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

Fixes #64625

…ext scoped

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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

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

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

TypeScript Bot (@typescript-bot) test it

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

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

Everything looks the same!

You can check the log here.

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

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

Everything looks good!

Jake Bailey (@jakebailey) Here are the results of running the top 400 repos 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

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Comment thread tsc/internal/checker/checker.go Outdated

Jake Bailey (jakebailey) reviewed Oct 5, 2026

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Comment thread tsc/internal/checker/nodebuilderimpl.go Outdated

Copilot AI reviewed Oct 5, 2026

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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

Jake Bailey (jakebailey) approved these changes Oct 6, 2026

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Wesley Wigham (weswigham) added this pull request to the merge queue Oct 6, 2026

Merged via the queue into microsoft:main with commit 253bcd8 Oct 6, 2026
29 checks passed

Wesley Wigham (weswigham) deleted the fix-emitcontext-emitresolver-layers branch October 6, 2026 22:35

github-project-automation Bot moved this from Needs merge to Done in PR Backlog Oct 6, 2026

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

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

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Cache one nodebuilder per emit resolver, make emit resolver emit context scoped - #64649

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