Support CompletionItemLabel

[matklad]

/**
 * A more detailed label for a completion item.
 *
 * @since 3.17.0 - proposed state
 */
export interface CompletionItemLabel {
	/**
	 * The name of a function or variable.
	 */
	name: string;

	/**
	 * The parameters without the return type.
	 */
	parameters?: string;

	/**
	 * The fully qualified name, like package name or file path.
	 */
	qualifier?: string;

	/**
	 * The return-type of a function or type of a property/variable.
	 */
	type?: string;
}

https://github.com/matklad/rust-analyzer/blob/52005ca22c5a32441af612d07d7e9857c863117b/crates/completion/src/item.rs#L17-L74

It's unclear what is the interplay between label and detail

[kjeremy]

This is CompletionItemLabelDetails as of microsoft/language-server-protocol@c7874b2

This should clarify the usage microsoft/language-server-protocol#1193 (comment)

[kjeremy]

client@7.1.0-next.1 has been released so once gluon-lang/lsp-types#199 is in we should have the LSP bits to implement this.

EDIT: This is now in.

[kjeremy]

One thing to keep in mind is that the label field may need to be different if we support the more advanced details:

         * If label details are provided the label itself should
	 * be an unqualified name of the completion item.

[matklad]

See #7900 (comment) for the next steps here.

[kjeremy]

This is now the more generic:

/**
 * Additional details for a completion item label.
 *
 * @since 3.17.0 - proposed state
 */
export interface CompletionItemLabelDetails {

	/**
	 * An optional string which is rendered less prominently directly after
	 * {@link CompletionItemLabel.label label}, without any spacing. Should be
	 * used for function signatures or type annotations.
	 */
	detail?: string;

	/**
	 * An optional string which is rendered less prominently after
	 * {@link CompletionItemLabel.detail}. Should be used for fully qualified
	 * names or file path.
	 */
	description?: string;
}