18 files declare their use of TagElementInterface in Extensible BBCode 4.0.x

CallbackTagProcessor.php in src/Parser/Processor/CallbackTagProcessor.php

CodeTagPlugin.php in standard/src/Plugin/XBBCode/CodeTagPlugin.php

EntityTagPlugin.php in src/Plugin/XBBCode/EntityTagPlugin.php

ImageTagPlugin.php in standard/src/Plugin/XBBCode/ImageTagPlugin.php

ListTagPlugin.php in standard/src/Plugin/XBBCode/ListTagPlugin.php

NullTagPlugin.php in src/Plugin/XBBCode/NullTagPlugin.php

PreparedTagElement.php in src/PreparedTagElement.php

RenderTagPlugin.php in src/Plugin/RenderTagPlugin.php

TableTagPlugin.php in standard/src/Plugin/XBBCode/TableTagPlugin.php

TagFormBase.php in src/Form/TagFormBase.php

TagPluginBase.php in src/Plugin/TagPluginBase.php

TagPluginInterface.php in src/Plugin/TagPluginInterface.php

TagProcessorBase.php in src/Parser/Processor/TagProcessorBase.php

TagProcessorInterface.php in src/Parser/Processor/TagProcessorInterface.php

TemplateTagPlugin.php in src/Plugin/TemplateTagPlugin.php

XBBCodeFilter.php in src/Plugin/Filter/XBBCodeFilter.php

XBBCodeParser.php in src/Parser/XBBCodeParser.php

XBBCodeTestPlugin.php in tests/xbbcode_test_plugin/src/Plugin/XBBCode/XBBCodeTestPlugin.php