QtConcurrent::mapped currently supports function pointers, pointer to member-functions, and functors which define a nested typedef result_type as map and reduce functions. Lambda expressions don't have that typedef, so compilation fails.

Workaround: stateless lambdas decay into function pointers, so you use the dereference operator to make them into function references, which again decay to function pointers, to force a function pointer deduction:
<code>
auto result = QtConcurrent::blockingMapped(someList, *[=](ListItem item)

);
</code>

QtConcurrent should not require result_type nested typedefs.