extensions/configuration-editing/src/settingsDocumentHelper.ts/SettingsDocument/provideLanguageCompletionItemsForLanguageOverrides
class SettingsDocument:	private provideLanguageCompletionItemsForLanguageOverrides(_location: Location, range: vscode.Range, formatFunc: (string: string) => string = (l) => JSON.stringify(l)): Thenable<vscode.CompletionItem[]> {
		return vscode.languages.getLanguages().then(languages => {
			const completionItems = [];
			const configuration = vscode.workspace.getConfiguration();
			for (const language of languages) {
				const inspect = configuration.inspect(`[${language}]`);
				if (!inspect || !inspect.defaultValue) {
					const item = new vscode.CompletionItem(formatFunc(language));
					item.kind = vscode.CompletionItemKind.Property;
					item.range = range;
					completionItems.push(item);
				}
			}
			return completionItems;
		});
	}