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

Issue Type: Bug

TypeScript Version: 3.8.3 Steps to reproduce crash 1. 2. 3. TS Server Error Stack

TypeError: Cannot read property 'flags' of undefined
    at Object.isGlobalScopeAugmentation (tsserver.js:13074:26)
    at initializeTypeChecker (tsserver.js:66347:33)
    at Object.createTypeChecker (tsserver.js:34785:9)
    at Object.getTypeChecker (tsserver.js:98416:79)
    at synchronizeHostData (tsserver.js:135228:21)
    at Proxy.getProgram (tsserver.js:135310:13)
    at InferredProject.Project.updateGraphWorker (tsserver.js:139786:53)
    at InferredProject.Project.updateGraph (tsserver.js:139729:42)
    at ProjectService.assignOrphanScriptInfoToInferredProject (tsserver.js:141705:25)
    at ProjectService.assignProjectToOpenedScriptInfo (tsserver.js:143132:26)
    at tsserver.js:143396:107
    at Object.mapDefined (tsserver.js:562:30)
    at ProjectService.applyChangesInOpenFiles (tsserver.js:143396:48)
    at Session.handlers.ts.createMapFromTemplate._a.<computed> (tsserver.js:144260:46)
    at tsserver.js:146003:88
    at IOSession.Session.executeWithRequestId (tsserver.js:145994:28)
    at IOSession.Session.executeCommand (tsserver.js:146003:33)
    at IOSession.Session.onMessage (tsserver.js:146027:35)
    at Interface.<anonymous> (tsserver.js:147342:27)
    at Interface.emit (events.js:203:13)
    at Interface._onLine (readline.js:316:10)
    at Interface._normalWrite (readline.js:461:12)
    at Socket.ondata (readline.js:172:10)
    at Socket.emit (events.js:203:13)
    at addChunk (_stream_readable.js:295:12)
    at readableAddChunk (_stream_readable.js:276:11)
    at Socket.Readable.push (_stream_readable.js:210:10)
    at Pipe.onStreamRead (internal/stream_base_commons.js:166:17)

VS Code version: Code - Insiders 1.45.0-insider (bd262894bbaac5156d5bf832160b7056c91decea, 2020-04-22T18:26:38.140Z) OS version: Darwin x64 19.4.0

System Info

Item	Value
CPUs	Intel® Core™ i9-8950HK CPU @ 2.90GHz (12 x 2900)
GPU Status	2d_canvas: enabled flash_3d: enabled flash_stage3d: enabled flash_stage3d_baseline: enabled gpu_compositing: enabled metal: disabled_off multiple_raster_threads: enabled_on oop_rasterization: disabled_off protected_video_decode: unavailable_off rasterization: enabled skia_renderer: disabled_off_ok video_decode: enabled viz_display_compositor: enabled_on viz_hit_test_surface_layer: disabled_off_ok webgl: enabled webgl2: enabled
Load (avg)	10, 15, 10
Memory (System)	32.00GB (4.50GB free)
Process Argv	-psn_0_6813311
Screen Reader	no
VM	14%

Extensions (32)

Extension	Author (truncated)	Version
rainbow-brackets	2gu	0.0.6
vscode-openapi	42C	3.0.1
vscode-apollo	apo	1.15.3
svelte-intellisense	ard	0.7.1
swagger-viewer	Arj	2.2.2
toml	be5	0.4.0
gitlens	eam	10.2.1
vsc-material-theme	Equ	32.5.0
vsc-material-theme-icons	equ	1.1.4
prettier-vscode	esb	4.5.0
vscode-pull-request-github	Git	0.15.0
svelte-vscode	Jam	0.9.3
vscode-styled-components	jpo	0.0.29
vscode-deno	jus	1.6.0
dotenv	mik	1.0.1
vscode-azureappservice	ms-	0.16.5
vscode-docker	ms-	1.1.0
vscode-kubernetes-tools	ms-	1.1.1
azure-account	ms-	0.8.9
Go	ms-	0.14.1
js-debug-companion	ms-	0.0.4
vsliveshare	ms-	1.0.2048
debugger-for-chrome	msj	4.12.6
vscode-versionlens	pfl	0.25.0
material-icon-theme	PKi	4.0.1
vscode-graphql	Pri	0.2.14
vscode-yaml	red	0.7.2
code-settings-sync	Sha	3.4.3
markdown-jira-preview	tra	0.0.1
alphabetical-sorter	ue	2.0.1
quokka-vscode	Wal	1.0.288
json	Zai	1.0.4

(4 theme extensions excluded)

[DanielRosenwasser]

Ping @admmasters, any update?

[sandersn]

My first guess for the cause is an incorrect tree that hasn’t had parent pointers set. It’s possible that a fix for #38556 will also fix this, but it’s hard to know without a repro.