Crash: infer from usage on create-react-app

[sandersn]

Simplified from create-react-app/packages/react-dev-utils/typescriptFormatter.js:

Code

function formatter(message/**/) {
  const { type } = false ? { type: message } : message;
}

Request codefixes at /**/

Expected behavior:
No crash, plus some jsdoc type for message.

Actual behavior:
Crash:

TypeError: Cannot read property 'flags' of undefined
    at Object.getCheckFlags (/home/nathansa/ts/built/local/tsserver.js:12910:23)
    at getTypeOfSymbol (/home/nathansa/ts/built/local/tsserver.js:37460:20)
    at getTypeOfNode (/home/nathansa/ts/built/local/tsserver.js:60574:24)
    at Object.getTypeAtLocation (/home/nathansa/ts/built/local/tsserver.js:32271:31)
    at inferTypeFromPropertyAssignment (/home/nathansa/ts/built/local/tsserver.js:117165:60)
    at inferTypeFromContext (/home/nathansa/ts/built/local/tsserver.js:116983:25)
    at inferTypeFromCallExpressionContext (/home/nathansa/ts/built/local/tsserver.js:117124:17)
    at inferTypeFromContext (/home/nathansa/ts/built/local/tsserver.js:116969:29)
    at inferTypeFromPropertyAccessExpressionContext (/home/nathansa/ts/built/local/tsserver.js:117138:17)
    at inferTypeFromContext (/home/nathansa/ts/built/local/tsserver.js:116976:25)
    at inferTypesFromReferences (/home/nathansa/ts/built/local/tsserver.js:116885:21)
    at /home/nathansa/ts/built/local/tsserver.js:116922:40
    at Array.map (<anonymous>)
    at Object.inferTypeForParametersFromReferences (/home/nathansa/ts/built/local/tsserver.js:116902:47)
    at annotateParameters (/home/nathansa/ts/built/local/tsserver.js:116709:58)
    at doChange (/home/nathansa/ts/built/local/tsserver.js:116669:25)
    at /home/nathansa/ts/built/local/tsserver.js:116570:109
    at Function.ChangeTracker.with (/home/nathansa/ts/built/local/tsserver.js:114937:17)
    at Object.getCodeActions (/home/nathansa/ts/built/local/tsserver.js:116570:64)
    at /home/nathansa/ts/built/local/tsserver.js:115958:121
    at Object.flatMap (/home/nathansa/ts/built/local/tsserver.js:567:25)
    at Object.getFixes (/home/nathansa/ts/built/local/tsserver.js:115958:23)
    at /home/nathansa/ts/built/local/tsserver.js:126009:35
    at Object.flatMap (/home/nathansa/ts/built/local/tsserver.js:567:25)
    at Object.getCodeFixesAtPosition (/home/nathansa/ts/built/local/tsserver.js:126007:23)

[sandersn]

Also crashes in prettier/src/language-html/parser-html.js -- very likely for the same reason. Here's a simplified repro:

function _parse(text) {
  const { frontMatter, content } = shouldParseFrontMatter
    ? parseFrontMatter(text)
    : { frontMatter: null, content: text };
}

[sandersn]

Doesn't repro on 3.5