r251874 stopped back-patching the AST when an Objective-C 'readonly'
property is redeclared in a class extension as 'readwrite'. However,
it did not properly handle merging of Objective-C property attributes
(e.g., getter name, ownership, atomicity) to the redeclaration,
leading to bad metadata. Merge (and check!) those property attributes
so we get the right metadata and reasonable ASTs. Fixes
rdar://problem/23823989.
llvm-svn: 255309
r251874 reworked the way we handle properties declared within
Objective-C class extensions, which had the effective of tightening up
property checking in a number of places. In this particular class of
cases, we end up complaining about "atomic" mismatches between an
implicitly-atomic, readonly property and a nonatomic, readwrite
property, which doesn't make sense because "atomic" is essentially
irrelevant to readonly properties.
Therefore, suppress this diagnostic when the readonly property is
implicitly atomic. Fixes rdar://problem/23803109.
llvm-svn: 255174
Douglas Gregor