Value extracting from a function returning a string enum may turn it into an character array #57077

🔎 Search Terms

Enum function union return

🕗 Version & Regression Information

• This is the behavior in every version I tried, and I reviewed the FAQ for entries about enums

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.3.3#code/MYewdgzgLgBApmArgWxgUQB4ENkAcA2caSqA3gFAxUwBqW+icAjDALwwBEAYgJYBO0WvUYcANJWp0GcAExtOAZTigwAEyHSxEqlMYBmeRwAqAC37rdcLQF9y5AGaIwwKD3DxseQlycu3YAAoASgAuGABtTBwCIhJRGGg+HjAAcwBdGAAfdE8Y4hQYCmoYPjgoRD4wHOjCfOQAOksZAG5yW3IAeg6YAGEsXHLSmCgTOBKyirA4dXKY+EJkBCgIchVBcIQUS3jE5JTLDPY4XO9fV3Bg1s7ugFUIMZGx4H7B6fm4RbBl1fAIEEJ6vgQCkAhwAEoTSpvOoaRghMTwEiWIKtNb-OCA4GgiGDKbqBRQJKpWFweE7Ql7ZHNIA

💻 Code

const enum ExampleEnum {
Value1 = "First Value",
Value2 = "Second Value",
Value3 = "Third Value",
}

function exampleFunction(): [ExampleEnum, string] | ExampleEnum {
return ExampleEnum.Value2;
}

// Capture the returned tuple elements
const [enumValue, stringValue] = exampleFunction();

// Use the captured elements
console.log("Returned Enum Value:", enumValue);
console.log("Returned String Value:", stringValue);

🙁 Actual behavior

Console logs the following lines:

S
e

The value extraction turned the returned "Second Value" to a char array.

🙂 Expected behavior

Second Value
null

Since the function is returning either a [enum, string] or just an enum, and the function returns just an enum, the extracted value should just fill enumValue and keep stringValue to null.

Having the enum's value be separated into a char array with each char assigned to one of the variables in order is confusing and doesn't seem to have any value.

Additional information about the issue

I think the error occurs as the string value is passed instead of the ExampleEnum.member. Passing the ExampleEnum as a return when the return type is the enum type should not return its value.

This should not break anything as dissecting an enum's string value in to individual characters via extraction is a weird and hacky way of turning a string into an array.