Default assigned generic type isn't generated

[Rene Haas]

• Version: 3.0.2
• Rollup Version: 2.76.0
• Operating System and version (if applicable): Windows 10
• Node Version (if applicable): 16.15.0
• Does it work with tsc (if applicable): Yes

Reproduction

I have two files: index.ts and SomeElse.ts:

// index.ts
export * from "./SomeElse";

// SomeElse.ts
export type SomeGeneric<T extends {} = any> = [string, T];

The input for rollup is the index.ts file.
Note: if the input file would be SomeElse.ts (so the re-export isn't happening) the output would be correct.

Not very familiar with repl, but here is a link: https://replit.com/@KingSora/rollup-plugin-ts-bug
The setup is actually really small, please just re-create it on your local machine if needed.
Run npm run build to build the output.

Expected Behavior

The type is exported correctly:

type SomeGeneric<T extends {} = any> = [string, T];
export { SomeGeneric };

Actual Behavior

The type is exported without the default assigned type any:

type SomeGeneric<T extends {}> = [
    string,
    T
];
export { SomeGeneric };

[Sagnik Pradhan]

@wessberg Do you know what or where the issue could be? I would be willing to fix it.

[Rene Haas]

@wessberg I would also be willing to fix it, if you could provide some insights of what you think where the issue could be. Your plugin is really good!

[Timmy Huang]

It seems like the default type is preserved if you use typescript@4.6. None of 4.7.x worked, so probably something specific to 4.7.x?

[Hien Truong]

I face the same issue too, with dependency versions:
"rollup": "2.78.1",
"rollup-plugin-ts": "3.0.2",
"typescript": "4.7.4"

export type Dict<Value = string> = { [key: string]: Value };

was built to

type Dict<Value> = {
    [key: string]: Value;
};

The default type parameter was stripped away. It doesn't happen when running tsc.

[Timmy Huang]

I face the same issue too, with dependency versions: "rollup": "2.78.1", "rollup-plugin-ts": "3.0.2", "typescript": "4.7.4"

export type Dict<Value = string> = { [key: string]: Value };

was built to

type Dict<Value> = {
    [key: string]: Value;
};

The default type parameter was stripped away. It doesn't happen when running tsc.

if you're blocked by this, try typescript 4.6. It worked for us!

[Hien Truong]

Thanks @tihuan, as you suggested, but instead of downgrading, I upgraded to "typescript": "4.8.2" and now it works.
But 4.8.2 version of TS seems to introduce quite many breaking changes and deprecation notes. I saw these notes when I built my project.

DeprecationWarning: 'updateImportTypeNode' has been deprecated since v4.6.0. Use the overload that accepts 'assertions'
DeprecationWarning: 'createTypeParameterDeclaration' has been deprecated since v4.7.0. Use the overload that accepts 'modifiers'
DeprecationWarning: 'isTypeAssertion' has been deprecated since v4.0.0. Use `isTypeAssertionExpression` instead.
DeprecationWarning: 'createConstructorTypeNode' has been deprecated since v4.2.0. Use the overload that accepts 'modifiers'