Model inheritance using macros?

[kjeremy]

We currently model inheritance using #[serde(flatten)] like below:

#[derive(Debug, PartialEq, Clone, Deserialize, Serialize)]
#[serde(rename_all = "camelCase")]
pub struct CompletionParams {
    // This field was "mixed-in" from TextDocumentPositionParams
    #[serde(flatten)]
    pub text_document_position: TextDocumentPositionParams,


    #[serde(flatten)]
    pub work_done_progress_params: WorkDoneProgressParams,


    #[serde(flatten)]
    pub partial_result_params: PartialResultParams,


    // CompletionParams properties:
    #[serde(skip_serializing_if = "Option::is_none")]
    pub context: Option<CompletionContext>,
}

The above corresponds to the following typescript

export interface CompletionParams extends TextDocumentPositionParams, WorkDoneProgressParams, PartialResultParams {


	/**
	 * The completion context. This is only available it the client specifies
	 * to send this using the client capability `textDocument.completion.contextSupport === true`
	 */
	context?: CompletionContext;
}

This becomes difficult to maintain when a concept like partial results or progress are added to the protocol (which changes server and client caps, params and result types). Maybe we should investigate a macro (or custom derive?) approach to make this sort of thing easier and less error prone.