Tslint: TypeError: Cannot read property 'flags' of undefined (no-unused-variable)

Created on 6 Jul 2017 · 11Comments · Source: palantir/tslint

"TypeError: Cannot read property 'flags' of undefined" with no-unused-variable rule.

TypeScript 2.4.1
https://unpkg.com/[email protected]/

TSlint 5.5.0
https://unpkg.com/[email protected]/

Running TSlint via CLI (package.json script with tslint --type-check --project "./tsconfig.json" -c "./tslint.json" "./src/**/*.ts")

TypeError: Cannot read property 'flags' of undefined
    at Object.getCheckFlags (/PROJECT/node_modules/typescript/lib/typescript.js:10137:22)
    at getTypeOfSymbol (/PROJECT/node_modules/typescript/lib/typescript.js:30957:20)
    at getTypeOfNode (/PROJECT/node_modules/typescript/lib/typescript.js:47329:24)
    at Object.getTypeAtLocation (/PROJECT/node_modules/typescript/lib/typescript.js:26823:31)
    at getImplicitType (/PROJECT/node_modules/tslint/lib/rules/noUnusedVariableRule.js:269:24)
    at cb (/PROJECT/node_modules/tslint/lib/rules/noUnusedVariableRule.js:259:20)
    at visitEachNode (/PROJECT/node_modules/typescript/lib/typescript.js:15956:30)
    at Object.forEachChild (/PROJECT/node_modules/typescript/lib/typescript.js:16143:24)
    at cb (/PROJECT/node_modules/tslint/lib/rules/noUnusedVariableRule.js:264:19)
    at visitNode (/PROJECT/node_modules/typescript/lib/typescript.js:15944:20)

tslint.json configuration:

{
  "extends": "tslint:recommended",
  "rules": {
    "no-floating-promises": true,
    "promise-function-async": true,
    "await-promise": true,
    "no-unused-variable": true,
    "no-unused-expression": true,
    "variable-name": [
      true,
      "ban-keywords",
      "check-format",
      "allow-leading-underscore",
      "allow-trailing-underscore",
      "allow-pascal-case"
    ],
    "ordered-imports": [
      true,
      {
        "import-sources-order": "case-insensitive",
        "named-imports-order": "lowercase-last"
      }
    ],
    "no-console": [
      false
    ],
    "interface-name": [
      false
    ]
  },
  "jsRules": {
    "ordered-imports": [
      true,
      {
        "import-sources-order": "case-insensitive",
        "named-imports-order": "case-insensitive"
      }
    ]
  },
  "rulesDirectory": []
}

Fixed

Source

danielweck

👍21

Most helpful comment

I have submitted PR for this: https://github.com/Microsoft/TypeScript/pull/17367

ochanje210 on 24 Jul 2017

❤5

All 11 comments

danielweck on 6 Jul 2017

I have been having the same problem for some months now too.
I personally don't want to use the typescript options that achieve the same result as no-unused-variable (mainly because when you are in dev mode, you don't really care if there is unused imports or stuffs like that…).

victornoel on 11 Jul 2017

@danielweck I don't think it is related, #2649 seems to appear only on windows and I have the same exact problem as you on linux :)

victornoel on 11 Jul 2017

See also #2876

victornoel on 11 Jul 2017

I have the exact same stacktrace in our (private) project,

From what I have read, the only difference I can spot between this error and #2876 is that it also occurs when there is no unused variable.
Wich means the stacktrace is part of the output on every build for us.