[analyzer] Fix more ObjC accessor body farms after 2073dd2.

Fix a crash when constructing a body farm for accessors of a property
that is declared and @synthesize'd in different (but related) interfaces
with the explicit ivar syntax.

This is a follow-up for 0b58b80.

(cherry picked from commit 3c50f25)

Author: haoNoQ

clang/lib/Analysis/BodyFarm.cpp

@@ -741,13 +741,17 @@ static Stmt *createObjCPropertyGetter(ASTContext &Ctx,
     // First, find the backing ivar.
   const ObjCIvarDecl *IVar = nullptr;
 
-  // Property accessor stubs sometimes do not correspond to any property.
+  // Property accessor stubs sometimes do not correspond to any property decl
+  // in the current interface (but in a superclass). They still have a
+  // corresponding property impl decl in this case.
   if (MD->isSynthesizedAccessorStub()) {
     const ObjCInterfaceDecl *IntD = MD->getClassInterface();
     const ObjCImplementationDecl *ImpD = IntD->getImplementation();
-    for (const auto *V: ImpD->ivars()) {
-      if (V->getName() == MD->getSelector().getNameForSlot(0))
-        IVar = V;
+    for (const auto *PI: ImpD->property_impls()) {
+      if (const ObjCPropertyDecl *P = PI->getPropertyDecl()) {
+        if (P->getGetterName() == MD->getSelector())
+          IVar = P->getPropertyIvarDecl();
+      }
     }
   }
 

clang/test/Analysis/properties.m

@@ -1049,6 +1049,8 @@ - (NSObject *)getShadowedIvar;
 - (void)clearShadowedIvar;
 - (NSObject *)getShadowedProp;
 - (void)clearShadowedProp;
+
+@property (assign) NSObject *o2;
 @end
 
 @implementation Shadowed
@@ -1078,12 +1080,18 @@ @implementation Shadowing
 @synthesize o;
 
 -(void)testPropertyShadowing {
-  NSObject *oo = self.o;
+  NSObject *oo = self.o; // no-crash
   clang_analyzer_eval(self.o == oo); // expected-warning{{TRUE}}
   clang_analyzer_eval([self getShadowedIvar] == oo); // expected-warning{{UNKNOWN}}
   [self clearShadowedIvar];
   clang_analyzer_eval(self.o == oo); // expected-warning{{TRUE}}
   clang_analyzer_eval([self getShadowedIvar] == oo); // expected-warning{{UNKNOWN}}
   clang_analyzer_eval([self getShadowedIvar] == nil); // expected-warning{{TRUE}}
 }
+
+@synthesize o2 = ooo2;
+
+-(void)testPropertyShadowingWithExplicitIvar {
+  NSObject *oo2 = self.o2; // no-crash
+}
 @end