For example, in Objective-C mode, the initialization of 'x' in:
@implementation MyType + (void)someClassMethod { MyType *x = self; } @end
is correctly diagnosed with an incompatible-pointer-types warning, but
in Objective-C++ mode, it is not diagnosed at all -- even though
incompatible pointer conversions generally become an error in C++.
This patch fixes that oversight, allowing implicit conversions
involving Class only to/from unqualified-id, and between qualified and
unqualified Class, where the protocols are compatible.
Note that this does change some behaviors in Objective-C, as well, as
shown by the modified tests.
Of particular note is that assignment from from 'Class<MyProtocol>' to
'id<MyProtocol>' now warns. (Despite appearances, those are not
compatible types. 'Class<MyProtocol>' is not expected to have instance
methods defined by 'MyProtocol', while 'id<MyProtocol>' is.)