_~	_440,762k	_441,007k	_{p=1.000 n=6}
_{Parse Time}	_{3.53s (± 0.73%)}	_{3.55s (± 0.78%)}	_~	_3.50s	_3.57s	_{p=0.145 n=6}
_{Bind Time}	_{1.32s (± 1.25%)}	_{1.31s (± 0.64%)}	_~	_1.29s	_1.31s	_{p=0.218 n=6}
_{Check Time}	_{19.02s (± 0.50%)}	_{18.96s (± 0.48%)}	_~	_18.82s	_19.04s	_{p=0.199 n=6}
_{Emit Time}	_{1.55s (± 0.97%)}	_{1.53s (± 0.72%)}	_{-0.02s (- 1.50%)}	_1.52s	_1.55s	_{p=0.018 n=6}
_{Total Time}	_{25.41s (± 0.41%)}	_{25.34s (± 0.39%)}	_~	_25.18s	_25.43s	_{p=0.227 n=6}
_{ts-pre-modules - node (v18.15.0, x64)}
_Errors	₇₀	₇₀	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_226,113	_226,113	_~	_~	_~	_{p=1.000 n=6}
_Types	_94,488	_94,488	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{371,733k (± 0.02%)}	_{371,773k (± 0.03%)}	_~	_371,636k	_372,003k	_{p=0.810 n=6}
_{Parse Time}	_{2.89s (± 0.97%)}	_{2.90s (± 1.28%)}	_~	_2.85s	_2.96s	_{p=0.871 n=6}
_{Bind Time}	_{1.61s (± 1.51%)}	_{1.60s (± 2.16%)}	_~	_1.57s	_1.66s	_{p=0.418 n=6}
_{Check Time}	_{16.47s (± 0.35%)}	_{16.50s (± 0.62%)}	_~	_16.36s	_16.64s	_{p=0.810 n=6}
_{Emit Time}	_{0.00s (±244.70%)}	_0.00s	_~	_~	_~	_{p=0.405 n=6}
_{Total Time}	_{20.97s (± 0.37%)}	_{21.00s (± 0.58%)}	_~	_20.79s	_21.12s	_{p=0.630 n=6}
_{vscode - node (v18.15.0, x64)}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_3,262,929	_3,262,929	_~	_~	_~	_{p=1.000 n=6}
_Types	_1,122,055	_1,122,055	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{3,336,525k (± 0.00%)}	_{3,336,537k (± 0.01%)}	_~	_3,336,018k	_3,336,789k	_{p=0.689 n=6}
_{Parse Time}	_{14.50s (± 0.64%)}	_{14.58s (± 0.70%)}	_~	_14.46s	_14.71s	_{p=0.172 n=6}
_{Bind Time}	_{4.58s (± 0.23%)}	_{4.56s (± 0.43%)}	_~	_4.53s	_4.58s	_{p=0.084 n=6}
_{Check Time}	_{88.55s (± 1.52%)}	_{89.69s (± 3.16%)}	_~	_87.65s	_95.01s	_{p=0.575 n=6}
_{Emit Time}	_{27.00s (± 7.85%)}	_{26.82s (± 7.55%)}	_~	_22.92s	_28.93s	_{p=0.471 n=6}
_{Total Time}	_{134.62s (± 0.73%)}	_{135.65s (± 1.38%)}	_~	_133.84s	_138.76s	_{p=0.575 n=6}
_{webpack - node (v18.15.0, x64)}
_Errors	₀	₁	_{🔻+1 (+ ∞%)}	_~	_~	_{p=0.001 n=6}
_Symbols	_292,550	_292,643	_{+93 (+ 0.03%)}	_~	_~	_{p=0.001 n=6}
_Types	_119,124	_119,168	_{+44 (+ 0.04%)}	_~	_~	_{p=0.001 n=6}
_{Memory used}	_{446,032k (± 0.03%)}	_{446,133k (± 0.03%)}	_~	_445,914k	_446,207k	_{p=0.199 n=6}
_{Parse Time}	_{4.05s (± 1.52%)}	_{4.07s (± 0.37%)}	_~	_4.05s	_4.08s	_{p=0.745 n=6}
_{Bind Time}	_{1.76s (± 0.93%)}	_{1.79s (± 0.84%)}	_{+0.03s (+ 1.70%)}	_1.77s	_1.81s	_{p=0.019 n=6}
_{Check Time}	_{18.80s (± 0.99%)}	_{19.04s (± 2.15%)}	_~	_18.79s	_19.87s	_{p=0.748 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{24.62s (± 0.75%)}	_{24.91s (± 1.63%)}	_~	_24.65s	_25.73s	_{p=0.173 n=6}
_{xstate-main - node (v18.15.0, x64)}
_Errors	₅	₅	_~	_~	_~	_{p=1.000 n=6}
_Symbols	_555,376	_555,376	_~	_~	_~	_{p=1.000 n=6}
_Types	_186,151	_186,151	_~	_~	_~	_{p=1.000 n=6}
_{Memory used}	_{494,406k (± 0.02%)}	_{494,394k (± 0.01%)}	_~	_494,345k	_494,441k	_{p=0.810 n=6}
_{Parse Time}	_{2.76s (± 0.30%)}	_{2.77s (± 0.20%)}	_~	_2.76s	_2.77s	_{p=0.859 n=6}
_{Bind Time}	_{0.96s (± 0.42%)}	_{0.96s (± 0.57%)}	_~	_0.96s	_0.97s	_{p=0.282 n=6}
_{Check Time}	_{16.32s (± 0.26%)}	_{16.30s (± 0.26%)}	_~	_16.23s	_16.35s	_{p=0.747 n=6}
_{Emit Time}	_0.00s	_0.00s	_~	_~	_~	_{p=1.000 n=6}
_{Total Time}	_{20.04s (± 0.20%)}	_{20.03s (± 0.20%)}	_~	_19.97s	_20.07s	_{p=0.872 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) · 2025-01-22T20:14:39Z

Jake Bailey (@jakebailey) Here are the results of running the top 400 repos with tsc comparing main and refs/pull/61013/merge:

Everything looks good!

Jake Bailey (jakebailey) · 2025-01-22T21:28:33Z

 // so our inference results for this call doesn't pollute expression types referencing the outer type parameter!
- const paramLocation = candidate.typeParameters[0].symbol.declarations?.[0]?.parent;
- const candidateParameterContext = paramLocation || (candidate.declaration && isConstructorDeclaration(candidate.declaration) ? candidate.declaration.parent : candidate.declaration);
+ const paramHost = getEffectiveTypeParameterHost(candidate.typeParameters[0]);


Do we actually use the term "host" like this elsewhere?

I guess "host" might only be appropriate in the JSDoc context but I don't have a better name for this that would cover both TS and JSDoc-based types

I mean "context" is what the PR title and the code below uses; could technically just inline it too. But, the existing JSDoc func used the term, so it's probably okay.

Mateusz Burzyński (Andarist) · 2025-01-22T21:46:16Z

Regarding this reported change. I don't quite know on the spot why this has changed but it looks like a correct change. At the very least the new behavior matches existing TS behavior. See those 2: JS playground and TS playground. It also looks like the original intention of this cast was a non-null-like assertion but accidentally [] were forgotten?

EDIT: this error was reported in TS 5.4 (TS playground) so that just assures me it's the "new" behavior is the correct one :p

Jake Bailey (jakebailey) · 2025-01-22T21:53:26Z

+ function getEffectiveTypeParameterHost(typeParameter: TypeParameter) {
 const tp = getDeclarationOfKind<TypeParameterDeclaration>(typeParameter.symbol, SyntaxKind.TypeParameter)!;
- const host = isJSDocTemplateTag(tp.parent) ? getEffectiveContainerForJSDocTemplateTag(tp.parent) : tp.parent;
+ return isJSDocTemplateTag(tp.parent) ? getEffectiveJSDocHost(tp.parent) : tp.parent;


This sort of makes me wonder when we really should be using getEffectiveJSDocHost where we are currently using getEffectiveContainerForJSDocTemplateTag...

Right, but to be fair - I had to use getEffectiveJSDocHost to fix this issue at hand and it didn't look to me like this older function would have to stick to the other one. There is a chance that it should not use this - but there is also a chance that this change fixed some other issue ;p
In the ideal world, I'd go through all of the callers to both and assess their needs but I just don't have time to do that right now 😢

Jake Bailey (jakebailey) · 2025-01-23T00:09:54Z

Regarding this reported change. I don't quite know on the spot why this has changed but it looks like a correct change. At the very least the new behavior matches existing TS behavior. See those 2: JS playground and TS playground. It also looks like the original intention of this cast was a non-null-like assertion but accidentally [] were forgotten?
EDIT: this error was reported in TS 5.4 (TS playground) so that just assures me it's the "new" behavior is the correct one :p

The thing I'm most confused about is that it says []any; why is it any? Just because it's T &?

Mateusz Burzyński (Andarist) · 2025-01-23T08:17:30Z

The thing I'm most confused about is that it says []any; why is it any? Just because it's T &?

It fails to infer it completely so it uses the default for an unconstrained type parameter. It happens that in JS files it's any and in TS files it's unknown.

…renced`

TypeScript Bot (typescript-bot) · 2026-03-24T21:21:12Z

With 6.0 out as the final release vehicle for this codebase, we're closing all PRs that don't fit the merge criteria for post-6.0 patches. If you think this was a mistake and this PR fits the post-6.0 patch criteria, please post to the 6.0 iteration issue with details (specifically, which PR and which patch criteria it satisfies).

Next steps for PRs:

For crash bugfixes or language service improvements, PRs are currently accepted at the typescript-go repo
Changes to type system behavior should wait until after 7.0, at which point mainline TypeScript development will resume in this repository with the Go codebase
Library file updates (lib.d.ts etc) continue to live in this repo or the DOM Generator repo as appropriate

Use better context scope for class constructor implementation signatu…
dd6e8f7
…res in JS files

TypeScript Bot (typescript-bot) added the For Uncommitted Bug PR for untriaged, rejected, closed or missing bug label Jan 22, 2025

Mateusz Burzyński (Andarist) added 2 commits January 22, 2025 11:27

reuse the new function
378786d

remove unused import
b352c0f

Jake Bailey (jakebailey) reviewed Jan 22, 2025
View reviewed changes

add test
230925a

Mateusz Burzyński (Andarist) mentioned this pull request Jan 22, 2025
chore: fixed incorrect typecast in DefaultStatsFactoryPluginwebpack/webpack#19156
Merged

Reuse getEffectiveTypeParameterHost in `isTypeParameterPossiblyRefe…
3107e11
…renced`

TypeScript Bot (typescript-bot) added For Backlog Bug PRs that fix a backlog bug and removed For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Jan 31, 2025

Mateusz Burzyński (Andarist) changed the title ~~Use better context scope for class constructor implementation signatures in JS files~~Use proper type parameter hosts in JS filesJan 31, 2025

TypeScript Bot (typescript-bot) closed this Mar 24, 2026

github-project-automationBot moved this from Not started to Done in PR Backlog Mar 24, 2026

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