src/vs/base/parts/quickinput/browser/quickInput.ts/QuickInputController/setValidationOnInput
class QuickInputController:	private setValidationOnInput(input: IInputBox, validationResult: string | {
		content: string;
		severity: Severity;
	} | null | undefined) {
		if (validationResult && isString(validationResult)) {
			input.severity = Severity.Error;
			input.validationMessage = validationResult;
		} else if (validationResult && !isString(validationResult)) {
			input.severity = validationResult.severity;
			input.validationMessage = validationResult.content;
		} else {
			input.severity = Severity.Ignore;
			input.validationMessage = undefined;
		}
	}