microsoft / microsoft/TypeScript
Compilation error when mixing promise and non promise types in promise.then's onfulfilled return type
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@rbuckton is already working on this.
Since Jan 13, 2021.
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Description
Bug Report
🔎 Search Terms
typescript compilation error on mix promise and non promise type in promise context
🕗 Version & Regression Information
- This is the behavior in every version I tried, and I reviewed the FAQ for entries about ???
⏯ Playground Link
Playground link with relevant code
💻 Code
Promise.resolve(true)
.then(result => result && Promise.resolve("hello"))
.then(something => console.log(something));
🙁 Actual behavior
Got a compilation error:
Argument of type '(result: boolean) => false | Promise<string>' is not assignable to parameter of type '(value: boolean) => string | PromiseLike<string>'. Type 'false | Promise<string>' is not assignable to type 'string | PromiseLike<string>'. Type 'boolean' is not assignable to type 'string | PromiseLike<string>'.
And something was inferred as boolean.
🙂 Expected behavior
No compilation error and something should have been inferred as boolean | string.
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Assessment
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