(typescript) snippet containing a lambda which parameters are enclosed in parens fails

[ChristianIvicevic]

Editor: Adding a list of samples we should add tests for:

const array = [1, 2, 3].reduce<number[]>((acc, next) => [...acc, next], []);
return this.sides.every((length,width=(3+2+(4/5))) => length > 0 );
const bad = ((a, b) => [...a, b]);
const bad = (a => [...a, b]);
const bad = (_ => doSomething());
const good = () => 0;
const bad = (() => 0);

• Nested parens in expressions
• () surrounded arguments
• flag argument with no ()
• _ argument

Possibly relevant:
https://stackoverflow.com/questions/18703187/count-parentheses-with-regular-expression

Since to do this I think we really need to count parens in the regex that's matching => functions.

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This is an issue I noticed downstream in VS Code itself and in the output of Asciidoctor which uses highlightjs. The snippet causing issues is this one:

const array = [1, 2, 3].reduce<number[]>((acc, next) => [...acc, next], []);
//                             ~~~~~~~~
// Type of the initial value, in our case making it an array of numbers.

And gets rendered in VS Code and Asciidoctor generated HTML as follows:

When removing the arrowhead of the lambda (even though syntactically incorrect) the formatting is correct once again (since the comment at the ends gets picked up as a comment):

[cdbax]

This seems to be something to do with the parens enclosing that arrow function. Here's some minimal reproductions:

Working: https://jsfiddle.net/cdbax/tsvn1gpj/8/

Broken: https://jsfiddle.net/cdbax/tsvn1gpj/9/

[joshgoebel]

You know you can put multiple examples in a single fiddle, right? 🙂

[cdbax]

Ahehe 😅 sure I knew that:
https://jsfiddle.net/cdbax/tsvn1gpj/11/

[joshgoebel]

Sure it’s not the number in brackets before it?

[ChristianIvicevic]

Even the following snippet will break the highlighting:

const good = () => 0;
// comment

const bad = (() => 0);
// comment

[joshgoebel]

Someone looking into this might want to look at Javascript which has this same type of structure, but I believe it works in that grammar.

[mondeja]

Just if someone try to fix this: Javascript and Typescript markups for enclosed lambda functions are broken, so both needs to be fixed. Javascript does not produce this error on the comment, but this is the rendered markup:

Note the paren at params start against a properly render markup:

See this for more.

[joshgoebel]

Thanks, I also updated the original message here with more detail.