Error 2488 only shown once

[danny12321]

Bug Report

When the error Type '{type}[] | undefined' must have a '[Symbol.iterator]()' method that returns an iterator.(2488) occurs multiple times in a project it only shows once.

As could be seen in the image above only data_1 has red underline, while I expect to also have red underline by data_2.

🕗 Version & Regression Information

When using es5 or older both errors are shown, but from es6 only one error shows.

⏯ Playground Link

Playground link with example

💻 Code

// using math.random to create type string[] or undefined
const data: string[] | undefined = Math.random() ? [] : undefined;

const data_1 = [...data]; // has a error shown
const data_2 = [...data]; // has no error shown

🙁 Actual behavior

The TypeScript compiler is only returning one of the multiple errors when the error is of type 2488.

🙂 Expected behavior

The TypeScript compiler should return all the locations of the errors, even if they are the same type. This would be handy for code analysis tools.

[andrewbranch]

The TypeScript compiler should return all the locations of the errors, even if they are the same type.

This is not something we’re interested in doing in general, but this particular example looks surprising to me and feels like probably a mistake.

[danny12321]

Even when ignoring the first error the second will still not show. This makes compiling with compile errors (that are not showing) possible.

But when creating a copy both errors show which is interesting.

[simondel]

I would expect all errors to be shown when the compilation fails so I can fix all errors at once.

[nicojs]

This is a more significant issue than it first appears. If you ignore the first error with // @ts-expect-error, one would expect the compiler to error on the next one, but it doesn't:

https://www.typescriptlang.org/play?#code/PTAEFcGcEsDsHNQFsCGAXAFgOgE4tgCYD2SoaRoAxjgKbo1kCeADg5GjnPANoC6oRHBEI0AZnBoEAUJSKx2oAuhQAuUO04I+oAD7CCYiQVABeUAFl02PIRIAKAJSgA-KG1rwI8bEkBuKVIgoAACaJAAtDQAHqyUaJE4OIIycgpKaCgA+gCMpm5YBekovL6gQRgokKAooDSJguoYRADusAGy8miKypkATHncBVhFJWVgFVWwFHVJQpBNrVJAA

This feels like a clear bug to me.

[RyanCavanaugh]

Everything bad we predicted from implementing ts-ignore continues to manifest 😕. Biggest regret I have honestly.

[nicojs]

Thanks for the response @RyanCavanaugh 🙏.

Also without the @ts-expect-error family of problems here, tools/users might rely on full error reporting. I believe that is also a design goal.

We at StrykerJS rely on a full error report in order to validate multiple mutants at the same time in stryker-mutator/stryker-js#3900.