typescript crashes when parsing certain invalid tsconfig files, instead of giving a useful error messages

[dgoldstein0]

TypeScript Version: 3.0.1 and 2.7.2 both repro. I suspect this bug is rather old as the custom json parser was introduced in 1.8.

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Code

tsconfig.json:

{
  "compilerOptions": {
    ## this comment does cause issues
    "types" : [
    ]
  }
}

and then tsc --project tsconfig.json

Expected behavior:

I expect typescript to tell me what about my tsconfig file is invalid

Actual behavior:

I get a mostly unhelpful stack trace:

/home/dgoldstein/node_modules/typescript/lib/tsc.js:9382
        return id.length >= 3 && id.charCodeAt(0) === 95 && id.charCodeAt(1) === 95 && id.charCodeAt(2) === 95 ? id.substr(1) : id;
                  ^

TypeError: Cannot read property 'length' of undefined
    at Object.unescapeLeadingUnderscores (/home/dgoldstein/node_modules/typescript/lib/tsc.js:9382:19)
    at convertObjectLiteralExpressionToJson (/home/dgoldstein/node_modules/typescript/lib/tsc.js:18925:34)
    at convertPropertyValueToJson (/home/dgoldstein/node_modules/typescript/lib/tsc.js:18997:32)
    at convertObjectLiteralExpressionToJson (/home/dgoldstein/node_modules/typescript/lib/tsc.js:18930:29)
    at convertPropertyValueToJson (/home/dgoldstein/node_modules/typescript/lib/tsc.js:18997:32)
    at convertToObjectWorker (/home/dgoldstein/node_modules/typescript/lib/tsc.js:18907:16)
    at parseOwnConfigOfJsonSourceFile (/home/dgoldstein/node_modules/typescript/lib/tsc.js:19396:20)
    at parseConfig (/home/dgoldstein/node_modules/typescript/lib/tsc.js:19318:13)
    at parseJsonConfigFileContentWorker (/home/dgoldstein/node_modules/typescript/lib/tsc.js:19204:28)
    at parseJsonSourceFileConfigFileContent (/home/dgoldstein/node_modules/typescript/lib/tsc.js:19183:16)

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