Error: Debug Failure. False expression. in 'findPrecedingToken' during 'quickinfo'

[aozgaa]

This issue comes from crash dumps in telemetry. We've tried to de-duplicate issues on a best-effort basis, comparing the sequence of methods called and the command requested while ignoring line numbers.
TypeScript Version Prefix: 2.7.1
VSCode Version 1.20.0-insider
command requested: quickinfo
hitting sessions: 13596
proportion of all sessions: 0.050755395280599386
five line hash: fb9201106c433477a5ba720a658689ce
stack

Error: Debug Failure. False expression.
    at findPrecedingToken (tsserver.js:64624:18)
    at getTokenAtPositionWorker (tsserver.js:64586:41)
    at getTouchingToken (tsserver.js:64558:16)
    at Object.getTouchingPropertyName (tsserver.js:64554:16)
    at Object.getQuickInfoAtPosition (tsserver.js:82852:27)
    at IOSession.Session.getQuickInfoWorker (tsserver.js:89781:62)
    at Session.handlers.ts.createMapFromTemplate._a.(anonymous function) (tsserver.js:88934:61)
    at unknown (tsserver.js:90355:88)
    at IOSession.Session.executeWithRequestId (tsserver.js:90346:28)
    at IOSession.Session.executeCommand (tsserver.js:90355:33)
    at IOSession.Session.onMessage (tsserver.js:90375:35)
    at Interface.<anonymous> (tsserver.js:91576:27)
    at emitOne (events.js:96:13)
    at Interface.emit (events.js:191:7)
    at Interface._onLine (readline.js:241:10)
    at Interface._normalWrite (readline.js:384:12)
    at Socket.ondata (readline.js:101:10)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:191:7)
    at readableAddChunk (_stream_readable.js:178:18)
    at Socket.Readable.push (_stream_readable.js:136:10)
    at Pipe.onread (net.js:560:20)

[mhegazy]

looks like a duplicate of #21799

[aozgaa]

This issue reproduced in the following context:
TypeScript Version Prefix: 2.7.2
VSCode Version 1.20.0
command requested: quickinfo
hitting sessions: 248
proportion of all sessions: 0.05772811918063315
stack

Error: Debug Failure. False expression.
    at findPrecedingToken (tsserver.js:64794:18)
    at getTokenAtPositionWorker (tsserver.js:64756:41)
    at getTouchingToken (tsserver.js:64728:16)
    at Object.getTouchingPropertyName (tsserver.js:64724:16)
    at Object.getQuickInfoAtPosition (tsserver.js:83050:27)
    at IOSession.Session.getQuickInfoWorker (tsserver.js:89979:62)
    at Session.handlers.ts.createMapFromTemplate._a.(anonymous function) (tsserver.js:89132:61)
    at unknown (tsserver.js:90553:88)
    at IOSession.Session.executeWithRequestId (tsserver.js:90544:28)
    at IOSession.Session.executeCommand (tsserver.js:90553:33)
    at IOSession.Session.onMessage (tsserver.js:90573:35)
    at Interface.<anonymous> (tsserver.js:91774:27)
    at emitOne (events.js:96:13)
    at Interface.emit (events.js:191:7)
    at Interface._onLine (readline.js:241:10)
    at Interface._normalWrite (readline.js:384:12)
    at Socket.ondata (readline.js:101:10)
    at emitOne (events.js:96:13)
    at Socket.emit (events.js:191:7)
    at readableAddChunk (_stream_readable.js:178:18)
    at Socket.Readable.push (_stream_readable.js:136:10)
    at Pipe.onread (net.js:560:20)