Fix 38219: signature helper works for optional function condition.

[ShuiRuTian]

Fixes #38219

[ShuiRuTian]

strange, how to add test?

/// <reference path='fourslash.ts'/>

//// interface Obj {
////     optionalMethod?: (current: any) => any;
//// };
////
//// const o: Obj = {
////   optionalMethod(/*1*/) {
////     return {};
////   }
//// };

verify.signatureHelp(
    {
        marker: "1",
        text: 'optionalMethod(current: any): any',
        parameterName: "current",
        parameterSpan: "current: any",
    },
);

This would pass in unfixed code.

[orta]

Yeah, agree, doesn't look like using verify.completions({ marker: "1", includes: [{ name: "current"}]}) is useful for verifying this either.

I'll ask around internally.

[orta]

@weswigham spotted the issue, your test wasn't using strict and so the optional-ness was dropped. I've pushed a test which fails on master and passes on this PR. Thanks!

[orta]

Cool, thanks @ShuiRuTian