TS Server fatal error: Cannot read property 'flags' of undefined

[vinniciusgomes]

Issue Type: Bug

❗️❗️❗️ Please fill in the sections below to help us diagnose the issue ❗️❗️❗️

TypeScript Version: 4.5.4

Steps to reproduce crash
1.
2.
3.

TS Server Log
❗️Server logging disabled. To help us fix crashes like this, please enable logging by setting:

"typescript.tsserver.log": "verbose"

After enabling this setting, future crash reports will include the server log.

TS Server Error Stack
Server: semantic

TypeError: Cannot read property 'flags' of undefined
    at getPropertyOfObjectType (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:57011:22)
    at getPropertyOfType (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:57671:24)
    at resolveESModuleSymbol (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:49817:54)
    at getTargetOfNamespaceImport (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:49002:28)
    at getTargetOfAliasDeclaration (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:49236:28)
    at resolveAlias (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:49281:30)
    at getSymbol (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:47838:38)
    at resolveNameHelper (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:48131:34)
    at resolveName (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:48114:20)
    at resolveEntityName (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:49453:42)
    at resolveEntityName (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:49461:33)
    at getSymbolOfPartOfRightHandSideOfImportEquals (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:49413:24)
    at getTargetOfImportEqualsDeclaration (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:48865:28)
    at getTargetOfAliasDeclaration (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:49232:28)
    at resolveAlias (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:49281:30)
    at resolveSymbol (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:49271:67)
    at mergeSymbol (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:47624:42)
    at /Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:47739:47
    at Map.forEach (<anonymous>)
    at mergeSymbolTable (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:47737:20)
    at mergeSymbol (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:47648:21)
    at /Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:47739:47
    at Map.forEach (<anonymous>)
    at mergeSymbolTable (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:47737:20)
    at mergeModuleAugmentation (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:47753:17)
    at initializeTypeChecker (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:85046:25)
    at Object.createTypeChecker (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:47395:9)
    at Object.getTypeChecker (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:114404:79)
    at synchronizeHostData (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:159898:21)
    at Object.getProgram (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:160019:13)
    at AutoImportProviderProject.Project.updateGraphWorker (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:165033:53)
    at AutoImportProviderProject.Project.updateGraph (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:164962:42)
    at AutoImportProviderProject.updateGraph (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:165807:70)
    at Object.updateProjectIfDirty (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:166444:45)
    at ConfiguredProject.Project.getPackageJsonAutoImportProvider (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:165582:32)
    at ConfiguredProject.Project.updateGraph (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:165000:26)
    at ConfiguredProject.updateGraph (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:165955:63)
    at ProjectService.createLoadAndUpdateConfiguredProject (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:167679:25)
    at ProjectService.assignProjectToOpenedScriptInfo (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:168762:44)
    at /Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:169102:97
    at Object.flatMap (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:522:25)
    at ProjectService.applyChangesInOpenFiles (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:169102:41)
    at Session.handlers.ts.Map.ts.getEntries._a.<computed> (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:170260:46)
    at /Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:172193:88
    at IOSession.Session.executeWithRequestId (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:172184:28)
    at IOSession.Session.executeCommand (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:172193:33)
    at IOSession.Session.onMessage (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:172219:35)
    at Interface.<anonymous> (/Applications/Visual Studio Code.app/Contents/Resources/app/extensions/node_modules/typescript/lib/tsserver.js:174824:31)
    at Interface.emit (events.js:315:20)
    at Interface._onLine (readline.js:337:10)
    at Interface._normalWrite (readline.js:482:12)
    at Socket.ondata (readline.js:194:10)
    at Socket.emit (events.js:315:20)
    at addChunk (internal/streams/readable.js:309:12)
    at readableAddChunk (internal/streams/readable.js:284:9)
    at Socket.Readable.push (internal/streams/readable.js:223:10)
    at Pipe.onStreamRead (internal/stream_base_commons.js:188:23)

VS Code version: Code - Insiders 1.64.0-insider (Universal) (9930557, 2022-01-03T05:15:53.904Z)
OS version: Darwin arm64 21.2.0
Restricted Mode: No

System Info

Item	Value
CPUs	Apple M1 (8 x 24)
GPU Status	2d_canvas: enabled gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on oop_rasterization: enabled opengl: enabled_on rasterization: enabled skia_renderer: disabled_off_ok video_decode: enabled webgl: enabled webgl2: enabled
Load (avg)	3, 4, 6
Memory (System)	8.00GB (0.25GB free)
Process Argv
Screen Reader	no
VM	0%

Extensions (24)

Extension	Author (truncated)	Version
better-comments	aar	2.1.0
html-snippets	abu	0.2.1
npm-intellisense	chr	1.4.0
path-intellisense	chr	2.6.0
bracket-pair-colorizer-2	Coe	0.2.2
vscode-eslint	dba	2.2.2
gitlens	eam	11.7.0
vscode-html-css	ecm	1.10.2
EditorConfig	Edi	0.16.4
vscode-npm-script	eg2	0.3.23
prettier-vscode	esb	9.0.0
auto-close-tag	for	0.5.13
auto-rename-tag	for	0.1.9
copilot	Git	1.7.4421
vscode-pull-request-github	Git	0.35.2021123010
vscode-codemetrics	kis	1.24.0
dotenv	mik	1.0.1
color-highlight	nau	2.5.0
vscode-versionlens	pfl	1.0.9
material-icon-theme	PKi	4.11.0
LiveServer	rit	5.6.1
vscode-styled-components	sty	1.7.2
highlight-matching-tag	vin	0.10.1
JavaScriptSnippets	xab	1.8.0

(1 theme extensions excluded)

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[mjbvz]

Please share a small project that triggers this issue so we can investigate this

[otto-liljalaakso-nt]

Please share a small project that triggers this issue so we can investigate this

Does this help?

#47038 (comment)

[mjbvz]

@otto-urpelainen-nt Thanks but that was reported with an old TS version. We need a repo that still crashes with TS 4.5.4 too

[otto-liljalaakso-nt]

@otto-urpelainen-nt Thanks but that was reported with an old TS version. We need a repo that still crashes with TS 4.5.4 too

I think it does crash with exactly that version.
At least that is what is written into that repo's package.lock.

There was a different problem with that repo though,
see this pull request in the reproducer repository: ttamminen/tsc-crash#1

[andrewbranch]

That repo looks completely unrelated. This issue and the attached stack trace can only possibly happen in an editor running TS Server. This repo demonstrates some simple compilation errors with tsc that are working as intended.

[otto-liljalaakso-nt]

That repo looks completely unrelated. This issue and the attached stack trace can only possibly happen in an editor running TS Server. This repo demonstrates some simple compilation errors with tsc that are working as intended.

It is related, but in an indirect way.
I do understand that the relation may be too indirect to be useful for debugging this issue.
The situation is explained in the comment I linked above,
but let me go through this once more.

So, we can reproduce this issue in our proprietary, large repository.
It manifests in two different ways:
as exact the issue reported in this ticket,
and as tsc crash during compilation:

$ yarn build
/home/otto/src/Novatron/manage/xmevents/node_modules/typescript/lib/tsc.js:47148
            if (type.flags & 524288) {
                     ^

TypeError: Cannot read property 'flags' of undefined
    at getPropertyOfObjectType (/home/otto/src/Novatron/manage/xmevents/node_modules/typescript/lib/tsc.js:47148:22)
    at getPropertyOfType (/home/otto/src/Novatron/manage/xmevents/node_modules/typescript/lib/tsc.js:47710:24)
    at resolveESModuleSymbol (/home/otto/src/Novatron/manage/xmevents/node_modules/typescript/lib/tsc.js:40904:54)
    at getTargetOfNamespaceImport (/home/otto/src/Novatron/manage/xmevents/node_modules/typescript/lib/tsc.js:40191:28)
    at getTargetOfAliasDeclaration (/home/otto/src/Novatron/manage/xmevents/node_modules/typescript/lib/tsc.js:40405:28)
    at resolveAlias (/home/otto/src/Novatron/manage/xmevents/node_modules/typescript/lib/tsc.js:40446:30)
    at getSymbol (/home/otto/src/Novatron/manage/xmevents/node_modules/typescript/lib/tsc.js:39225:38)
    at resolveNameHelper (/home/otto/src/Novatron/manage/xmevents/node_modules/typescript/lib/tsc.js:39464:34)
    at resolveName (/home/otto/src/Novatron/manage/xmevents/node_modules/typescript/lib/tsc.js:39448:20)
    at resolveEntityName (/home/otto/src/Novatron/manage/xmevents/node_modules/typescript/lib/tsc.js:40573:42)

The call stack looks very similar for both problems!

Thanks to excellent debugging effort of @ttamminen,
the problem was traced to these two lines we have somewhere in the repository:

import FullCalendar from "@fullcalendar/react"
import { EventInput } from "@fullcalendar/core"

The reproducer repository is a minimal example having those lines and tsc.
For some reason, there VS Code functions as expected and there is no tsc crash.
But there are regular looking compilation errors.
Applying the fix for those in our main repo
also solves the "Cannot read property 'flags' of undefined" issue,
both for VS Code and the tsc run.

Let me know if this is still to indirect to get forward.
If so, I will not bother you any more with this,
and hope that eventually, somebody will encounter the issue in an open source project.

[andrewbranch]

Unfortunately, it’s a total coincidence that https://github.com/ttamminen/tsc-crash has the same fix as the crash you’re experiencing. The repro you are experiencing in your proprietary codebase does indeed look related, but the supposed minimal repro is in fact completely unrelated. If you can give me private read access to your proprietary repo, then we can make some progress on this problem. But sadly https://github.com/ttamminen/tsc-crash doesn’t help with it 😕

[otto-liljalaakso-nt]

Unfortunately, it’s a total coincidence that https://github.com/ttamminen/tsc-crash has the same fix as the crash you’re experiencing. The repro you are experiencing in your proprietary codebase does indeed look related, but the supposed minimal repro is in fact completely unrelated. If you can give me private read access to your proprietary repo, then we can make some progress on this problem. But sadly https://github.com/ttamminen/tsc-crash doesn’t help with it 😕

Thank you for taking a look at this.
And sorry for giving such bad reproducer.

I put some effort to this and distilled a better reproducer from our repository.
I kept removing parts as long as the issue kept appearing.
The result is in this repository: otto-urpelainen-nt/tsc-crash-reproducer.
I can reproduce the original issue there in three different setups:
Linux, WSL 2 with VS Code remoting, Windows (needs a bit of workaround, because yarn does not play nice with PowerShell)

If this is still not useful,
I can try to get a permission for privately sharing the original repository.

[andrewbranch]

Yes, that repros for me! Thank you so much @otto-urpelainen-nt, I know it’s not easy to create a minimal repro from a huge project. We were really stuck and now we’re not 🥳

[ttamminen]

@andrewbranch @otto-urpelainen-nt Excellent!

Great work Otto and thank you, Andrew, for taking look at this. I on the other hand have to check (out of curiosity) what were the differences between our repos. 👍