src/vs/workbench/contrib/codeEditor/browser/languageConfigurationExtensionPoint.ts/LanguageConfigurationFileHandler/_extractValidCommentRule
class LanguageConfigurationFileHandler:	private _extractValidCommentRule(languageIdentifier: LanguageIdentifier, configuration: ILanguageConfiguration): CommentRule | null {
		const source = configuration.comments;
		if (typeof source === 'undefined') {
			return null;
		}
		if (!types.isObject(source)) {
			console.warn(`[${languageIdentifier.language}]: language configuration: expected \`comments\` to be an object.`);
			return null;
		}

		let result: CommentRule | null = null;
		if (typeof source.lineComment !== 'undefined') {
			if (typeof source.lineComment !== 'string') {
				console.warn(`[${languageIdentifier.language}]: language configuration: expected \`comments.lineComment\` to be a string.`);
			} else {
				result = result || {};
				result.lineComment = source.lineComment;
			}
		}
		if (typeof source.blockComment !== 'undefined') {
			if (!isCharacterPair(source.blockComment)) {
				console.warn(`[${languageIdentifier.language}]: language configuration: expected \`comments.blockComment\` to be an array of two strings.`);
			} else {
				result = result || {};
				result.blockComment = source.blockComment;
			}
		}
		return result;
	}