[Semantic sugar] type aliases are lost using IntelliSense

[Sgt-Nukem]

When using a type alias in an interface (as semantic sugar) ... (A)

... this sugar is lost when using IntelliSense's "blue bulb" click -> "Implement interface XY" function. (C)

(See (B) for concrete type alias used here)

Appendix: Also, this semantic sugar is lost in IntelliSense hover tooltips -- see (D), where semantic sugar type "UUID" gets de-aliased down to "string" in the tooltip.

[mjbvz]

Please provide repo steps with example code (as text)

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[yume-chan]

It (at least your figure D) should be caused by a limitation of TypeScript (see microsoft/TypeScript#34778).

Basically TypeScript will not record you are using a type aliases, only the resolved type.

[Sgt-Nukem]

Please provide repo steps with example code (as text)

Minimal Repo:

export type UrlString = string;
export type UUID = string;

export interface I_IdToUrlMapper {
	mapIdToUrl(id: UUID): UrlString
	mapUrlToId(url: UrlString): UUID
}

export class IdToUrlMapper implements I_IdToUrlMapper {

}

Now click the "blue bulb" that appears after clicking "IdToUrlMapper" (underlined in red) and choose "Implement interface 'I_IdToUrlMapper'" --> the resulting code is stripped off of any semantic sugar type aliases:

mapIdToUrl(id: string): string { throw new Error('Method not implemented.'); } mapUrlToId(url: string): string { throw new Error('Method not implemented.'); }

N.B.: Why is the code formatting here not working as expected?

[mjbvz]

Thanks! Opened microsoft/TypeScript#36761 to track upstream