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flow: Cannot call getGraphQLParams(...).then with function bound to onFulfill

See original GitHub issue

$ flow check --show-all-branches Error ┈ node_modules/express-graphql/dist/index.js.flow:158:13

Cannot call getGraphQLParams(...).then with function bound to onFulfill because in the return value:

Either OptionsData [1] is incompatible with Promise [2].
Or cannot call validationRules.concat because in type argument Item:
- Either cannot call validate with validationRules bound to rules because mixed [3] is incompatible with ValidationRule [4] in array element.
- Or cannot call validate with validationRules bound to rules because array type [5] is incompatible with ValidationRule [4] in array element.

        node_modules/express-graphql/dist/index.js.flow
    [1]  43│     ) => OptionsResult)
           :
 [5][3]  78│   validationRules?: ?Array<mixed>,
           :
        151│
        152│     // Parse the Request to get GraphQL request parameters.
        153│     return getGraphQLParams(request)
        154│       .then(graphQLParams => {
        155│         params = graphQLParams;
        156│         // Then, resolve the Options to get OptionsData.
        157│         return typeof options === 'function'
        158│           ? options(request, response, params) // 🔥
        159│           : options;
        160│       })
        161│       .then(optionsData => {
        162│         // Assert that optionsData is in fact an Object.
        163│         if (!optionsData || typeof optionsData !== 'object') {

        /tmp/flow/flowlib_27f728ff/core.js
    [2] 595│       onFulfill: (value: R) => Promise<U> | U,

        node_modules/graphql/validation/validate.js.flow
    [4]  40│   rules?: $ReadOnlyArray<ValidationRule> = specifiedRules,