src/vs/workbench/contrib/tasks/common/problemMatcher.ts/AbstractLineMatcher/appendProperty
class AbstractLineMatcher:	private appendProperty(data: IProblemData, property: keyof IProblemData, pattern: IProblemPattern, matches: RegExpExecArray, trim: boolean = false): void {
		const patternProperty = pattern[property];
		if (Types.isUndefined(data[property])) {
			this.fillProperty(data, property, pattern, matches, trim);
		}
		else if (!Types.isUndefined(patternProperty) && patternProperty < matches.length) {
			let value = matches[patternProperty];
			if (trim) {
				value = Strings.trim(value)!;
			}
			(data as any)[property] += endOfLine + value;
		}
	}