src/vs/workbench/api/common/extHostDiagnostics.ts/ExtHostDiagnostics/_getDiagnostics
class ExtHostDiagnostics:	private _getDiagnostics(resource: vscode.Uri): ReadonlyArray<vscode.Diagnostic> {
		let res: vscode.Diagnostic[] = [];
		for (const collection of this._collections.values()) {
			if (collection.has(resource)) {
				res = res.concat(collection.get(resource));
			}
		}
		return res;
	}