The Typescript compiler conveniently overlooks a "non-assignable" error when it comes to tuples

When looking at the following code:

const xyz: [string, number] = [10, "sample"];

    console.log(xyz);

An unexpected red squiggly line appears under 'xyz' with the error message:

[ts] Type '[number, string]' is not compatible with type '[string, number]'. Type 'number' is not compatible with type 'string'.

Despite this error, the code still compiles down to JavaScript like this:

var xyz = [10, "sample"];
    console.log(xyz);

Is there a compiler option that I may have missed, or could this be a bug?

typescripttuplesvisual-studio-codetypescript-typings

Answer №1

In TypeScript, the standard behavior is for the compiler to still generate a JavaScript file even when there are errors present. While a non-zero exit code is returned that build scripts can use for detection and action.

You can test this by introducing other types of errors, such as mistyped variable names like:

let num: number = 5;
console.log(name);

and observe the same outcome.

Additionally, remember that there is an option to alter this behavior using a compiler flag. By utilizing:

tsc --noEmitOnError test.ts

you can prevent the generation of the test.js file if any errors are encountered.

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