Flow: Computed property cannot be assigned with String

[boopathi]

Input:

function a (values: Array<String> = []) {
  return values.reduce(
    (acc, cur) => Object.assign(acc, { [cur]: cur }),
    {}
  );
}

Error:

3:     (acc, cur) => Object.assign(acc, { [cur]: cur }),
                                        ^ object literal. Computed property cannot be assigned with
3:     (acc, cur) => Object.assign(acc, { [cur]: cur }),
                                           ^ String

REPL

Similar issue: #3258

[madbence]

workaround (string instead of String):

function a(values: Array<string> = []): { [string]: string } {
  return values.reduce(
    (acc, cur) => Object.assign(acc, { [cur]: cur }),
    {}
  );
}

(i've added the annotation for the return type too, because flow wasn't able to infer it)

[AMongeMoreno]

Is there any plan on adding this? It is quite bad that we can't use computed properties as keys ...

[goodmind]

I think you shouldn't use String

[seantcanavan]

This is happening for me with the ?boolean type even though my map contains values for true, false, and null, all 3 types a ?boolean can take.

export const selectedOptionMap = {
[true]: "Yes",
[false]: "No",
[null]: "Undo",
}

Error: src/actions/report.js:456
456:     selected_option: selectedOptionMap[isCorrect],
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ computed property. Computed property cannot be accessed with
456:     selected_option: selectedOptionMap[isCorrect],
                                            ^^^^^^^^^ boolean

Error: src/actions/report.js:456
456:     selected_option: selectedOptionMap[isCorrect],
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ computed property. Computed property cannot be accessed with
456:     selected_option: selectedOptionMap[isCorrect],
                                            ^^^^^^^^^ null

Error: src/actions/report.js:456
456:     selected_option: selectedOptionMap[isCorrect],
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ computed property. Computed property cannot be accessed with
456:     selected_option: selectedOptionMap[isCorrect],
                                            ^^^^^^^^^ undefined