ObjCInterfaceDecl::lookupInstanceMethod() needs to look through a categories protocols.

Fixes <rdar://problem/6418640> clang on prokit: error: incompatible type returning 'id', expected 'NSSize'



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@60716 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AST/DeclObjC.cpp b/lib/AST/DeclObjC.cpp
index 0458282..85b8ec1 100644
--- a/lib/AST/DeclObjC.cpp
+++ b/lib/AST/DeclObjC.cpp
@@ -685,6 +685,14 @@
     while (CatDecl) {
       if ((MethodDecl = CatDecl->getInstanceMethod(Sel)))
         return MethodDecl;
+        
+      // Didn't find one yet - look through protocols.
+      const ObjCList<ObjCProtocolDecl> &Protocols =
+        CatDecl->getReferencedProtocols();
+      for (ObjCList<ObjCProtocolDecl>::iterator I = Protocols.begin(),
+           E = Protocols.end(); I != E; ++I)
+        if ((MethodDecl = (*I)->getInstanceMethod(Sel)))
+          return MethodDecl;
       CatDecl = CatDecl->getNextClassCategory();
     }
     ClassDecl = ClassDecl->getSuperClass();