extensions/typescript-language-features/src/languageFeatures/callHierarchy.ts/TypeScriptCallHierarchySupport/provideCallHierarchyIncomingCalls
class TypeScriptCallHierarchySupport:	public async provideCallHierarchyIncomingCalls(item: vscode.CallHierarchyItem, token: vscode.CancellationToken): Promise<vscode.CallHierarchyIncomingCall[] | undefined> {
		const filepath = this.client.toPath(item.uri);
		if (!filepath) {
			return undefined;
		}

		const args = typeConverters.Position.toFileLocationRequestArgs(filepath, item.selectionRange.start);
		const response = await this.client.execute('provideCallHierarchyIncomingCalls', args, token);
		if (response.type !== 'response' || !response.body) {
			return undefined;
		}

		return response.body.map(fromProtocolCallHierarchyIncomingCall);
	}