[SemaObjC] Fix composite pointer type calculation for `void*` and pointer to lifetime qualified ObjC pointer type

[erik.pilkington]

Summary

This fixes a regression introduced in 9a6f4d451ca7aa06b94a407015fbadb456bc09ef:

void f() {
  NSString *__strong* sptr;
  void *vptr;
  vptr == sptr; // new error: incompatible pointer types
}

We're now erroring out on this code because FindCompositePointerType is rejecting the qualifier mismatch between void and NSString *__strong after stripping one level of pointer types.

rdar://70101809

[rjmccall]

LGTM

clang/lib/Sema/SemaExprCXX.cpp

if (!Steps.empty()) {
                                       : Q2.getAddressSpace());
       } else {
         return QualType();
       }
 
       // FIXME: In C, we merge __strong and none to __strong at the top level.
       if (Q1.getObjCGCAttr() == Q2.getObjCGCAttr())
         Quals.setObjCGCAttr(Q1.getObjCGCAttr());
+      else if (T1->isVoidPointerType() || T2->isVoidPointerType())
+        assert(Steps.size() == 1);
       else
         return QualType();
 
       // Mismatched lifetime qualifiers never compatibly include each other.
       if (Q1.getObjCLifetime() == Q2.getObjCLifetime())
         Quals.setObjCLifetime(Q1.getObjCLifetime());
+      else if (T1->isVoidPointerType() || T2->isVoidPointerType())
+        assert(Steps.size() == 1);
       else
         return QualType();
 
       Steps.back().Quals = Quals;
       if (Q1 != Quals || Q2 != Quals)
         NeedConstBefore = Steps.size() - 1;
     }
 

clang/test/SemaObjCXX/arc-ptr-comparison.mm

-// RUN: %clang_cc1 -std=c++11 -triple x86_64-apple-darwin11 -fsyntax-only -fobjc-arc -verify %s
+// RUN: %clang_cc1 -std=c++11 -triple x86_64-apple-darwin11 -fsyntax-only -fobjc-runtime-has-weak -fobjc-arc -verify %s
 // RUN: %clang_cc1 -std=c++11 -triple x86_64-apple-darwin11 -fsyntax-only -verify -DNOARC %s
 #ifdef NOARC
 // expected-no-diagnostics
 #endif
 
 int testObjCComparisonRules(void *v, id x, id y) {
   return v == x;
 #ifndef NOARC

 // expected-note@-4 {{use __bridge_retained to make an ARC object available as a +1 'const void *'}}
 #endif
 
   // FIXME: Shouldn't these be rejected in ARC mode too?
   return ca == cv;
   return a == cv;
   return ca == v;
 }
+
+#ifndef NOARC
+int testDoublePtr(void *pv, void **ppv, A *__strong* pspa, A *__weak* pwpa, A *__strong** ppspa) {
+  return pv == pspa;
+  return pspa == pv;
+  return pv == pspa;
+  return pv == pwpa;
+  return pspa == pwpa; // expected-error {{comparison of distinct pointer types}}
+  return ppv == pspa; // expected-error {{comparison of distinct pointer types}}
+  return pspa == ppv; // expected-error {{comparison of distinct pointer types}}
+  return pv == ppspa;
+  return ppv == ppspa; // expected-error{{comparison of distinct pointer types}}
+}
+#endif