AbstractBlock->addError() accepts $type, $message and $extra.
Error messages are saved in an array with $type as key. Adding multiple errors of the same type will cause these errors to overwrite one another. As a result, only tge last error-of-a-type is displayed.
Implementation idea: we can probably just add an array of errors per type (instead of only 1 error per type) and have getErrorMessage() concatenate all messages & have getErrorExtra() combine all extras (perhaps we have to enforce extra to be an array here)?
Version: unspecified
Severity: normal