Error when using const modifier in type parameters (Typescript 5 + Preact + Vite)

[german664]

Hi! I'm getting an error when running vite dev in a project with Preact + Vite + Typescript.

This issue happens when trying to use the new "Const type parameters" functionality available since Typescript 5.

Steps to reproduce:

• Create a component with Preact + Vite + Typescript >5 + Preact plugin (from preset-vite).

• Copy the following function:

    function testConstTypeParams<const T extends { name: string }>(props: T): T['name'] {
        return props.name
    };

    const name = testConstTypeParams({name: 'Han Solo'});

Issue

The code works and is accepted by TS compiler, but no by Vite.

The error in the console is the following:

[project] 2:59:59 PM [vite] Internal server error: /Users/user1/folder/project/src/components/internal/component.tsx: Unexpected keyword 'const'. (17:33)
[project] 
[project]       };
[project]   
[project] >     function testConstTypeParams<const T extends { name: string }>(props: T): T['name'] {
[project]                                     ^
[project]           return props.name
[project]       }
[project]   
[project]   Plugin: vite:preact-jsx
[project]   File: /Users/user1/folder/project/src/components/internal/component.tsx:17:33
[project]        };
[project]     
[project]         function testConstTypeParams<const T extends { name: string }>(props: T): T['name'] {
[project]                                       ^
[project]             return props.name
[project]         }

So it seems it's an issue with Plugin: vite:preact-jsx.

Tried to debug it and I think the culprit is the version of @babel/core being used. According to this PR the const modifier in type parametersis available since version 7.21.0, but I'm not really sure that upgrading the version will solve the issue.

I really hope that I was clear enough with my explanation. Please let me know if you need more info. Thanks!

[JoviDeCroock]

Have you tried upgrading your version of @babel/core?

[TvojTatk0]

I have similar issue. Would like to use new keyword using from TS 5.2.0 but it is not possible (probably) due preset-vite plugin. Im getting this error:

Support for the experimental syntax 'explicitResourceManagement' isn't currently enabled

It would be really awesome to have updated dependencies in this great plugin.