A WebAssembly project with imported QQC2 Treeview(QtQuick.TreeView 2.15)  module  throws the following error in the browser console :

qrc:/main.qml:36: Error: Qt.createQmlObject(): failed to create object: qtloader.js:382:25
qrc:/inline:1:1: Type Delegate unavailable qtloader.js:382:25
qrc:/Delegate.qml:4:1: module "QtQuick.TreeView" is not installed  

The same project runs fine with Desktop kits-  tested with  MinGW 32 and 64 bit kits.

Example projects without the TreeView module seem to run fine as well.

Qt for Webassembly and Emscripten compiler are configured according to the official documentation - https://doc.qt.io/qt-5/wasm.html

A way to reproduce:

1)Since QQC2 TreeView is an extension, it needs to be installed according to the instructions in its repository - https://code.qt.io/cgit/qt-extensions/qttreeview.git/

2)Configure Qt for WebAssembly according to official documentation - https://doc.qt.io/qt-5/wasm.html and https://doc.qt.io/qtcreator/creator-setup-webassembly.html

3)Try to run a new project with imported QtQuick.TreeView 2.15 and WebAssembly build configuration