Cache one nodebuilder per emit resolver, make emit resolver emit context scoped by weswigham · Pull Request #64649 · microsoft/TypeScript

Wesley Wigham (weswigham) · 2026-10-05T19:51:42Z

Fixes #64625

…ext scoped

Copilot

Note

Copilot was unable to run its full agentic suite in this review.

Copilot review overview

Review effort: Lite
Findings: 5

Open (5)

Panicking on a nil emitContext creates a sharp edge because the new public API accepts… · New
checker.GetEmitResolver(emitContext) now constructs a new resolver each call, and… · New
checker.GetEmitResolver(emitContext) now constructs a new resolver each call, and… · New
checker.GetEmitResolver(emitContext) now constructs a new resolver each call, and… · New
EmitResolver.CreateLiteralConstValue now owns parsing via its bound emitContext… · New

What changed in this PR

This PR refactors emit resolver creation to be EmitContext-aware, updates related interfaces, and adjusts transformer/checker call sites to use the new API while sharing resolver link state via Checker.

Changes:

Update GetEmitResolver APIs to accept an EmitContext and remove EmitContext parameters from EmitResolver node-construction methods.
Centralize resolver link stores on Checker (EmitResolverLinks) and adjust EmitResolver to use them.
Update transformers, compiler emit host, language service, and tests to pass/create an EmitContext when requesting an emit resolver.

File	Description
tsc/internal/transformers/tstransforms/importelision_test.go	Updates tests to create an `EmitContext` and pass it into `GetEmitResolver`.
tsc/internal/transformers/declarations/util.go	Switches helper functions from `DeclarationEmitHost` to `printer.EmitResolver` for flag checks.
tsc/internal/transformers/declarations/transform.go	Routes flag checks and type construction through `tx.resolver` (context-bound) and updates resolver method calls.
tsc/internal/printer/emitresolver.go	Changes `EmitResolver` interface to no longer take `EmitContext` for node construction methods.
tsc/internal/printer/emithost.go	Updates `EmitHost.GetEmitResolver` signature to require an `EmitContext`.
tsc/internal/ls/findallreferences.go	Creates an `EmitContext` when requesting an emit resolver for visibility checks.
tsc/internal/compiler/emitter.go	Passes `emitContext` into `host.GetEmitResolver`.
tsc/internal/compiler/emitHost.go	Reworks emit host to produce emit resolvers via a function taking `EmitContext`.
tsc/internal/checker/symbolaccessibility.go	Switches to `getDiagnosticsEmitResolver()` for diagnostics-layer checks.
tsc/internal/checker/nodebuilderimpl.go	Switches to `getDiagnosticsEmitResolver()` for helper visibility/undefined checks.
tsc/internal/checker/exports.go	Switches to `getDiagnosticsEmitResolver()` for implicit undefined check.
tsc/internal/checker/emitresolver.go	Makes `EmitResolver` context-bound, caches a node builder per resolver, and moves link stores to `Checker`.
tsc/internal/checker/checker.go	Adds `EmitResolverLinks`, introduces `GetEmitResolver(emitContext)`, and renames cached resolver accessor to `getDiagnosticsEmitResolver()`.

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…mit contexts so they have finite lifetimes

Jake Bailey (jakebailey) · 2026-10-06T00:23:36Z

 import (
 	"context"
+	"sync"
+	"weak"


Is this strictly required? This will lock us out of tinygo for sure...

What, the weak map? Yeah, we don't wanna leak emit contexts - since those retain node factories which in turn retain nodes (unless explicitly cleared). The cache has to be weak - or we have to break the contract of emit hosts managing emit contexts and shove emit host knowledge into the emit context just to manage a cache, which is.... bad.

You could always not cache but then every caller needs to be mindful of the lifetime, rather than letting the GC handle it.

GC's always been bad to us anyway, so I made ownership and freeing of emit contexts explicit now instead of having a cache - no more global cache, callers should either take one or create one for long duration tasks.

What this means in practice is that since we make one emitHost per thread per file, that emitHost now makes one EmitResolver during the course of emitting that file (shared for both declaration and js emit), which was made with one EmitContext used throughout the whole process. Since the same checker is used for multiple files, the resolver still needs to use the checker lock... but nothing else should need any threading stuff.

…ion up to operation bounds (or remove entirely)

…ven...

…context from the resolver now that it owns one

Jake Bailey (jakebailey) · 2026-10-06T18:15:18Z

Now this I like, though that double pointer is weird.

TypeScript Bot (@typescript-bot) test it

typescript-automation · 2026-10-06T18:15:24Z

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

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

typescript-automation · 2026-10-06T18:40:52Z

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

Everything looks the same!

You can check the log here.

typescript-automation · 2026-10-06T18:45:09Z

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 - native}
_Errors	₄₁	₄₁	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_115,276	_115,276	_~	_~	_~	_{p=1.000 n=12}
_Types	_79,613	_79,613	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{142,562k (± 0.44%)}	_{139,492k (± 0.04%)}	_{-3,070k (- 2.15%)}	_139,315k	_139,633k	_{p=0.000 n=12}
_{Memory Allocs}	_{2,193,586 (± 0.01%)}	_{2,190,770 (± 0.01%)}	_{-2,815 (- 0.13%)}	_2,190,429	_2,191,328	_{p=0.000 n=12}
_{Config Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.040s (± 4.32%)}	_{0.040s (± 3.22%)}	_~	_0.037s	_0.043s	_{p=0.499 n=12}
_{Bind Time}	_{0.012s (±11.52%)}	_{0.013s (±17.49%)}	_~	_0.010s	_0.018s	_{p=0.919 n=12}
_{Check Time}	_{0.503s (± 0.83%)}	_{0.494s (± 0.66%)}	_{-0.009s (- 1.84%)}	_0.487s	_0.503s	_{p=0.002 n=12}
_{Emit Time}	_{0.272s (± 2.94%)}	_{0.271s (± 2.31%)}	_~	_0.253s	_0.282s	_{p=0.560 n=12}
_{Total Time}	_{0.835s (± 0.74%)}	_{0.824s (± 0.83%)}	_{-0.011s (- 1.34%)}	_0.810s	_0.844s	_{p=0.027 n=12}
_{angular-1 - native}
_Errors	₃	₃	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_{845,762 (± 0.06%)}	_{845,459 (± 0.06%)}	_~	_843,931	_846,406	_{p=0.443 n=12}
_Types	_{248,123 (± 0.00%)}	_{248,124 (± 0.00%)}	_~	_248,121	_248,132	_{p=0.172 n=12}
_{Memory Used}	_{788,548k (± 0.05%)}	_{784,468k (± 0.02%)}	_{-4,080k (- 0.52%)}	_784,001k	_784,749k	_{p=0.000 n=12}
_{Memory Allocs}	_{12,871,146 (± 0.10%)}	_{12,845,426 (± 0.05%)}	_{-25,720 (- 0.20%)}	_12,836,882	_12,869,908	_{p=0.000 n=12}
_{Config Time}	_{0.017s (± 1.07%)}	_{0.016s (± 1.90%)}	_{🟩-0.001s (- 3.45%)}	_0.016s	_0.017s	_{p=0.009 n=12}
_{Parse Time}	_{0.260s (± 1.96%)}	_{0.255s (± 2.69%)}	_~	_0.240s	_0.274s	_{p=0.183 n=12}
_{Bind Time}	_{0.061s (± 8.82%)}	_{0.062s (± 8.74%)}	_~	_0.057s	_0.088s	_{p=0.755 n=12}
_{Check Time}	_0s	_0s	_~	_~	_~	_{p=1.000 n=12}
_{Emit Time}	_{1.589s (± 0.59%)}	_{1.615s (± 1.43%)}	_~	_1.571s	_1.684s	_{p=0.071 n=12}
_{Total Time}	_{1.938s (± 0.61%)}	_{1.965s (± 1.51%)}	_~	_1.917s	_2.060s	_{p=0.311 n=12}
_{mui-docs - native}
_Errors	_11,405	_11,405	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_4,359,614	_4,359,614	_~	_~	_~	_{p=1.000 n=12}
_Types	_1,376,379	_1,376,379	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{2,955,951k (± 0.05%)}	_{2,954,395k (± 0.04%)}	_~	_2,951,435k	_2,957,715k	_{p=0.242 n=12}
_{Memory Allocs}	_{32,838,929 (± 0.05%)}	_{32,826,804 (± 0.05%)}	_~	_32,781,399	_32,862,915	_{p=0.630 n=12}
_{Config Time}	_{0.017s (± 1.95%)}	_{0.017s (± 1.99%)}	_~	_0.016s	_0.017s	_{p=1.000 n=12}
_{Parse Time}	_{0.497s (± 4.20%)}	_{0.493s (± 3.74%)}	_~	_0.440s	_0.543s	_{p=0.766 n=12}
_{Bind Time}	_0.002s	_0.002s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{8.674s (± 0.62%)}	_{8.641s (± 0.64%)}	_~	_8.512s	_8.753s	_{p=0.259 n=12}
_{Emit Time}	_{0.444s (± 7.09%)}	_{0.528s (±14.24%)}	_{🔻+0.084s (+18.89%)}	_0.417s	_0.689s	_{p=0.004 n=12}
_{Total Time}	_{10.381s (± 0.74%)}	_{10.447s (± 0.37%)}	_~	_10.322s	_10.520s	_{p=0.183 n=12}
_{strada-build-src - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,390,229	_1,390,229	_~	_~	_~	_{p=1.000 n=12}
_Types	_441,498	_441,498	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,666,734k (± 0.58%)}	_{1,674,692k (± 0.90%)}	_~	_1,651,159k	_1,717,637k	_{p=0.932 n=12}
_{Memory Allocs}	_{91,966,181 (± 0.18%)}	_{92,136,607 (± 0.15%)}	_~	_91,704,632	_92,399,092	_{p=0.078 n=12}
_{Config Time}	_{0.004s (± 9.04%)}	_{0.004s (±12.12%)}	_~	_0.002s	_0.004s	_{p=1.000 n=12}
_{Parse Time}	_{0.192s (± 3.82%)}	_{0.193s (± 2.85%)}	_~	_0.181s	_0.206s	_{p=0.410 n=12}
_{Bind Time}	_{0.000s (±217.90%)}	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{1.842s (± 0.41%)}	_{1.816s (± 0.78%)}	_{-0.026s (- 1.43%)}	_1.771s	_1.838s	_{p=0.003 n=12}
_{Emit Time}	_{0.300s (± 3.62%)}	_{0.293s (± 4.60%)}	_~	_0.246s	_0.327s	_{p=0.434 n=12}
_{Total Time}	_{23.697s (± 0.68%)}	_{23.414s (± 0.57%)}	_{-0.283s (- 1.19%)}	_22.997s	_23.809s	_{p=0.020 n=12}
_{strada-compiler - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_334,953	_334,953	_~	_~	_~	_{p=1.000 n=12}
_Types	_197,616	_197,616	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{313,311k (± 0.02%)}	_{313,246k (± 0.04%)}	_~	_312,847k	_313,500k	_{p=0.630 n=12}
_{Memory Allocs}	_{4,623,069 (± 0.01%)}	_{4,623,422 (± 0.01%)}	_~	_4,622,268	_4,623,995	_{p=0.128 n=12}
_{Config Time}	_0.001s	_0.001s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.113s (± 4.58%)}	_{0.115s (± 5.01%)}	_~	_0.100s	_0.131s	_{p=0.580 n=12}
_{Bind Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Check Time}	_{1.065s (± 0.55%)}	_{1.053s (± 0.44%)}	_{-0.012s (- 1.10%)}	_1.042s	_1.066s	_{p=0.004 n=12}
_{Emit Time}	_{0.123s (±12.61%)}	_{0.132s (±12.44%)}	_~	_0.097s	_0.158s	_{p=0.523 n=12}
_{Total Time}	_{1.360s (± 0.85%)}	_{1.353s (± 1.04%)}	_~	_1.323s	_1.380s	_{p=0.523 n=12}
_{ts-pre-modules - native}
_Errors	₈₇	₈₇	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_303,834	_303,834	_~	_~	_~	_{p=1.000 n=12}
_Types	_181,663	_181,663	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{273,921k (± 0.01%)}	_{273,954k (± 0.01%)}	_~	_273,859k	_274,034k	_{p=0.164 n=12}
_{Memory Allocs}	_{1,615,797 (± 0.01%)}	_{1,616,020 (± 0.01%)}	_~	_1,615,475	_1,616,727	_{p=0.114 n=12}
_{Config Time}	_0.000s	_{0.000s (±217.90%)}	_~	_0.000s	_0.001s	_{p=1.000 n=12}
_{Parse Time}	_{0.097s (± 2.80%)}	_{0.099s (± 5.61%)}	_~	_0.090s	_0.113s	_{p=0.944 n=12}
_{Bind Time}	_{0.036s (±12.98%)}	_{0.035s (± 7.79%)}	_~	_0.030s	_0.047s	_{p=0.787 n=12}
_{Check Time}	_{0.830s (± 0.63%)}	_{0.823s (± 0.56%)}	_{-0.007s (- 0.89%)}	_0.814s	_0.833s	_{p=0.043 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{0.979s (± 0.85%)}	_{0.973s (± 0.76%)}	_~	_0.960s	_0.996s	_{p=0.259 n=12}
_{vscode - native}
_Errors	₃₈₀	₃₈₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_10,709,444	_10,709,444	_~	_~	_~	_{p=1.000 n=12}
_Types	_3,547,731	_3,547,731	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{6,933,123k (± 0.02%)}	_{6,932,406k (± 0.02%)}	_~	_6,930,041k	_6,936,304k	_{p=0.203 n=12}
_{Memory Allocs}	_{53,138,143 (± 0.02%)}	_{53,205,842 (± 0.02%)}	_{+67,698 (+ 0.13%)}	_53,190,927	_53,233,893	_{p=0.000 n=12}
_{Config Time}	_{0.073s (± 0.45%)}	_{0.073s (± 0.42%)}	_~	_0.073s	_0.074s	_{p=0.680 n=12}
_{Parse Time}	_{1.782s (± 3.65%)}	_{1.772s (± 3.86%)}	_~	_1.654s	_1.954s	_{p=0.799 n=12}
_{Bind Time}	_{0.575s (±17.50%)}	_{0.627s (±18.04%)}	_~	_0.441s	_0.887s	_{p=0.326 n=12}
_{Check Time}	_{14.057s (± 1.07%)}	_{13.975s (± 1.25%)}	_~	_13.606s	_14.233s	_{p=0.561 n=12}
_{Emit Time}	_{4.725s (±11.82%)}	_{4.903s (±12.53%)}	_~	_4.014s	_6.089s	_{p=0.514 n=12}
_{Total Time}	_{21.297s (± 2.14%)}	_{21.437s (± 2.29%)}	_~	_20.703s	_22.362s	_{p=0.514 n=12}
_{webpack - native}
_Errors	₅₈₉	₅₈₉	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,301,301	_1,301,301	_~	_~	_~	_{p=1.000 n=12}
_Types	_615,528	_615,528	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{1,005,782k (± 0.02%)}	_{1,005,769k (± 0.01%)}	_~	_1,005,501k	_1,006,107k	_{p=0.932 n=12}
_{Memory Allocs}	_{6,547,417 (± 0.02%)}	_{6,547,308 (± 0.03%)}	_~	_6,544,081	_6,554,808	_{p=0.478 n=12}
_{Config Time}	_0.009s	_0.009s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.289s (± 4.46%)}	_{0.285s (± 3.05%)}	_~	_0.262s	_0.303s	_{p=0.681 n=12}
_{Bind Time}	_{0.086s (±16.94%)}	_{0.089s (±18.79%)}	_~	_0.064s	_0.131s	_{p=0.619 n=12}
_{Check Time}	_{1.929s (± 0.57%)}	_{1.921s (± 0.68%)}	_~	_1.881s	_1.946s	_{p=0.401 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{2.349s (± 0.42%)}	_{2.340s (± 0.73%)}	_~	_2.283s	_2.375s	_{p=0.541 n=12}
_{xstate-main - native}
_Errors	₀	₀	_~	_~	_~	_{p=1.000 n=12}
_Symbols	_1,054,027	_1,054,027	_~	_~	_~	_{p=1.000 n=12}
_Types	_387,065	_387,065	_~	_~	_~	_{p=1.000 n=12}
_{Memory Used}	_{611,524k (± 0.03%)}	_{611,359k (± 0.02%)}	_~	_611,084k	_611,742k	_{p=0.081 n=12}
_{Memory Allocs}	_{4,871,147 (± 0.08%)}	_{4,867,469 (± 0.06%)}	_~	_4,860,096	_4,877,048	_{p=0.128 n=12}
_{Config Time}	_0.003s	_0.003s	_~	_~	_~	_{p=1.000 n=12}
_{Parse Time}	_{0.142s (± 4.05%)}	_{0.142s (± 4.36%)}	_~	_0.130s	_0.163s	_{p=0.766 n=12}
_{Bind Time}	_{0.047s (±19.89%)}	_{0.048s (±19.76%)}	_~	_0.033s	_0.071s	_{p=0.878 n=12}
_{Check Time}	_{1.209s (± 0.76%)}	_{1.204s (± 0.51%)}	_~	_1.188s	_1.218s	_{p=0.433 n=12}
_{Emit Time}	_0.000s	_0.000s	_~	_~	_~	_{p=1.000 n=12}
_{Total Time}	_{1.409s (± 0.89%)}	_{1.404s (± 0.76%)}	_~	_1.376s	_1.426s	_{p=0.560 n=12}

System info unknown

Hosts

native

Scenarios

Compiler-Unions - native
angular-1 - native
mui-docs - native
strada-build-src - native
strada-compiler - native
ts-pre-modules - native
vscode - native
webpack - native
xstate-main - native

_Benchmark	_Name	_Iterations
_Current	_pr	₁₂
_Baseline	_baseline	₁₂

Developer Information:

Download Benchmarks

typescript-automation · 2026-10-06T18:55:03Z

Jake Bailey (@jakebailey) Here are the results of running the user tests with tsc comparing baseline and pr:

Everything looks good!

Wesley Wigham (weswigham) added 4 commits October 5, 2026 11:37

Cache one nodebuilder per emit resolver, make emit resolver emit cont…

610e736

…ext scoped

Use links from checker, monitor locks better

b5f8011

Simplify

60e9ff8

Merge branch 'main' into fix-emitcontext-emitresolver-layers

4ef1599

Wesley Wigham (weswigham) requested review from Andrew Branch (andrewbranch) and Jake Bailey (jakebailey) and a balanced review from Copilot October 5, 2026 19:51

typescript-automation Bot assigned Wesley Wigham (weswigham) Oct 5, 2026

typescript-automation Bot added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Oct 5, 2026

Jake Bailey (jakebailey) reviewed Oct 5, 2026

View reviewed changes

Comment thread tsc/internal/checker/checker.go Outdated

Jake Bailey (jakebailey) reviewed Oct 5, 2026

View reviewed changes

Comment thread tsc/internal/checker/nodebuilderimpl.go Outdated

Copilot AI reviewed Oct 5, 2026

View reviewed changes

Comment thread tsc/internal/checker/emitresolver.go

Comment thread tsc/internal/compiler/emitHost.go Outdated

Comment thread tsc/internal/compiler/emitHost.go Outdated

Comment thread tsc/internal/compiler/emitHost.go Outdated

Comment thread tsc/internal/transformers/declarations/transform.go

Rename get->new where apprpriate, cache in the emitHost, and unpool e…

4399701

…mit contexts so they have finite lifetimes

Jake Bailey (jakebailey) reviewed Oct 6, 2026

View reviewed changes

Wesley Wigham (weswigham) added 6 commits October 5, 2026 17:36

Quick NewEmitContext usage audit now that its not pooled - move creat…

38f28de

…ion up to operation bounds (or remove entirely)

And toss in some releases for good measure

1c48062

Alright, lets just remove the cache and see if we have perf issues, e…

1d31075

…ven...

To-done another related TODO and actually relayer all the awkward stuff

1bc388e

And hoist construction of emit resolvers up a bit and borrow an emit …

a5efea3

…context from the resolver now that it owns one

Move emit arena free a smidge so it applies to declaration emit, too

234fc09

Wesley Wigham (weswigham) requested a review from Jake Bailey (jakebailey) October 6, 2026 17:58

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